ISOEM Active 4-20mA Signal Isolator with HART Pass-Through

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. The ISO 4-20mA-HT achieves true two-wire passive operation with full HART bidirectional passthrough — no conventional isolator can match this. Drawing operating energy directly from the 4-20mA loop via Sunyuan's patented power-stealing technology, it eliminates external auxiliary power while allowing HART protocol signals to flow transparently between field instruments and control room DCS. A HART handheld communicator can configure and diagnose smart transmitters sitting behind the isolator as if directly connected. With an ultra-low voltage drop of just 3.5V at 20mA and an 8.5–32VDC input voltage range, engineers gain complete galvanic isolation plus full digital access to intelligent field devices through a single cable pair.

2.Every channel achieves 3,000VDC/rms galvanic isolation between signal input and output, tested at AC 60Hz for 10 seconds with leakage current below 1mA. Insulation resistance exceeds 100MΩ at 500VDC, and leakage holds at just 0.5μA at 240Vrms. The module also withstands 3KV peak impulse surges at 1.2/50μs, blocking transient events that would destroy unprotected input cards. This architecture effectively suppresses ground loop currents, common-mode interference, and crosstalk in multi-channel installations, protecting PLC, DCS, and distributed I/O analog channels from field-side electrical faults across power generation, chemical processing, and mining applications.

3. Available in accuracy grades of 0.1, 0.2, and 0.5, the module delivers full-scale nonlinearity error below 0.2% and output distortion under 0.2%. Temperature drift is held to just 50 ppm/°C typical across the entire -40°C to +85°C operating range, with a coefficient of only 0.0050% F.S./°C. This means a 4-20mA signal measured at -40°C reads essentially the same value at +85°C — eliminating seasonal recalibration cycles that plague optocoupler-based isolation. Load regulation stays below 0.05% per 100Ω change, ensuring consistent output accuracy regardless of downstream input impedance variations across different PLC analog cards.

4.The isolation engine ships in three deployment formats. The SIP12 IC module with UL94V-0 flame-retardant encapsulation and +300°C lead temperature tolerance solders directly onto instrument PCBs for embedded integration. The DIN3 ultra-compact single-channel rail-mount version fits space-constrained cabinets. The DIN35 multi-channel platform supports 1-in-1-out, 2-in-2-out, and 3-in-3-out configurations — each channel independently isolated with built-in overvoltage, overcurrent, and reverse-polarity protection. One technology platform covers every scenario from board-level sensor integration to dense multi-channel cabinet wiring, simplifying BOM management across product lines.

5. The module inserts directly into any standard 4-20mA loop between two-wire, three-wire, or four-wire transmitters and PLC, DCS, or distributed I/O analog input channels. No external components, no firmware, no calibration — simply wire through and it delivers isolated 4-20mA output with simultaneous HART bidirectional communication. HART test signals up to 500mV peak-to-peak pass through transparently. Response time of ≤100ms preserves process variable dynamics, while 12VDC output at 20mA drives loads up to 250Ω supporting most PLC cards, data acquisition modules, and panel instruments without external buffer stages.

6. With an operating range of -40°C to +85°C, storage tolerance to +105°C, and 10–90% non-condensing humidity, the ISO 4-20mA-HT serves smart transmitters, industrial automation, mining safety barriers, medical device isolation, industrial robotics, chemical processing, and nuclear safety instrumentation. The electromagnetic isolation design delivers fundamentally better long-term drift and linearity than optocoupler-based alternatives — critical in safety systems where signal degradation during temperature extremes could compromise interlock reliability. Sunyuan's patented magnetic-electric coupling isolates 4-20mA analog signals while preserving bidirectional HART communication, supporting both legacy analog and modern smart instrumentation in a single passive module.

Technical Parameters

Product Uses

Here are seven specific application scenarios of the ISO 4-20mA-HT Series Two-Wire Passive HART-Passthrough 4-20mA Loop Isolator:

1.Smart transmitters: The isolator is used to passively isolate and transmit 4-20mA signals between field smart transmitters and control room DCS systems, while HART passthrough enables bidirectional digital communication for remote calibration, configuration, and diagnostics without requiring any external power supply.

2.Industrial control intelligence: The isolator is used in industrial automation control systems to isolate analog 4-20mA signals from sensors and instruments, eliminating ground loop interference and ensuring high-precision signal transmission between field devices and centralized control systems in smart manufacturing environments.

3.Mining equipment: The isolator is used to provide safe signal isolation for sensors and monitoring instruments in harsh mining environments, with 3KVDC isolation voltage protecting personnel and equipment from electrical hazards while maintaining reliable 4-20mA signal and HART communication transmission underground.

4.Medical equipment safety isolation barriers: The isolator is used as a safety isolation barrier between patient-connected measurement circuits and backend acquisition systems, preventing hazardous leakage currents while preserving signal accuracy and supporting HART-based remote instrument configuration in medical device applications.

5.Industrial robots: The isolator is used to isolate and distribute 4-20mA sensor signals across multi-axis robot systems, with passive loop-powered operation simplifying wiring and HART passthrough enabling real-time communication with smart position sensors, torque sensors, and other field instruments on robotic production lines.

6.Chemical industry: The isolator is used to isolate signals from temperature, pressure, flow, and level transmitters in chemical processing plants, where the passive two-wire design eliminates the need for additional power wiring in hazardous areas while HART passthrough supports remote instrument management without entering explosion-risk zones.

7.Nuclear power safety equipment: The isolator is used to transmit critical sensor signals in nuclear power plants with 3KVDC isolation ensuring safety-grade separation between field instrumentation and control systems, while the passive design and wide-temperature operation guarantee reliable performance in radiation-shielded and environmentally demanding nuclear facility environments.