Sensoray 518 - Manual (Page 43)

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Thermistor/Custom Resistive Sensors
In the following discussion, thermistor is used interchangeably with custom resistive sensor.
Thermistors have much higher resistance than RTD’s over most of their operating range. As a
result, the RTD two-wire configuration is recommended if your sensor will be operating only at
higher resistance values. If your thermistor will be operating at lower resistance values, you
should consider implementing a three- or four-wire hookup to prevent cable-losses.
Thermistors should be connected using shielded cable. The shield should be connected only to
the 7409TC S terminal.
Strain and Pressure Gages
In a typical strain/pressure gage, four wires connect the gage to the measurement system. Two
wires supply gage excitation, while the other two wires carry the gage output signal. If you are
using a six-wire gage, you must connect the gage’s excitation source and sense leads together at
the 7409TC I+ and I- terminals.
Strain and pressure gages should use shielded cable. The shield should be connected only to the
channel S terminal on the 7409TC.