$20 LCR ESR Transistor checker project

[bateau020]

Budget: one often mentioned candidate is the "Bob Parker ESR" meter. EVB meters make them for example. 2 digits, 10mOhm resolution at the lowest range. Simple, fast, and easy to use: 1 button. But lots of others are mentioned over here.
Personally I have it, but it gets less use since I got myself some LCR Research Pro tweezers (somewhat budget), as that is much more versatile, and smaller.

[cigmas]

Budget: one often mentioned candidate is the "Bob Parker ESR" meter. EVB meters make them for example. 2 digits, 10mOhm resolution at the lowest range. Simple, fast, and easy to use: 1 button. But lots of others are mentioned over here.

That one looks great and is designed specifically for in-circuit capacitor testing. The problem is with the "budget" definition going an order of magnitude more than the title of this thread. Looks like it won't be any cheaper than ~$150 CAD + shipping/etc, and that would be if it were not sold out. https://flippers.com/catalog_oc/index.php?route=product/product&path=675&product_id=64 A bit difficult to justify for occasional hobby use.

[bateau020]

Yes indeed, it is not in the price range of the title, although I got one in europe for 65% of the price you mentioned.
How about the MESR-100? That is around 35 USD. Getting closer. Don't know if it is any good though.

[madires]

If you like to discuss other ESR meters then please start a new thread to keep this one focused.

[Vague]

Hi
Can the AY AT colour kit be fitted with a fixed calibration capacitor or does it need a chip with more pins?
Thank you

[madires]

The fixed cap for self-adjustment needs an ADC pin and an I/O pin for the resistor. Therefore it's an option for an ATmega324/644/1284 based tester.

[de_light]

Probably another stupid question but...

Why does my GM328A only occasionally read the ESR of caps?

I cannot work out any pattern to this. All caps read the capacitance accurately and leakage current, but only sometimes will measure the ESR.

My instinct says that this isn't a fault - I think there must be an explanation for this.

[indman]

de_light, what capacitors are you measuring? If the ESR of the capacitor is close to zero, then on the m-firmware it is not always displayed as a result on the display.

[madires]

... or when the ESR measurement detects invalid values. Do you use an SMPSU to power the tester?

[Fuzzy Star]

...Why does my GM328A only occasionally read the ESR of caps?
I cannot work out any pattern to this.

The manual says "Measurement of ESR value of capacitors with value of above 20nF ."
So, the occasion may be the "capacitors with value of above 20nF. "

[de_light]

I've tried with both a 9V and standard 'wall-wart' SMPSU for the DC in.

Here are some examples:

Salvaged 6800uF/63V cap from an 80s device - reading 6026uF, ESR of 0.00 and iLeak of 36uA
Second salvaged cap as above, reading 6195uF, ESR 0.00 and iLeak 30uA

New 470uF/100V cap - 444.8uF and iLeak 3.55uA, no ESR displayed
Salved 1000uF35V - 888 uF, iLeak 15.98uA and no ESR displayed
New 1000uF/16V - 946 uF, iLeak 11.23uA no ESR displayed
Film polypropylene unknown capacitance, old - 1030nF ESR 0.03

[madires]

Film polypropylene unknown capacitance, old - 1030nF ESR 0.03

That's way too low. Have you run the self-adjustment?

[de_light]

I did run it immediately after upgrading stock firmware. It completed without issue.

I have rerun the adjustment now and it completed fine.

Film cap ESR now reading 0.38
Big old salvaged caps still reading 0.00 Ohms 

[indman]

de_light,compare the readings of your capacitors with the measurements on BSideESR02. If they are of the same order, then everything is fine with your clone.

[madires]

Film cap ESR now reading 0.38
Big old salvaged caps still reading 0.00 Ohms 

A bit more reasonable, but still too low for a low value film cap. A good 4.7mF cap has around 0.02 Ohms, so your 6.8mF cap could be 0.01 which is the lowest value the tester can measure. In that case 0.00 Ohms (which means <0.01) would be fine.

[Szybkijanek]

My ESR results from LCR meter and compensated Hiland M644, all cap's are electrolytic and used condition:
6800uF 50V
" alt="" class="bbc_img" />
" alt="" class="bbc_img" />
1000uF 25V
" alt="" class="bbc_img" />
" alt="" class="bbc_img" />
100uF 16V
" alt="" class="bbc_img" />
" alt="" class="bbc_img" />
and 0,47uF 50V
" alt="" class="bbc_img" />
" alt="" class="bbc_img" />

[indman]

Szybkijanek
This is not an entirely correct comparison for measuring ESR. Madires notes in the instructions that:
"The tester tries to measure the ESR for capacitors with more than 10nF.
But since the ESR measurement isn't done via an AC signal with a
specific frequency, please don't expect a solid result. The method used might
be comparable with a 1kHz test."
The capacitance value for electrolytic capacitors is usually measured at a frequency of 100-120Hz.
Your LCR meter must not only have AUTO mode, but also MANUAL to select the measurement frequency.

[Szybkijanek]

All measurements was in manual mode but only 4 test was with 1,2kHz. First 3 cap's was in 100Hz mode.

[madires]

... and you should carefully select the right measurement mode (series/parallel) based on the impedance if supported by the LCR meter.

[Szybkijanek]

Ofcourse, I do this, with this original table:
" alt="" class="bbc_img" />

[madires]

Maybe you've already seen one of the cheap PIC LC meters which are based on a simple LC oscillator circuit. I've started to work on implementing the same measurement method with the LC oscillator as a hardware option. It's meant as option for ATmega644/1284 based testers. If you like to build one please find the schematic attached.

EDIT: C4 is the reference cap, not C3

[Szybkijanek]

I have LC-100A, it,s STM8 based LC meter but this meter have very bad accuracy (maybe only my model), before buying LCR meter I measure L element with scope method, accuracy ca. 5% when compare with professional LCR meter and software modeling, the smallest value I could measure is 20nH.
https://circuitdigest.com/electronic-circuits/how-to-measure-inductance-or-capacitance-using-oscilloscope

[indman]

Maybe you've already seen one of the cheap PIC LC meters which are based on a simple LC oscillator circuit. I've started to work on implementing the same measurement method with the LC oscillator as a hardware option. It's meant as option for ATmega644/1284 based testers. If you like to build one please find the schematic attached.

Madires, what LC range are you planning to use with this option?

[madires]

The ranges of the PIC LC meter are 10nH - 100mH and 0.1pF - 900nF with a reference frequency about 595kHz. If you take 600,000 Hz as reference frequency and 599,999 Hz for the lowest possible L or C which can be measured, the ranges could go down to about 0.2nH and 3.3fF theoretically. At the moment the m-firmware starts at 10nH and 0.1pF, same as the PIC LC meter, and I have to figure out what the feasible limits are. The math provides more digits, but how many are reasonable for the measurement? The upper limit for inductance is higher than 100mH, possibly 150mH (have to check). And for capacitance I've ran into an issue with the output signal for caps above 22 or 33nF. Rising and falling edge start to have some "kinks" causing the frequency counter to see more pulses than there really are.

[madires]

Some updates. 150mH work fine (around 12kHz), and lower limits of 1nH and 10fF seem to be reasonable. I'm not sure, but the PIC LC meter uses a gate time of 100ms for the frequency counter while the m-firmware uses auto-ranging with 100ms and 1s. So we get a better frequency resolution for low value L/Cs. The auto-ranging for the LC frequency counter does exactly the opposite (longer gate time for high frequencies) of what a normal frequency counter would do (longer gate time for low frequencies). The LC meter code increases the firmware size by about 5.5kB.