Mitsubishi PLC Module D/A Converter Unit Q68DAVN

Mitsubishi Q68DAVN | MELSEC-Q 8-Channel ±10V Digital-to-Analog Output Module — 16-Bit / High Resolution / Short-Circuit Protected

8 Analogue Voltage Outputs — From Digital Values to Field Signals

The Q68DAVN provides eight independent ±10V DC analogue output channels for the Mitsubishi MELSEC-Q PLC platform. Each channel accepts a 16-bit signed binary digital value from the Q-series CPU and converts it to a proportional analogue voltage. This analogue voltage drives field devices that require a continuously variable voltage setpoint — servo amplifiers, proportional valve controllers, variable frequency drive speed references, and process control loops.

Two resolution modes extend the module's applicability across different precision requirements. Standard mode maps −4,096 to +4,095 digital counts across the ±10V output range — 12-bit effective output resolution. High resolution mode increases this to −12,288 to +12,287 or −16,384 to +16,383 depending on the configuration, delivering finer output voltage steps for precision control applications where standard resolution is insufficient.

The output short-circuit protection prevents damage to the module when an output is accidentally short-circuited to ground or another voltage — a failure mode that would otherwise destroy the output circuit. The protection circuit limits the output current, protecting the DAC and output stage while the fault is present. This protection does not replace proper field wiring practice but provides a safety margin during commissioning and wiring faults.

Key Specifications

Wiring Terminal Notes

The Q68DAVN uses crimp terminal connections. FG (frame ground) terminals accept: R1.25-3, 1.25-YS3, RAV1.25-3, or V1.25-YS3A crimp terminals. All other signal terminals accept R1.25-3 crimp terminals only — sleeved (insulated) crimp terminals cannot be used on signal terminals. This is a wiring specification constraint, not a recommendation: using the incorrect terminal type risks unreliable connections or physical non-compliance with the module's terminal strip.

EEPROM Write Endurance — A Parameter Management Consideration

The Q68DAVN stores channel parameters (output range settings, output enable configuration) in EEPROM with a maximum write endurance of 100,000 operations. This limit applies to the module's internal EEPROM, not to the analogue output values themselves. PLC programmes that continuously write module parameters (rather than writing once during commissioning) can exhaust this limit over extended operation. Design the programme to write parameters only when they change, not on every scan cycle.

FAQ

Q1: What is the difference between standard resolution mode and high resolution mode on the Q68DAVN?

In standard resolution mode, the digital-to-analogue conversion spans −4,096 to +4,095 counts across the ±10V output range — approximately 2.44mV per count. In high resolution mode, the same ±10V range is mapped to a wider digital count range (up to −16,384 to +16,383), producing finer voltage steps per count — approximately 0.61mV per count. Select high resolution mode for applications where fine output resolution matters, such as precision motion setpoints or tight process control loops.

Q2: What minimum load resistance does the Q68DAVN output require?

The output specification requires a minimum load resistance of 1kΩ. Connecting loads below 1kΩ may cause the output voltage to deviate from the commanded value or activate the short-circuit protection. High-impedance loads up to 1MΩ are supported — the output buffer can drive this range reliably. Confirm the input impedance of the connected device is within 1kΩ to 1MΩ before wiring.

Q3: Does the Q68DAVN provide current loop (4–20mA) output?

The Q68DAVN provides voltage output only (−10V to +10V DC). For current loop (4–20mA) analogue outputs on the MELSEC-Q platform, Mitsubishi offers dedicated current output DA modules. Confirm the output type required by the connected field device — a voltage DA module cannot substitute for a current loop module without additional signal conversion.

Q4: What happens if a Q68DAVN output is short-circuited to ground?

The short-circuit protection circuit limits the output current to protect the module's output stage. The output voltage collapses during the short, but the internal circuitry is not damaged. When the short circuit is removed, the output returns to the commanded value. The PLC programme may receive a module error signal indicating the short-circuit condition, depending on the diagnostic configuration. Always resolve the wiring fault before returning the module to normal operation.

Q5: How many Q68DAVN modules can be installed in one MELSEC-Q system?

The Q68DAVN installs in any available intelligent function module slot in a MELSEC-Q main base or extension base. The maximum number of modules is limited by the Q-series CPU's maximum intelligent module count (typically up to 64 intelligent modules per CPU, depending on the CPU type) and by the total base unit slot count. Each Q68DAVN occupies one slot. Confirm the specific CPU's intelligent module limit from the MELSEC-Q CPU user's manual before configuring a multi-module system.