SCXI-1303 pull-up resistor networks

[lmd2]

The system in question had several SCXI-1102/1303 modules and was working fine for several years. The bias resistors, and the pull-up resistors were all fitted with the 10Mohm networks.
Several new 1102/1303 pairs were recently added to increase the channel count.Instead of replacing the 10 ohm bias resistors with the spare 10Mohm reisitors, the tech apparently swapped the bias resistors and the pullup resistors so that the terminal blocks now had 10Mohm bias resistors (good) but only 10 ohm resistors in locations RP 5 - 8 (the pull up resistors).
Several questions: could having a small pull-up resistance in line to the 5V DAQ board source have damaged anything (either the DAQ card, or the 1102 - maybe due to increased current flow)? Would this account for some (but not all) thermocouple locations reading too low? Could this issue have somehow caused erroneous readings on the original modules (I know that this is a stretch, but at least one of the original, correctly configured modules is reading off now - maybe something on the bus, or something on the DAQ card itself)?

thanx
lmd2

Lawrence M David Jr
Underwriters LAboratories Inc.
Lab Support Group

[AlanArmstead]

Lawrence,
While it is recommended that you use 10Mohm resistors for both the bias and pullup networks when using the SCXI-1303 with the SCXI-1102, using a 10ohm resistor network as the pullup with a 10Mohm resistor as the bias would not damage the 1102 or your data acquisition board. It certainly would not damage any of the other SCXI-1102s.
-Alan A.