Calibration method for ESR meter

[lpkf2018]

Hello, I am very interested in your ESR meter. I plan to make one myself, but I found that there is no calibration method for the meter. Could you please publish a brief document on ESR meter calibration? I really need it. thank you!

[latchdevel]

Hi, I'm glad you're interested.
I'm sure you won't regret making one, it works great.

You have to keep in mind that there are two stages, first you need to set the "hardware-based parameters" after assembly. This is extremely simple, only two resistors and a reference capacitor are needed.

To obtain the ESR parameters, pressing the "minus button" shows the RAW values ​​of the ADC, both for the 1 ohm range and for the 10 ohm range.

• First, open the probes, both readings should saturate the ADC and show 1023 and 1023. If not, there is a problem.
• Second, short the probes, a low value will be displayed for the 1 ohm range, for example 29, and zero for the 10 ohm range, and without releasing the minus button, press the menu button to set this ADC value as zero ERS.
• Third, place a 1 Ohm reference resistor as DUT, and note the value for 1 Ohm range, for example 570. This is the approximate value that will be set as the value of M_ESR_1 in the code.
• Fourth, place a 10 Ohm reference resistor as the DUT, and note the value for the 10 Ohm range, for example 890. This value divided by 10 will be set as the value of M_ESR_10 in the code.

To obtain the Cx parameters, pressing the "plus button" shows the RAW value of the Timer1 tick counter.

• Place the reference capacitor, for example 100 uF, and note the counter value. This value divided by the capacitor capacitance in uF is what should be set as the value of M_Cx in the code.
• Cx fine tuning is done by varying the value of add_Cx in the code.

You can then perform a fine calibration adjustment which is stored in the EEPROM and can be modified from the user menu, accessed by holding the menu button at power up.

And the ESR zeroing is always available and easily accessible, since it depends a lot on the connected probes.

But you are right, it is necessary to publish a complete document on this topic.
I have just made a small update to the circuit, it may be the right time to publish the rest of the documentation.

I hope to be able to do it in the next few weeks.
Regards.