ICL7107 Voltmeter calibration

[123mmm]

Hi, I need some advice regarding the attached schematic. I built the schematic, it is working but I don't know how to calibrate it. I need to measure between 0 V and 50 V.
I set the Rx1= 100R and Rx2a= 100k, but if I rotate R4, then the displayed value modifies.
Do I need to calibrate it using a standard voltmeter ?

 

[Diver300]

Yes.

However, you could just measure the output of the 7805 which will be within 2 % of 5 V.

 

[KeepItSimpleStupid]

Your options are as follows. Calibrate the 200 mV range and let the resistors to their thing. e.g 1%, 0.1% etc,

or calibrate near the nominal voltage you need to measure accurately. e.g. inject 25V and calibrate to 25V.

A calibration source is usually better than your meter. It might be a 2.500 V source.

 

[123mmm]

The calibration should be as follows.
1. Set the values for Rx1 and Rx2a
2. Set the displayed value by rotating R4 ?

 

[Diver300]

The calibration should be as follows.
1. Set the values for Rx1 and Rx2a
2. Set the displayed value by rotating R4 ?

That's correct.

You do need some voltage reference that is a known value to calibrate against.

 

[gophert]

https://airborn.com.au/circuits/mas830l.gif

 

[shokjok]

Please translate the warning at the bottom left of the schematic.

 

[123mmm]

Hello shokjok , the text is this:
FIGYELEM!! A 2000V csak egy elméleti határ.
Eszébe se jusson senkinek kipróbálni!
Using google translate: