Analog inputs

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AI type:

1 2

Extension

If you are looking for information on the Extension xS52, xS53 and xS54, please see Analog inputs - type 2

Analog inputs type 1 are available in the Extension xS51. To measure voltage or current, the negative pole of the external device to be measured is connected to the AGND terminal of the connector and its positive pole (signal) to the AIx (or AIy.x) terminal. The wiring for resistance measurement varies depending on the measurement mode.

(i)

Please note:
In its factory settings, the device is set to voltage measurement to prevent any potential damage of connected devices or sensors in case an unsuitable device/sensor is connected.

(!)

Attention:
Before connecting the measuring device, it is necessary to check measurement settings by the chosen software and according to the type of the connected device - see the measurement description below.

The following images illustrate the setup for measuring a voltage and current source on AI and AGND terminals.

Voltage measurement

Current measurement

Resistance sensors can be connected to analog inputs using a two-wire or three-wire method. The three-wire method holds the advantage of preventing measuring errors caused by the resistance of the used wire.

Two-wire method

Three-wire method

Mode description

Analog inputs on Extension xS51 can perform accurate measurements of current, voltage or resistance. Measurement mode needs to be set first in the control software. In voltage and resistance mode you can choose from two accuracy modes. The measured value is of float32 (real) data type and corresponds with the measured input value (V⎓, mA, Ω).

This type of analog input supports the following modes:

0–10 V⎓ voltage
0–2.5 V⎓ voltage
0–20 mA current
0–1960 Ω resistance (three-wire)
0–100 kΩ resistance (two-wire)

Method of setting the measurement mode depends on the software used:

Mervis: instructions for configuring the analog input measurement mode can be found at this link
Evok (Node-RED): the measurement mode configuration is available within the “analog input” device and its “mode” property, see the Evok documentation for more information
Modbus: if the Evok cannot be used, or if Modbus communication is preferred, it is also possible to configure the analog I/O measurement mode by writing directly to the registers (1000-1100) according to the Modbus table

Reading depends on the software used:

Mervis: see guide Connecting to Unipi extension
Evok: see the Evok documentation
Node-RED: using prepared nodes communicating with the Evok API via Websocket
Modbus: reading and writing registers according to the Modbus table (registers 0-100)

Aside from the standard inputs and outputs, Unipi Extension modules also feature additional functions for broadening the possible applications, performance optimization and monitoring of the entire project. These functions are calculated directly by the Extension's microprocessor and are thus independent on the control software.

Default configuration
This function is used to save the current configuration of the section (extension module) into its memory. In the case of power cycle of the device or reboot of the section (extension module), the stored configuration is loaded and applied. This functionality is also known as “copy running-config to startup-config”.

Stored data	Default configuration
Measurement mode	voltage measurement

Master Watchdog
This function runs on the section's (extension module's) microprocessor and continuously monitor the commands from the application running on the unit. If no commands are detected within a configured time (MWD Timeout), the section's (extension module's) processor automatically reboots and reverts to the default configuration described above. This function ensures a safe configuration is set in case of emergency situations (unit failure, communication error or software issues) to prevent damage to controlled devices or any hazards to personnel.

Input terminals	AI, AIS
Common conductor	AGND
Galvanic isolation	Yes
Input functions	0–10 V⎓ voltage measurement, 0–20 mA current measurement, 0–1960 Ω or 0–100 kΩ resistance measurement
Resolution	24 bits (resistance measurement), 16 bits (voltage and current measurement)
Conversion time	400 ms (resistance measurement), 60 μs (voltage and current measurement)
Protection type	Integrated overvoltage protection
Maximum input voltage	15 V⎓
Measurement accuracy	±0.2 %
Input resistance (voltage measurement)	44 kΩ
Input resistance (current measurement)	100 Ω

Analog inputs

Connection

Mode description

Mode setting and input reading

Special functions

Technical parameters