Cold Junction Compensation (Cjc) - VTI Instruments EX1000A User Manual

The measurement range of the EX10xxA in terms of temperature is a function of its input voltage
range and the capabilities of the thermocouple sensors themselves. Specifically, the measurement
range of the EX10xxA for the standard thermocouple types is the following:
In addition to the standard thermocouple types, the EX10xxA can accept and measure a custom
thermocouple of any type. The effective measurement range in temperature is subsequently
determined by the input voltage range of the EX10xxA and the thermocouple transfer function of
the custom thermocouple.
In terms of voltage, the thermocouple connectors may only accept an input voltage of ±67 mV when
performing temperature conversion. When in voltage mode, these connectors can accept either
±0.067 V or ±0.1 V inputs. The voltage connectors may use either ±0.01 V, ±0.067 V, ±0.1 V,
±1.0 V, or ±10.0 V inputs for both EU temperature conversion or voltage measurements. When
temperature is selected, the instrument automatically switches the selected channel(s) to the ±67 mV
range. The EX1000A-TC is a special case where thermocouple inputs are used for voltage
measurement and may utilize all input ranges available to the voltage connectors. Table 1- provides
an overview of each models capabilities.
C J C
OLD UNCTION OMPENSATION
For highest accuracy and stability, the EX1000A-TC, EX1016A, EX1032A, EX1048A and RX1032
provide embedded isothermal input sections that are monitored by twelve precision thermistors
(based on Model#, number of thermistors may vary), one for every four thermocouple channels.
(Note, the EX1000A may utilize external thermistors as described in the Voltage Connections
section). To ensure that CJC information is current and time correlated with the input channels, CJC
channels are measured with every scan, providing a maximum time separation of less than 4 ms
between the input channel measurement and its associated CJC measurement. Table 3-3 shows the
association between the CJC and input channels.
EX10xxA Triggering
Type Min (°C)
J -200
K -200
-200
T
-200
E
S -50
R -50
250
B
-200
N
T 3-2: EX10
ABLE XX
(CJC)
CJC #
CJC0
CJC1
CJC2
CJC3
CJC4
CJC5
CJC6
CJC7
CJC8
CJC9
CJC10
CJC11
T 3-3: CJC C
ABLE HANNEL
Max (°C) Min (°F)
1200 -328
1372 -328
400 -328
900 -328
1768 -58
1768 -58
1820 482
1300 -328
A M R
EASUREMENT ANGE
Channel Input Channel
48 0-3
49 4-7
50 8-11
51 12-15
52 16-19
53 20-23
54 24-27
55 28-31
56 32-35
57 36-39
58 40-43
59 44-47
/ I C R
NPUT HANNEL ELATIONSHIP
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Max (°F)
2192
2502
752
1652
3214
3214
3308
2372
59