4 Analog Inputs 20mA

4 Analog Input Modbus Remote I/O Module

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

Key Features

• 4 Channel 0–20mA Analog Inputs
• 16-bit analog resolution
• Raw analog value resolution of 0.001mA
• Sensor open / broken wire indication
• Individual channel offset and gain calibration
• Integer and IEEE754 float value support
• Modbus RTU over RS-485
• 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/

Ordering Information

Product Code	Description
UIO-4IN-20MA	4-Channel Analog Input Module (0–20mA)
MIO-2AI-VI	2-Channel Analog Input Module (0–20mA / 0–36V DC)
UIO-8IN-20MA	8-Channel Analog Input Module (0–20mA)
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 in PLC and SCADA systems
• Process Monitoring – Measure current loop signals from transmitters and sensors
• Energy & Utilities – Monitor current-based process parameters from field instrumentation
• Building Management – Integrate current-loop sensors for HVAC, power monitoring, and environment control
• Remote Monitoring – Ideal for distributed installations and remote data acquisition

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	4
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

Mechanical Dimensions

Terminal Details

Top Connector – RS-485

Pin	1	2	3
Signal	A	B	Shield

Analog input Connector

| Pin | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | | – | ------------- | — | – | ------------- | | Signal | CH1+ | CH1- | CH2+ | CH2- | CH3+ | CH3- | CH4+ | CH4- |

Wiring Diagrams

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

Communication Interface

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

Basic Process Registers

Signal	Address	Type	Description
AI1–AI4 (0–20mA)	30001–30004 / 30021–30028	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	10601–10604	Bit	AI1 to AI4 alarm indication
Discrete Inputs	10621–10624	Bit	AI1 to AI4 sensor open indication
Discrete Inputs	10641–10644	Bit	AI1 to AI4 latched alarm indication
Coils	00601–00604	Bit	Reset AI alarm counter
Input Registers	30001–30004	int16	AI1 to AI4 raw value
Input Registers	30021–30028	float	AI1 to AI4 scaled value
Input Registers	30601–30604	int16	AI1 to AI4 alarm counters
Holding Registers	40101	int16	Slave address
Holding Registers	40102	int16	Baud rate selection
Holding Registers	40103	int16	Serial format
Holding Registers	40601–40604	int16	AI1 to AI4 offset
Holding Registers	40621–40628	float	AI1 to AI4 gain
Holding Registers	40661–40664	int16	AI1 to AI4 alarm mode
Holding Registers	40681–40684	int16	AI1 to AI4 alarm minimum
Holding Registers	40701–40704	int16	AI1 to AI4 alarm maximum

Detailed Register Tables

Discrete Inputs (1xxxx)

Analog Input Live Alarm Status

Function	Address Range	Type	Description
Discrete Inputs	10601–10604	Bit	AI1 to AI4 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	10621–10624	Bit	AI1 to AI4 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	10641–10644	Bit	AI1 to AI4 latched alarm status, Auto clears on read

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	00601–00604	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	30001–30004	int16	AI1 to AI4 raw value
Input Registers	30021–30028	float	AI1 to AI4 scaled value
Input Registers	30601–30604	int16	AI1 to AI4 alarm counters

Holding Registers (4xxxx)

Analog Input Calibration

Function	Address Range	Type	Description
Holding Registers	40601–40604	int16	AI1 to AI4 offset
Holding Registers	40621–40628	float	AI1 to AI4 gain

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

Analog Input Alarm Configuration

Function	Address Range	Type	Description
Holding Registers	40661–40664	int16	AI1 to AI4 alarm mode
Holding Registers	40681–40684	int16	AI1 to AI4 alarm minimum
Holding Registers	40701–40704	int16	AI1 to AI4 alarm maximum

Alarm Modes Values: -

0 = Disabled

1 = Outside minimum or maximum 2 = Maximum only

4 = Inside minimum and maximum window 3 = Minimum only

Communication Settings

Address	Type	Description
40101	int16	Modbus server (slave) address (switch value)
40102	int16	Baud rate selection
40103	int16	Serial format selection

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.

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

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

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	5.0 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