PR131 module in DIN rail enclosure, front three-quarter view

Manual call point read-out, 16 inputs to Modbus RTU

Article number PR131s02

The PR131s02 is used to read the buttons of manual call points via Modbus. For each input it measures the line resistance and reports whether the button is pressed and whether there is an open circuit or a short circuit. Switches with or without an internal resistor are connected directly. The module is not a certified part of a fire alarm system.

Supply 10 to 31 V DC; ripple ±20 mV max.
Input 16 analogue inputs for switches with or without an internal resistor
Output modbus RTU over RS485, function codes 3 (holding registers) and 4 (input registers); Modbus TCP over Ethernet optional

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Specifications

Specifications
Supply	10 to 31 V DC; ripple ±20 mV max.
Input	16 analogue inputs for switches with or without an internal resistor
Output	Modbus RTU over RS485, function codes 3 (holding registers) and 4 (input registers); Modbus TCP over Ethernet optional
Setup	Slave address with two rotary switches: SW1 (tens) and SW2 (units)
Modbus settings	19,200 baud, 1 stop bit, no parity
Read-out per input	Register 1 input open (line resistance > 2.6 kΩ), register 2 input closure (< 20 Ω), register 3 status A (active at 420 to 520 Ω, inactive at 840 to 1030 Ω), register 4 status B (contact closed, < 20 Ω); tolerance ±5 %
Protection	Reverse polarity protection, overvoltage protection, earth fault detection and fuses on the supply
Indication	LEDs PWR (power), ACT (communication) and ERR (error)
Ambient temperature	0 to 55 °C
Mounting	DIN rail; screw terminals for wire up to 3 mm²

Connections

Connections
Terminal	Function
Terminal Power +	Supply plus
Terminal Power E	Earth
Terminal Power -	Supply minus
Terminal Comm A	RS485 A
Terminal Comm B	RS485 B
Terminal Comm 0	RS485 0 V
Terminal IN1 – IN16	Inputs 1 to 16, a plus and a minus terminal per input

Datasheet (PDF)PDF, 130 kB

Setup

Make sure the supply cable is de-energised before connecting.
Connect the buttons to the inputs, and the supply and RS485 to the Power and Comm terminals, according to the markings on the module. Use wire up to 3 mm².
Set the slave address with SW1 (tens) and SW2 (units).
Set the Modbus master to 19,200 baud, 1 stop bit and no parity.
Read the registers of each input with function code 3 or 4; the wire break status is in the holding registers.

Application

Reading manual call point buttons via Modbus RTU, with line monitoring

PR131: 16 inputs to Modbus RTU

The PR131 reads 16 inputs and passes the values on via Modbus RTU over RS485 (function codes 3 and 4). The slave address is set with two rotary switches. LEDs show power (PWR), communication (ACT) and errors (ERR). The module is protected against reverse polarity and overvoltage and has fuses. Supply 10 to 31 V DC, ambient temperature 0 to 55 °C, DIN rail mounting. A version with Modbus TCP over Ethernet is optional.

The PR131s01 is the general version for analogue and digital signals: 0-10 V, 4-20 mA, 0-30 V, resistances, potentiometers and contacts. The PR131s02 is set up to read the buttons of manual call points, reporting open circuits and short circuits; it is not a certified part of a fire alarm system.

More about the PR131 series