Mitsubishi Module A1S68DAI New and Original

Mitsubishi A1S68DAI | MELSEC-A Slim Series 8-Channel 4–20mA Analog Current Output — A1S Rack / PLC Expansion I/O 

8-Channel Analog Current Output in a Single A1S Rack Slot

The A1S68DAI provides eight 4–20mA current output channels from one A1S rack slot. In a MELSEC-A control system managing multiple analogue field devices — valve positioners, speed setpoints to variable frequency drives, remote indicators, signal converters — eight channels from one module concentrates the analogue output section of the panel without spreading single- or two-channel output modules across multiple rack positions.

The 4–20mA current loop is the dominant analogue signal standard in process control and industrial automation. Current signals carry reliably over longer cable runs than voltage signals because the current magnitude is independent of cable resistance up to the loop's compliance voltage limit. For field devices mounted at distances from the control cabinet — remote valve positioners, level transmitters, or speed references on distributed drives — 4–20mA current output is the correct signal type.

The "DAI" suffix in the Mitsubishi naming convention designates an analog output module (D = digital/analog converter, A = analog, I = current). This distinguishes it clearly from the A1S68ADN or similar modules which are analog inputs. The output vs input distinction is fundamental — an output module generates the signal; an input module reads it. Specifying the wrong direction means a completely non-functional replacement regardless of channel count.

Key Specifications

A1S68DAI in the MELSEC-A Analogue Module Family

Within the A1S slim series analogue module range:

• A1S68ADN: 8-channel analog voltage/current input (input, not output)
• A1S62DAV: 2-channel analog voltage output
• A1S62DAI: 2-channel analog current output
• A1S68DAI: 8-channel analog current output (this module)

The A1S68DAI provides the highest channel density for current output in the A1S slim series — four times the channel count of the 2-channel A1S62DAI in the same rack space ratio. For systems driving multiple current-loop field devices, the 8-channel density minimises the number of rack slots consumed by analogue outputs.

Application Scenarios

Multi-axis drive speed references: Eight VFDs receiving 4–20mA speed setpoints from the MELSEC-A controller. One A1S68DAI slot handles all eight drive references, keeping the analogue output wiring concentrated in one module location.

Process valve positioners: Eight analogue control valves (flow control, pressure control, level control) each receiving their position setpoint over 4–20mA. The 4–20mA current loop's distance tolerance allows valve positioners at remote field locations to receive accurate setpoints.

Legacy system spare: MELSEC-A systems using A1S68DAI for multi-channel analogue output remain in service in process and factory automation. When an A1S68DAI fails, a direct replacement restores the analogue output section without address or wiring changes.

FAQ

Q1: Is the A1S68DAI an analog output or analog input module?

It is an analog current output module — it generates 4–20mA signals driven by values written to it by the MELSEC-A CPU programme. It does not read field signals. The "DAI" suffix designates a D-to-A (digital-to-analog) converter with current output. Analog input modules in the A1S family carry different designations (ADN, ADI suffixes).

Q2: Is the A1S68DAI compatible with full-size A-series racks, or only A1S slim racks?

The A1S designation indicates the slim form factor — this module fits A1S slim-series racks only. Full-size A-series racks (A2US, A3U, etc.) use physically larger modules with different slot dimensions. The full-size equivalent is the A68DAI. Confirm the rack type — A1S slim or full-size A — from the installed hardware before ordering.

Q3: What does the MELSEC-A programme need to drive the A1S68DAI outputs?

The MELSEC-A CPU writes output values to the module's buffer memory (BFM — Buffer Memory) using the TO instruction. The A1S68DAI converts the digital value in each channel's BFM register to the corresponding 4–20mA current on the output terminal. Channel enable, output range, and operating mode are also configured through BFM writes during programme initialisation.

Q4: What programming software programmes the MELSEC-A CPU that controls the A1S68DAI?

GX Developer — Mitsubishi's programming environment for the MELSEC-A series. GX Works2 provides limited A-series support. Programming connects to the A-series CPU's RS-422 port using a compatible USB adapter. GX Works3 does not support MELSEC-A hardware.

Q5: Where is the A1S68DAI sourced today?

Through the MELSEC-A legacy aftermarket — specialist Mitsubishi A-series parts dealers, industrial surplus suppliers, and legacy automation distributors. The A-series is long discontinued; standard Mitsubishi distribution does not stock A1S68DAI. Confirm the A1S slim format, 8-channel 4–20mA current output specification, and test the module in an A1S rack before committing to critical production use.