Make a very simple ESR meter.

Thread Starter

bob2

Joined Jun 15, 2019
213
2. Add a known resistance like 0.1 Ohms
Hi,
To do this, I will need to find resistors of the corresponding ratings and with minimal inductance.
A large inductance will introduce a large error in the measurement result.
Now I can allow myself to do this - select such maximally suitable resistors, having a very accurate inductance meter.
 

Thread Starter

bob2

Joined Jun 15, 2019
213
Having measured the inductance of different resistors, I came to the conclusion that the best of all are chip resistors of a certain type, which have the lowest inductance.
 

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MrAl

Joined Jun 17, 2014
8,158
Oh let me repeat this...

I noticed the oscillator in post 44 does not look good or else it is drawn wrong.
There is no resistor to the positive supply.

That's important. The best is when the cap voltage goes from Vcc/3 to 2*Vcc/3.
The worst is probably that posts oscillator because the cap voltage must go very low.
 

Thread Starter

bob2

Joined Jun 15, 2019
213
After experimenting a little more with transformers, I came to an unexpected conclusion.
It turns out that with TL072, using different transformers and increasing the supply voltage (up to 30V), you can significantly increase the sensitivity and, accordingly, stretch the scale very close to zero. What does this give us?
This makes it possible to measure the ESR of different types of LOW ESR capacitors.
Naturally, this version of the ESR meter will already work with a microammeter.
 

Thread Starter

bob2

Joined Jun 15, 2019
213
The circuit with the use of LEDs will be so with TL072 and a voltage of 5V. The meter may look something like this.
 

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Thread Starter

bob2

Joined Jun 15, 2019
213
The limitation in the supply voltage of 5V inhibits the development of this circuit.
As I already said, the use of other transformers requires an increase in the supply voltage, up to 36V.
In addition, to expand the range near zero, a significant decrease in the resistance of the resistors R5, R6 is required. Perhaps even up to 0.1 Ohm. Well, it’s clear that the microammeter should be 10-100 μA, it will be selected experimentally. It is even possible to use an analog tester in the mode 50-100 μA, and even better 10 μA.
We must not forget about the quality of the supply voltage.It should be as stable as possible and with the least ripple.
And lastly.
The probes should have a minimum resistance and the design of the ESR meter should be as in the LCR Pro1 Plus, that is, in the form of tweezers.
This is how a simple circuit can turn with an appropriate approach into an in-circuit ESR meter, with the technical specifications we need.
 

MrAl

Joined Jun 17, 2014
8,158
The limitation in the supply voltage of 5V inhibits the development of this circuit.
As I already said, the use of other transformers requires an increase in the supply voltage, up to 36V.
In addition, to expand the range near zero, a significant decrease in the resistance of the resistors R5, R6 is required. Perhaps even up to 0.1 Ohm. Well, it’s clear that the microammeter should be 10-100 μA, it will be selected experimentally. It is even possible to use an analog tester in the mode 50-100 μA, and even better 10 μA.
We must not forget about the quality of the supply voltage.It should be as stable as possible and with the least ripple.
And lastly.
The probes should have a minimum resistance and the design of the ESR meter should be as in the LCR Pro1 Plus, that is, in the form of tweezers.
This is how a simple circuit can turn with an appropriate approach into an in-circuit ESR meter, with the technical specifications we need.
Well just to note, some of the resistances can be zeroed out.
 

Thread Starter

bob2

Joined Jun 15, 2019
213
Hi,
The idea is clear. What are the advantages we get?
How will this affect the stretching of the scale?
 

bertus

Joined Apr 5, 2008
21,330
Hello,

If you want to try the 555 version, take the bilpolair version of the 555.
The CMOS can only drive 100 mA, as the bipolair can drive 300 mA.

Bertus
 

MrAl

Joined Jun 17, 2014
8,158
Hi,
The idea is clear. What are the advantages we get?
How will this affect the stretching of the scale?
Advantages of what?
What do you mean "stretching"?

Advantage of a crystal are super frequency stability. A 555 is of course another good option.

Zeroing out means that if you have resistance in series already before the measurement, you first measure that and then subtract that from the overall reading. For example, you connect the two probes together, measure 0.1 Ohms, then when you connect them to the DUT if you aread 0.3 Ohms then the DUT has 0.2 Ohms resistance. Yes it affects the scale somewhat because you have to be able to measure small increments, but i think you need that anyway so a digital meter is probably the way to go rather than analog.
For example if you measure 0.1 Ohms with the two probes touching and the DUT has 0.01 Ohms resistance, it may be hard to read 0.11 Ohms as opposed to 0.1 Ohms it may be hard to tell the difference.
On the other hand, we can incorporate a zeroing pot like all Ohm meters have, and then you can zero out the lead resistance first.
But it sounds like for what you are looking for you would do better with a digital readout that can read a count like 9.999 or something like that.
 

Thread Starter

bob2

Joined Jun 15, 2019
213
For example if you measure 0.1 Ohms with the two probes touching and the DUT has 0.01 Ohms resistance, it may be hard to read 0.11 Ohms as opposed to 0.1 Ohms it may be hard to tell the difference.
You mean resolution. This is typical for digital ESR meters, but not for analog ones.
By stretching the scale, I mean the ability to measure ESR-0.1Ohm or 0.01Ohm.
To make it more clear, I suggest, for example, calibrating the microammeter scale with resistors with an interval of 0.005 Ohm.
0.005Ohm
0.01Ohm
0.015Ohm
0.02Ohm
etc.
I think this will be enough.
 

Thread Starter

bob2

Joined Jun 15, 2019
213
Finished and calibrated the ESR meter.
Applied OPA 2140. Well this is a completely different matter. The scale of the microammeter immediately stretched. Schottky diodes were carefully selected.
I used a super-sensitive, unique microammeter 100uA from a medical device.
All resistors are 0.01-0.1% accuracy.
Supply voltage -30v.
Thank you all for the good advice and useful information.
 
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