Data acquisition & sensors, Copper Corrosion, Failures, and ‘Name that device’
Posted by aonomus on July 15, 2009
So my new recent project has been to develop a bunch of sensors and a data acquisition unit (DAQ), and I have already finished a few tiny boards with some more work to be done. Just as some eye candy, a voltage sensor (divider for a ADC on a microcontroller, selectable to 1:2, 1:3, or 1:5), and a current sensor (resistive 0.001ohm shunt with a current sense amplifier, MAX4372).
Another thing I thought I would bring up is the effect of silicone caulk on electronics. While on the ASV project, despite my protest that caulk would corrode circuit boards due to the release of acetic acid fumes, we ended up moving ahead with it anyways. Regardless, here are some photos of a circuit board exposed to some fumes from caulk, even at a far away distance.
Everyone has had some failure when trying to develop a new device, and as part of my line of sensors, I was going to use a strain gauge taken out of an electronic bathroom scale. Unfortunately I’ve noticed that the resultant sensitivity is far too low with a differential opamp, and that even 1% resistors are not good enough to get the desired value of 0V difference between the two ends of the wheatstone bridge. I’ll have to revisit it at some point, mainly because a strain gauge would be a useful piece of kit. I’m sure that if I get it trimmed out properly and maybe use a higher Vcc for more resolution that the strain gauge will be useful, but until then its a bit of a failure.
And now for a new thing, ‘name that device’. I don’t have anything to give away or award to whoever gets it right, but regardless here are some photos. If you have any idea of what this device is, leave a comment to this post. I’ll reveal its identity after a week or so.