Alpes Lasers TC-3, User Manual

Page: 25 / 41

TC-3 Temperature Controller User’s Manual · Page 25
The TC-3 automatically determines which equation to use based on
the conditions at the time of the measurement.
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 become a
significant error in the sensor measurement. The
TC-3 offers 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 sensor and source lines to remotely sense the actual
resistance of the RTD and eliminate the cable or connector resistances.
When using 4-wire measurement mode, you must select ‘RTD (4-wire)’
as the sensor type, and then connect the and Remote
at one side of the RTD, and Sensor– and Remote Sensor– to
the other side of the RTD. Make these connections as close to the
sensor as possible.
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 and 1263 cables carry this
connection through to the mount, but the 1260 and 1261 cables do
not.
RTD 2-wire Measurement
RTD 4-wire Measurement
Mount 5300
RTD
Sensor
Sensor–
5300
RTD
Sensor
Remote
Remote Sensor–
Sensor–
Mount