Agilent Technologies U2802A - Manual (Page 33)

Features and Functions 2
Agilent 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 M
Ω 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 Friday, November 25, 2011 10:57 AM