13
INSTALLATION AND OPERATING INSTRUCTIONS PRECISION
®
FILTER CLEANING SYSTEM CONTROLS
BASIC INFORMATION
The P-CTX card provides voltage-free contacts for alarm outputs, basic remote control inputs and a 4–20 mA output for differential
pressure reporting (P2 only). Figure 2 shows the P-CTX mounted correctly on the left side of the baseboard. The table on page
12 provides a description of each I/O point, which may be connected to remote push-buttons, lights, sirens, data-loggers, control
panels and programmable logic controllers.
Voltage-free.Outputs.
The P-CTX provides a number of voltage-free output contacts that can be used for alarm reporting. Each alarm output consists
of an output terminal and a common terminal. Any voltage applied to the common terminal will be present on the output
terminal when the alarm is raised.
Voltage-free.Inputs.
The P-CTX provides a number of voltage-free input contacts that can be used for basic remote control of the P1 or P2. Each
input consists of an input terminal and a common terminal; bridging these two contacts triggers the corresponding function.
4–20.mA.Output.
The P-CTX features a 4–20 mA output that can be used for differential pressure reporting. The output consists of a ground terminal,
24 V DC terminal and 0 V DC. An output current of 4 mA corresponds to a dP
=
0 kPa and 20 mA corresponds to a dP
=
2.5 kPa.
The table over the page provides a description and details of each output terminal on the P-CTX.
P-MOD: MODBUS COMMUNICATIONS CARD
Figure 13:
P-MOD.
1
2
3 4 5
Key.to.Figure.13
1
Switch for terminating resistor (DIP switch No.1)
2
Communications LED
3
Bus A (RS485
+
)
4
Bus B (RS485
−
)
5
GND (Ground/Drain)
BASIC INFORMATION
The P-MOD card is a network card which operates using the Modbus RTU communication protocol. Via the P-MOD the
controller can be connected to a DCS or SCADA system, allowing remote programming and monitoring of all menu items,
alarms and system details.
RS485 Modbus system specification is:
ITEM
DETAIL
Protocol
Modbus RTU
Hardware layer
2-wire, half-duplex RS485
Communications speed
9600 BPS
Stop bits
1
Data bits
8
Parity
None
If the P-MOD is the last device connecting the Modbus RTU network, ensure DIP 1 of the terminating resistor switch (Figure 13,
item 1) is set to ‘ON’. This enables the 120 ohm resistor on the P-MOD; no separate resistor is required.
