Analog voltage input references

[markl951]

Are the pins labeled 0V all common to each other and are they or are they not connected to the main power return for the dash?

I would like to measure the voltage drop across a resistor. Like you might do with a hand held voltmeter. Neither end of the resistor is at ground potential so I need to know if the 0V pins on the dash are isolated from chassis ground. If they are all common to each other and another sensor pulls 0V to chassis ground then I might be stuck.

I don't have a dash here to play with so I don't have a way to figure it out by trial and error at this point. If some one could let me know that would be great.

Thanks,
Mark

[David Ferguson]

The Signal and Reference 0V are all tied internally to the Battery Minus pin. If you need to measure a simple resistance, the easiest way is to use a Analog Temperature input. These inputs have a 1000 ohm internal resistor tied to the 5V reference voltage, and can basically measure a resistance directly. The calibration can even be provided in ohms!

If your resistive value is very large (so that you would want to measure it using a much larger pull-up resistor), then provide your own precision pull-up to the 5V reference voltage. When calibrating with your own pull-up, you will have to calculate the voltage provided by the voltage divider circuit for various resistance.

[markl951]

Thanks David,

I'm trying to measure the voltage drop across a resistor that has current flowing through it. That is not the same as measuring a resistance. But if what you say is true about all the 0V pins being tied to the Battery Minus pin then you've answered my question.

I'll find another way to get the measurement I need.

[SprinterTRD]

If the voltage you want to measure is within the range of the ADL inputs, use 2 av inputs to measure each end of the resistor. then use a table with the 2 av channels as the x & y axis to generate correct value.