ISO DA Isolated RS485/RS232 to Analog Output Converter

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. Remote Signal Reconstruction Without Continuous Host Control

The ISO DA Series pairs with a compatible ISO 4021 to reproduce remotely measured signals as local analog outputs. Host mode is enabled by linking HOST (pin 12) to GND (pin 11) before applying power. The module then reads the ISO 4021 through Modbus and transfers the two input-channel values to its corresponding outputs.

The link can use RS-485 directly or suitable external converters for fiber, wireless or Ethernet transmission. After configuration, the modules exchange data without ongoing PC or PLC supervision, providing an alternative where long analog cable runs are impractical.

2. Separate Startup Presets for Each Channel

Users can assign an initial output to each channel with the #AASN(data) command. The values remain stored in non-volatile memory and are applied when the module powers up or resets.

These presets establish defined analog commands while the supervisory controller initializes. They can support a planned equipment startup sequence, but do not define the output response to a subsequent communication failure.

3. Current and Voltage Options with Flexible Data Representation

Available ranges include 4–20 mA, 0–20 mA, ±20 mA, 0–5 V, 0–10 V, 1–5 V, ±5 V and ±10 V. Custom ranges are available on request. Both channels share an output ground and must use the same selected range.

Commands accept engineering units, percentage of full scale or the hexadecimal representation specified in the datasheet. For 4–20 mA and 1–5 V versions, the minimum output corresponds to 20% in percentage format and 0x333 in hexadecimal format. These mappings describe command values; physical output resolution remains 12-bit.

4. Isolated Analog Outputs and Protected Serial Communication

The analog output section is separated from the communication interface by a 3,000 VDC isolation barrier, specified for a one-minute withstand test at the stated 1 mA leakage condition. The serial interface and power supply share a common ground.

Additional measures include ±15 kV communication-port ESD protection, transient suppression diodes and digital filtering. The datasheet also specifies 3 kVAC impulse withstand using a 1.2/50 μs waveform. Appropriate grounding, shielding and external protection complement these features in industrial installations.

Technical Parameters

Product Uses

1. Remote Setpoint Control for Field Equipment

The ISO DA Series converts RS232 or RS485 commands into 4–20 mA or 0–10 V setpoints for compatible valve positioners, motor drives and heating controllers. This allows a central controller to adjust field equipment through a serial connection while maintaining electrical separation between the communication and analog output sections.

2. Analog Output Expansion for PLC and DCS Networks

Distributed control systems can use the module to place analog outputs closer to connected equipment. ASCII and Modbus RTU protocols provide communication options for compatible PLC, DCS and industrial computer platforms. Network capacity and cable distance depend on the protocol, baud rate, wiring and installation conditions.

3. Multi-Zone Building Automation

Programmable addresses allow modules to serve different building zones over a shared communication network. Typical connections include HVAC damper actuators, lighting controllers and other devices accepting analog commands. The 8–50 VDC supply range accommodates different control-panel power arrangements.

4. Digital Transfer and Analog Signal Restoration

Paired with an ISO 4021 acquisition module, the ISO DA reconstructs remote measurements as local current or voltage outputs. Host mode supports data exchange without continuous PC or PLC supervision. Suitable external converters extend the connection through fiber, wireless or Ethernet links, offering an alternative to long analog cable runs.

5. Isolated Commands for Instrument Subsystems

Compatible instrument drive stages and positioning controllers can receive programmed analog commands from the module. In medical equipment development, suitability must be assessed within the complete device design. The isolation rating and output accuracy alone do not establish patient protection or medical compliance.

6. Analog References for Power-System Control

A supervisory system can send Modbus RTU commands to generate analog references for compatible regulating equipment. Output isolation and communication-port protection help address electrical disturbances between connected circuits. Breaker operation, capacitor switching and similar functions require appropriate downstream control interfaces.

7. Commissioning and Control-Loop Verification

Engineers can apply programmed output levels to check instrument scaling, actuator response and receiving-channel operation. Configurable addresses, baud rates and output-value readback assist setup and troubleshooting. Readback reports the module’s output data; verification of the physical signal requires an external measuring instrument, with a suitable reference used for traceable calibration.