Campbell Scientific AM16/32B AM16/32B Relay Multiplexer - Page 41

AM16/32B Relay Analog Multiplexer 21X/ CR7 CR10(X) CR3000/ CR800/CR/ 850/ CR23X/CR0 1000/ CR5000 "4 X 16" Mode H H L L H H L L H CU COM ODD H L CO COM ODD L CU H COM EVEN H CO L COM EVEN L G COM ODD H CU ODD L CO EVEN H CU EVEN L CO SENSOR SHIELDS FIGURE 6-8. Differential thermocouple measurement with reference junction at the datalogger CR23X/ CR800/ CR850/ CR1000 21X/ CR7 CR10(X) CR30/00/ CR50000 H H H H L L L L EX E E VX H H H H AG H H H H L L L L G "4 X 16" Mode CU COM ODD H CU COM ODD L ODD H CU ODD L CO 107 CU COM EVEN H CU COM EVEN L COM EVEN H CU EVEN L CO SENSOR SHIELDS FIGURE 6-9. Differential thermocouple measurement with reference junction at the AM16/32B If a mix of TCs and other sensor types are multiplexed through the AM16/32B, it is generally best to locate the reference junction on the AM16/32B, as shown in FIGURE 6-9. AM16/32B Reference - An external reference, usually a thermistor, can be located at the AM16/32B, as shown in FIGURE 6-9. This approach requires an additional single-ended datalogger input to measure the reference. Position the reference next to the COM terminals and, when practical, measure the thermocouples on SETs that are in close proximity to the COM terminals in order to minimize thermal gradients. 31