Hello there,
I'm seeking some advice on the following concept:
I'm designing a VRLA battery monitoring system that also requires measurement of some temperatures and some other 2-20ma current loop sensors. There are 420 batteries in a string, and there will be two physically separate data acquisition modules used to monitor a battery string. Because of the high common-mode voltage of the series connected battery cells, my measurement front-end will probably use difference amplifiers, and I'll probably partition the cells into groups of 32 or 64 (32 x 2.75 volts = 88 volts common-mode) per data acquistion card. This battery string is used to drive a large PWM electric motor, so EMI and transients are prevalent.
My primary question is, should I optically (galvanically) isolate the inputs using linear optocouplers, using the difference amp in front of the optocoupler in the servo-feedback circuit to linearize the optocoupler? Or do you think this isolation is overkill?
On another note, I would like to employ digital-to-analog converter chips that have a built-in I2C interface for the acquiring the data on the (maybe) isolated side (eg. TI DAC5574). Any comments/advice here?
Final note, I am thinking of using PC/104 CPU boards, and QNX to run the show. Any comments/advice here?
Thank you, one and all!
Vic