SY LED2 4-20mA Loop-Powered LED Digital Panel Meter

Product Advantage

1. Genuine Two-Wire Passive Architecture — Install in Minutes, Run Forever

The SY LED2's defining advantage is its true two-wire passive operating principle: it needs absolutely no external power supply, no battery, and no auxiliary wiring — just two wires connected in series with the existing 4-20mA transmitter loop. The meter's ultra-low-power design extracts its operating energy from the same current loop it measures, functioning reliably at loop currents as low as 3mA and surviving transients up to 100mA with built-in over-current and reverse-polarity protection. This architecture eliminates common failure modes (power supply malfunction, wiring errors, ground loops) while drastically simplifying field installation — especially valuable in retrofit scenarios where running new power conduits to remote instrument locations would be prohibitively expensive. The ≤3.2V loop voltage drop ensures minimal impact on loop budget, preserving compatibility with legacy transmitters and long cable runs. For distributed monitoring applications with dozens or hundreds of measurement points, the cumulative savings in power supplies, wiring, and installation labor make the SY LED2 an exceptionally economical choice.

2. High-Visibility Large-Format LED Display — Readable Across the Control Room

Where the SY LED1 prioritizes extreme miniaturization (35mm width), the SY LED2 optimizes for readability with 14.1mm (0.56-inch) digit height — 40% larger than the LED1 — making it suitable for control panels, equipment racks, and operator stations where readings must be legible from several meters away. The black LED display panel employs per-segment constant-current driving, ensuring uniform brightness across the full 4-20mA measurement range regardless of loop current level. This is a critical engineering detail: in conventional voltage-driven LED designs, brightness can vary noticeably with loop current, but the constant-current architecture maintains consistent visibility whether the loop is at 4mA, 12mA, or 20mA. The display supports both direct and inverse linear scaling (e.g., 4mA→0 / 20mA→8000 or 4mA→1000 / 20mA→-1000), with over-range conditions clearly indicated by "oHH" (over high) and "oLL" (over low) diagnostic codes rather than ambiguous readings. The ABS plastic enclosure with panel cutout dimensions of 57.5×24.0mm (+0.2mm) enables straightforward push-fit mounting into standard instrument panels, secured from behind with hot-melt adhesive.

3. CPU-Controlled Programmability — Zero, Span, Alarm, and Damping at Your Fingertips

Unlike traditional analog panel meters that rely on imprecise potentiometer adjustments susceptible to temperature drift and mechanical wear, the SY LED2 is built around a microcontroller platform with full digital configurability via two tactile push-buttons. Users can independently set the 4mA display value and 20mA display value anywhere within -1999 to 9999, position the decimal point at any digit location, configure damping time from 0 to 20 seconds (in 0.5s increments) to smooth fluctuating process signals, and enable or disable the dual-channel alarm subsystem. The alarm configuration is particularly sophisticated: each of the two alarm channels supports independent threshold setting (as a percentage of the 4–20mA span), rising-edge or falling-edge trigger direction, and delay time from 0 to 30 seconds (in 1.0s increments) to prevent nuisance alarms from momentary signal fluctuations. When an alarm condition is active, the last decimal point on the LED panel flashes as a conspicuous visual indicator, and the isolated optocoupler outputs provide open-collector signals to drive external relays, indicators, or PLC digital inputs. All configuration is stored in non-volatile memory, so settings persist through power cycles without battery backup. This flexibility allows a single SY LED2 model to serve diverse applications — from simple local tank level indication to complex multi-threshold process alarming — without hardware changes.

Technical Parameters

Product Uses

1.Industrial process pressure monitoring: The module is used to display real-time pressure values in industrial pipelines and vessels by connecting in series with a 4-20mA pressure transmitter loop. Since the meter operates in 2-wire passive mode without auxiliary power, it draws energy directly from the current loop, making it ideal for remote installation sites where power supply is unavailable. The large 14.1mm LED digits ensure clear readability even from a distance or in low-light environments, while the programmable zero and span settings allow operators to map display values to any engineering pressure unit.

2.Temperature display in HVAC systems: The module is used to provide local temperature readouts in heating, ventilation, and air conditioning systems by interfacing with 4-20mA temperature transmitters. The programmable damping time function (0-20 seconds) smooths fluctuating sensor signals from dynamic thermal environments, ensuring stable display output. The dual-channel alarm outputs can trigger alerts via optocoupler isolation when temperature exceeds preset thresholds, enabling automatic ventilation or heating control responses without requiring a separate control system.

3.Flow rate monitoring in petrochemical pipelines: The module is used to display flow rate data from electromagnetic or vortex flow transmitters along petrochemical transportation pipelines. The 2-wire passive design eliminates the need for separate power wiring in hazardous field locations, complying with intrinsic safety requirements. With programmable alarm direction settings, the meter can activate upstream or downstream alarm devices when flow rates exceed or fall below configured limits, driving optocoupler-isolated open-collector outputs (up to 120mA) to prevent potential pipeline incidents.

4.Liquid level indication in water treatment facilities: The module is used to display liquid level measurements from 4-20mA level transmitters in storage tanks, clarifiers, and reaction vessels. The large-size LED panel (digit height 14.1mm) provides operators with a clear visual reference of tank levels from across the equipment room. The alarm delay time setting (0-30 seconds) prevents false alarms caused by surface turbulence, while the 61.4×26.0mm panel mount size allows easy integration into existing control cabinet fronts with minimal cutout modification.

5.PLC and DCS system data acquisition display: The module is used as a supplementary local display unit in PLC and DCS control systems, providing field operators with a direct visual reference of analog signal values without needing to access the central HMI screen. The meter connects in series within the 4-20mA signal loop between the field instrument and the PLC/DCS analog input card. Its high measurement accuracy (±2 digits) and programmable decimal point positioning ensure that displayed values correspond precisely to the engineering units used in the control system.

6.Mining industry safety monitoring: The module is used to display critical safety parameters in mining operations, including methane gas concentration, ventilation shaft pressure, and water level. The passive 2-wire design is particularly advantageous in underground mine environments where power infrastructure is limited and intrinsic safety requirements prohibit high-voltage equipment. The wide operating temperature range (-40°C to 70°C) ensures reliable performance in varying temperature conditions found at different mine depths, while the reverse-connection and over-current protection safeguards the meter against accidental wiring errors during maintenance.

7.Medical and laboratory equipment signal display: The module is used to provide precision readouts of sensor signals in medical devices and laboratory instruments that utilize 4-20mA analog signal transmission. The meter's ability to display both positive and negative values (range -1999 to 9999) with configurable decimal point positions makes it suitable for applications such as centrifuge speed indication, analytical instrument output display, or patient monitoring parameter readout. The dual alarm outputs can be configured to drive external indicator lights or audible alarms through the optocoupler-isolated open-collector circuit when measured values cross critical safety thresholds.