Can picaxe do this? Low ohm range

[Captain Haddock]

I have some oil pressure gauges and senders that are mismatched and the senders are a right git to get at so.....
The gauges are 0-5 bar range and senders are 0-10 bar range so I only half readings, the range of the senders and gauges is 10 ohm bottom to 180 ohm top and linear, can picaxe be used in this range to check the resistance and somehow give out resistance x2? And how of course?
It would save me a whole heap of trouble if I could make a circuit to sort it at the gauge end, any help greatly appreciated.

 

[AllyCat]

Hi,

Provided the sender is connected directly to ground, it should be relatively easy to measure its resistance. You only need to apply around 1 volt, e.g. via a 1k resistor from 5 volts, and a READADC10 can resolve to better than 1% even if using a 5 volt reference.

However, we probably need more details of the meter/gauge (e.g. its resistance and type) and how it is wired. If fed from a regulated supply, is this linear (i.e. analogue, dissipating) or (perhaps very slow) PWM ? For example, if the sender and meter are normally wired in series directly across a 12 volt rail, then the current and/or voltage might be quite high (e.g. for a "hot wire" ammeter) and the PICaxe will at least need an output driver transistor or FET.

Cheers, Alan.