Can I use SCC platform efficiently for YSI-400 thermistors?

[Kedgamatic]

We would like to use our existing SC-2345 platform using SCC signal conditioning modules to implement up to (16) YSI-400 thermistor input channels.  For the temperature range of 0 to 100°C the thermistor resistance should range from 7355 to 152.8 Ohms respectively.  We can use up to (2) SCC-CO20 Isolated Current Output modules to generate the fixed 100ua excitation current for (2) banks of (8) thermistors wired in series but we would need to have SCC analog input modules that are isolated not only from bank to bank but channel to channel.  The SCC-AI05 would give us the acceptable gain to recieve the voltage we would measure across the thermistor ranging from 735.5mv to 15.28mv.  Since the SCC-AI05 is not isolated channel to channel every other thermistor would be effectively shorted out by the SCC modules internal wiring.

Ideally the SCC module for this thermistor application would be isolated bank to bank and channel to channel, have a gain of 10 and filter frequency cutoff of 30Hz or less.

We have considered building our own or purchasing a bank of (16) 100ua fixed excitation current supplies to individually source each thermistor.  This would allow us to use the SCC-AI05 less the filtering capabilities or maybe the SCC-AI14 with a lower gain but a 4Hz cutoff frequency.

Perhaps the best solution is to jump up to the SCXI platform but I thought I inquire to try to use the hardware investment we already have on hand.

[Logan_K]

For the most part you are correct, except that there is one option that I didn't see you mention in your post:

Embrace the fact that there is no channel to channel isolation, and reference both inputs to the same ground. So, you would only need to use one current source for all thermistors, and tie them all together in series. Then on a single SCC-AI module you could reference Ch0 and Ch1 to the ground of one of the thermistors, but since they are in series the voltage on the second thermistor with reference to the first thermistor is equivalent to adding them up. So, one channel will read the values that you expect, and the other channel will read the equivalent of Ch1 + Ch2. So, as long as you know the value of Ch2, then you can compute Ch1 by subtracting Ch2 from your readings. This will double your input range, so you won't be able to apply as much gain to your measurements, but it will still work.

Also, for the filtering, you could cascade the output of the SCC-AI modules to the input of a SCC-LP filter module:
http://digital.ni.com/public.nsf/websearch/7B801B3C9E0B82A386256C25007640CA?OpenDocument

Regards,
Logan K