4-20mA Two-Wire Isolated Signal Conditioner with LED Display

Product Advantage

1. Active-to-Passive Signal Conversion — Solving the Power Conflict at the Interface Boundary，The fundamental problem addressed by the "4-20mA-E" variant is the electrical incompatibility between two common but mutually exclusive 4-20mA interface types. Active (sourcing) sensors — such as three-wire and four-wire transmitters, powered analyzers, and PLC analog output modules — generate a 4-20mA current by sourcing it from their own internal power supply. Their output terminals present a current source, not a current sink. Passive two-wire loop-powered receivers — including the input channels of many PLCs, DCS systems, and intrinsically safe barriers — are designed to supply loop power (typically 24VDC) and expect the connected transmitter to modulate the current by varying its effective resistance. Connecting an active sensor directly to a passive receiver results in two power supplies fighting each other, with consequences ranging from inaccurate readings to permanent hardware damage. The DIN 1X1 ISO 4-20mA-E sits at this interface boundary: its input side (pins 1–2) presents a low-impedance current-sink load to the active sensor, accepting 4-20mA at any loop voltage from 5 to 32VDC. The isolation stage digitizes and magnetically couples this signal across the 3KVDC barrier. The output side (pin 11: IOut+, pin 12: +24VDC) then reconstructs the isolated 4-20mA signal as a properly loop-powered output — with pin 12 providing the regulated +24VDC supply voltage that the downstream two-wire loop expects. The sensor's power supply and the receiver's loop power remain electrically isolated from each other, eliminating ground loops, common-mode noise, and power supply interaction while preserving the full measurement bandwidth (100Hz at 20mA).

2. Ultra-Wide 5–32VDC Input Voltage Range for Universal Active Sensor Compatibility，The input voltage specification of 5–32VDC for the -E variant represents a significant expansion over the non-E version's 12–36VDC range, particularly at the low end. This 5VDC minimum enables compatibility with sensors operating from low-voltage power rails — including 5VDC-powered microcontroller-based sensor modules, USB-powered data acquisition front-ends, and battery-operated field instruments where the loop supply voltage may be as low as 5V. The 32VDC upper limit covers standard 24VDC industrial supplies with generous headroom for supply variation and cable voltage drop. The low equivalent input resistance (a deliberate design feature of the loop-powered architecture) means the device extracts the minimum necessary energy from the input signal to power its CPU, LED display, and isolation stages while preserving the signal fidelity. The wide input range also simplifies system design: the same -E module can be deployed across an entire plant where different sensor types operate at different supply voltages — 12VDC for panel-mounted instruments, 15VDC for legacy systems, 24VDC for field transmitters — without requiring voltage-specific variants or external level-shifting circuits. This universality reduces spare parts inventory, simplifies procurement, and eliminates the risk of installing the wrong voltage-rated module during maintenance.

3. Integrated 24VDC Loop Power Supply Output for Single-Device Drop-In Deployment，A distinctive feature of the 4-20mA-E variant visible in the pinout is pin 12, labeled "+24VDC" — a regulated 24V power supply output derived from the input signal energy. This eliminates the need for a separate DC power supply module to energize the downstream two-wire loop. The output voltage range is specified at 13–24–36VDC (min/typ/max at RL=250Ω), providing stable loop power for the connected receiver, barrier, or load. The output load driving capability is rated at 600Ω at 24VDC — sufficient to drive the input impedance of a typical PLC analog input card (250Ω shunt resistor), a panel meter, an intrinsic safety barrier, and several hundred meters of signal cable in series. The output linear range extends from 1.2mA to 22mA with an output current capability of 0.5–24mA, ensuring faithful reproduction of the 4-20mA signal including slight over-range conditions for diagnostic purposes. The output ripple is specified at 10–20mV RMS (unfiltered) — higher than the non-E's 5mV due to the active power supply regulation stage, but well within acceptable limits for process control applications where downstream PLC/DCS inputs typically employ their own low-pass filtering. The frequency response of 100Hz (small-signal bandwidth at 20mA output) and 20–50ms response time ensure the -E handles dynamic process signals without introducing significant phase lag or amplitude attenuation that could affect control loop stability.

4. 0.1%/0.2% Precision-Grade Isolation with <0.2% Nonlinearity，Despite the added complexity of the active-to-passive conversion circuitry and integrated loop power supply, the 4-20mA-E variant maintains the same precision specifications as the non-E version: accuracy grades of 0.1% and 0.2%, nonlinearity below 0.2% FSK, hysteresis below 0.5%, and temperature drift of ±50 to ±100 PPM/°C across the -25°C to +70°C operating range. This is noteworthy because the signal path in the -E involves additional processing stages (input conditioning to accept sourcing-mode signals, power extraction from the input loop, and output-side loop power regulation) that could introduce additional error sources. The maintained precision demonstrates robust front-end design that preserves signal integrity through all stages. The 3KVDC isolation (tested at DC 50Hz for 10 seconds, leakage 1mA) provides the same level of galvanic protection as the non-E variant, with ≥20MΩ insulation resistance, 0.5μA leakage at 240Vrms/60Hz, and 3KV impulse withstand (1.2/50μs). For applications in power generation, traction systems, and high-energy physics — or any environment where 3KVDC is insufficient — the 6KVDC isolation option provides doubled protection. The precision and isolation specifications make the -E suitable not just for monitoring, but for applications where the isolated output feeds safety instrumented systems, custody transfer measurements, or regulatory compliance data — signal paths where accuracy and isolation integrity have direct safety and financial consequences.

Technical Parameters

Product Uses

1.Active 4-20mA signal matching for PLC/DCS current loop control: The module is used to solve the power conflict between active 4-20mA signal acquisition and two-wire loop-powered receiving ports in PLC and DCS control systems. Unlike the standard ISO 4-20mA (LED1) which handles passive loop signals, the -E variant accepts active 4-20mA signals with a wide input voltage range of 5~36VDC, converts them into isolated passive control signals, and drives active loads within the current loop. This enables seamless integration between active sensor outputs and two-wire powered (intrinsically safe) 4-20mA receiving circuits without auxiliary power supply.

2.Intrinsically safe explosion-proof signal isolation in petrochemical facilities: The module is used to isolate and display 4-20mA signals from active transmitters in hazardous petrochemical environments requiring explosion-proof installations. The two-wire loop-powered design eliminates the need for separate power wiring, complying with intrinsic safety requirements for Zone 0 and Zone 1 hazardous areas. The 3KVDC galvanic isolation between input and output prevents spark-over and ground fault propagation between the hazardous field circuit and the safe-area control room, while the integrated LED display provides operators with real-time local verification of loop current values during routine field inspections.

3.Industrial process variable monitoring with active load driving capability: The module is used to monitor temperature, pressure, flow, and level signals from active 4-20mA transmitters while simultaneously driving active loads such as solenoid valves, electronic regulators, or I/P converters connected within the same current loop. The output can deliver up to 24mA with a load capacity of 600Ω at 24VDC, providing sufficient drive capability for loop-powered actuators. The 0.1-class accuracy and programmable dual alarm outputs with configurable direction and delay (0-30s) enable automatic triggering of shutdown or adjustment mechanisms when process variables deviate from safe operating envelopes.

4.Long-distance analog signal distortion-free transmission with signal regeneration: The module is used to regenerate and isolate degraded 4-20mA signals that have traveled over long cable runs in large industrial facilities such as refineries, power plants, and mining complexes. The internal signal modulation/demodulation circuitry recreates a clean isolated 4-20mA output from the active input signal, compensating for voltage drops and electromagnetic interference accumulated over hundreds of meters of cabling. The 100Hz frequency response bandwidth and 20-50ms response time ensure faithful signal reproduction for dynamic process measurements, while the low equivalent input resistance minimizes additional loading on the sensor loop.

5.Power monitoring instrumentation isolation safety barrier: The module is used as an isolation safety barrier between high-voltage power monitoring circuits and low-voltage data acquisition systems in electrical substations and power distribution facilities. The 3KVDC isolation voltage, 3KV impulse withstand (1.2/50μs peak), and low leakage current (0.5μA at 240Vrms/60Hz) meet power industry safety standards for protective separation. The active signal input capability (5~36VDC) accommodates the higher voltage levels present in power monitoring transducer outputs, while the loop-powered operation eliminates the need for auxiliary power supply in space-constrained switchgear cabinets.

6.Sensor and transmitter signal reliability monitoring with field display: The module is used to monitor the operational health of active 4-20mA sensors and transmitters by providing isolated signal retransmission and local display functionality. Maintenance technicians can verify actual transmitter output values at the point of installation using the integrated 4-digit LED display, without disconnecting the loop or carrying a multimeter. The programmable zero and span settings allow the display to be calibrated to any engineering unit range, while the dual-channel isolated alarm outputs (OC gate, up to 120mA with external pull-up) can flag signal loss, out-of-range conditions, or sensor drift, enabling predictive maintenance strategies in critical industrial processes.