Signal Conditioning

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Can I configure a voltage divider on a SCXI-1100 card in order to read battery voltage from a car without external circuitry?

I would like to know if I can cofigure a voltage divider without having to wire external circuitry. I know that there are pads for a filter capacitor and current to voltage resistor on the SCXI-1100. COuld these pads be used to solder in a precision resistor to serve as a voltage divider? Our current system uses an external circuit with two 500k precision resistors that cut the voltage in half so that we are within the +-10V range of the card. The voltage I am trying to measure is from a car battery (12-15V).
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Yes, you should be able to build a voltage divider by putting a resistor into the filter capacitor socket (not the current loop resistor socket). Set the gain on the module to 1 and use a resistor value around 3kohm, or slightly lower, to bring your 15 VDC down to 10 VDC. Keep in mind that the amplifier input impedance will be reduced to ~4.6kohm, however, a car battery will source plenty of current as long as there are no other significant resistances in the circuit. You will need to calibrate this circuit, since the resistors on the SCXI-1100 are +/- 2%.

Best Regards,

Brent Runnels
Applications Engineer
National Instruments
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