VTI Instruments Metek EX1202 - Page 98

VTI Instruments Corp.
98 Basic EX1200 DMM Operation
(Series 44004)
(Series 44007)
(Series 44006)
A
0.0014733
0.0012880
0.0010295
B
0.0002372
0.0002356
0.0002391
C
1.074 x 10
-7
9.557 x 10
-8
1.568 x 10
-7
TABLE 4-12: THERMISTOR CURVE FITTING CONSTANTS
Connecting to the DMM
Any thermistor can be connected to the front panel terminals of the DMM using suitable
connectors. Though this method is not preferred in fixed installation, this can be used to quickly
make readings, and troubleshoot field wiring. Since thermistors is a bilateral resistive device, there
are no polarity restrictions.
DMM Front Panel
Sense HI
Input HI
Input LO
Sense LO
Thermistor
FIGURE 4-20: DMM/THERMISTOR CONNECTIONS
If the thermistors are connected to a multiplexer card, the wiring is similar to that of a 2-wire
voltage measurement without the polarity constraints, as the thermistors are bilateral passive
devices.
DMM Backplane
BPL_HI
BPL_LO
BPL_SHI
BPL_SLO
CH 1
CH 2
CH n
Thermsitors
EX1200
Multiplexer Cards
EX1200 Mainframe
FIGURE 4-21: THERMISTOR CONNECTIONS VIA DMM BUS