Industrial 4G Wireless Bidirectional Analog Transmission Technology & Full-Scenario Deployment
I. Industry Pain Points & Technical Evolution

In industrial automation, 4-20mA current and 0-10V voltage signals are the dominant standards. Traditional wired solutions face several "unbreakable" bottlenecks:

1. Construction Barriers

  • High Costs: Long-distance or cross-factory wiring requires extensive cabling, bridges, and labor, often exceeding tens of thousands of dollars per kilometer.

  • Physical Constraints: In old plants, explosion-proof zones, or along rivers, breaking ground for cables is often impossible.

  • Mobility Issues: Mobile equipment (cranes, robotic arms) or temporary sites cannot use fixed wiring.

2. Stability and Interference

  • EMI Distortion: Motors and high-voltage lines generate electromagnetic interference, causing signal distortion or jumps.

  • Signal Decay: Signals degrade significantly over 300 meters, necessitating complex repeaters.

  • Maintenance Nightmares: Aging cables, rodent damage, or mechanical wear lead to frequent, hard-to-trace faults.

II. Core Technology & Architecture

2.1 K624-ATU4G Technical Principles

The K624-ATU4G utilizes a dual-hardware core with a fully isolated passthrough architecture:

  • Front-end Analog Acquisition: 16-bit high-precision ADC supporting 2-channel 4-20mA/0-10V input with hardware low-pass filtering.

  • Main Control Unit: Industrial-grade 32-bit MCU with a hardware watchdog and data caching for packet loss retransmission.

  • 4G Communication: LTE CAT1 module supporting global bands with a typical network latency of 150–300ms.

  • Back-end Analog Output: 16-bit high-precision DAC for signal restoration with a response time of <5ms.

  • Isolation Protection: 1500~2000Vrms electrical isolation between ports, power, and the 4G module to resist industrial EMI.

2.2 Transmission Topologies

  1. Point-to-Point: A-side collection $\rightarrow$ 4G $\rightarrow$ B-side restoration.

  2. Many-to-One: Multiple remote sensors $\rightarrow$ Cloud/Server $\rightarrow$ Centralized output at the PLC.

  3. One-to-Many: Single source $\rightarrow$ Cloud/Server $\rightarrow$ Multiple synchronized control outputs.

2.3 Technical Comparison

Dimension Traditional Wiring Analog Fiber Converter K624-ATU4G (4G DTU)
Medium Copper Cable Fiber Optic 4G Cellular (Wireless)
Max Distance 300~500m 2~20km No limit (Global coverage)
Installation Complex/Expensive High (Requires splicing) Zero wiring / Plug-and-play
Interference Weak Strong (Immune) Strong (Isolated + Protected)
Mobility No No Yes (Mobile equipment)
Total Cost Medium-High Very High Low (Device + Data plan)

III. Engineering Deployment Solutions

Solution 1: Legacy PLC Wireless Retrofit (Smart Factory)

Pain Point: 12 decentralized pressure/level sensors (4-20mA) are 800m away from the control room. Roadways prevent cable laying.

  • Field Side: Install 6 K624-ATU4G units. Connect sensors directly to the module inputs.

  • Control Side: 1 K624-ATU4G receiver outputs analog signals directly into the PLC analog input card.

  • Result: Retrofit completed in one day without production downtime. Signal accuracy maintained at ±0.2%FS.

Solution 2: Municipal Water Level Monitoring (Environmental)

Pain Point: 5 monitoring points spread across 20km. No power or cabling available.

  • Field Side: 5 K624-ATU4G units powered by solar panels (12V/10Ah).

  • Control Side: AO output connected to a local PLC or SCADA system.

  • Result: Real-time remote monitoring across mountains/suburbs with zero geographical restrictions.

IV. Best Practices & Expert Guide

1. Signal Matching and Calibration

  • Preferred Signal: For long-distance sensor connections to the module, prefer 4-20mA over 0-10V for better noise immunity.

  • Calibration: Perform a single-point calibration during the first deployment using a standard signal generator to verify accuracy across the 4-20mA range.

2. 4G Antenna and Network Optimization

  • Indoors: Use a 5dBi suction cup antenna placed high, at least 1 meter away from frequency converters or motors.

  • Weak Signal Areas: Use a 8~12dBi high-gain directional antenna pointed toward the nearest base station.

  • Data Planning: Typical daily traffic per point is <50MB. Use industrial IoT SIM cards with APN private network support for added security.

3. Industrial Interference Protection

  • Electrical Isolation: Ensure the analog ports and power supply are reliably isolated and do not share a common ground to avoid common-mode interference.

  • Protection: Use DC 12–24V industrial power supplies with surge protectors. Install in waterproof boxes for outdoor use (-40°C to +85°C).

V. FAQ

Q1: What is the core difference between K624-ATU4G and a standard 4G DTU? A: Standard DTUs only transmit serial data (RS232/485) and require external AD/DA modules to handle analog signals. The K624-ATU4G is a dedicated analog DTU with built-in 16-bit high-precision ADC+DAC, allowing direct hardware-level passthrough of 4-20mA/0-10V signals.

Q2: Is there latency or packet loss with 4G wireless? A: Typical latency is 150–300ms, sufficient for almost all industrial monitoring. The module includes a packet retransmission mechanism and a 72-hour data cache to ensure no data is lost during temporary network outages.

Q3: Do I need to modify my PLC program to use this? A: No. The K624-ATU4G restores the signal transparently. If you input 12mA at the field side, the receiver outputs 12mA to the PLC. The PLC perceives it as a direct wired connection, making the retrofit "zero-code."