Auto Ranging Voltmeter design with PIC uC

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ericvic

Joined: 22 Oct 2009
Posts: 7
Location: USA

07 Nov 2009 7:21 Auto Ranging Voltmeter

Not sure if this is the right forum to ask this since it is analog and digital.

I want to make a voltmeter for a PIC. I know how to use a resistor divider to get the input voltage what I need but what if I want to measure multiple ranges and have a circuit that the range can be programatically changed (like an auto ranging multimeter). I have been looking at digital potentiometers but they seem to have a limit of input voltage on their resistor pins.

Also I would like to have the input floating so that it doesn't have to use the same ground as the PIC.

Can anybody help point me in the right direction.

Thanks,
Eric

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bobcat1

Joined: 10 Jul 2002
Posts: 1118
Helped: 48

07 Nov 2009 10:47 Re: Auto Ranging Voltmeter

Hi

To do autoranging voltmeter you will need an external programmable divider controled by the micro in use
The switch for the divider can be electronic (cmos switch ) or mech (relay)
you can switch range by placing a limit value on the A2D result - depend on the ref volatge used
For instance if you are using 3V ref volatge and you get read result from A2D as 2.9999 depend on A2D resolution (8bit,10bit,12bit ....) you will need to swich to the next range

All the best

Bobi