Laurel Electronics LTM DPM SERIES ANALOG INPUT, SERIAL DATA OUTPUT - Manual (Page 21)

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13. RTD & OHMS SIGNAL CONDITIONER BOARD JUMPER SETTINGS
The same signal conditioner board is used for 4 RTD types and 5 resistance ranges, as selected
by jumpers. Corresponding selections also have to be made in Instrument Setup software. With
RTDs, display in °C or °F and resolution of 1°, 0.1° or 0.01° are user programmable. 0.01°
resolution should only be used for relative readings, not absolute readings, and with software
selectable digital filtering.
1. Use 2.5 mm (0.1") jumpers.
2. Store spare jumpers on an unused jumper post.
PROVISIONS FOR LEAD WIRE RESISTANCE
RTD and resistance measurement allow 2-, 3- or 4-wire hookup to compensate for lead wire
resistance. Please see Section 6 for hookup diagrams.
• In 2-wire hookup, the transmitter 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 transmitter setup, as prompted by Instrument Setup software. 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.
• In 3-wire hookup, the transmitter automatically compensates for lead resistance by mea-
suring the voltage drop in one current-carrying lead and assuming that the voltage drop in
the other current-carrying lead is the same.
•
In 4-wire hookup, there is no lead wire resistance error, as different pairs of wires are used
for excitation and sensing.
RTD Type or Ohms E1 Jumper
Pt100, Ni120
Cu10, 20
200.00 Ω
2000.0 Ω
20000 Ω
200.00 kΩ a
b
c
d
e
f
Connection E2 Jumper
2- or 4-wire
3-wire none
g