The battery cell voltage is to be monitored through PLC analog inputs . There are 10 cells stacked in series in a given battery pack. And there are 12 nos. such battery packs.The voltage across each cell is to be monitored on a continous basis as the battery is getting discharged. Thus there are 120 nos. analog inputs( 0 - 5VDC)to be monitored. The PLC panel has limited mounting space .

The voltage output of each cell is floating and hence cannot be directly connected to the PLC analog input module which typically has input channels connected in groups of 4 or 8 or 16 with a common ground. For a error free measurement the PLC analog input GND has to be isolated from the floating GND of each Cell. Also the voltage outputs of the individual Cells have to be isolated from each other .

Since +24VDC power is available & a large number of analog inputs are to be measured, a solution with SIM-Micro series Multichannel isolator modules can be realized. The application requirements can be fulfilled by using Signal isolator with 2 port input side isolation. This provides isolation between the input & output and also between the input & the supply.

Effectively , the voltage output of each cell is measured by an independent input circuit . This input circuit is completely isolated from the output stage & also the +24VDC power supply. The measured signal is filtered & applied to a chopper circuit which chops the signal & converts it into a frequency signal .This frequency signal is then transmitted across an optical isolator to the output side of the isolator. The output side then recreates the original signal & amplifies the same to 0-10VDC.