Two-Wire Rtd Hookup; Three-Wire Rtd Hookup - Measurement Computing CIO-EXP-RTD16 User Manual

5.6.1 Two-wire RTD Hookup

A two wire RTD has two leads, one to each side
of the temperature sensitive resistor.
excitation current is connected directly to the
leads at the CIO-EXP-RTD16 screw terminals. A
two wire connection is less accurate than the 4
wire type, and so is not the first choice for the
best measurements. The reason for the inaccuracy
is that there is a varying resistance associated with
the excitation current flowing in the sense leads
and this resistance is added to the measurement.
The amount of inaccuracy is determined by the
wire gauge and length.

5.6.2 Three-Wire RTD Hookup

A three-wire RTD connection allows the use of
special circuit to compensate for resistance
variations in the lead wires with temperature
changes (Figure 5-5 at right).
NOTE: The +Sense terminal is not used in this
non-standard hookup.
The
2-WIRE
RTD
Add Jumper Wires
Between Terminals
Figure 5-4. Two-Wire RTD Connections
3-WIRE
RTD
NOTE: The CIO-EXP-RTD uses a non-standard 3-wire hook-up.
Figure 5-5. Three-Wire RTD Connections
16
CIO-EXP-RTD BOARD
+IEXC (EXCITATION CURRENT (+))
+ SENSE
- SENSE
-IEXC (EXCITATION CURRENT (−))
-
? ? ? ? ? C A O
CIO-EXP-RTD BOARD
+IEXC (EXCITATION CURRENT (+))
+ SENSE
- SENSE
-IEXC (EXCITATION CURRENT (−))
-
? ? ? ? ? C A O