How to calibrate full scale o/p range of ICL7107 (ADC)?

[henry77]

Hello Friends,

I have built a DC voltmeter with intersil ic ICL7107PCL. Maximum full scale output possible with it is 2V. I want to measure voltages upto 50V, so how can i do it? Can anyone suggest me kind of attenuator section which can be used at input or any other way i can measure upto 50V? I have used following circuit provided in datasheet

https://www.electro-tech-online.com/custompdfs/2009/11/fn3082.pdf

Please help me with this issue.

Thank you all.

 

[Nigel Goodwin]

It's VERY simple - to drop 50V down to 2V you need to drop 48V across the top resistor of the attenuator, and 2V across the bottom one. So they need a ratio of 48/2 (or 24/1).

A 24K for the top and 1K for the bottom would do.

 

[henry77]

Hi Nigel,

by using 24K and 1K resistor we can scaled down voltage in the range of 50-3V to 0-2V, but when i feed this voltage to ADC it displays voltage in 0-2v range.

My question is how can i change scale of the ADC, so that it displays voltages in the range of 0-50 Volts?

Please reply.

Thanking you

 

[mneary]

My question is how can i change scale of the ADC, so that it displays voltages in the range of 0-50 Volts?

You scale the input down 100:1 so you get 0-0.5V and move the decimal point.

The 7107 only will display 0-1999.

 

[henry77]

Hi mneary,

Thanx for your help, its working fine now. I used a voltage divider n/w to scale down the i/p, and it displays the i/p fine now.

Thanks again

 

[mneary]

Can you tell me the English words for n/w and i/p?