Mitsubishi FXAOM01BD Analog Output Module

The Mitsubishi FXAOM01BD is an analog output expansion module for the MELSEC FX series programmable logic controllers (FX0, FX0N, FX1S, FX1N, FX2N). It provides four channels of current output (0-20mA or 4-20mA) with a maximum range up to 80mA aggregated. This module allows the FX PLC to control variable frequency drives, actuators, chart recorders, and other analog-controlled devices. It is powered by the PLC's 5V DC bus and requires an external 24V DC supply for the output loops.

Technical Specifications

Number of channels: 4 analog outputs. Output type: current, 0-20mA or 4-20mA (selectable via range selection). Resolution: 8 bits (0-20mA: 0-255 data; 4-20mA: 51-255 data). Accuracy: ±1% of full scale (at 25°C), ±2% over temperature. Output load resistance: maximum 500 Ω (for 0-20mA), 400 Ω (for 4-20mA). Maximum output current per channel: 20 mA nominal; cumulative for module: 80 mA (all channels active). Conversion time: 2 ms per channel (sequential). Input data format: 8-bit binary from PLC (from D register). Power supply: 5V DC from PLC (70 mA typical), external 24V DC (from field power, 200 mA typical). Optical isolation between PLC and field. Dimensions: 90mm H x 45mm W x 70mm D. Weight 0.2 kg. Operating temperature: 0-55°C.

Key Features

• 4 current output channels

• Selectable 0-20mA or 4-20mA range

• 8-bit resolution (0-255)

• Easy programming: data sent from PLC data registers

• DIN rail or direct mounting

• Terminal block for easy wiring (screw terminals)

• LED indicator for module status (POWER)

• Compatible with FX0, FX0N, FX1N, FX2N, FX2NC

Wiring and Connections

The module has a removable terminal block with 10 positions. Pins: V+ (24V external supply), V- (common), and four pairs of output channels (AO0+, AO0-; AO1+, AO1-; AO2+, AO2-; AO3+, AO3-). The 24V external supply must be connected to V+ and V-. The load (e.g., VFD analog input) is connected between the output (+) and output (-) of the respective channel. The output - terminals are internally connected to V- (common) but can be left floating if required by the load. For 4-20mA operation, ensure the load is within the specified resistance range.

Programming Example

In the FX PLC program, analog output data is written to special data registers D8170 to D8173 (for FX1N/FX2N) or other specific registers depending on module position. For example, to set channel 0 to 10mA (half scale), move the value 128 (0-255) into D8170. The PLC automatically updates the analog output each scan. The module does not require additional FROM/TO instructions; it is automatically mapped. For FX0N, the assignment is different; refer to the FX0N analog manual. The data can be scaled using simple arithmetic: desired output value (mA) / 20mA * 255.

Calibration and Range Selection

Range selection (0-20mA vs 4-20mA) is done by setting two DIP switches on the module's side. Off/On combinations define the range for all channels simultaneously (individual channel selection not possible). Calibration is performed via two potentiometers per channel: gain and offset. Factory calibration is provided, but field calibration may be needed after long use. Use a precision ammeter in series with the load, write the minimum and maximum data values, and adjust trim pots accordingly.

Applications

The FXAOM01BD is used for controlling analog actuators such as:

• Variable frequency drives (speed reference)

• Electropneumatic positioners (valve control)

• Chart recorders (process variable recording)

• Current-to-pressure converters (I/P transducers)

Common in HVAC, water treatment, small process control, and packaging machinery.

Troubleshooting and Diagnostics

If the module does not output current, check: external 24V supply present, correct data register values, DIP switch setting, load resistance not exceeded, and the POWER LED on. If output is inaccurate, recalibrate or check for ground loops. The module does not have wire break detection; open load will drive output to compliance voltage (approx 12V) but may saturate.

Environmental and Compliance

Operating temperature 0-55°C, storage -20-70°C, humidity 35-85% non-condensing. The module meets CE and UL standards. It is not isolated between channels but has isolation between PLC logic and field.

Conclusion

The Mitsubishi FXAOM01BD analog output module extends the FX PLC family with four channels of current control. Its simple programming, reliable performance, and compact size make it a practical choice for applications requiring analog signal generation.