Laurel Electronics LAUREATE SERIES 2 DIGITAL PANEL METER - Manual (Page 35)

35
RTD & RESISTANCE CONNECTION
With the appropriate jumper settings, RTD
and resistance measurements allow 2, 3 or 4-
wire RTD hookup to the J5 connector, as
illustrated. The meter applies a fixed excita-
tion current.
In 4-wire hookup, lead resistance is not a
factor, since different pairs of wires are used
for excitation and sensing.
In 3-wire hookup, the meter automatically
compensates for lead resistance by measur-
ing the voltage drop in one current-carrying
lead and assuming that the voltage drop in
the other current-carrying lead is the same.
In 2-wire hookup, the meter senses the
voltage drop across the load and both lead
wires. The effect of the lead wires can be
measured and subtracted by shorting out the
load during meter setup. The short should be
as close as possible to the load. Ambient
temperature changes will still cause some
error in the readings -- the higher the lead
resistance, the greater the error.
To eliminate lead wire resistance, follow this procedure:
1. Set the InPut menu item and jumpers for the desired range
2. Set COnFG to 00011 .
3. Short the two leads at the sensor end.
4. When the display has settled, push the key. The meter will then store a value propor-
tional to lead resistance, automatically change COnFG to
00010 , and then reset. The same
result is obtained by grounding a Control Input that has been selected for Peak or Valley
(SEtuP
00_0Y , where Y = 1, 2, 4, A, C ).
5. Remove the short and connect the sensor. The meter now processes the sensor resistance
only.
If the range and associated jumpers are subsequently changed, the above procedure must be
repeated. This procedure is also available through Instrument Setup software, Revision 2.7.0
or later.