john larkin
2025-03-23 01:49:24 UTC
Reply
PermalinkDiscussion:
Add Reply
How about thermal imaging a surface-mount resistor?
Bill Sloman
2025-03-23 02:32:08 UTC
Reply
Permalinkand just as fast, if not faster.
--
Bill Sloman, Sydney
Bill Sloman, Sydney
Sergey Kubushyn
2025-03-23 03:59:46 UTC
Reply
PermalinkPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* ***@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Bill Sloman
2025-03-23 05:31:55 UTC
Reply
PermalinkPost by Sergey Kubushyn
even more difficult.
But John hasn't spelled out any advantage that thermal imaging might offer.Post by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Post by Sergey Kubushyn
Wideband current shunts made for AC-DC transfer are all of very special
construction and cost arm and leg.
Mainly because it's a small and specialised market. You need a resistiveWideband current shunts made for AC-DC transfer are all of very special
construction and cost arm and leg.
material whose resistance doesn't change much as it warms up and
wideband means that you need something flat and compact.
Post by Sergey Kubushyn
If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Measuring AC isn't - in principle - different from measuring DC. YouIf you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
just have to do it more frequently.
Post by Sergey Kubushyn
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
Nothing to do with thermal imaging.Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
--
Bill Sloman, Sydney
Bill Sloman, Sydney
john larkin
2025-03-23 05:47:14 UTC
Reply
PermalinkPost by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
Sergey Kubushyn
2025-03-23 07:14:09 UTC
Reply
PermalinkPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
Fluke 5790A is good to 1MHz on itself, without the wideband option. TheOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
option makes it to 30 MHz but with limited voltage. The 5790A measures up to
1kV at 50 kHz.
However, with its accuracy and resolution it is not all that trivial to do
precise measurements at higher frequencies. You wouldn't notice it at all on
8-1/2 digit (on some ranges :)) 3458A. However, on the 5790A even a 12" coax
is NOTICEABLE starting from 50kHz and shows SIGNIFICANT drop at higher
frequency. 12" N-type to BNC cable like this:
https://www.amazon.com/dp/B07SJZMKRV
and BNC to dual banana like this:
https://www.amazon.com/dp/B0BTYKYS3Z
show significant losses at higher frequencies. Actually Fluke tells that 12"
is the MAXIMUM cable length for everything over 100kHz but they don't tell
WHAT cable it is :)
The N-type side is connected to 5790A, the banana part goes into my
Wavetek/Datron 4808 calibrator. 4808 stands right on the 5790A and the
shortest cable that I can use is a custom made 8" thick LMR400 with
right-angle N-type connector on the 5790A side. This cable is not
noticeable.
Hoping to measure wideband AC current by measuring a voltage drop over
regular resistor is simply insane.
This is what's used to measure AC current ACCURATELY:
https://www.ebay.com/itm/126975629050
It is not that it is the only option and it is very old (but still good and
usable) up to 50-100kHz range. They are guaranteed to be 1:1 for DC and AC
within that range and one should do a TRANSFER, not direct voltage
measurement. That is why the ABSOLUTE ohmic value is not all that important.
One applies that unknown AC current and gets a reading on the voltmeter.
Then, some KNOWN and characterized DC current, close to the expected unknown
AC current is applied and DC reading is taken. The shunts are guaranteed to
be 1:1 AC:DC so knowing the DC current and the ratio between known DC and
unknown AC readings allows to find the AC current.
That is if one wants good precise measurement. If it is to, say, plus/minus
couple per cents, all that complication is not needed.
And that is up to something like 50kHz, maybe up to 100kHz tops. Higher
frequencies require more sophisticated and significantly more expensive
measures.
Jeff Layman
2025-03-23 08:31:19 UTC
Reply
PermalinkPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
There is a skin effect in a surface-mount resistor (seeOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
--
Jeff
Jeff
Cursitor Doom
2025-03-23 09:06:08 UTC
Reply
PermalinkPost by Jeff Layman
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
What's the big deal here? Just use a oscilloscope with a currentPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
There is a skin effect in a surface-mount resistor (seeOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
probe.
john larkin
2025-03-23 17:05:31 UTC
Reply
PermalinkPost by Cursitor Doom
probe.
Most such probes are AC-only, and none can clamp onto a PCB trace.Post by Jeff Layman
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
What's the big deal here? Just use a oscilloscope with a currentPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
There is a skin effect in a surface-mount resistor (seeOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
probe.
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
holes. This ain't bad for a first try:
Loading Image...
No, a surface-mount bridge rectifier isn't supposed to smoke.
Phil Hobbs
2025-03-23 18:08:21 UTC
Reply
PermalinkPost by john larkin
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
My Tek one goes dc-20 MHz. It uses a Hall sensor and a regular currentPost by Cursitor Doom
probe.
Most such probes are AC-only, and none can clamp onto a PCB trace.Post by Jeff Layman
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
What's the big deal here? Just use a oscilloscope with a currentPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
There is a skin effect in a surface-mount resistor (seeOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
probe.
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
transformer.
Cheers
Phil Hobbs
(In Austin visiting #1 daughter)
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
john larkin
2025-03-23 20:01:20 UTC
Reply
PermalinkPost by Phil Hobbs
transformer.
What model is that? Maybe we could put a little loop thingie on aPost by john larkin
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
My Tek one goes dc-20 MHz. It uses a Hall sensor and a regular currentPost by Cursitor Doom
probe.
Most such probes are AC-only, and none can clamp onto a PCB trace.Post by Jeff Layman
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
What's the big deal here? Just use a oscilloscope with a currentPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
There is a skin effect in a surface-mount resistor (seeOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
probe.
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
transformer.
board and clip onto that.
Check out the bats at sunset.
Phil Hobbs
2025-03-24 03:09:38 UTC
Reply
PermalinkPost by john larkin
On Sun, 23 Mar 2025 18:08:21 -0000 (UTC), Phil Hobbs
board and clip onto that.
I lied—it’s 50 MHz.On Sun, 23 Mar 2025 18:08:21 -0000 (UTC), Phil Hobbs
Post by Phil Hobbs
transformer.
What model is that? Maybe we could put a little loop thingie on aPost by john larkin
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
My Tek one goes dc-20 MHz. It uses a Hall sensor and a regular currentPost by Cursitor Doom
probe.
Most such probes are AC-only, and none can clamp onto a PCB trace.Post by Jeff Layman
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
What's the big deal here? Just use a oscilloscope with a currentPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
There is a skin effect in a surface-mount resistor (seeOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
probe.
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
transformer.
board and clip onto that.
Tektronix P6042 50MHz Current Probe
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Cursitor Doom
2025-03-26 23:57:49 UTC
Reply
PermalinkPost by john larkin
On Sun, 23 Mar 2025 18:08:21 -0000 (UTC), Phil Hobbs
board and clip onto that.
I liedits 50 MHz.On Sun, 23 Mar 2025 18:08:21 -0000 (UTC), Phil Hobbs
Post by Phil Hobbs
transformer.
What model is that? Maybe we could put a little loop thingie on aPost by john larkin
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
My Tek one goes dc-20 MHz. It uses a Hall sensor and a regular currentPost by Cursitor Doom
probe.
Most such probes are AC-only, and none can clamp onto a PCB trace.Post by Jeff Layman
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
What's the big deal here? Just use a oscilloscope with a currentPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
There is a skin effect in a surface-mount resistor (seeOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
probe.
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
transformer.
board and clip onto that.
Tektronix P6042 50MHz Current Probe
Cheers
Phil Hobbs
(at the 3db down point) and also requires the Type 131 current
amplifier which I do have (although it seems quite happy to work
without it for higher currents (will take up to 15A). I very rarely
use it but it's really handy for those odd times when it is needed.
Does the 6042 need a separate current amp?
Phil Hobbs
2025-03-27 00:32:12 UTC
Reply
PermalinkPost by Cursitor Doom
On Mon, 24 Mar 2025 03:09:38 -0000 (UTC), Phil Hobbs
Tektronix P6042 50MHz Current Probe
Cheers
Phil Hobbs
Rats, Phil. You have a better one than my P6016! It only goes to 17Mhz
(at the 3db down point) and also requires the Type 131 current
amplifier which I do have (although it seems quite happy to work
without it for higher currents (will take up to 15A). I very rarely
use it but it's really handy for those odd times when it is needed.
Does the 6042 need a separate current amp?
It has all the signal conditioning built in.On Mon, 24 Mar 2025 03:09:38 -0000 (UTC), Phil Hobbs
Post by john larkin
On Sun, 23 Mar 2025 18:08:21 -0000 (UTC), Phil Hobbs
board and clip onto that.
I liedits 50 MHz.On Sun, 23 Mar 2025 18:08:21 -0000 (UTC), Phil Hobbs
Post by Phil Hobbs
transformer.
What model is that? Maybe we could put a little loop thingie on aPost by john larkin
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
My Tek one goes dc-20 MHz. It uses a Hall sensor and a regular currentPost by Cursitor Doom
probe.
Most such probes are AC-only, and none can clamp onto a PCB trace.Post by Jeff Layman
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
What's the big deal here? Just use a oscilloscope with a currentPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
There is a skin effect in a surface-mount resistor (seeOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
probe.
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
transformer.
board and clip onto that.
Tektronix P6042 50MHz Current Probe
Cheers
Phil Hobbs
(at the 3db down point) and also requires the Type 131 current
amplifier which I do have (although it seems quite happy to work
without it for higher currents (will take up to 15A). I very rarely
use it but it's really handy for those odd times when it is needed.
Does the 6042 need a separate current amp?
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Cursitor Doom
2025-03-27 00:54:14 UTC
Reply
PermalinkPost by Phil Hobbs
Cheers
Phil Hobbs
Yeah, I kind of thought so. Much more recent than my ancient oldPost by Cursitor Doom
On Mon, 24 Mar 2025 03:09:38 -0000 (UTC), Phil Hobbs
Tektronix P6042 50MHz Current Probe
Cheers
Phil Hobbs
Rats, Phil. You have a better one than my P6016! It only goes to 17Mhz
(at the 3db down point) and also requires the Type 131 current
amplifier which I do have (although it seems quite happy to work
without it for higher currents (will take up to 15A). I very rarely
use it but it's really handy for those odd times when it is needed.
Does the 6042 need a separate current amp?
It has all the signal conditioning built in.On Mon, 24 Mar 2025 03:09:38 -0000 (UTC), Phil Hobbs
Post by john larkin
On Sun, 23 Mar 2025 18:08:21 -0000 (UTC), Phil Hobbs
board and clip onto that.
I lied?it?s 50 MHz.On Sun, 23 Mar 2025 18:08:21 -0000 (UTC), Phil Hobbs
Post by Phil Hobbs
transformer.
What model is that? Maybe we could put a little loop thingie on aPost by john larkin
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
My Tek one goes dc-20 MHz. It uses a Hall sensor and a regular currentPost by Cursitor Doom
probe.
Most such probes are AC-only, and none can clamp onto a PCB trace.Post by Jeff Layman
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
What's the big deal here? Just use a oscilloscope with a currentPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
There is a skin effect in a surface-mount resistor (seeOn Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
handle the audio range.
The resistor has great common-mode rejection too.
<https://www.vishay.com/docs/60107/freqresp.pdf>). If an AC current
flows nearer the surface of the resistor, would that make it "hotter"
the higher the frequency? In other words, would the ammeter also be a
frequency meter?
probe.
My current (in both senses) issue is to measure true RMS currents in a
high-frequency isolated power supply. The idea is to have one
STSPIN958 full-bridge make anti-phase 48-volt 500 KHz square waves
that drive some number N of DRQ127 isolation transformers and then
schottky bridge rectifiers, for some unknown N. Four would be nice.
I have an engineer, a kid right out of school, working on this. It's a
great educational project. He'd never heard of core satutation,
shoot-through current, diode reverse recovery, skin effect, The
Devil's Staircase, the quirks of STspice, any of that practical stuff.
And I'm teaching him how to Dremel and solder and shear and drill
https://www.dropbox.com/scl/fi/bje0zqt3okjbsaycp16of/STSPIN_Proto.jpg?rlkey=yzyi1hf0r05hbex8zhppxdln4&raw=1
No, a surface-mount bridge rectifier isn't supposed to smoke.
transformer.
board and clip onto that.
Tektronix P6042 50MHz Current Probe
Cheers
Phil Hobbs
(at the 3db down point) and also requires the Type 131 current
amplifier which I do have (although it seems quite happy to work
without it for higher currents (will take up to 15A). I very rarely
use it but it's really handy for those odd times when it is needed.
Does the 6042 need a separate current amp?
Cheers
Phil Hobbs
thing. Mind you, it still works as advertised even after 60 odd years.
Old Tek gear is hard to beat and I very much doubt anything come out
of China today will still be around in 60 years from now.
piglet
2025-03-23 09:12:36 UTC
Reply
PermalinkPost by john larkin
On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
handle the audio range.
The resistor has great common-mode rejection too.
Some so called true RMS dvms on AC ranges do not respond to DC.On Sun, 23 Mar 2025 03:59:46 -0000 (UTC), Sergey Kubushyn
Post by Sergey Kubushyn
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
---
******************************************************************
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************
Many otherwise great DVMs have an AC bandwidth that doesn't evenPost by Bill Sloman
Why bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
That depends on what you actually want to measure. And "wideband" makes itWhy bother? Measuring the voltage drop across the same device is easier,
and just as fast, if not faster.
even more difficult.
Wideband current shunts made for AC-DC transfer are all of very special
costruction and cost arm and leg. If you want to measure the voltage drop
over those resistors, without making AC-DC transfer, you're up to another
challenge, measuring the AC voltage. Should start from the definition, what
IS the AC voltage? What the actual number your measurement shows means and
so on.
Look at e.g. not all that precise but much better than most LT1088 chip,
long obsolete. There is another one, proprietary and much better precision
inside e.g. Fluke 5790A Standard (which is a misnomer -- it is actually an
AC and DC voltmeter, 10x more precise that the venerable HP/Agilent/Keysight
3458A).
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handle the audio range.
The resistor has great common-mode rejection too.
Thermal measurement is inherently true RMS
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piglet
piglet