Setra System Model 321 - Manual (Page 2)

2
Diagram 1
Setra Model CWS 321
Gas Cylinder Weighing Scale
1.0 GENERAL INFORMATION
Every Model CWS 321 has been tested and calibrated before shipment. Specific
performance specifications are listed on Page 3 of this Guide.
Setra Systems CWS 321 Gas Cylinder Scale is specifically designed to weigh gas
cylinders in gas cabinets and gas distribution systems. No mechanical adjust-
ments should be required providing the Model CWS 321 is installed on a flat
surface. The CWS 321 converts the weight of the gas cylinder to a proportional
high level analog 4 to 20 mA output.
2.0 ELECTRICAL INSTALLATION
2.1 Current Output Units
The Model CWS 321 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
CWS 321 is available with multiconductor cable, or end of cable Bayonet style
connector. Diagram 1 shows the electrical connection wiring for the current
output CWS 321.
The power supply must be a DC voltage source with a voltage range between
15 and 30 measured between the + and - terminals. The unit is calibrated at the
factory with a 24 VDC loop supply voltage and a 250 ohm load.
A regulated power supply or a power supply with low ripple noise is
recommended for best performance.
Current must flow in one direction only - Please observe polarity. The cable
shield drain wire should be connected to the system’s loop circuit ground for
optimum electrical noise rejection.
Zero and span adjustments can be made by adjusting the zero and span
potentiometers on the back of the unit.
CABLE BAYONET
CONNECTION WIRE PIN
+ EXC RED A
- EXC WHITE D & B
CASE GND BLACK SHELL
CONNECTOR PIN WIRING FOR CURRENT TRANSMITTERS
Minimum Supply Voltage = 15 + 0.02 x Loop Resistance
Maximum Supply Voltage = 30 + 0.004 x Loop Resistance