1. Introduction
IOMOD T is used for temperature data monitoring over Modbus or IEC-60870-103 using resistance
temperature detector (RTD) platinum sensor and negative temperature coefficient (NTC) thermistors.
Device is also capable of reading up to count pulses of three bidirectional digital inputs up to ±24 volts.
2. Features
●Temperature sense with ±0.5 °C accuracy over all operating conditions;
●Three bidirectional digital inputs - 12-24 VDC, 2 kV isolation voltage;
●Selectable PT100 ar PT1000 temperature sensor (2, 3 or 4 wire);
●Possibility to connect NTC resistor to system;
●Configurable temperature and sensors’ fault detection;
●Temperature sensing range from -200 up to 800 °C when using platinum RTD sensors, from -
40 up to 200 °C when using NTC thermistors;
●Configurable Modbus or IEC-60870-103 settings: Slave ID, baud rate, parity and stop bits,
RS485 terminating resistor, etc.
●Firmware upgrade over USB;
●Two connectors for RS485, for easier device connection on one line.
3. Device operational information
IOMOD uses Modbus (RTU) or IEC-60870-103 protocols over RS485 connection. Default Modbus
and IEC-60870-103 settings are: 9600 bauds/s baudrate, 8N1, Slave (Link) address - 1.
To read temperature using Modbus (RTU) protocol user can use device with default settings without
configuring it. To read temperature from RTD sensor, send 04 Modbus command (Read Input
Registers) with resolution of first (0) and second (1) registers. To read temperature from NTC sensor,
send 04 Modbus command (Read Input Registers) with resolution of third (2) and fourth (3) registers.
Two words read by Modbus represent a float type variable.
To read temperature from any of aforementioned sensors using IEC-60870-103 protocol user should
first configure it over USB. To send RTD or NTC sensor temperature it should first be enabled in RTD
parameters menu. Only RTD sensor temperature sending is enabled by default. After enabling
transmission from any of the two sensors data will be available as cyclically read values. These values
are represented as 12 bit integers in a range from -200°C to 200°C - temperature value is therefore
multiplied by 10 to have resolution of 0.1 °C unless full range of RTD (from -200°C to 800°C) is
selected - then 1 °C resolution is achieved and temperature is not multiplied by any number.
Thermistor temperature with 0.1 °C fits into 12-bit measurand, so there is no range selection for NTC
sensors and temperature can be measured from from -40°C to 200°C.
For further information regarding setting temperature parameters, reading digital inputs, their counter
values and configurable options please refer to table shown below, also supported MODBUS and IEC-
60870-103 functions described in paragraphs described below.
