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ammeter/voltmeter/ciruits

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ammeter/voltmeter/ciruits

Postby caleb » Thu Feb 19, 2004 1:42 am

HI im wondering If any one knows where I can find circuits for these two devices.
I am doing a project now to make a combo ammeter/ voltmeter/ time till battery goes flat meter. I want to display all this Info on to a 7 segment or LCD display. I also would like to have a mode button so that all three devices (ammeter/ voltmeter/ time till battery goes flat meter) can share the same screen. Its kind of like a multi meter but with the added time till battery goes flat meter. I want this to run of the 12v dc battery that it is testing If that is at all possible. Any help would be greatly appreciated.
:D
:?: Im at 6th form level at school am I out of my depth with the complexity of this circuitry. :?:
caleb
 
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Postby Matthew » Thu Feb 19, 2004 11:03 am

The easiest option is to use a microcontroller with A/D converter. The majority of A/D converters will measure between 0-5v, so you will need a voltage divider to measure up to 12v. Current can be obtained by measuring the voltage across a low value resistor. If we look at V = IR we can see that voltage across the resistor is dependant upon the current passing through it, assuming the value of the resistor remains constant. You will likely need a high wattage resistor to handle the current through your entire circuit.

If you still don't understand how to construct the circuit, you should probably consider a different project.

Matthew
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