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A while ago I came across a really simple capacitance meter at ?? https://wordpress.codewrite.co.uk/pic/2014/01/21/cap-meter-with-arduino-uno/index.html
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.? It puts the DUT and a reference capacitor in series, applies a DC step voltage and measures the resulting voltage across the reference capacitor.? A? disadvantage is that the DUT is floating, the reference capacitor being the input capacitance of the Arduino.? The article is the start of a thread which has links to notes on resolution and expanding the measuring range.
The original scheme uses a PC to display the results, but it is fairly trivial to add an LCD or OLED to make a small self contained bench meter using an Arduino Pro-Mini module or similar - example attached.? Ditto to add an offset calibration mode to compensate for different test lead capacitances.
I have tried a number of capacitance meter circuits over the years and tested several devices of the AADE/LC100 self-oscillating type, which although they use sound principles and theoretically offer good accuracy, in practice suffer from drift when measuring small values of capacitance (and sometimes huge errors when measuring larger capacitors).? This circuit is both sensitive and stable, even on the plugboard I used to try it out.
Peter S ??? ??? G8EZE
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The example .pdf went AWOL on the first pass!
PeterS???????????? G8EZE
-----Original Message-----
From: swallowp via groups.io <swallowp@...>
To: [email protected]
Sent: Sat, 3 Sep 2022 9:29
Subject: [Test Equipment Design & Construction] A stable and repeatable low value capacitance meter
A while ago I came across a really simple capacitance meter at ?? https://wordpress.codewrite.co.uk/pic/2014/01/21/cap-meter-with-arduino-uno/index.html
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.? It puts the DUT and a reference capacitor in series, applies a DC step voltage and measures the resulting voltage across the reference capacitor.? A? disadvantage is that the DUT is floating, the reference capacitor being the input capacitance of the Arduino.? The article is the start of a thread which has links to notes on resolution and expanding the measuring range.
The original scheme uses a PC to display the results, but it is fairly trivial to add an LCD or OLED to make a small self contained bench meter using an Arduino Pro-Mini module or similar - example attached.? Ditto to add an offset calibration mode to compensate for different test lead capacitances.
I have tried a number of capacitance meter circuits over the years and tested several devices of the AADE/LC100 self-oscillating type, which although they use sound principles and theoretically offer good accuracy, in practice suffer from drift when measuring small values of capacitance (and sometimes huge errors when measuring larger capacitors).? This circuit is both sensitive and stable, even on the plugboard I used to try it out.
Peter S ??? ??? G8EZE
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A while ago I came across a really simple capacitance meter at ??
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.?
I might have misunderstood it. The adverts on the page, PDF and circuit in separate files didn¡¯t make for easy reading.?
For small capacitors, unless the DC voltage is very high little energy will be stored in the reference capacitor in a reasonable time. That would suggest to me that a very high impedance voltage measurement would be needed to measure the voltage capacitor due to the short T=Cref Rload time constant.?
I have probably misunderstood the design.??? ?
I recall a thread on the Keysight forum where a guy had bought a Keysight handheld LCR meter. He measured a capacitor, then compared the valve to that measured by a Fluke and other handheld multimeters. All the multimeters gave approximately the same value, but the LCR meter something significantly different. I suggested that this may be due to the different methods of measurement - the LCR meter using AC and (probably) a 4 terminal connection, and the DMMs charging/discharging a capacitor and measuring the time constant. I don¡¯t know if that was the reason or not, but I do see significant differences between my handheld Tektronix DMM which hasn¡¯t been calibrated for decades, and an HP 4284A Precision LCR meter which has been calibrated by Keysight - not some Mickey Mouse lab.?
Peter S ??? ??? G8EZE
Dave
-- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
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An interesting article.
I've built the Roman Black C Meter, which drifts a couple of pF over a short time, and the van Dijk code change, which seemed like it took a couple of minutes before the correct reading appeared.
So a meter that doesn't drift and has fast cycle times is desirable, but one tied to a computer for readout is not useful and my brain is far too old to learn how to modify Arduino code to add a LCD display to make a portable unit. If someone does, please publish.
John
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Show quoted text
On 9/3/2022 1:29 AM, swallowp via groups.io wrote: A while ago I came across a really simple capacitance meter at
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.? It puts the DUT and a reference capacitor in series, applies a DC step voltage and measures the resulting voltage across the reference capacitor.? A? disadvantage is that the DUT is floating, the reference capacitor being the input capacitance of the Arduino.? The article is the start of a thread which has links to notes on resolution and expanding the measuring range.
The original scheme uses a PC to display the results, but it is fairly trivial to add an LCD or OLED to make a small self contained bench meter using an Arduino Pro-Mini module or similar - example attached.? Ditto to add an offset calibration mode to compensate for different test lead capacitances.
I have tried a number of capacitance meter circuits over the years and tested several devices of the AADE/LC100 self-oscillating type, which although they use sound principles and theoretically offer good accuracy, in practice suffer from drift when measuring small values of capacitance (and sometimes huge errors when measuring larger capacitors).? This circuit is both sensitive and stable, even on the plugboard I used to try it out.
Peter S ??? ??? G8EZE
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David,
Arduino CPU pin impedance when configured as an analogue input is specified as 100MegOhms.? The charging source/sink is capable of 20mA and the measurement is a voltage ratio, essentially independent of the supply.? Quite interesting to do the sums for the sampling.? I agree that the thread is not easy to follow if you are in a hurry.
It was not the absolute accuracy but the stability and repeatability that surprised me, having assembled? the basic circuit on a prototyping board out of curiosity.? I realised it would be useful to me as a stand alone device for measuring/sorting SMD capacitors in the 2-1000pf range, and I would commend it on that basis.
PeterS???????? G8EZE
-----Original Message-----
From: Dr. David Kirkby, Kirkby Microwave Ltd <drkirkby@...>
To: [email protected]
Sent: Sat, 3 Sep 2022 13:12
Subject: Re: [Test Equipment Design & Construction] A stable and repeatable low value capacitance meter
A while ago I came across a really simple capacitance meter at ??
I am usually sceptical about claims for such designs, but this one does not drift or require constant re-zeroing when measuring capacitors of a few pF.?
I might have misunderstood it. The adverts on the page, PDF and circuit in separate files didn¡¯t make for easy reading.?
For small capacitors, unless the DC voltage is very high little energy will be stored in the reference capacitor in a reasonable time. That would suggest to me that a very high impedance voltage measurement would be needed to measure the voltage capacitor due to the short T=Cref Rload time constant.?
I have probably misunderstood the design.??? ?
I recall a thread on the Keysight forum where a guy had bought a Keysight handheld LCR meter. He measured a capacitor, then compared the valve to that measured by a Fluke and other handheld multimeters. All the multimeters gave approximately the same value, but the LCR meter something significantly different. I suggested that this may be due to the different methods of measurement - the LCR meter using AC and (probably) a 4 terminal connection, and the DMMs charging/discharging a capacitor and measuring the time constant. I don¡¯t know if that was the reason or not, but I do see significant differences between my handheld Tektronix DMM which hasn¡¯t been calibrated for decades, and an HP 4284A Precision LCR meter which has been calibrated by Keysight - not some Mickey Mouse lab.?
Peter S ??? ??? G8EZE
Dave
--
Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
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John K,
I appended the circuit to show just how simple the meter is even with an added display.? The basic measurement code is in the original article. There are dozens if not hundreds of examples of LCD/OLED interface code for Arduino, not least on the Arduino Forum. ?
I'm afraid this is an old project for me now, I came across the files and thought the principles might be of interest to this group.
PeterS???????? G8EZE
-----Original Message-----
From: John Kolb <jlkolb@...>
Sent: Sat, 3 Sep 2022 22:14
So a meter that doesn't drift and has fast cycle times is desirable, but
one tied to a computer for readout is not useful and my brain is far too
old to learn how to modify Arduino code to add a LCD display to make a
portable unit. If someone does, please publish.
John
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I use this LC meter and am very satisfied with it:
LC meters on Ebay that look the same have a much worse specification.
73, Hans, ON4CDU
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On Sun, 4 Sep 2022 at 11:57, Hans Wagemans < on4cdu@...> wrote:
I use this LC meter and am very satisfied with it:
LC meters on Ebay that look the same have a much worse specification.
73, Hans, ON4CDU
I don¡¯t have one, but this LCR meter from Hungary quite impressed me
Note it is 4-terminal, and works on the principle of an autobalancing bridge, like at least some of the HP/Agilent/Keysight ones do. My Agilent 4284A (0.05% basic accuracy) works on that principle.
On my HP 4284A one has to enter the length of the test leads (either 0 m, 1 m, 2 m or 4 m). There¡¯s no facility to enter the test lead length on that meter.?
I don¡¯t know why HP consider the test lead length important, but they obviously do. On the 4284A, option 006, which adds support for 4 m test leads, was an extra cost option. It¡¯s a software only option, but the instrument needs recalibration - I assume to check the 4 m results meet the specification. My meter didn¡¯t originally have that option, so I asked Keysight the cost of upgrading. They said when I sent it for calibration they would add it free of charge. The maximum frequency of the 4284A is 1 MHz (wavelength of 300 m), so even 4 m test leads are very small compared to the wavelength.?
Obviously 2 different imp¨¦dances would present the same impedance at the end of test leads, if those leads were of a different length. But I would have thought that as long as the 4 test leads were of the same length, the 4-wire Kelvin connection would have compensated fully for the length.?
Dave?
-- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
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I've had one of those "Hutale" LCR
meters with Kelvin probes from Dr Le Hung for six years or so.? It
works well and gives sensible answers, but really needs to be
fitted into a box.? I broke one of the switches through
carelessness. It only goes up to 10 kHz sine wave for testing
capacitors, so the lead lengths are probably not critical.? I made
a four-wire jig for testing SMD components.
Neil
On 04/09/2022 12:59, Dr. David Kirkby,
Kirkby Microwave Ltd wrote:
toggle quoted message
Show quoted text
On Sun, 4 Sep 2022 at 11:57, Hans Wagemans < on4cdu@...> wrote:
I use this LC meter and am very satisfied with it:
LC meters on Ebay that look the same have a much worse specification.
73, Hans, ON4CDU
I don¡¯t have one, but this LCR meter from
Hungary quite impressed me
Note it is 4-terminal, and works on the
principle of an autobalancing bridge, like at least some of
the HP/Agilent/Keysight ones do. My Agilent 4284A (0.05%
basic accuracy) works on that principle.
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A while ago I compared the performance of a number of units like that from several different sources.? Some of them were very good, some were really bad.? I tracked this down to (mostly) the quality of the reference inductor.? The good ones had inductances that remained fairly constant over the frequencies generated by the unit. The inductance of the bad ones varied significantly so the accuracy became worse as the calibration and? DUT test frequencies diverged (no compensation in the software as far as I could tell).? I suspect they were all "copies" of the same design, but some manufacturers saved a few pennies on the inductor.? Some of the worst were wound on toroids, but from measurement it looked as though the ferrites were designed for EMI suppression rather than inductor applications.
Hang on to your good unit!
PeterS???????? G8EZE
-----Original Message-----
From: Hans Wagemans <on4cdu@...>
Sent: Sun, 4 Sep 2022 11:57
I use this LC meter and am very satisfied with it:
LC meters on Ebay that look the same have a much worse specification.
73, Hans, ON4CDU
_._,_._,_
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hi Neil,
sorry...but what are those "Kelvin probes from Dr Le Hung"???
I "googled" but couldn't find any plausible answer!
best 73
de
i2NDT Claudio
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When I googled, among the top several hits was this one:
There is a picture of the Kelvin clips in the doc.
--Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 9/5/2022 00:05, i2NDT Claudio via
groups.io wrote:
toggle quoted message
Show quoted text
hi Neil,
sorry...but what are those "Kelvin probes from Dr Le Hung"???
I "googled" but couldn't find
any plausible answer!
best 73
de
i2NDT Claudio
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Hi Claudio, it's the Hutale meter.? I
emailed Dr Le Hung directly to buy the meter.? I don't know if he
still has them for sale.
The video shows the use of the Kelvin
clips.
Neil
On 05/09/2022 08:05, i2NDT Claudio via
groups.io wrote:
toggle quoted message
Show quoted text
hi Neil,
sorry...but what are those "Kelvin probes from Dr Le Hung"???
I "googled" but couldn't find
any plausible answer!
best 73
de
i2NDT Claudio
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On Sun, 4 Sep 2022 at 13:13, Neil Smith G4DBN < neil@...> wrote:
I've had one of those "Hutale" LCR
meters with Kelvin probes from Dr Le Hung for six years or so.? It
works well and gives sensible answers, but really needs to be
fitted into a box.? I broke one of the switches through
carelessness. It only goes up to 10 kHz sine wave for testing
capacitors, so the lead lengths are probably not critical.? I made
a four-wire jig for testing SMD components.
Neil
The latest version goes up to 50 kHz.?
I would suggest that if fitted in case, it would be sensible to fix 4 x female BNCs on the front, spaced 22 mm apart, in the order shown in the attachment, which is a photograph I just took from my Agilent 4285A LCR meter. Then it would fit any of the standard fixtures from HP/Agilent/Keysight or their clones. I attach a few pictures of such fixtures.?
Note the fixtures have male BNCs, with at least two having levers on them. Those BNC connectors can be found on eBay. You will probably need to take the levers off and put them in a slightly different position, because the levers need to be angled such that they are at the 1:30 position on a clock when mated.?
The red and black Kelvin clips can be found on eBay too, but I have found some need a bit of modification as poor manufacturing has resulted in the two halves of the clip being electrically joined. It may be necessary to take them apart to add an insulator.?
I have a couple of laboratory LCR meters (HP/Agilent 4284A and 4285A), but if I didn¡¯t, I would probably buy that one.?
The DE-5000 is a small LCR meter that was sold by IET Labs). There are many clones of that sold. I don¡¯t know if the quality of the clones varies. A friend has a DE-5000 clone. I loads him a few precision components?
1 H inductor? 100 mH inductor Various 0.005 or 0.01% resistors Variable 0-100 pF variable capacitor.
He was very impressed with his DE-5000.?
-- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
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On Mon, 5 Sep 2022 at 09:42, Neil Smith G4DBN < neil@...> wrote:
Hi Claudio, it's the Hutale meter.? I
emailed Dr Le Hung directly to buy the meter.? I don't know if he
still has them for sale.
The video shows the use of the Kelvin
clips.
Neil The webpage says to contact him by email. I don¡¯t think it was any different - I don¡¯t recall a PayPal button for example.?
I wish I knew why the HP/Agilent/Keysight meters need one to enter the lead length. The 1 MHz 4284A will take cables up to 4 m in length (with option 006) and the 30 MHz 4285A up to 2 m. Given one performs an open, short, and optionally load at the end of the cables, I can¡¯t understand why the cable length is important. The dielectric is important too. I have a set of HP extension cables, and made my cables for the LCR meter the same electrical length, as I used a different dielectric, with a slightly different relative permittivity. I thought the electrical length was more likely to be important than the physical length.? -- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
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For low capacitance values. I am happy with my vintage Tektronix 130. This was developed in the vacuum tube age and was probably originally intended for in-house measurments of CRT and vacuum tube interelectrode capacitances.
When mine developed power supply sickness, I replaced all the vacuum tube electronics with a solid state design. This instrument measures at a frequency in the 125-140 kHz range. With the solid state electronics, the frequency is stable to +/-0.1 Hz (the longest counter gate time I use is 10 S), corresponding to ~+/-0.002 pF.? I use 0.40 Vp-p voltage across the capacitor; this can probably be reduced to 0.20 Vp-p or less. Full scale ranges are 3 through 300? (either pF or uH). By measuring the raw RF frequency, the capacitance range can be extended beyond 1000 pF (inductance seems to fail with my oscillator circuit above ~600 uH; I could probably change a few component values to extend this limit).
It is somewhat tolerant of parallel resitance (75 k), but not as tolerant as the original Tektronix (20k). Warmup drift is <0.002 pF/min after 30 minutes. Total startup drift is <1 pF (first 15 minutes), which is easily zeroed out. It has a guard voltage output, which is very useful in getting rid of stray capacitance effects.
It does have a zeroing control. I consider this an advantage; it allows immediate use upon turn-on. Also, it allows capacitor matching to great accuracy (zero with one capacitor attached and measure the capacitance with the other to get the difference). Lead length is no problem if the instrument has a zeroing capability since one merely zeros out the lead capacitance.
At 0.4V p-p, it seems to work well for semiconductor junctions. I am still working on guarded fixtures for this have not yet done a complete evaluation.
As a final note, one should pay attention to the frequencies used to measure capacitances. A capacitor may measure quite differently at DC or audio frequencies from high kHz or MHz frequencies, where resistive effects may be less but inductive effects more.
Stephen Menasian
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Check this out
I will build it in a few weeks, as soon as the Nokia Display comes in
its also L and C meter.. and can work on higher frequencies
Nice jOB and project
JP
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On Mon, 5 Sept 2022 at 14:30, Jempi ( ON7MA ) < on7ma@...> wrote: Check this out
I will build it in a few weeks, as soon as the Nokia Display comes in
its also L and C meter.. and can work on higher frequencies
Nice jOB and project
JP
It appears to assume ideal components - it does not give you series R or parallel R. The test frequency depends upon the component, but as
Stephen Menasian pointed out, the test frequency is important. That's not something I would personally build, even if I did not have professional LCR meters. I think I would rather buy
and spend the time sticking it in my own box.
Dave
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I made my own test clips.? You can see how I did it at, ?
? I hope posting this link is not against the rules.? ? 73 (Regards). ? Max K 4 O D S. ? I've Never Lost the Wonder. ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Tom Lee
Sent: Monday, September 05, 2022 2:45 AM
To: [email protected]
Subject: Re: [Test Equipment Design & Construction] A stable and repeatable low value capacitance meter? When I googled, among the top several hits was this one:
There is a picture of the Kelvin clips in the doc.
--Cheers,
Tom
-- Prof. Thomas H. Lee Allen Ctr., Rm. 205 350 Jane Stanford Way Stanford University Stanford, CA 94305-4070 On 9/5/2022 00:05, i2NDT Claudio via groups.io wrote: hi Neil,
sorry...but what are those "Kelvin probes from Dr Le Hung"???
I "googled" but couldn't find any plausible answer!
best 73
de
i2NDT Claudio
?
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On Mon, 5 Sept 2022 at 16:17, MAX < max@...> wrote: I made my own test clips.? You can see how I did it at, ?
? I hope posting this link is not against the rules.?
No, post any links you want, as long.
Dave (group owner)
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Dr. David Kirkby, Kirkby Microwave Ltd
John Kolb
Jempi ( ON7MA )