Hi Tom,

Here's the circuit so far... the ad620 only seems to respond between 0 and 1.3mV input now. This wasn't intentional, but as far as I can see with my (insensitive) voltmeter, that is about the maximum I can squeeze out of the strain gauge by hand, which is comparable pressure to the pump I'm using. Could still do with doubling that to 2.5mV to be safe, though.

The voltage at the bottom of C1 is not that stable; 2.72-2.95V. As in last version of circuit, but less so.

Suddenly LTspice tells me it can't open ad620a.cir... why? and why now? Good job I saved a copy, which is fine...how random.

Does this look okay to you? Not done anything other than a DC sweep so far, but I'm quite pleased with it now!

Just got to work out why my actual circuit doesn't work...tomorrow.

Rich

 

This one's better behaved. Any coments on the increased R values? Pros/cons?

Further to the noise issue, would encasing the circuit and it's batteries (if used) in an earthed metal box attached to the shielding on the twisted input wires help. I'm thinking 'Faraday cage ' really.

Thanks, Richard B

 

Sorry, I've been on travel all week. I will try to get a good look at it over the weekend.

Tom

 

iI gootee,

No hurry, honesstly. I've been busy on other stuff, and will be for a few weeks, so it's not urgent.

Richard B