The Novus DigiRail-2A (8811100001) turns two analogue sensor signals into Modbus RTU registers on an RS485 network. Each universal input accepts thermocouples, Pt100 RTDs, mV, V or mA, with cold junction compensation, 3-wire Pt100 lead compensation and sensor break detection built in. Temperatures and process signals can then be read directly by a PLC, HMI, SCADA system or data logger acting as Modbus master, without a separate transmitter and analogue input card.
Inputs are isolated from the power and communication circuits (1000Vac), which removes ground loops between sensors and the RS485 network and keeps readings stable in electrically noisy panels. With 17-bit resolution and ±0.15% accuracy on Pt100 and process signals, it is one of the most economical ways to add precise analogue inputs to an existing Modbus system. Address, baud rate and input types are set with free DigiConfig software.
How It Fits Your System
Sensors wire to the DigiRail-2A on the DIN rail, and a 2-wire RS485 cable links it to your Modbus master. To read it from a PC or laptop, use the Novus USB-i485 converter. If you need Ethernet (Modbus TCP), analogue outputs or digital I/O as well, see the DigiRail Connect RAMIX.
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Technical Details
Order code: 8811100001 (DigiRail-2A)
Analogue inputs: 2, universal, programmable for thermocouple J, K, T, E, N, R, S, B; Pt100; mV; V; mA
Resolution: 17 bits
Accuracy (@25°C): Pt100, mV, V, mA ±0.15% of full scale; thermocouples ±0.25% of full scale
Sampling rate (1 input): 10Hz for mV, V and mA; 5Hz for thermocouples and Pt100
Cold junction compensation: 1°C at 25°C, ±0.05°C/°C. Pt100 3-wire lead compensation
Sensor break detection: thermocouples, Pt100 and mV
Temperature effect: 0.003% of full scale/°C
Isolation: 1000Vac between inputs and power/communication
Communication: 2-wire RS485, Modbus RTU slave, configurable address and baud rate (1,200 to 115,200bps)
Indicators: LEDs for communication and status, key to reset communication parameters to factory default
Power supply: 10-35 Vdc, 50mA max
Configuration software: DigiConfig (free Windows download)
Dimensions: 72 x 78 x 19mm. Mounting: 35mm DIN rail. Working temperature: 0 to 70°C
Frequently Asked Questions
What signals can the DigiRail-2A read?
Each of the two inputs can be set independently for a thermocouple (J, K, T, E, N, R, S or B), a Pt100 RTD, or a mV, V or mA process signal, so one module can read a temperature sensor and a 4-20mA transmitter side by side.
What do I need to read the values?
A Modbus RTU master on RS485, such as a PLC, HMI, SCADA system or data logger. The DigiRail-2A is a slave, so it responds to register reads from the master.
Can I put several modules on one RS485 network?
Yes. Each module has its own configurable Modbus address, so several can share one 2-wire RS485 bus alongside other Modbus instruments.
When should I choose DigiRail Connect instead?
Choose DigiRail Connect RAMIX if you need Ethernet (Modbus TCP), analogue outputs or digital I/O in the same module. For analogue inputs on RS485 only, the DigiRail-2A is the simpler, lower-cost option.
Industry Applications
- Temperature monitoring — brings oven, kiln, tank and process temperatures into SCADA or a data logger.
- PLC analogue expansion — adds isolated analogue inputs to a PLC with spare RS485 instead of buying an analogue card.
- HVAC & BMS — integrates duct, water and pressure sensor signals onto a Modbus building network.