Connections; 2-Wire - Time Electronics 7000 User Manual

Time Electronics
7000 RTD Calibrator
3

Connections

An RTD (Resistance Thermometer Device) temperature measurement relies on the fact that
the probe, in a repeatable manner, predictably changes its resistance for changes in
temperature. Connecting lead resistance will influence the reading. In a process installation
where the probe is situated some distance from the measuring instrument the lead
resistance may introduce significant reading errors. For a particular process applications the
temperature measuring instrument is selected based on the required range, resolution and
accuracy. This in turn influences the choice of probe and type of connection. There are three
commonly used wiring connection arrangements (2, 3 and 4 wire).
The 7000 is designed to operate with all three wiring
configurations. The top side button is used to select the
appropriate connection type.
3.1

2-wire

This is the least accurate as the resistance in the length of the
two uncompensated transmission wires will affect the sensor
reading. Therefore, this type of connection is not normally
recommended. To connect in this mode, select 3-wire
and add external links between the black and blue
terminals and brown and red terminals. Keep the
connection as short as is practical.
3.2 3-wire
Process instruments using 3-wire connections arrange input
circuitry in such a way as to compensate for lead resistance
changes. The transmission leads should be of equal
length and as short as possible.
3.3 4-wire
The 4- wire connection provides the most accurate
measurement. The leads are compensated for, so can be
any convenient length. To connect in this mode select
4-wire and connect as shown.
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User Manual