looking for meter to interface with arduino

I have been fooling around with arduino for a few months basically copying other's projects and finally have a project of my own that I would like to work on.

Basically I am looking to measure fuel consumption on a vehicle and combine this with gps data to hopefully yield some useful information. So, I have already successfully combined arduino and gps , and now need to figure out the fuel consumption part. I figure that I need an inline fluid meter with a serial interface. Has anyone ever successfully used such a device with an arduino? Any tips for seeking out a suitable device? thanks in advance for any help you can provide.

It is not very difficult to interface an amp meter to the arduino using the pwm output. but you will need to use a very low current one (like around 1-10mA) as the arduino can only source 40mA on an output pin. I did this to make an analog clock

I think the way to go would be a device that is like a motorless pump. As fuel flows through it, an impeller is turned. Each time it turns, it behaves as if someone pressed a doorbell once briefly. you feed that signal either direct to the Arduino if it isn't too busy to watch the input sufficiently continuously that it doesn't miss an on/off, or, more likely to work, feed the signal from the sensor to a counter. The Arduino then reads the counter when and as the Arduino wants.

There's more on counters at...

http://sheepdogsoftware.co.uk/sc2sn.htm

I you feed that signal either direct to the Arduino if it isn't too busy to watch the input sufficiently continuously that it doesn't miss an on/off, or, more likely to work, feed the signal from the sensor to a counter.

The Arduino has some decent IO Interrupt support.

and now need to figure out the fuel consumption part. I figure that I need an inline fluid meter with a serial interface.

If you are putting this on a car that has fuel injection, you maybe able to use the injection control signal. Typically these “open” for different lengths of time each stroke depending on the throttle setting. If you can measure how long the pulse is, you can use that as a measure of how much fuel is being used.

Failing this, you might be able to track down a fuel sensor used on a pre-fuel-injected car which you can then interface to.

Let us know what you come up with.

Mike