HART 4-20mA Two-Wire Passive Isolated Loop Power Distributor

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-FHT is an isolated power distributor first and foremost — it supplies 16–21VDC loop power to front-end two-wire smart transmitters while simultaneously receiving, isolating, and forwarding their 4-20mA analog signals with full HART bidirectional transparency. No separate power supply, no external DC-DC converter, no additional wiring. Sunyuan's patented back-end feeding technology eliminates the need for an auxiliary power source in the entire sensor-to-controller signal chain, reducing cabinet component count, simplifying field wiring, and cutting deployment costs. A single module replaces the traditional three-device stack of power supply, signal isolator, and HART modem — true system-level integration in a compact package.

2. The output is engineered for the standard 24VDC plus sampling resistor (load resistor) two-wire supply loop architecture commonly used in field explosion-proof installations. It matches directly with analog input interface boards, PLC, DCS, and other instrument analog input ports without adaptation. Output voltage range spans 12–30VDC with up to 500Ω load driving capability at 24VDC, providing ample headroom for long cable runs and high-impedance input cards. The design supports the full current loop specification from 0–24mA output linear range with up to 40mA peak capability, ensuring reliable operation across all standard process control signal levels.

3. Galvanic isolation of 2,000–4,000Vrms (tested at AC 60Hz for 10 seconds) between signal input and output blocks ground potential differences, suppresses common-mode noise, and eliminates ground loop currents that degrade measurement accuracy. Insulation resistance exceeds 100MΩ at 500VDC, with leakage current held to just 0.5μA at 240Vrms. The module also withstands 3KV peak impulse surges at 1.2/50μs, providing robust protection against transient events in power generation, mining, and chemical processing environments where electrical disturbances are common. This isolation grade is certified for safety-critical applications including medical device barrier isolation and nuclear safety instrumentation.

4. The internal circuit integrates dedicated HART digital signal isolation alongside the 4-20mA analog isolation and distribution path, enabling complete bidirectional HART protocol communication between field smart instruments and control room DCS while maintaining analog accuracy of 0.2 or 0.5 grade. Nonlinearity stays below 0.2% full scale, temperature drift is limited to 50 ppm/°C, and load regulation remains under 0.05% per 100Ω change. HART test signals up to 500mV peak-to-peak pass through without modification or content alteration. Temperature coefficient of 0.0050% F.S./°C ensures measurement stability across the full -40°C to +85°C operating range — eliminating seasonal recalibration requirements.

5. The core technology ships in three form factors for flexible deployment. The SIP12 IC module with UL94V-0 flame-retardant encapsulation and +300°C solder tolerance embeds directly onto instrument PCBs — SIP12 pins include dedicated Vo+ power output, Iin+ signal input, Iout+ signal output, and Vin+ voltage input. The DIN3 ultra-compact single-channel rail-mount version fits tight cabinet spaces with zero external components. 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 dedicated power distribution. One platform covers embedded sensor electronics, compact field junction boxes, and dense multi-channel control cabinet wiring.

6. With an operating range of -40°C to +85°C, storage tolerance to +120°C, and 10–90% non-condensing humidity, the ISO 4-20mA-FHT serves smart transmitters, industrial automation, mining safety barriers, medical equipment isolation, industrial robotics, chemical processing, and nuclear safety instrumentation. Response time of ≤100ms preserves process variable dynamics for all standard control loops. The electromagnetic isolation core delivers inherently better long-term stability and temperature linearity than optocoupler-based alternatives — critical in safety systems where signal drift during temperature extremes or component aging could compromise interlock reliability. Patented loop feeding plus HART transparency makes this the most integrated single-module solution for smart field instrumentation.

Technical Parameters

Product Uses

Here are seven specific application scenarios of the ISO 4-20mA-FHT Series HART-Passthrough 4-20mA Two-Wire Passive Isolation Power Distributor:

1.Smart transmitters: The distributor is used to provide isolated 16-21VDC feed power to two-wire smart transmitters while receiving their 4-20mA output signals, isolating and filtering them into standard 4-20mA outputs for DCS/PLC systems, with HART passthrough enabling bidirectional digital communication for remote transmitter configuration, calibration, and diagnostics.

2.Industrial control intelligence: The distributor is used to isolate and distribute analog signals from field sensors and instruments in smart manufacturing systems, combining signal isolation with power distribution in a single module, eliminating the need for separate power supply wiring while ensuring high-precision 4-20mA signal transmission and HART-based remote instrument management across automated production lines.

3.Mining equipment: The distributor is used to power and isolate signals from two-wire monitoring sensors in underground mining environments, where the passive rear-stage feed design eliminates the need for additional power wiring in confined spaces, and 3KVDC isolation protects control systems from electrical hazards while maintaining reliable HART communication with remote field instruments.

4.Medical equipment safety isolation barriers: The distributor is used as a safety isolation barrier that simultaneously powers and isolates signals from patient-connected two-wire medical sensors, with 3KVDC insulation preventing dangerous leakage currents while preserving signal accuracy, and HART passthrough supporting remote configuration of medical transducers without disrupting patient monitoring operations.

5.Industrial robots: The distributor is used to provide isolated power and signal conditioning for two-wire smart position and torque sensors on multi-axis robotic systems, with the integrated power distribution function simplifying wiring harnesses and HART passthrough enabling real-time sensor status monitoring and parameter adjustment during robotic assembly and material handling operations.

6.Chemical industry: The distributor is used to isolate and power two-wire transmitters measuring temperature, pressure, flow, and level in chemical processing plants, where the explosion-proof output design compatible with 24VDC loop power supply meets hazardous area requirements, and HART passthrough allows remote instrument management without entering explosion-risk zones.