Agilent Technologies U2802A manual Analog input channel circuitry

Features and Functions 2

The major functional blocks of the U2802A module are:

•Analog input channel circuitry

•Cold junction sensor

•Digital control logic

•EEPROM

Analog input channel circuitry

The analog circuitry for each channel consists of an instrumentation amplifier with a fixed gain of 97.673, a 4 Hz RC low- pass filter, and an output buffer. The multiplexers at the input and output of each channel allows each channel to be configured for three modes of operation as listed below:

Thermocouple input mode: In thermocouple mode, the thermocouples (or any floating voltage source) should be connected to the TCn+ and TCn– terminals as illustrated in Figure 2- 4. All TCn– terminals are internally tied to module ground with a 10 MΩ resistor. The TCn+ and TCn– signals are routed to the differential inputs of the instrumentation amplifier. Differential voltage signals at the TCn+ and TCn– terminals are amplified, filtered and driven out by single- ended output voltage to the corresponding AI channel on Rear Connector 1.

Figure 2-4Functional block diagram for thermocouple mode in U2802A

Agilent U2802A 31-Channel Thermocouple Input User’s Guide 31