As stated in its datasheet:
Count = Vin x 1000
Vref

But when I measure the Vref and Vin on ICL7107 and do the calculation, the Count doesnt show exactly on the 7segment display as in my calculation.
Let say Vin = 0.076 and Vref = 1.293. So, Count = 58.
but my 7segment display 78.

Can anyone help me on this?

 

What instruments did you use to measure the voltages ? Is it calibrated?

What is your supply voltage ? Single or pos/neg?

 

I'm using fluke multimeter (it's calibrated). And I use both pos/neg for ICL7107.

 

Did you read page 6 "differential input/differential reference" of this datasheet?

Some possible error causes are described here.

Can you post a picture of how you wired it up and the corresponding schematic?

 

My bench meter is built around the 7107. I added an external reference like the LM4041 and it eliminated a lot of the reading errors. The internal chip heating from the drivers makes the built in reference pretty inaccurate.