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8 Analog Inputs 20mA

8 Analog Input Modbus Remote I/O Module Datasheet pdf

Compact Modbus RTU remote I/O module with eight 0–20mA analog inputs, configurable alarm logic.

Product image

Key Features

  • 8 Channel 0–20mA Analog Inputs
  • 16-bit analog resolution
  • Factory calibrated accuracy: ± 0.1% from upper-range
  • Raw analog value resolution in steps of 0.001mA
  • Sensor open / broken wire indication
  • Configurable individual alarms indication
  • Retentive alarm counters on power cycle
  • Individual channel offset and gain calibration
  • Integer and IEEE754 float value support
  • Modbus RTU over Isolated RS-485
  • Modbus RTU remote write master mode
  • Easy to use free ModViz software
  • Rotary address switch for address selection from 1 to 99
  • Wide Supported baud rates from 300 to 115200
  • DIN rail mountable
  • Dimensions: 110mm × 50mm × 55mm

ModViz – Modbus Configuration & Visualization Tool

ModViz is a powerful yet simple configuration and visualization tool designed to work seamlessly with Veawe Modbus I/O modules. It enables engineers, system integrators, and technicians to quickly configure, monitor, and test field devices through an intuitive graphical interface.

The software can be downloaded from https://veawe.io/modviz/

Modviz Image

Ordering Information

Product Code Description
UIO-8IN-20MA 8-Channel Analog Input Module (0–20mA)
UIO-4IN-20MA 4-Channel Analog Input Module (0–20mA)
MIO-2AI-VI 2-Channel Analog Input Module (0–20mA / 0–36V DC)
UIO-4IN-10V 4-Channel Analog Input Module (0–10V DC)
UIO-444-20mA 4-Channel Analog Input with DI and DO

Applications

  • Industrial Automation – Monitor 4–20mA analog sensors across up to 8 channels in PLC and SCADA systems
  • Process Monitoring – Measure current loop signals from transmitters and sensors on high-density installations
  • Energy & Utilities – Monitor current-based process parameters from field instrumentation
  • Remote Monitoring – Ideal for distributed installations and remote data acquisition
  • Modbus Gateway – Master Mode writes AI1–AI8 values to a remote Modbus slave device, retransmitting analog values to legacy PLCs or building a Modbus-to-analog gateway

Specifications

Parameter Value
Mounting DIN rail
Dimensions 110 mm x 50 mm x 55 mm (L x W x H)

Electrical Specifications

Parameter Value
Supply Voltage 15–24V DC
Analog Input Range 0–20mA
Communication Port RS-485

Input/Output Specifications

Parameter Value
Channel Count 8
Signal Range 0–20mA
Resolution 0.001 mA

Isolation & Protection Specifications

Parameter Value Notes / Description
Supply Reverse Polarity Protection Integrated Series protection diode (continuous protection, zero reverse leakage)
Supply Isolation Non-Isolated Common ground between input power, internal circuitry, analog outputs
Transient Voltage Clamping Up to 600W Clamps overvoltage spikes (10/100 µs peak pulse rating)
EMC & Immunity Standards Class-Compliant Meets IEC 61000-4-2 (ESD), IEC 61000-4-4 (EFT), & IEC 61000-4-5 (Surge)
RS-485 Bus ESD Protection 15kV HBM/Air IEC61000-4-2 Integrated high-ESD protected transceiver on A/B lines
RS-485 Isolation 2.5kVrms Isolated RS485 signal with other circuitry

Mechanical Dimensions

Mechanical Dimension

Terminal Details

Top Connector – RS-485

Pin 1 2 3
Signal A B Shield

Analog input Connector

Pin 1 2 3 4 5 6
Signal GND CH1+ CH2+ CH3+ CH4+ GND
Pin 7 8 9 10 11 12
Signal GND CH5+ CH6+ CH7+ CH8+ GND

Wiring Diagrams

Note: All images and connection diagrams shown are for illustrative purposes only and may differ from the actual product.

Wiring

Communication Interface

Protocol Physical Layer Default Baud Rate Default Format
Modbus RTU RS-485 19200 8N1

Basic Process Registers

Signal Address Type Description
AI1–AI8 (0–20mA) 30001–30008 / 30021–30036 int16 / float Raw analog (0.001mA) / Scaled engineering value

Supported Modbus Function Codes

Read Write
01 – Read Coils 05 – Write Single Coil
02 – Read Discrete Inputs 06 – Write Single Register
03 – Read Holding Registers 15 – Write Multiple Coils
04 – Read Input Registers 16 – Write Multiple Registers

Register Map Overview

Function Address Range Type Description
Discrete Inputs 10601–10608 Bit AI1 to AI8 alarm indication
Discrete Inputs 10621–10628 Bit AI1 to AI8 sensor open indication
Discrete Inputs 10641–10648 Bit AI1 to AI8 latched alarm indication
Coils 00601–00608 Bit Reset AI alarm counter
Input Registers 30001–30008 int16 AI1 to AI8 raw value
Input Registers 30021–30036 float AI1 to AI8 scaled value
Input Registers 30601–30608 int16 AI1 to AI8 alarm counters
Holding Registers 40101 int16 Slave address
Holding Registers 40102 int16 Baud rate selection
Holding Registers 40103 int16 Serial format
Holding Registers 40601–40608 int16 AI1 to AI8 offset
Holding Registers 40621–40636 float AI1 to AI8 gain
Holding Registers 40661–40668 int16 AI1 to AI8 alarm mode
Holding Registers 40681–40688 int16 AI1 to AI8 alarm minimum
Holding Registers 40701–40708 int16 AI1 to AI8 alarm maximum

Detailed Register Tables

Discrete Inputs (1xxxx)

Analog Input Live Alarm Status

Function Address Range Type Description
Discrete Inputs 10601–10608 Bit AI1 to AI8 alarm indication

If an analog sensor vale is out of the range set in Alarm Configuration:

  • Alarm indication status bit is set

Analog Sensor Open Status

Function Address Range Type Description
Discrete Inputs 10621–10628 Bit AI1 to AI8 sensor open indication

If an analog sensor is disconnected or open:

  • Analog value reads as 0.000mA
  • Corresponding sensor open status bit is set

Analog Input Latched Alarm Status

Function Address Range Type Description
Discrete Inputs 10641–10648 Bit AI1 to AI8 latched alarm status, Auto clears on read

Baud Rate image

Latched alarm status stays high even after the alarm is cleared and auto clears only after the master reads this bit

Coils (0xxxx)

AI Alarm Counter Reset

Function Address Range Type Description
Coils 00601–00608 Bit Reset AI alarm counter

Writing 1 to the coil resets the corresponding Retentive Alarm counter value, This bit is self clearing

Input Registers (3xxxx)

Analog Input Values

Function Address Range Type Description
Input Registers 30001–30008 int16 AI1 to AI8 raw value
Input Registers 30021–30036 float AI1 to AI8 scaled value
Input Registers 30601–30608 int16 AI1 to AI8 alarm counters

Holding Registers (4xxxx)

Analog Input Calibration

Function Address Range Type Description
Holding Registers 40601–40608 int16 AI1 to AI8 offset
Holding Registers 40621–40636 float AI1 to AI8 gain

Gain image

Examples: Offset value 1000 = +1.000mA, Gain value 0.005 = multiplier correction

Analog Input Alarm Configuration

Function Address Range Type Description
Holding Registers 40661–40668 int16 AI1 to AI8 alarm mode
Holding Registers 40681–40688 int16 AI1 to AI8 alarm minimum
Holding Registers 40701–40708 int16 AI1 to AI8 alarm maximum

Alarm Config image

Alarm Modes Values: -

0 = Disabled

1 = Outside minimum or maximum 2 = Maximum only

4 = Inside minimum and maximum window 3 = Minimum only

Analog Input Master Mode Configuration

These values are applicable when the device is in Master Mode and 40104 = 1.

Address Type Description
40791 int16 Remote device destination register type to write. 0 = Holding Register
40792 int16 Remote device destination data type to write. 0 = int16 raw data (0 to 20000 for 0~20.000 mA), 1 = float scaled data as per offset and gain, 2 = int16 scaled data as per offset and gain
40793 int16 Remote device destination start address
40794 int16 Remote destination channel count. Max channels is 8

Communication Settings

Address Type Description
40101 int16 Modbus server (slave) address (switch value)
40102 int16 Baud rate selection
40103 int16 Serial format selection
40104 int16 Serial device mode. 0 = Server (slave), 1 = Client (master)
40105 int16 Remote read/write poll interval. Example: 10 = 1 second
40106 int16 Watchdog interval. Example: 10 = 1 second
40107 int16 Watchdog action. 0 = Modbus Watchdog Disabled, 1 = Reset Outputs on Modbus Watchdog Expire

Modbus Address (40101)

This is set using the rotary or DIP switches.

Baud Rate Register (40102) and Serial Format Register (40103)

Value Baud Rate Value Baud Rate Value Format
0 300 7 9600 0 8N1
1 600 8 14400 1 8E1
2 1200 9 19200 2 8O1
3 1800 10 38400 3 8N2
4 2400 11 57600 4 8E2
5 4800 12 62500 5 8O2
6 7200 13 115200

Default: 19200 baud, 8N1.

Baud Rate image

Default Settings

Setting Default
Slave Address As per switch position
Baud Rate 19200
Serial Format 8N1

Configuration Settings

Default Mode

Default mode is useful when communication settings are unknown.

When the rotary address switch is set to 00:

  • Server address = 1
  • Baud rate = 19200
  • Serial format = 8N1

Switch

Changing to default mode does not overwrite stored settings. Stored settings remain unchanged until written through Modbus.

Write Remote Device – Master Mode

When 40104 is set to 1, the module operates in Modbus Master Mode.

In this mode, the module periodically writes data to another Modbus slave device and automatically updates its analog inputs to the remote device.

Working of Master Mode:

  • Master Mode polls the remote device ID as set in the rotary or DIP switch.
  • Master Mode polls the remote device at the interval defined by 40105.
  • The destination device register type is selected using 40791.
  • The destination data type is selected using 40792.
  • The start address of the remote data is defined in 40793.
  • The number of channels to write is defined in 40794.
  • Values of AI1 ~ AI8 are automatically written to the mapped address as per the count.
  • If float mode is selected, two Modbus registers are used per channel.
  • If int16 mode is selected, one Modbus register is used per channel.
  • Offset and gain settings are still applied in Master Mode.
ModViz Baud Rate / Bit Setting Config - Master Config highlighted ModViz Master Mode Register Types dialog

LED Indications and Diagnostics

LED Description
Power Module power ON indication
Tx RS-485 transmit activity
Rx RS-485 receive activity

Calibration and Engineering Values

The module internally measures analog current input as a raw integer value.

Examples:

  • 0mA = 0
  • 4mA = 4000
  • 12mA = 12000
  • 20mA = 20000

Raw values are stored in int16 registers with a resolution of 0.001mA.

Engineering value registers allow the raw current value to be converted into user units such as pressure, temperature, tank level, flow, weight, and percentage.

Sensor Type Input Range Engineering Value Range
Pressure transmitter 4–20mA 0 to 10.0 Bar
Tank level sensor 4–20mA 0 to 100%
Temperature transmitter 4–20mA 0 to 200°C

Engineering values are available in float format using IEEE754 registers.

Formula:

Engineering Value = (Raw Value + Offset) × Gain

Where:

  • Raw Value = measured current in 0.001mA units
  • Offset = calibration correction in 0.001mA units
  • Gain = engineering unit multiplier

Example:

  • Raw input = 12000
  • Offset = -4000
  • Gain = 0.01
  • Engineering value = 80

This can be used for a transmitter scaled from 0–20mA to -40 to +160°C.

Raw to mA Raw Value Offset Gain Result
4–20mA to 0–100% 12000 0 0.001 50.0%
4–20mA to 0–10 Bar 12000 4000 0.00625 5 Bar
4–20mA to 0–200°C 12000 4000 0.0125 100.0°C

Revision History

Revision Date Changes
Rev 1.0 2026-08-10 Initial datasheet, HW Version = 3, FW Version = 2

Get the latest version of this datasheet : click here..

Support

Website: www.veawe.io

Email: info@veawe.io