The features of EX08AI analog input module

The features of EX08AI analog input module are unique in the market. No similar product offers, at the same price, eight analogue channels with a resolution of 20000 points and a wide range of configurability to adapt to many sensors and analog signals.
The following are the main features of EX08AI analog input module:

  • I/O interface – remotable on RS485 fieldbus

    Compact interface for PLCs and automation PC systems with RS485 serial communication port. Using a two-wire serial bus allows you to position the EX08AI module near the sensors to get the best performance in terms of signal quality. Moreover, the remote connection, using only one cable reduces the complexity and cost of wiring.

  • 8 analog inputs, 16 bits, isolated and configurable

    The module provides for the connection of eight configurable analog input signals converted to digital values by two parallel ADCs. The converters are 24-bit sigma-delta type and are used to obtain stable and calibrated 16-bit measurements. Connections to analog input signals are galvanically isolated from the power supply and serial communications.

  • Voltage reading from μV range up to ±50V

    The analog input module can measure voltages in a very wide range. Voltages in the range from one micro-volt to a few tens of milli-volt are particularly used in thermocouples reading while voltages up to hundreds of milli-volt allow reading of RTD sensors. The 5V and 10V measurements are a standard in the industrial applications, while the measurements up to 50V are a unique feature of the EX08AI module.

  • Current reading from μA range up to ±24mA

    The currents measurement is obtained by reading the voltage on the high stability shunt resistor inside the module. Thanks to the high resolution in the voltage measurement, the shunt resistance has a value of only 50 ohms and this reduces the voltage drop in the circuit to only 1V for the 20mA measurement. The high resolution of analog to digital converters allows stable reading of 20000 points and thus of 1 micro-ampere.

  • Direct resistance reading up to 130kΩ

    The EX08AI analog input module allows for direct measurement of ohm resistance to expand the variety of usable analog sensors in addition to those already provided (RTD and NTC). Software examples, using structured text language, are also available to implement, within the PLC application, the conversion from the resistance value to the sensor temperature.

  • Thermocouples with internal / ext. compensation

    Eight different types of thermocouples can be connected directly to the analog input module. The software of module provides the conversion and linearization of the sensor voltage-temperature curve using a high-order polynomial. Additionally, the module performs the thermocouple cold junction compensation by means of an internal temperature sensor or by reading a remote sensor through an additional channel.

  • RTD thermal resistances, 2 / 3 wires connection

    The RTD temperature sensors can be connected to the analog input module both in two-wire configuration and in three-wire configuration. Sensor temperature reading, expressed in tenths of degrees, is obtained by the measurement of the resistance of the sensor and the subsequent conversion and linearization by a polynomial of high degree.

  • No channels are lost in 3 wires connection

    The three-wire connection of the RTD sensors eliminates measurement error due to the presence of long connecting cables. The module can also measure the cable resistance to compensate this error. The measurement of this additional resistance is realized by the same sensor channel without requiring the use of a further channel of the module.

  • Direct temperature reading with NTC sensors

    The NTC temperature sensors can be read from the analog input module, obtaining a reading with a resolution of a tenth of degree. The software within the module allows the conversion and linearization of two different families (B = 3960 and B = 3435) of 10kΩ NTC sensors. Additional NTC models can be read using the resistance measurements.

  • 12 bits channel with internal temperature sensor

    An internal NTC sensor is connected to a ninth analogue channel in order to read the module temperature. This temperature can be used to compensate the cold junction of the thermocouples but can also be acquired directly through the Modbus communication protocol.

  • RS485 serial port with high speed (1Mb/s max)

    The EX08AI interface module communicates with the control system using a high-speed RS485 serial port. This port implements the standard modbus protocol up to 115kb/s, but it can also reach communication speeds up to 1 Mb/s when used with OVERDIGIT PLCs.

  • Modbus RTU protocol, configurable over RS485

    The EX08AI analog input module uses the RTU modality of standard modbus protocol. Communication parameters can be set, in programming mode, using the supplied software Modbus tool. In addition, these parameters can be modified by the application software on the PLC using the standard modbus protocol functions.

  • CoDeSys libraries for configuration and use

    Using the EX08AI with OVERDIGIT PLCs is extremely simple and powerful thanks to the CoDeSys library supplied. Just insert the module into the “PLC Configuration” of CoDeSys tool and add a simple function block to the application. This function block will update the module resources without writing any other program code.

  • PC Modbus tool for configuring and testing modules

    A powerful software Modbus tool for PC is provided free of charge for module configuration and test operations. The tool also provides a complete values acquisition system with the ability to create graphs and save data in CSV format.

  • Compact dimension on 17.5mm of DIN rail

    The EX08AI analog input module is realized with a robust case for DIN rail mounting with extremely compact dimensions. Only 17.5mm of DIN rail are required for its installation. Acquisition systems with a large number of analog input channels can be achieved by joining multiple modules in a very small space.

analog input module dimensions

General specification

The general specification of the EX08AI analog input module are shown below. The high stability of the performances is achieved by reading the internal temperature of the module according to which the factory calibration values are constantly corrected.
For further details refer to the EX08AI brochure.

  • Analog inputs

    8 differential channels, 3V max from AGND

  • Max over-voltage

    ±80V (single-ended V), ±25V (other scales)

  • Isolation

    1500Vac max (from bus and power supply)

  • Samples resolution

    16 bits (from 2x Sigma-Delta 24 bits ADC)

  • Samples mean

    62.5ms steps programmable (N = 1÷255)

  • Acquisition time

    62.5ms min (2 channels), 250ms (8 channels)

  • Errors signalling

    Underflow / Overflow / sensor fault

  • Thermal drift

    50 ppm/°C

  • Temperature sensor

    Internal NTC placed near input terminals

  • Conversion

    12 bits ADC (indipendent from 8 channels)

  • Temperature reading

    -20°C to 80°C, 0.1°C resolution, ±0.5°C error

  • Fieldbus

    RS485 with EMI filter, thermal prot. / ESD 15kV

  • Max nodes / Terminination

    64 / insertable 120Ω load

  • Baudrate

    300b/s ÷ 1Mb/s (continuosly programmable)

  • Protocol

    Modbus RTU, address 1 ÷ 247, parity N/O/E

  • Function codes

    3, 4, 6, 16, 17, 23, 100, 101, 102, 109, 110

  • Max performance

    Complete I/O update within 700μs (@ 1Mb/s)

  • Power supply

    24Vdc ±15% / 60mA max

  • Operative temp.

    -20°C to 70°C

  • Connections

    Plug-in screw terminals 28÷12AWG / 2.5mm2

  • Box

    ABS with 35mm DIN rail mount / IP20

  • Max dimensions

    113 x 17.5 x 119 mm (H x W x D)