Analog Outputs; Rtd Sensor Connections - GE Multilin 489 Instruction Manual

CHAPTER 3: INSTALLATION
3.2.8

Analog Outputs

3.2.9

RTD Sensor Connections

489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
Courtesy of NationalSwitchgear.com
FIGURE 3–16: Loop Powered Transducer Connection
The 489 provides four analog output channels, which when ordered, provide a full-scale
range of either 0 to 1 mA (into a maximum 10 kΩ impedance), or 4 to 20 mA (into a
maximum 1.2K Ω impedance). Each channel can be configured to provide full-scale output
sensitivity for any range of any measured parameter.
As shown in the Typical Wiring Diagram on page 3–10, these outputs share one common
return. The polarity of these outputs must be observed for proper operation. Shielded cable
should be used, with only one end of the shield grounded, to minimize noise effects.
The analog output circuitry is isolated as a group with the Analog Input circuitry and the
RTD circuitry. Only one ground reference should be used for the three circuits. Transorbs
limit this isolation to ±36 V with respect to the 489 safety ground.
If a voltage output is required, a burden resistor must be connected at the input of the
SCADA measuring device. Ignoring the input impedance of the input:
For example, for a 0 to 1 mA input, if 5 V full scale corresponds to 1 mA, then R
0.001 A = 5000 Ω. For a 4 to 20 mA input, this resistor would be R
A = 250 Ω.
The 489 can monitor up to 12 RTD inputs for Stator, Bearing, Ambient, or Other
temperature monitoring. The type of each RTD is field programmable as: 100 Ω Platinum
(DIN 43760), 100 Ω Nickel, 120 Ω Nickel, or 10 Ω Copper. RTDs must be three wire type.
Every two RTDs shares a common return.
V
FULL-SCALE
R
----------------------------- -
=
LOAD
I
MAX
(EQ 3.1)
= 5 V /
LOAD
= 5 V / 0.020
LOAD
3–15