How accurate needs an ESR meter be?

[Bob Parker]

Re: How accurate needs an ESR meter be?

I want to explain to some nuclear physicists why we need a transformer in this circuit.
It compensates for the error introduced by masuring probes therefore it is possible to use longer probes.
Transformer provides more current measurement,so it is possible to measure small values of ESR
This can not be achieved without transformer circuits.

Fascinating. So we're just imagining those circuits which measure down to 10 milliohms without using a transformer. Thanks for telling us.

[devid21]

Re: How accurate needs an ESR meter be?

And i thought that the topic you are not interested
It discusses the analog ESR meter using a transformer.
Always glad to help good people
I can also offer a good beer

[devid21]

Re: How accurate needs an ESR meter be?

Fascinating. So we're just imagining those circuits which measure down to 10 milliohms without using a transformer. Thanks for telling us.

With regard 10 milliohms,this value has long been reached

[Th3_uN1Qu3]

Re: How accurate needs an ESR meter be?

Update! It occured to me that the one major loss of this circuit is the voltage drop of the 1N4148s. So i realized that adding a gain stage would be pointless because whatever it would make up would be lost again.

And then it hit me. Use schottkys! I used one SBL1040CT with both diodes in parallel and one SBL2040CT which had one diode blown so i only used half. And... watch that meter swing full scale. There you go, now you have an use for those half-blown 20A diodes.

[devid21]

Re: How accurate needs an ESR meter be?

It´s all long ago it occurred
In this scheme 1N4148 nobody uses.
Columbus when it discovered America.

[Th3_uN1Qu3]

Re: How accurate needs an ESR meter be?

Good one. But anyway, the resolution of the meter basically remained the same, just that it now has higher efficiency hence lighter on that 9 volt. So it occurs to me that my problem is the transformer - luckily i'd just bought a spool of 0.2mm, so i'll proceed making my own transformer.

[devid21]

Re: How accurate needs an ESR meter be?

Today is Saturday.
Let´s listen RAINBOW- Wolf to the moon.

[Th3_uN1Qu3]

Re: How accurate needs an ESR meter be?

Well, almost Sunday hehe. Anyway, i've finally understood 100% what are the factors that influence the reading.

#1. The sense resistor
#2. The primary:secondary turns ratio (the higher, the better)
#3. Resistance of the secondary winding which is actually the most important factor. Therefore it is impossible to obtain good accuracy with a small core like EE16 or EE19 which is what i've been using.

My cheapo dB meter needs about 15mV to move a clearly visible amount. So, i came up with a circuit that increases the reading by 15mV per 0.001 ohms. Yup, one milliohm resolution. The lower limit will be 0.2 ohms. Since my current one has 0.1 ohm resolution i'll just build a separate meter and not worry about any range switch. I'll be building it next week.

[devid21]

Re: How accurate needs an ESR meter be?

An excellent example for veterans.

[PCBONEZ]

Re: How accurate needs an ESR meter be?

The upper end of low ESR is about 0.1 ohms so if your lower limit is 0.2 ohms it's will not be suitable for testing low ESR caps.
.

[Th3_uN1Qu3]

Re: How accurate needs an ESR meter be?

I meant lower limit = minimum reading, highest ESR it can read. I said it's gonna go down to one milliohm and it will.

[PCBONEZ]

Re: How accurate needs an ESR meter be?

If it's highest then that would be upper and maximum, not lower and minimum.

[devid21]

Re: How accurate needs an ESR meter be?

Well, almost Sunday hehe. Anyway, i've finally understood 100% what are the factors that influence the reading.

#1. The sense resistor
#2. The primary:secondary turns ratio (the higher, the better)
#3. Resistance of the secondary winding which is actually the most important factor. Therefore it is impossible to obtain good accuracy with a small core like EE16 or EE19 which is what i've been using.

My cheapo dB meter needs about 15mV to move a clearly visible amount. So, i came up with a circuit that increases the reading by 15mV per 0.001 ohms. Yup, one milliohm resolution. The lower limit will be 0.2 ohms. Since my current one has 0.1 ohm resolution i'll just build a separate meter and not worry about any range switch. I'll be building it next week.

Transformer serves as consent to provide low output impedance voltage source measurement.
When measuring the ESR of about 0,it is not included in the regime of short circuit.
Therefore,the output stage is not overloaded and the shape and amplitude of the output signal does not change.
The amplitude of the measuring pulse-125mv.
When short-circuiting the probes amplitude slightly decreases to 115mv,and the shape of the pulses slightly rounded.
This means that measurement ESR of about 0 shape and amplitude of the pulse is almost exact same as the unloaded.
This ensures the accuracy and reliability of measurements.
Resistance R5,R6-3-5ohm;R8-18k.
Diodes-1N5851.
Resistance in the generator should be put precision 1%.