EWS-102 CONTROL UNIT SUPPLEMENTARY INFORMATION
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Rev 2.1 subject to alteration
Supplementary Information
EWS 102 4-20mA Load Weighing Device
Use of the Analogue Output Signal With Pre-Torque Anti-Rollback Systems
The EWS 102, when supplied with the optional analogue output, provides a 4-20mA signal that is proportional to the elevator load
including any attached compensation chain. This signal allows a suitably equipped drive to pre-torque the traction machine, minimising
any lift car rollback.
4mA = empty elevator (Zero)
•
20mA = elevator capacity (Full Load)
•
The EWS can be configured to “transmit” its output signal as either current or voltage. The output used will depend on the requirement of
the equipment that will “receive” the signal.
The standard 4-20mA output can be converted to give voltage output signals as follows:
1-5V output signal - connect a 250 ohm resistor across the “receiver” input.
•
2-10V output signal - connect a 500 ohm across the “receiver” input.
•
The loop power supply voltage needs to be high enough to include the voltage required by the “transmitter” (the EWS 102), and the voltage
required by the Receiver.
The EWS 102 is a type 2 isolated 2-wire loop circuit with a compliance voltage of 10V. The required loop power supply voltages are:
Receiver Input
Supply Voltage
Note
4-20 mA
12-30V
12V assumes 100 ohm max across receiver input
1-5V
15-30V
With 250 ohm resistor across receiver input
2-10V
20-30V
With 500 ohm resistor across receiver input
Warning:
Care must be taken choosing the power supply for the recommended wiring scheme (see below). To avoid damage to the
EWS 102, any power supply connected to its power supply input must not exceed 24 Volts DC.
Wiring schematic
Cal
Load
Zero
Model EWS 102
Elevator Load Weighing Device
12-24VDC
1
2
3
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.garan.co.uk
+Exc
+Sig
-Sig
-Exc
Scn
Control
Signal
4-20mA
Loop
Power Supply
Common Ground
4-20mA Output to Elevator Drive Unit
