EX08AI is a modbus analog module with unique features that can be used to simultaneously acquire up to 8 analog input channels with extremely high precision. Each channel can be configured independently for direct connection to electrical signals and sensors of any type. This flexibility allows you to use the EX08AI in many applications where you frequently need to use a set of different products that are only suitable for specific signal types.

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All signals in one product

The interface of EX08AI modbus analog module allows reading voltages from 1uV to 50V, currents from 1uA to 24mA and resistances from 0.01Ω to 130kΩ using different programmable scales. In addition, each channel can be configured for direct connection to thermocouples, RTD (2/3 wires) and NTC sensors. Potentiometers can be connected with three wires to obtain a 100% proportional position with 0.01% resolution, regardless of the potentiometer nominal value.

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High resolution and precision

Highly accurate reading is achieved by two parallel 24 bit ADC converters used to obtain 20000 stable points, factory-calibrated by storing in the module 14 values for each of the eight channels. An automatic calibration system at the factory ensures very low calibration errors and high repeatability of the measurements over time. A constant small correction of the factory-calibration values, as function of the difference between working-current and factory-calibration temperatures, guarantees unique precision performances.

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Advanced Modbus protocol

The EX08AI modbus analog module communicates over RS485 fieldbus using standard “Modbus protocol”. However, the module has advanced extensions over “standard protocol” to achieve much higher performance than any other modbus module on the market. Some of the improvements can only be used with OVERDIGIT PLCs because there is no other master PLC capable of communication with baudrates up to 1Mb/s. Used with an OVERDIGIT PLC, the total engagement time of the RS485 bus to read the values of eight channels is only 700us.

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Compact module on DIN rail

No other modbus analog module on the market offers eight configurable channels with high performance in such a compact size. The EX08AI module is made of a DIN rail case with only 17.5mm width. In addition, the EX08AI module are designed to maintain its high performance over a temperature range from -20°C to +70°C thanks to the measurement compensation obtained with a built-in temperature sensor available also for modbus reading.

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