Communication
LAN: 100 (yellow), 10 (yellow), link (green). The green link LED is on when the LAN network
is connected. The two yellow LEDs indicate if it is a 10/100 Mbit connection.
RS485: TxD 2 (red), Tx2 EN (yellow), RxD 2 (green), TxD 1 (red), Tx1 EN (yellow), RxD 1
(green) Profibus: RxD (green), TxD (red), RTS (yellow)
SD card busy, 1 (Red)
Light in diode = SD card is busy.
Processor status, 1 (Green).
Flashing diode = Processor is active. The green light diode must flash irregularly whenever
Unisab III is electrified. A constant light or no light is a sign of malfunctioning.
Processor reset, 1 (Red) Light in diode = Processor is resetting. The red light diode must
usually be off. It is only on for brief moments in case the CPU tries to restart the program.
This may only happen while Unisab III is switched on.
Power on, 1 (Green)
Light in diode = Power is on.
9.1.3 Digital inputs
If a digital input is disconnected, the specific input will never become active. If the digital in-
put is short circuit to ground the status of the specific input will switch to active.
9.1.4 Analogue inputs
If any of the analogue inputs (PT100 sensors, pressure or position transmitters) fail it will
usually cause Unisab III to shutdown the compressor. Unisab III will react differently depend-
ing on the failure but the following description can be used to evaluate the error.
PT100 inputs
If the sensor is disconnected, Unisab III will show a temperature of 200°C and the compressor
will usually shut down on high temperature.
If the sensor is short circuit the temperature will show -200°C and the compressor will usually
shut down on low temperature.
Pressure inputs (4-20 mA)
If the transmitter is disconnected, Unisab III will show a pressure of -2 to -4 bar and the com-
pressor will usually shut down on low pressure. If the transmitter is short circuit the pressure
will show 12/33/77 bar depending on the pressure ratio for the specific transmitter and the
compressor will usually shut down on high pressure.
The pressure transmitters are supplied by 24 VDC from Unisab III. If the power supply is
short circuit to ground the pressure will show -2 to -4 bar and the compressor will usually
shut down on low pressure. The internal safety circuit will shut down if the power supply for
the specific transmitter in the event of short circuit to ground and Unisab III will not be dam-
aged. When the error has been corrected, Unisab III will operate normally.
Capacity and Vi slide position inputs (4-20 mA)
If the transmitter is disconnected, Unisab III will show a position of approximately -24%. The
exact reading depends on the software calibration of the specific input in Unisab III. If the
compressor is running in Auto mode it will show a capacity error alarm or shut down on Vi po-
sition error or after operating for a while. If the compressor is running in Remote mode it will
shut down on capacity error, Vi position error or after operating for a while.
Troubleshooting
Engineering manual - Unisab III 1.10
001930 en 2014.09
285/319
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