Setra System GCT-225 - Manual (Page 4)

4
3.2 Current Output Units
The Model GCT225 is a two-wire loop-powered 4 to 20mA current output unit
and delivers rated current into any external load of 0-800 ohms. The Model
225 is available with 6ft. of multiconductor cable or Bayonet style connector.
Diagram 3 shows electrical connection wiring for current output transducers.
The power supply must be a DC voltage source with a voltage range between
10 VDC and 30 VDC measured between the + and - terminals. The unit is
calibrated at the factory with a 24 VDC loop supply voltage and a 250 ohm
load.
Current must flow in one direction only - Please observe polarity. (See
Diagram 4) We suggest that the cable shield Drain Wire be connected to the
system’s loop circuit ground for optimum electrical noise rejection. Trans-
ducer case connection can be achieved by tying the cable drain/shield wire to
the cable mounted Bendix connector shell.
Note 1: The transducer case and integral Bayonet connector Shell is electrically connected.
Note 2: ETL Listed to UL1604 Standards: The current output unit may be installed in Class 1 Hazardous
(Classified) Group A, B, C, D Division 2 locations, if the unit was ordered for these locations. (This is
denoted by an N1 designation in the Part Number, 12th and 13th digits). Safety barriers are not
required, as long as the unit is operated under normal conditions with a maximum excitation voltage
of 30 VDC between the input terminals.
Note 3: ATEX 94/9/EC Approved: Special hazardous area instructions for GCT225 transducers (with the N1
suffix) with ATEX approval: The GCT225 transducer (with the N1 suffix) is designed for use in
hazardous areas indoor applications with ATEX rating: Non-incendive II 3G Eex nL IIC T4 X -
30
°
C<Ta<+80
°
C. (Note: Units ordered with the Mini Din Shell are not ATEX approved for use in
hazardous locations.)
• The device can only be used for “Indoor Applications”.
• Power must be turned off before connecting or disconnecting.
• For the connector version, the connector must be secured before applying power
and DO NOT SEPARATE WHEN ENERGIZED.
• The shielded cable must be used and the drain wire of the cable must be connected
to the earth ground. The drain wire of the cable must connect to the connector metal
outer shell for the connector version.
• The maximum allowable transient disturbance must not exceed more than 40% of
the maximum excitation voltage.•
4.0 CALIBRATION
All Setra pressure transducers are carefully calibrated to the specific input
pressure range vs. output voltage or current at the factory so little or no field
calibrating is necessary. Zero and span adjustments can be made by turning
the rotatable cover to expose zero and span pots. We recommend closing the
rotatable cover after calibration adjustments are finished.
Diagram 3
Minimum Supply Voltage = 10 + 0.02 x Loop Resistance
Maximum Supply Voltage = 30 + 0.004 x Loop Resistance
CONNECTOR PIN WIRING FOR CURRENT OUTPUT TRANSDUCERS
CABLE BAYONET
CONNECTION WIRE PIN
+EXCITATION RED A
-EXCITATION BLACK D&B
CASE GND SHIELDING SHELL
and w/N1 option, see Notes 2 and 3.) (