You may be able to use a fuel pressure transducer from a petrol car* (try eBay or a boot-sale) - something that can handle 8-10 bar (water mains is said to be 4 bar - dependent on supplier and site) You will need to apply a voltage for the sensor to work - check that the DrDAQ may be able to supply ...

That's pretty cool!

Will give it a go later.

Volt-free is, in basic terms, an isolated circuit - you supply the volts! Some people call this 'dry contact'. The meters pulse is simply relay or opto-isolator switching. As scopes measure voltage and there is none, you will read nothing. Commonly in gas and electric meters, it'll be a N.O. relay. ...

Have you updated the Arduino 2560 firmware? Does the Picoscope 5203 work ok if it is used first? (connected and PicoScope 6 running, after which the Arduino is then connected) Apparently the newer Arduino 2560 firmware changes its USB VID/PID. I cannot find what the early ID's were. It's unlikely to...