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SECTION VII
THEORY OF OPERATION
7
Figure 7-1: Model 1140A Block Diagram
OPERATING MODES
The Model 1140A has four basic modes of operation: thermocouple simulator, thermocouple
meter, precision voltage source, and precision voltmeter. Additionally, the instrument can support
connections to user wires of either thermocouple alloy or copper.
The following equations give the equivalent output for each of the above eight conditions. In the
equations, the function f
(T) represents the theoretical emf that would be produced by a
cn
thermocouple of the selected type at temperature T.
Thermocouple Simulator (Alloy Output)
The general equation for the Model 1140A when it is simulating a thermocouple in the alloy
mode is
+ T
T
= T
,
OUTPUT
SIMULATED
OFFSET
where T
is the equivalent temperature of the simulated thermocouple, T
is the user-
OUTPUT
SIMULATED
specified simulation temperature shown on the display, and T
is the offset temperature set in
OFFSET
the THERMOCOUPLE → THERMOCOUPLE OFFSET menu.
7-1
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