SC-2071 Board
Chapter 3
SC-207X Series User Manual
3-16
© National Instruments Corporation
Channel 1
AIGND
R5
(+ in)
Component Positions
Input Schematic
R8
(a 1
µ
F cap)
R6
(10 k
Ω
)
10 k
Ω
Resistor
1
µ
F Capacitor
10 M
Ω
Resistor
R7
10 M
Ω
+ Channel
+5 V
AIGND
AIGND
To
Input
Multiplexer
+
B
C
D
1
µ
F
10 k
Ω
10 M
Ω
Figure 3-13. Thermocouple Circuit with Open Thermocouple Detect and
Lowpass Noise Filter
Selecting the Gain and Input Ranges
Because thermocouple output voltages are very low, a gain of 100 is usually necessary for best
resolution. The input range on the Lab/1200 device should usually be set to
±
5 V to improve
resolution. These settings can be used in all but a few cases, such as a fairly high output
thermocouple type used at elevated temperatures. Table 3-3 lists the voltage extremes from
several popular thermocouple types. Use this Table as a guide for determining the best gain and
input range settings to use. If the thermocouples are being used in a known temperature range,
consult a book of thermocouple tables to determine the approximate millivolt output and the best
gain and input range settings.
Summary of Contents for SC-207 Series
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