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Universal transmitter




typically in stock



The RTC685 is a single-channel DIN rail mounted industrial transmitter for temperature sensors and for signal conversion. A thermocouple, an RTD, or an analog process signal (mA or V) can be connected to the input. Various processing options are provided: filtering, table linearization, custom functions.

An analog output (mA or V) is provided, along with an RS485 serial bus. The serial bus supports the Nokeval SCL and the Modbus RTU protocols.

The device can be configured with a computer and a programming cable, or remotely over the RS485 bus. The programming cable is DCS772 combined with an adapter POL-3PIN.

Each functional block is independent and interacts the other functions minimally unless configured to do so, which removes the need to study and configure all the functions before using the device. E.g. to use this device to convert a temperature sensor signal to an analog output signal, it is sufficient to configure just the input and output, not touching the other functions.

Other highlights:

Provides a supply for an external transmitter or sensor 15 V 50 mA.
Low noise measurement: 0.01 °C rms with 4-wire Pt100 at 8 samples/s.
High speed measurement optionally: 50 samples/sec, available on the serial bus.
Two point free input scaling, also for temperature sensors allowing easy two-point thermal bath calibration.
10 point linearization table.
Jumperless: no need to open the enclosure.
Supply voltage 24 VDC ±15%. Power consumption 0.6 W without an analog output.
Detachable 2.5mm2 connectors.
Three-way galvanic isolation: analog input, power, everything else.
ELo language for customized operations. Allows mathematical operations (basic calculation, polynomial, square root), conditional execution, timing, and sensor fault processing.



Input details


Pt100, thermocouples, mV, V, mA, Ohm, closing contact, Ni100

supply for transmitter

+15 V, 50 mA

input channels


measuring rate

8 samples/s, 50 samples/s with serial output

Output details

output range

mA: 0...20 mA or smaller; V: 0...10 V or smaller

output loading

mA: 0...600 Ω

output channels



mA, V

Connection details

connector model

2.5mm², detachable

bus interface


baud rates

1200, 2400, 4800, 9600, 19200, 38400, 57600, 115000

bus protocol

Nokeval SCL, Modbus RTU

Power supply

power consumption

1 W

supply voltage

24 VDC

General information

galvanic isolation

500 VDC, 1 min Cat 0


130 g


22,5 x 100 x 110 mm


35 mm DIN rail

minimum ambient temperature


maximum ambient temperature


case material


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Universal transmitter

A single-channel DIN rail mounted industrial transmitter for temperature sensors and for signal conversion.