ISO 4021 Isolated Analog to RS485/RS232 Converter Module

Device features:

1. Protect the control loop of the upper stage of the host computer.

2. Reduce the impact of environmental noise on the test circuit, and can overcome inverter noise and various high and low frequency pulsation interference.

3. It suppresses the interference of circulating currents in public ground wires and pulses of frequency converters, solenoid valves, thyristors, etc. to equipment. It also has the function of limiting voltage and current for lower-level equipment. It is a faithful protection for transmitters, instruments, frequency converters, solenoid valves, PLC/DCS input and output, and communication interfaces.

The DIN35 series standard 35mm guide rail card holder structure is easy to install and can effectively isolate: the potential difference between signal input, signal output, power supply and earth.

Product Advantage

1. Precision Analog Acquisition with Effective Noise Rejection

The ISO 4021 uses a 24-bit sigma-delta ADC to acquire analog signals at 10 samples per second, with a specified measurement accuracy of 0.05%. Temperature drift is ±15 ppm/°C typical and ±30 ppm/°C maximum, while the stated current-input offset drift is ±0.1 µA/°C.

At 50/60 Hz, common-mode rejection reaches 120 dB with a 1 kΩ source imbalance, complemented by 60 dB normal-mode rejection. Voltage-input impedance exceeds 1 MΩ, and current-input resistance varies with the selected range. Digital filtering reduces power-frequency interference, while internal transient suppression diodes help limit electrical disturbances at the input.

2. Input Options for Industrial Current and Voltage Signals

Available current ranges include 0–1 mA, 0–10 mA, 0–20 mA, 4–20 mA, ±1 mA, ±10 mA and ±20 mA. Voltage options cover 0–5 V, 0–10 V, 0–75 mV, 0–2.5 V, ±5 V, ±10 V and ±100 mV. Custom input requirements can be specified when selecting the module.

Both acquisition channels use the same input range and share a common ground reference. Software-selectable data formats include engineering units, percentage of full scale and the hexadecimal representation defined in the communication documentation. These options allow the reported measurements to match the host system’s processing requirements.

Standard ranges are factory calibrated. For later adjustment, ASCII calibration commands support field recalibration using a suitable precision signal source and reference meter.

3. Electrical Separation Between Sensor and Communication Circuits

A 3,000 VDC isolation barrier separates the analog input section from the communication and power-supply side. The specified withstand test lasts one minute at the stated 1 mA leakage condition. This arrangement helps reduce the influence of ground-potential differences between field instrumentation and the receiving system.

The serial interface includes ±15 kV ESD protection, with transient suppression and digital filtering providing additional measures against electrical interference. The communication interface and power supply share a common ground; the two analog channels are not individually isolated from each other. Appropriate shielding, grounding and external protection remain part of the installation design.

4. Flexible DC Supply with Low Power Consumption

The ISO 4021 operates from an 8–50 VDC supply, accommodating nominal 12 V, 24 V and 48 V systems when their actual operating voltage remains within this range. Power consumption below 1 W keeps the module’s contribution to cabinet power demand and heat generation low.

Built-in reverse-polarity and overvoltage protection help address common power-input faults. Sharing a ground between the supply and serial interface simplifies connections on the digital side, while the isolated analog section maintains electrical separation from the sensor circuits. Enclosure ventilation and environmental suitability should follow the module’s specified operating conditions.

Technical Parameters

Product Uses

Here are seven specific application scenarios of the ISO 4021 Series 4-20mA/0-5V to RS232/485 Intelligent Sensor (AD Conversion Intelligent Transmitter):

1.PLC and DCS signal remote measurement and monitoring: The module is used to acquire analog 4-20mA or 0-5V signals from field sensors and convert them to digital data via 24-bit A/D conversion, transmitting to PLC or DCS control systems via RS-485 bus, with 3000VDC isolation protecting control circuits from field-side electrical interference, enabling remote measurement, monitoring, and control of industrial process parameters across distributed manufacturing facilities.

2.Smart building and security automation systems: The module is used to collect analog signals from temperature, humidity, and environmental sensors deployed throughout smart buildings and security systems, converting them to RS-485 digital data for building management platforms, with up to 256 modules addressable on a single bus spanning 1200 meters, and the wide 8-50VDC power supply accommodating various building power distribution conditions.

3.Industrial field data acquisition and long-distance transmission: The module is used to acquire low-level analog signals from industrial field sensors, perform signal isolation and linearization, and transmit digital data over RS-485 twisted-pair shielded cable for distances up to 1200 meters, with internal digital filtering effectively suppressing 50/60Hz power frequency interference and transient suppression diodes protecting against surge pulses in harsh industrial environments.

4.Power equipment monitoring and control: The module is used to monitor analog parameters from power distribution equipment including voltage, current, and power sensors, transmitting real-time data via RS-485 bus with Modbus RTU protocol to power automation supervisory systems, with ±15KV ESD protection and 3000VDC isolation safeguarding communication interfaces from high-voltage transients encountered in electrical power grid environments.

5.Multi-channel sensor signal acquisition networks: The module is used to simultaneously acquire two channels of current or voltage signals from multiple sensors, with each RS-485 bus supporting up to 256 modules, enabling large-scale multi-point sensor data acquisition networks for applications such as industrial process monitoring, environmental monitoring stations, and equipment condition monitoring across extensive industrial facilities.

6.Medical instrument analog signal acquisition: The module is used to collect and isolate analog physiological sensor signals in medical monitoring and diagnostic equipment, with 3000VDC galvanic isolation serving as a safety barrier between patient-connected measurement circuits and digital processing systems, while 0.05% measurement precision and 24-bit A/D resolution ensure accurate acquisition of critical vital signs for RS-485 transmission to hospital information systems.

7.Industrial equipment safety operation monitoring and control: The module is used to acquire analog signals from equipment safety sensors such as bearing temperature monitors, vibration detectors, and pressure transmitters, performing real-time data acquisition and isolation with programmable alarm thresholds, and transmitting via RS-485 to central control systems for equipment safety operation monitoring, predictive maintenance, and fault diagnosis in industrial manufacturing facilities.