Make a very simple ESR meter.

Alec_t

Joined Sep 17, 2013
10,424
Looks to be a conventional design. The transformer properties could significantly affect the circuit's working/sensitivity/accuracy.
 

Thread Starter

bob2

Joined Jun 15, 2019
135
Looks to be a conventional design. The transformer properties could significantly affect the circuit's working/sensitivity/accuracy.
I don’t know. Maybe it’s even better. I’ll be able to adjust the desired range or sensitivity.
 

Thread Starter

bob2

Joined Jun 15, 2019
135
The circuit is quite simple. And it is good. All electronic components are available. The transformer can be used ready from old TVs and monitors or you can wind the transformer yourself.
Microammeters are large, so the use of LEDs is much better.
 

MrAl

Joined Jun 17, 2014
6,602
Hi,

Thanks bob, and i was asking partly for the OP too.

But i think if i was going to build one i would eliminate the transformer and use a higher current output op amp.
It's only 200mv so the current would be approximately max at 20ma. Maybe a regular op amp could handle that but i think i would go with one that could go higher in current anyway.
I'll see if i can find a part that will do this but anyone else wants to look around feel free to do so.
National Semi used to make a good higher power op amp so now it would be TI that would make it.

Ok i see way too many on the TI site.
One is LT1970A but check the data sheet before buying.
An op amp like that would eliminate the transformer as it can drive the device under test without a problem.
AD8656 maybe, but again check the data sheet to make sure it can run at the required voltage and has the right input requirements.
 
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Thread Starter

bob2

Joined Jun 15, 2019
135
Hi,
Thanks for the idea,MrAI.
Yes, it is quite interesting. Apply an opamp.
I would be very happy if this business was completed. Make a circuit without a transformer.
And at the same time I will deal with this scheme.
I have several ready-made transformers. I measured the inductances of the windings of these transformers.
Selected for experiments 5 transformers.
Previously, I could not do this, because there was no good inductance meter. Now I can confidently and accurately make these measurements.
 

MrAl

Joined Jun 17, 2014
6,602
Hi,
Thanks for the idea,MrAI.
Yes, it is quite interesting. Apply an opamp.
I would be very happy if this business was completed. Make a circuit without a transformer.
And at the same time I will deal with this scheme.
I have several ready-made transformers. I measured the inductances of the windings of these transformers.
Selected for experiments 5 transformers.
Previously, I could not do this, because there was no good inductance meter. Now I can confidently and accurately make these measurements.

Here is a new schematic with the basic idea shown.
The 10k and 1k resistor are typical.
The polarity of the 100uf cap is plus (+) goes to the output of the op amp.
 

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bob2

Joined Jun 15, 2019
135
I will try to do it with a transformer, because the board is already drawn ready for a transformer. After that, we will try your modified circuit without a transformer. It will be interesting to compare.
 

Thread Starter

bob2

Joined Jun 15, 2019
135
Here is a new schematic with the basic idea shown.
Looking at your scheme, a few questions arose.
Is a 100µF capacitor normal, or are there any higher requirements?
What are some ideas for protecting your circuit from a charged capacitor?
 

MrAl

Joined Jun 17, 2014
6,602
Looking at your scheme, a few questions arose.
Is a 100µF capacitor normal, or are there any higher requirements?
What are some ideas for protecting your circuit from a charged capacitor?
Well maybe 1000uf.

For protection two doides in series, then two more in series antiparallel to clamp the voltage.
 

Thread Starter

bob2

Joined Jun 15, 2019
135
Thanks MrAI.
I have some new ideas.
Replace R8 with a trimming resistor of 47k.With this resistor it will be possible to increase the gain of the measuring amplifier and compensate for the insufficient transformation ratio.
D1, D2 apply Schottky.
What do you think?
 

MrAl

Joined Jun 17, 2014
6,602
Hello,

You just have to watch the gain bandwidth product of the op amp if you increase R8, in fact you may want to check it the way it is now too. The oscillator frequency looks like it is around 88kHz?
You mean D1 and D2 the protection diode type? Schottky might work. Othersize fast Si.
 
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