53
The unit does not switch on (the power LED on the main board is
switched off ).
Check:
1. The presence of main power;
2. The transformer output voltage;
3. That the power supply connector is correctly inserted;
4. That the overload fuse is intact.
When switching on, there are general problems with the LCD
(strange characters, blank display).
Check:
1. That the software in the fl ash is correct;
2. The addresses of the PC3 control board and the Graphic
terminal (check that they comply with the requirements of the
current application);
3. The connection between the Graphic terminal and the PC3
board.
Erroneous readings of the input signals.
Check:
1. The correct power supply to the control board and probes;
2. The separation between the power supply of the digital inputs
and that of the control board;
3. That the cables from the probes are connected according to
the instructions;
4. That the probe cables are located far enough away from possible
sources of magnetic interference (power cables, contactors,
high voltage cables or cables connected to units with high
current peaks);
5. That there is not a high level of heat resistance between the
probe and the sensor cap (if present). If necessary, apply
conductive paste or oil into the caps to ensure good temperature
transfer.
6. If there is a probe error or PC3 board conversion error, the
checks to be carried out would vary depending on the type of
probe:
Active temperature/humidity probes with 0/1V signal:
Using a voltmeter, measure the probe signal between the Bn and
GND terminals and check that the voltage corresponds to the
temperature/humidity value: 1 mVdc corresponds to 0.1% HR.
Example: reading 200 mVdc (0.2 Vdc), the probe sends a signal
which corresponds to 20%RH; applying the same logic, 0 mVdc
corresponds to 0ºC/0% RH;
Pressure sensors:
If there are errors when reading these probes, check that:
- The analogue inputs of these sensors are set to receive 4/20
mA signals;
- Check that the probe capillary is not blocked.
- The full scale set by the software corresponds to that used
by the sensors.
Using a voltmeter to measure the voltage between the Bn
and GND terminals, an indication is obtained of the current
probe signal, considering that the input has an impedance
of 100, by applying the formula I= V/R.
The pressure value “Ps” sent by the probe could be calculated
as follows (FS = full scale):
Ps = (Vmed/100 - 0.004) x (FSmax - FSmin) / 0.016 + Fsmin
Example: the probe used has Fsmin = -0.5 bar, Fsmax = 7
bar; the voltage read is equal to Vmed = 1.0 Vdc.
The pressure Ps that the probe is measuring is thus:
Ps = (1.0/100 - 0.004) x [7 - (-0.5)] / 0.016 + (-0.5) = 2.3 bar
NTC probes:
The probe signal is a resistive value which depends on the
temperature.
The following table indicates some of the resistance values for
di erent temperatures. By disconnecting the input probe and
measuring the resistance with a multimeter, the table can be
consulted for the corresponding temperature value.
To check the setting of the probe inputs.
Switch o the control board and perform the following measurements
with a tester between the Bn and AVSS probe inputs:
16 - TROUBLESHOOTING
probe type voltage measured
NTC 2.5 V
4/20mA 0 V
0/1V; 0/5v; 0/10V 0 V
Unusual alarm signal from the digital input.
Check whether the alarm signal is present in the input, measure
the voltage between the “IDC" common terminal and the digital
input terminal which indicates the alarm “IDn”:
- if voltage is present (24 Vac or Vdc, depending on the
power supply used for the digital inputs), the contact of the
connected alarm device is closed;
- if the voltage is near 10 Vac or 10 Vdc (see above) the contact
is open.
Unless otherwise expressly stated, the control generates an
alarm when detecting open contacts.
°C k °C k °C k
-20 67,7 0 27,2 20 12,0
-15 53,3 5 22,0 25 10,0
-10 42,2 17 17,9 30 8,3
-5 33,8 15 14,6 35 6,9
To Next Page
Loading...
