SY LED2-45 Low-cost and small volume two-wire passive smart loop 4-20mA current (LED) digital meter,It employs a passive design with input and output lines connected in series to the transmitter's 4-20mA loop. This allows the 4-20mA analog signal within the loop to be linearly converted and displayed as a decimal digital value within a preset range.This product supports 485 communication, enabling remote connection to PLC/HMI for reading and displaying values. It allows configuration or modification of relevant parameters such as module address, baud rate, and alarm thresholds.The SY LED2 digital meter operates on a two-wire passive principle，the electrical signal passing through the measurement circuit serves both as the input signal for the display meter and as its operating power source. This two-wire passive mode of operation requires no additional auxiliary power supply, therefore, it features simple and convenient wiring during use, compact size, high precision, and low cost. Traditional analog digital meters utilize potentiometers for adjustment, offering limited parameter flexibility and being highly susceptible to temperature variations. In contrast, this digital meter employs two built-in buttons for operation, controlled by a central processing unit (CPU). It enables the configuration of multiple parameters including zero point, full scale, decimal point, alarms, and delay settings, delivering enhanced flexibility and practicality. The digital meter utilizes an LED display panel with constant-current drive for each LED segment, ensuring uniform brightness across the 4-20mA range. It incorporates reverse polarity and overcurrent protection, making it suitable for monitoring control points of physical quantities such as temperature, pressure, flow rate, and liquid level in industrial sites, petrochemical plants, environmental monitoring, and mining industries. In most applications, various sensors convert physical quantities such as temperature, pressure, flow rate, and liquid level into 4-20mA electrical signals. These signals are then fed into the SY LED2 digital display meter, which provides real-time visualization of these physical parameters. This enables users to perform comprehensive on-site control.
The SY LED2-485 digital meter is designed to measure 4-20mA DC current signals. It can draw power directly from the 4-20mA loop signal for measurement without requiring an external power supply. The displayed figures are not direct current measurements but rather preset values of 4mA and 20mA. The measured current values are displayed linearly relative to these two preset values, for example: If 4mA is set to 0 and 20mA is set to 8000, then an input of 8mA will cause the meter to display 2000, and an input of 12mA will cause it to display 4000. Alternatively, if 4mA is set to 1000 and 20mA is set to -1000, an input of 12mA will cause the meter to display 0, and an input of 16mA will cause it to display -500. The digital display meter's maximum display range is 9999, and the minimum is -1999.
The SY LED2-485 digital meter features built-in alarm functionality with two isolated digital outputs, enabling local display, control, and alarm capabilities. This feature is implemented programmatically, with two PC452 optocoupler solder pads reserved for future installation when alarm requirements arise.The digital meter features two alarm points with configurable positive and negative alarm directions.The alarm point targets the displayed reading. When an alarm occurs, the last decimal place on the LED panel flashes. Alarm information is output via the port, capable of driving an optocoupler alarm signal.
The SY LED2-485 digital meter adopt a panel-mounted design with a flame-retardant plastic housing. The panel cutout dimensions are 57.5 × 24.0 mm (+0.2 mm tolerance). It is suitable for displaying control instrumentation or transmitter signals within cabinets.
Important Notes:
1. Never reverse the input signal (current direction), as this may damage the digital display meter.
2. Input current signals should generally not exceed 25 mA. Input currents reaching 100 mA will cause immediate and irreparable damage to the digital display meter.
When testing or connecting to a current loop, it is recommended to series-connect a resistor of 200Ω or higher for protection.
3. Do not use in humid environments or areas with corrosive gases, as this may shorten the service life or cause complete damage.
SY LED2-485 Digital Meter Technical Specifications
1. Operating Conditions:
(1) Current Through:
Rated Range: 3–22 mA
Limit Range: Less than 100 mA
(2) Temperature Range:
Rated Operating Range: -40°C to +85°C
Extreme operating range: -45°C to +125°C
(3) Relative Humidity: 20% to 90% RH
(4) Shock and Vibration: Complies with Ministry of Electronics Industry standard environmental test requirements for Group II instruments.
2. Panel Display Method:
Black LED (light-emitting diode) digital and decimal point display, character height 14.2mm (0.56 inches).
3. Digital Display Setting Range:
(1) 4mA: -1999 to 9999
(2) 20mA: -1999 to 9999
4. Voltage Drop:
Voltage drop ≤ 3.2V, with overcurrent protection
5. Polarity Conversion:
Displays “-” when below zero point value; no polarity symbol displayed when above zero point value.
6. Accuracy:
Full-scale linear deviation ±2 digits (relative to 2000 specification)
7. Temperature Effect Error:
≤50PPM/℃
8. Over-range display: “oHH” or “oLL”.
9. RS-485 Communication
Communication Interface: 1 standard RS-485 communication interface.
Communication Protocol: Supports MODBUS RTU communication protocol. Enables network communication with PLCs, RTUs, or computer monitoring systems from various brands.
Data Format: 10 bits. 1 start bit, 8 data bits, 1 stop bit.
Communication Address: Configurable (00H-FFH) and baud rate (1200, 2400, 4800, 9600, 19200 bps). Maximum communication network distance reaches 1200 meters via shielded twisted-pair cable. Communication interface features high anti-interference design with ±15KV ESD protection and communication response time under 100ms.
10. Dimensions: 61.4 × 26.0 × 17.7 mm
Panel mounting cutout dimensions: 57.5 × 24.0 mm +0.2 mm
