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[SOLVED] ICL7107 Voltmeter problem

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Michael_N

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Hi,

I have wired up a voltmeter on my breadboard, using the ICL7107 ic. I have connected 4 LED 7-segments to it.
It is set up like the datasheet says, with a +-5 V supply witch allows my to measure on its own supply voltage.

The problem is that the voltmeter shows random numbers on the display. There is no difference when I connect the input to a voltage.

Can anyone guide me a little?

Best regards
Michael
 

Dear Michael
Hi
I think your soldering has problem. because that circuit is a completely digital circuit and you should pay more attention to soldering them . for example , wash your PCB lines, with alcohol .
Respect
Goldsmith
 

Thanks for your replies:)

I'm using batteries so that's not the problem.
I'm using a breadboard for test so bad connections could be the problem, I Will check that.

But I forgot to tell that when I put the test pin High the circuit fiols 1888, that works fine.

Best regards
 

Best that you don't wire the card yourself .Problems of static leakages ruin the chip.
Vhi and Vlo inputs capacitance make glitch pickups at readout .
The PCB card (bare or assembled) are readily available to fit up and start operation .
regards
 

From looking at two schematics I see different component arrangements near the input pin(s). Might be worth trying various schematics to see if any works for you.
 

Putting it on a PCB helped.....alot:)

Thanks alot for you advice:)
 

Great work done.
Problem was only static capacitance pickup which was eliminated by the pcb design....
However , for a 4 1/2 dig. version you may need to elevarte the Hi ,Lo input terminals above the main PCB.
best of luck in applications
 

What do you mean by elevating the HI and Lo input above the main pcb?
 

I want the input terminals 5mm away from the main PCB so that all static pickup impedance /capacitance etc are minimized and you get a true response without interference .
Present Glass epoxy card has 3-5pf caps pickup between the Hi and Lo terminals .As such , there shall be a frequency limit for the dual slope integration for input accuracy determination.
 

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