Two-Wire Rtd Lead Compensation - GE 269Plus Instruction Manual

C RTD CIRCUITRY
An illustration of how to compensate a two-wire RTD with a run of wire to a central terminal is shown below.
Wires must all be the same gauge, type, and length to ensure that they all have the same
resistance, otherwise additional calculations are required.
NOTE
269/269 PLUS 269/269 PLUS
RTD #8 RTD #8
The value of the compensation resistor is equal to the resistance of RETURN 1 plus HOT 1. Assuming
we have
V
Since V
Lead Compensation
V
,
17 18
This implies
(
V
The illustration shown in Figure C–3: 2-WIRE RTD LEAD COMPENSATION is for RTD #8, but it may be
applied to any of the RTDs.
GE Power Management
Courtesy of NationalSwitchgear.com
20
19
COMPENSA COMPENSATION TION
18
RETURN
17
HOT HO
Figure C–3: 2-WIRE RTD LEAD COMPENSATION
R
Lead Compensation
V V
,
17 18 Lead Hot Lead Hot 1
V V
Lead Comp R Comp
V , we have
Lead Hot
(
V V V
,
18 19 Lead Hot Lead Hot 1
(
V
Lead Comp
(
V V
Lead Hot 1
)
V V
, , o n l y i f
17 18 18 19 RTD
269Plus Motor Management Relay

TWO-WIRE RTD LEAD COMPENSATION

C.3 TWO-WIRE RTD LEAD COMPENSATION
COMPENSATION RESISTOR COMPENSATION RESISTOR
RETURN 1 RETURN 1
HOT 1 HOT 1
TERMINAL
R
Lead Hot
V V
RTD Lead Return 1
V
Lead Return
V V
RTD Lead Return 1
)
V V
R Comp Lead Return
) V
V
RTD Lead Return 1 R Comp
V V
R Comp Lead Hot 1
R R
o r
Comp Lead Hot 1
MOTO OTOR
V
Lead Return
)
V
Lead Return
V
Lead Return 1
R
Lead Return 1
C
C-
3