Multimeter with inductance?

[Helmholtz]

That's what I suspected originally. Means that the spec sheet is cheating. Confused by the improvements shown in the video. Could still be a 3-wire measurement, which is better than 2 wires if done correctly. This can eliminate/compensate lead wire resistance but not contact resistance.

Anyway, the PeakTech 2170 recommended above does full 4-wire measurement. Absolutely not necessary for PU measurements but highly welcome when measuring ESR or Q of caps and for designing a dummy load emulating speaker impedance .

[g1]

Thanks!
It seems that for the 4-wire measurement the Kelvin adapter is required, which uses the blade contacts plus at least one of the normal receptacles.

Edit: 4 wire measurement is supported. Each single banana socket is split in 2 inside. The blade terminals are double sided, so 2 conductors per blade.
Unfortunately, no accessories are sold for 4 wire measurement with this unit. You must build your own by modification of the TL-21 or TL-22.

[Helmholtz]

Thanks!
It seems that for the 4-wire measurement the Kelvin adapter is required, which uses the blade contacts plus at least one of the normal receptacles.

[Jazz P Bass]

From what I have read, the socket itself is '4 wire'.

The TL-21 lead adapter joins the wires inside the adapter box.

The TL-22 SMD tweezers join the wires very near the tip.


Here is a nice 'teardown' of the unit: https://www.eevblog.com/forum/testge...-and-teardown/

[nosaj]

I have a question to owners of the DE-5000:

The spec sheet lists 4-wire (Kelvin) measurement as a feature. Looking at the picture I can spot only 3 receptacles. How is this supposed to work? Are one or two of the receptacles actually coaxial double contacts?

I have the meter but not the Kelvin adapter. Maybe this video will show you something?
http://electricalandelectronicsandst...lvin-clip.html
nosaj

[Helmholtz]

I have a question to owners of the DE-5000:

The spec sheet lists 4-wire (Kelvin) measurement as a feature. Looking at the picture I can spot only 3 receptacles. How is this supposed to work? Are one or two of the receptacles actually coaxial double contacts?

[Helmholtz]

The Q is this divided by 10,992 ohms, or 1.58. I think that is the smallest I have measured.

In an earlier post you wrote "Many guitar pickups have Q values of 1.0 and below." And I replied that I never saw one having a Q that low.

As indicated above, the ELC131D has been available since around 1993. It works perfectly down to a Q of 0.4 and certainly lower.
Apart from that, I don't see a need to measure PU inductance to better than say +/- 3%.

The OP asked for advice regarding L meters suitable for PUs and I recommended a couple that I am familiar with and know that work just fine.
These µC-based LCR meters are much easier to handle than traditional bridges. And they are really accurate.

[Joe Gwinn]

typo

Never saw one. But both meters are within 1% with an inductor having a Q of 0.4.

I recall discussions of units with very low Q, with lots of #42 wire. Probably for a Base <something>.

In my notes (of 21 February 2005): "The Eastman" by Kent Armstrong, Model HJGS-1. Rdc = 7.978 Kohms. Test at 1 KHz. 2.776 Henrys, Rac= 10.99 Kohms. (The excess of Rac over Rdc is 3.012 Kohms; this is the eddy current burden, which does count in Q computation.)

At 1000 Hz, Reactance is 2.776*(2 Pi 1000) = 17,442 Ohms. The Q is this divided by 10,992 ohms, or 1.58. I think that is the smallest I have measured.

PM 6302

I found the service manual. It sure looks plausible; don't know why there would have been a problem. Hmm - it may have been hard to detect when the bridge was actually balanced if one is only measuring the amplitude of the bridge null signal, and not the phase. I recall having to bounce between phase and amplitude to find the null. I'll read the manual more deeply.

I forgot to mention when this all happened. I built the impedance bridge in mid 2004, and very few of the handheld LRC meters of that day worked correctly with pickups.

[Helmholtz]

Hmm.. Many guitar pickups have Q values of 1.0 and below.

Never saw one. But both meters are within 1% with an inductor having a Q of 0.4.

What is the model number of the old Philips?

PM 6302

[Joe Gwinn]

If you look at the pdf spec, you will find that accuracy is specified for DF(D)<0.5, i.e. Q>2.0. I never cared, because I verified by direct comparison. Just measured a lossy steel core inductor:

ELC131D:
Ls= 636.4µH/Q= 1.88 @1kHz and Ls= 1.19H /Q= 1.37 @ 120Hz

PT 2170:
Ls= 639.1µH/Q= 1.91 @1kHz and Ls= 1.20H/ Q= 1.42 @120Hz

Hmm.. Many guitar pickups have Q values of 1.0 and below.

That seems to be matter of priorities. My ECL131D was about 150€ when new.
The ELC131D has been around since the early 90s.

Well, yes. There are many needs and few dollars.

Both my digital meters work better with low-Q inductors than my old Philips which uses a Maxwell-Wien bridge.

This is odd. What is the model number of the old Philips?

I built my bridges from discrete components, each componet's value having been measured to 1% before assembly.

[Helmholtz]

What's needed is numerical specification of the range of D or Q values over which the meter will achieve stated accuracy. I did not find this in the ELC131D datasheet.

If you look at the pdf spec, you will find that accuracy is specified for DF(D)<0.5, i.e. Q>2.0. I never cared, because I verified by direct comparison. Just measured a lossy steel core inductor:

ELC131D:
Ls= 636.4µH/Q= 1.88 @1kHz and Ls= 1.19H /Q= 1.37 @ 120Hz

PT 2170:
Ls= 639.1µH/Q= 1.91 @1kHz and Ls= 1.20H/ Q= 1.42 @120Hz

Not everybody is up for $250.

That seems to be matter of priorities. My ECL131D was about 150€ when new.
The ELC131D has been around since the early 90s.

Both my digital meters work better with low-Q inductors than my old Philips which uses a Maxwell-Wien bridge.

[Joe Gwinn]

Yes, it measures Q/D. See datasheet "Features" and "Display". I did compare the meters. Even compared both to the >10k $ HP impedance analyzer in our lab. I tend to make sure before I recommend something.

I wasn't precise enough. Mention of D and Q isn't enough. What's needed is numerical specification of the range of D or Q values over which the meter will achieve stated accuracy. I did not find this in the ELC131D datasheet.

The ELC131D was standard lab equipment with my EEs. I've had mine for 8 years or so.

That's good to know. Not everybody is up for $250.

I am used to search the global market.

In the US, this was difficult until relatively recently. Now it's easy, and I buy many things directly from Europe and China.

Like Jens Putzier: https://www.jensputzier.com/. This is a one-man shop, but he has stuff that's hard to get in the US.

[Helmholtz]

I could not find a Q or D spec anywhere in the ELC131D datasheet. Have you calibrated this unit against the Peak 2170? That would be useful.

Yes, it measures Q/D. See datasheet "Features" and "Display". I did compare the meters. Even compared both to the >10k $ HP impedance analyzer in our lab. I tend to make sure before I recommend something.
The ELC131D was standard lab equipment with my EEs. I've had mine for 8 years or so.

Here in the US, we had a lot of trouble with handheld (simple = cheap enough?) LCR meters that measured only the absolute magnitude of the reactance, and thus implicitly assumed that the components were pure inductors or capacitors (as defined by which button the user pressed).

I am used to search the global market.

[Joe Gwinn]

I also own one of these:

https://www.ebay.com/p/Escort-ELC131...ter/1978183468

It is accurate and reliable, completely sufficient for PU inductance measurements. Measuring frequencies 120Hz/1kHz.

https://www.otdl.com/131d.pdf

I could not find a Q or D spec anywhere in the ELC131D datasheet. Have you calibrated this unit against the Peak 2170? That would be useful.

[Joe Gwinn]

This may be true for simple DMMs with L measuring function. but I never noticed such inaccuracies with the digital LCR meters I used. Fact is that apparent inductance varies with measuring frequency and mode (series vs parallel) for several reasons. I always use the series equivalent circuit mode.

You are very fortunate. Here in the US, we had a lot of trouble with handheld (simple = cheap enough?) LCR meters that measured only the absolute magnitude of the reactance, and thus implicitly assumed that the components were pure inductors or capacitors (as defined by which button the user pressed).

This works OK for transformers and inductors, but failed miserably for guitar pickups: The errors were by large factors, and not by percentages, and at the time we did not know why.

This initially drove me to build a Maxwell-Wien Impedance Bridge, which was widely used by national standards labs before the days of digital. The results were then used to qualify digital LCR meters, and showed that the root cause was that high-impedance pickups are low-Q inductors. Now days, with cheap digital components and expired patents, any LCR meter that specifies an acceptable range of Q or D values is probably acceptable. If no Q or D spec, beware -- assume that it is not suitable until proven otherwise.