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TECMount
User’s Manual
For the Arroyo Instruments controllers that support RTD sensors, the default
coefficients are different for this mount. They must be changed to use the
0.00385
Ω
/
Ω
/ °C curve, which has the following coefficients:
A = 3.9080x10
-3
B = -0.58019x10
-6
C = -4.2735x10
-12
R
0
= 100
These coefficients can be changed in the Sensor menu.
2-Wire versus 4-Wire Measurements
One concern in using RTDs are their relatively low resistance (typically 100
Ω
at
0°C), and small
Ω
/
°C. Because of these two factors, the resistance of the cable
used to connect to the sensor can create significant absolute error in the sensor
measurement. Most Arroyo Instruments controllers offer two RTD measurement
modes: a conventional two wire measurement mode, which is subject to this
error, and a four wire measurement mode that uses separate sense and source
lines to remotely sense the actual resistance of the RTD and eliminate the cable
and connector resistances.
In the
286-xx-150
LaserMount
, the 4-wire connection is made inside the mount.
To use this measurement mode, you must select ‘RTD (4-wire)’ as the sensor
type.
The drawings below illustrate how 2-wire and 4-wire connections work. Note that
4-wire measurements require all four wires to be brought through the cable to
the mount. The
1262-17W2
and
1264 TECSource
cables carry these
connections through to the mount, but the
1260
cable does not.
RTD 2-wire Measurement
RTD 4-wire Measurement
Mount
Temperature
Controller
RTD
Sensor
Sensor–
Temperature
Controller
RTD
Sensor
Remote
Remote Sensor–
Sensor–
Mount
