Please tell me if this is possible using the MCP4100 digital pot..

Hi,

I am trying to make a voltmeter using the ICL7107 my circuit will be based on the circuit given in this link, **broken link removed**

The circuit is the fourth drawing on the page.

In my voltmeter I am planning to use a digital potentiometer instead of fixed resistances, the digital pot is the MCP41100 from Microchip, see link for datasheet https://ww1.microchip.com/downloads/en/DeviceDoc/11195c.pdf

It is a 100K linear digital pot.

Please let me know if this is feasible using digital pots...also what would the expected accuracy be.

I know the 7107 is used in digital voltmeters, and they are quite accurate is it possible to achieve similar accuracies if I make my my own voltmeter using the 7107 ??

I am sorry if the above description is sketchy as the idea is still in my head and I have not made any prototypes yet to get accurate information.

thanks
arbj2

Hi,

No, totally unsuitable.

You would need a micro with SPI to set the digital pots in the first place.

The input resistors on a meter are critial values essential for the accuracy of the meter, using resistors with a 1% or better tollerance is needed.

Thanks for the reply....

So instead of fixed resistances I will use the auto-range circuit instead so no selection of resistances would be required.

Is there any way of increasing the resolution of the circuit, it is at present 0.1 mV, ie: values will be displayed as 12.1, 12.2 etc. I want to display 12.123 instead would this possible ??

you can always do that,
like in arduino you can use

it will gives you 7 decimal places,so in your case 12.123 it would be 3
and you have to make sure the datatype is right for your value,use float number for the safe-way