Laurel Electronics LT: 4-20 mA Current Loop Transmitter for Resistance Input in Ohms - Manual (Page 4)

LAUREL ELECTRONICS INC., 3183-G Airway Ave., Costa Mesa, CA 92626, USA • Tel 714-434-6131 • www.laurels.com 4
RTD Hookup
In 4-wire hookup, different pairs of leads are used to apply
the excitation current and sense the voltage drop across the
unknown resistance, so that the IR drop across the excitation
leads is not a factor.
In 3-wire hookup, the transmitter senses the combined voltage
drop across the unknown resistance plus two excitation leads.
It also senses the voltage drop across one excitation lead, and
then subtracts twice this voltage from the combined total. This
technique effectively subtracts all lead resistance and compen-
sates for ambient temperature changes if the two excitation
leads are identical.
In 2-wire hookup, the transmitter senses the combined voltage
drop across the unknown resistance and both lead wires. The
voltage drop across the lead wires can be measured by shorting
out the resistance during transmitter setup, and this voltage is
then automatically subtracted from the combined total. However,
changing resistance of the lead wires due to ambient tempera-
ture changes will not be compensated.
Ordering Guide
Create a model a model number in this format: LT20R1
Transmitter Type LT Laureate Transmitter
Main Board 2 Standard Main Board
Power 0 Isolated 85-264 Vac
1 Isolated 10-48 Vdc or 12-32 Vac
R1 0-20 ohms
R2 0-200 ohms
R3 0-2 kohms
R4 0-20 kohms
R5 0-200 kohms
R6 0-2 Mohms (factory special fixed range) Resistance Range
Note: The same signal conditioner board can be used for resistance and RTD
temperature measurement.
Accessories CBL04 RS-232 cable, LTA to computer or USB adapter
CBL02 USB to RS-232 cable adapter