For the modified circuit:

Measurements are taken with the M2038 voltammeter, on the 0,75mA / x1 range (that means 750uA full scale). The scale is marked 0-150, so multiply by 5 to obtain the uA value.

Its internal resistance, measured on this range (0,75ma x1) with a multimeter is

**21,7ohms**Connecting the meter to the circuit (no pot/resistor in series) and

shorting the probes, I get a reading of exactly 70, multiplying by 5 ->

**350uA**Measuring the voltage on the terminals of the voltammeter:

**0,007V**The ESR deflection

**on the linear scale of the voltammeter** is the same as yours:

Your meter deflection (taken from page 1):

Notice that the

2 ohm inscription is on the

*left side* of the middle line.

The voltammeter deflection is the same as above, if I connect a 2 ohm load across the probes of the circuit, it shows 32 -> 160 uA, that's right below 175uA (half of 350uA).

But I got issues when I use a

VU meter.

I don't think that the circuit is the problem, because when connecting the voltammeter, that has a linear scale, the deflection is the same as yours.

The VU meters:

They both have the same "problem".

I don't think it's a problem, maybe is something that vu meters do, and maybe you guys know:

So, I connected the meter circuit as below:

With the help of the 250k pot, I can adjust/peak the needle of the VU meter, and the voltammeter offers a precise reading of the current passing thru the VU meter.

So I peaked the VU meter (capacitor probes shorted):

I get a reading of

**57,5** -> 287,5uA, let s call this the

full deflection point.Logically, the mid point will be at 57,5/2=

**28,75** -> 143,7uA

I adjusted the pot so I can get the needle right in the middle:

BUT I get a reading of

**22** ->

**110uA.**This means that the mid point is shifted 33uA below what it should be (110ua instead of 143ua) and the delflection on the VU meter would look like this:

The left side (the higher ESR values) have more space on the scale than the ones on the right side (the lower ESR values). This makes the reading of low ESR values harder, that is a little of a problem.

At the beginning, I mentioned that a 2 ohm reading will be at the

**left side of the scale**.

If I connect a 2 ohm resistance at the capacitor probes:

See, the needle is in the right side of the scale...

Why is it so? Are the VU meters not linear? I get the exact same problem with the black grundig vu meter, the mid point is not at the half of the full curent deflection.

Thanks!