RS485/RS232 to Analog Output Converter with LED Display

Product Advantage

1. Controller-Free Signal Reconstruction with ISO 4021

Pairing the ISO DA (LED1) with an ISO 4021 creates a link between remote analog inputs and local analog outputs. The ISO 4021 acquires and digitizes the measurements; the ISO DA retrieves that data and reproduces the corresponding current or voltage signals.

Host mode is activated by connecting HOST (pin 12) to GND (pin 11) before power-up. Once configured, the ISO DA continuously reads the paired module through Modbus and updates its two output channels without ongoing PC or PLC supervision.

The connection can use RS-485 directly or suitable external converters for fiber, wireless or Ethernet transmission. This approach is useful where routing and maintaining long analog cables is impractical.

2. Range Selection and Defined Power-Up Outputs

The series offers current outputs of 4–20 mA, 0–20 mA and ±20 mA, alongside voltage options of 0–5 V, 0–10 V, 1–5 V, ±5 V and ±10 V. Custom ranges are available on request. Both channels must use the same selected range.

Output commands support engineering units, percentage of full scale and the hexadecimal representation defined in the communication documentation. Each channel also accepts a separate startup preset through the #AASN(data) command.

Stored settings establish the required initial output after power-up or reset, before routine control commands arrive. Startup presets define initialization behavior; they do not provide a communication-loss fallback function.

3. Electrical Separation and Interface Protection

A 3,000 VDC isolation barrier separates the analog outputs from the serial communication section. The specified withstand test lasts one minute at the stated 1 mA leakage condition. The communication interface and supply share a common ground.

The communication port includes ±15 kV ESD protection. Internal transient suppression diodes and digital filtering provide additional measures against surge pulses and power-frequency interference. The datasheet also lists a 3 kVAC impulse withstand specification using a 1.2/50 μs waveform.

These features support integration into industrial control systems alongside appropriate grounding, cable routing and external protection.

Technical Parameters

Product Uses

1. Remote Actuator Setpoint Control

The ISO DA (LED1) translates RS232 or RS485 commands into analog setpoints for compatible electric valve positioners, motor drives and temperature controllers. Its current or voltage outputs connect digital control systems to equipment requiring an analog input, while the LED display allows operators to inspect output values locally.

2. Distributed PLC and DCS Output Expansion

Add analog output points near field equipment through a serial connection to a PLC, DCS or industrial computer. Selectable ASCII and Modbus RTU protocols provide integration options for compatible hosts. Network size and transmission distance depend on addressing, baud rate, cabling and installation conditions.

3. Building Automation Interfaces

Building management systems can use the module to send analog commands to compatible HVAC damper actuators, lighting controllers and other building equipment. The local display assists commissioning, and the 8–50 VDC supply range accommodates different control-panel power arrangements.

4. Remote Analog Signal Reconstruction

When paired with an ISO 4021, the module restores digitally transmitted measurements as analog outputs at the receiving location. Host mode allows the pair to operate without continuous PC or PLC supervision. Fiber, wireless and Ethernet transmission require suitable external communication equipment.

5. Analog Control in Instrument Subsystems

The module can provide isolated analog commands to compatible positioning stages, drive controllers and other instrument subsystems. For medical equipment development, its electrical ratings must be evaluated within the complete device design; isolation withstand voltage alone does not establish patient protection or medical compliance.

6. Supervisory Setpoints for Power Equipment

Compatible power-management systems can send Modbus RTU commands to the module to generate analog references for regulating or monitoring equipment. Output isolation and communication-port protection support integration where ground-potential differences and electrical disturbances must be managed. Direct switching of breakers or capacitor banks requires appropriate control interfaces.

7. Commissioning and Control-Loop Checks

Technicians can program a sequence of current or voltage levels to check receiving instruments, actuator responses and control-loop scaling. Configurable communication settings and the LED readout simplify setup and troubleshooting. Calibration work requiring traceable accuracy should use an appropriate reference instrument.