Exactly what are you demonstrating here? I see that there is considerable difference in the first two ESR measurements, and I don't know what the reading in the third measurement is.

It is to be expected that when measuring ESR using the pulse or square wave technique that the result will not be accurate when, at the frequency of measurement, the impedance of the capacitor is much larger than the ESR. In that case the only way to get a good measurement is to use sine wave excitation.

There are some relatively low cost meters that use sine wave excitation, such as the DE-5000. Do you have any meters that use sine wave excitation?

**1+**I don't see anything in Tigr's design that is revolutionary or offers any significant improvements.

The design can be simplified a current source, a standard resistor and a current detector:

The MAX253 and the resistor form a current source. The current is split between a resistor, which I will call the standard resistor and the

**impedance** of the capacitor being tested. The current through the capacitor under test is measured and displayed.

The meter will read a maximum if the impedance of the capacitor is zero. The meter will read half-scale if the

**impedance** of the capacitor is equal to the standard resistor.

The impedance of the capacitor consists of three parts, the capacitance, the ESR and inductance.

The impedance is only equal to the ESR if 1/(2 x pi x Freq x C) = 2 x pi x Freq x L

So if the frequency is swept the results are:

**Sweeping the value of C**If change the model. I have fixed the frequency at 300 kHz and I am sweeping the value of capacitance. I am measuring the RMS current in the capacitor under test.

Results with Resr = 10m

Results with Resr = 200m

The desirable result is to have the ESR reading independent of the value of the capacitor.

All this shows that it not possible to accurately measure the ESR of capacitor by simply measuring the impedance.

You need to also measure the phase angle or use a phase sensitive detector that measure the component of the impedance that is in-phase with excitation current.

The ESR adapter that I shared here:

https://www.eevblog.com/forum/projects/esr-meter-adapter-design-and-construction/msg341177/#msg341177This circuit uses a phase sensitive detector, which helps but it is not super accurate for low values of capacitance.

I have attached the LTspice models for those playing along at home.

The best DIY solution I have seen was done by Jaxbird:

https://www.eevblog.com/forum/projects/impedance-analyzer-build-and-experiments/Unfortunately, some of the pictures are lost.

Regards,

Jay_Diddy_B