I have a CR1000 and a series of am16/32 multiplexers. I would like to make multiplexed measurements of water conductivity in the range of 5-200 microsiemens. I assume I need to set up a half-bridge circuit, but I'm not sure how to do it, I can figure out the multiplexing later.
Would anyone kindly advise on the desigin of such a circuit, how to program it and if I need some kind of resistor as a "jumper" to get the proper conductivity range.
Many thanks!!
I recommend getting a CS547A. With a conductivity probe, you have to worry about probe geometry and temperature. The CS547A is about as simple as a probe can be. You need to use blocking capacitors so the probe doesn't quickly degrade. For the CS547A, we make the A547 to contain the blocking capacitors.
Thanks for the suggestion. After looking at the construction of the probe, the flow through design doesn't work for my application. I want to test the conductivities of water with plant electrolytes in it. These would be placed small wells in a block with a volume of approxmately 1 ml of solution each. Idealy the probe would consist of small electrodes that could be inserted into the wells. I have access to a robotic arm/actuator, so I could see having 8 micro-probes that the arm dips into a row of wells or alternatively a 8X12 block of wells could have a matching block of multiplexed electrotrodes set on top.
Would you suggest a good reference to built and sample the circuit with a cr1000? I assume the half bridge is the way to go, but not sure of the nuances of design, i.e. blocking capacitors. This would be a lab device used in controlled conditions. If I can get satisfactory results from the circuit and design a mini electrode this will be a huge time saver for me.
Thanks!
You can use the CS547A manual as an example both for how to build the circuit and how to measure it. Blocking capacitors are a must. Running through a multiplexer, the capacitors could be a single set on the signal lines from the multiplexer.
Thats very helpful, I will purchase the CS547 interface to make it easier.