User`s guide

Features and Functions 2
Keysight U2802A 31-Channel Thermocouple Input User’s Guide 23
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 2-4 Functional block diagram for thermocouple mode in U2802A
U2802A_UG.book Page 23 Monday, January 19, 2015 10:28 PM