EX08AI channels configuration

The EX08AI modbus analog module has eight high resolution input channels, individually configurable to acquire various types of signal and analog sensor.
No product on the market offers the ability to measure voltages up to 50V so it is possible, for example, to read the 24Vdc power supply voltage or the status of a backup battery.
RTD sensors can be connected in two-wire or three-wire mode for the cable resistance compensation. In three-wire mode, however, all eight channels can be used unlike similar products that use two distinct channels for one sensor resulting in a reduction in the number of available channels.
For each type of analog sensor, different measurement scales can be set to obtain the best resolution for the specific application.

analog sensor types
  • Single-ended voltage
    ±50V, ±20V, ±10V, ±5V, ±2V
  • Differential voltage
    ±1V, ±0.5V, ±0.2V, ±0.1V, ±0.05V, ±0.02V, ±0.01V
  • Differential current
    ±20mA, ±10mA, ±5mA, ±2mA, 4÷20mA, ±24mA
  • Thermocouple sensors
    E, J, K, N, R, T, S, B
  • RTD 2/3 wires sensors
    Pt100, Pt200, Pt500, Pt1000, Ni100, Ni1000
  • NTC sensors
    DKF103, 10K3435
  • Resistance
    130kΩ, 30kΩ, 3kΩ, 300Ω
  • Potentiometer
    1÷100kΩ

Analog sensor connection

Each of EX08AI channels can measure the differential voltage, with high resolution, between the specific two screw terminals. For a three-wire connection (RTD and potentiometer) the AGND screw terminal is also used. The internal analog-to-digital converters can also measure the terminal voltages referred to the AGND terminal and the current circulating in the sensor. This information allows the measurement of the resistances of the analog sensor and the connecting cable.
The different types of measurement require the setting of four dip–switches that configure the internal hardware front-end. For each type of analog sensor, a specific configuration value must also be set via software, which defines the measurement scale. The documentation of EX08AI module shows the values to be used for the different sensors and scales.

analog sensor connections

Analog signal specifications

The EX08AI analog module is calibrated using a high-precision automatic system, specifically developed for EX08AI, that stores 14 parameters for each single channel inside the module permanent memory. These calibration values (a total of 112 points) results in a high precision of the measurement for all the measuring scales as follows:

  • Single-ended voltage ±50V

    Reading: ±10000
    Resolution: 0.01% fs
    Precision: ±0.05% fs

  • Single-ended voltage ±20V

    Reading: ±10000
    Resolution: 0.01% fs
    Precision: ±0.03% fs

  • Single-ended voltage ±10V

    Reading: ±10000
    Resolution: ±0.01% fs
    Precision: 0.03% fs

  • Single-ended voltage ±5V

    Reading: ±10000
    Resolution: ±0.01% fs
    Precision: ±0.05% fs

  • Single-ended voltage ±2V

    Reading: ±10000
    Resolution: ±0.01% fs
    Precision: ±0.08% fs

  • Differential voltage ±1V

    Reading: ±20000
    Resolution: 0.005% fs
    Precision: ±0.01% fs

  • Differential voltage ±0.5V

    Reading: ±20000
    Resolution: 0.005% fs
    Precision: ±0.01% fs

  • Differential voltage ±0.2V

    Reading: ±20000
    Resolution: ±0.005% fs
    Precision: 0.01% fs

  • Differential voltage ±0.1V

    Reading: ±20000
    Resolution: ±0.005% fs
    Precision: ±0.02% fs

  • Differential voltage ±0.05V

    Reading: ±20000
    Resolution: ±0.005% fs
    Precision: ±0.01% fs

  • Differential voltage ±0.02V

    Reading: ±20000
    Resolution: ±0.005% fs
    Precision: ±0.02% fs

  • Differential voltage ±0.01V

    Reading: ±20000
    Resolution: ±0.005% fs
    Precision: ±0.04% fs

  • Differential current ±20mA

    Reading: ±20000
    Resolution: 0.005% fs
    Precision: ±0.01% fs

  • Differential current ±10mA

    Reading: ±20000
    Resolution: 0.005% fs
    Precision: ±0.01% fs

  • Differential current ±5mA

    Reading: ±20000
    Resolution: ±0.005% fs
    Precision: 0.01% fs

  • Differential current ±2mA

    Reading: ±20000
    Resolution: ±0.005% fs
    Precision: ±0.02% fs

  • Differential current 4÷20mA

    Reading: ±20000
    Resolution: ±0.005% fs
    Precision: ±0.01% fs

  • Differential current ±24mAV

    Reading: ±20000
    Resolution: ±0.005% fs
    Precision: ±0.01% fs

  • Resistor 130kΩ

    Reading: 0÷65000
    Resolution: 0.0016% fs
    Precision: ±0.05% fs

  • Resistor 30kΩ

    Reading: 0÷30000
    Resolution: 0.0033% fs
    Precision: ±0.03% fs

  • Resistor 3kΩ

    Reading: 0÷30000
    Resolution: 0.0033% fs
    Precision: ±0.01% fs

  • Resistor 300Ω

    Reading: 0÷30000
    Resolution: 0.0033% fs
    Precision: ±0.03% fs

  • Potentiometer 1÷100kΩ

    Reading: 0÷10000
    Resolution: 0.01% fs
    Precision: ±0.05% fs

  • NTC 10kΩ B=3960

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.05% fs

  • NTC 10kΩ B=3435

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.05% fs

  • Thermocouple type E

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.025% fs

  • Thermocouple type J

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.025% fs

  • Thermocouple type K

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.025% fs

  • Thermocouple type N

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.025% fs

  • Thermocouple type R

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.05% fs

  • Thermocouple type T

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.05% fs

  • Thermocouple type S

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.05% fs

  • Thermocouple type B

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.05% fs

  • Pt100 2 (3) wires RTD

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.05% (±0.05%) fs

  • Pt200 2 (3) wires RTD

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.04% (±0.07%) fs

  • Pt500 2 (3) wires RTD

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.03% (±0.06%) fs

  • Pt1000 2 (3) wires RTD

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.025% (±0.05%) fs

  • Ni100 2 (3) wires RTD

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.08% (±0.16%) fs

  • Ni1000 2 (3) wires RTD

    Reading: 10 x °C
    Resolution: 0.1°C
    Precision: ±0.04% (±0.08%) fs