The QD62 is a 2-channel high-speed counter module from Mitsubishi Electric for the MELSEC-Q series, capable of counting input pulse signals at frequencies up to 200 kHz per channel for precise position measurement, speed detection, and quantity counting applications. In stock at Atlantech Drives. Request your quote within 24–48 hours with worldwide shipping and 12-month warranty.
What Is the Mitsubishi QD62?
The QD62 is an intelligent function module that accepts incremental encoder pulse signals and high-frequency pulse trains independently of the MELSEC-Q CPU scan cycle, storing counts in internal 32-bit counters that the CPU reads via buffer memory. Because counting is performed at the module level rather than in ladder logic, the QD62 reliably captures pulses at rates far exceeding what the CPU’s built-in input refresh could handle. Each of the 2 channels supports single-phase, dual-phase (2-phase 1x/2x/4x multiplication), and CW/CCW pulse input modes, making it compatible with a wide range of incremental encoders and pulse-output sensors. Coincidence output signals (comparison outputs) are available per channel for hardware-level position comparison without CPU intervention, enabling sub-millisecond response to position events.
Key Technical Specifications
- Number of counter channels: 2
- Maximum counting frequency: 200 kHz per channel
- Counter data length: 32-bit signed (–2,147,483,648 to +2,147,483,647)
- Count modes: Single-phase (1-count), dual-phase (1x/2x/4x multiplication), CW/CCW
- Input signal voltage: 5 V DC or 12/24 V DC (selectable per channel)
- Input signal type: Voltage input (open collector or line driver compatible)
- Coincidence output: 1 point per channel (transistor, NPN open collector)
- Preset function: Yes (load preset value to counter via buffer memory)
- Latch counter function: Yes (capture counter value on external signal)
- Number of occupied I/O points: 32
- Power consumption: 5 V DC, 0.50 A; 24 V DC, 0.07 A (external)
- Operating temperature: 0 to 55°C
Typical Industrial Applications
The QD62 is deployed wherever reliable high-frequency pulse counting is required independently of PLC scan time. Representative applications include: rotary encoder position feedback for linear axis positioning on machine tools, where the 32-bit counter range accommodates travel distances of several metres at sub-micron encoder resolution without counter overflow; web tension control systems using encoder-based speed measurement on feed and take-up rolls, where dual-phase 4x multiplication provides 4× the resolution of the raw encoder output; flow metering systems using pulse-output turbine or oval gear flowmeters, where the QD62’s latch counter function captures totalised flow volume at precise time intervals; and conveyor length measurement using wheel encoders for cut-to-length and batch counting applications. The coincidence output function is particularly valuable in registration and synchronisation applications where a hardware output must fire at an exact count value — the QD62 generates the coincidence signal within microseconds of the count reaching the setpoint, compared to the 1–10 ms latency of a software comparison in ladder logic.
Installation Advice
When connecting incremental encoders to the QD62, use shielded twisted-pair cable for all encoder signal lines and connect the shield to the module’s shield terminal at one end only. For 5 V line driver (RS-422 differential) encoders, connect the A+/A−, B+/B− differential pairs to the corresponding QD62 input terminals — differential input significantly improves noise immunity over single-ended connections and is strongly recommended for encoder cable runs exceeding 5 m. Select the input voltage range (5 V or 12/24 V) in GX Works2 module parameters to match the encoder output voltage — incorrect voltage range selection is the most common cause of missed counts or erratic counter behaviour at commissioning. Set the count mode (single-phase, dual-phase 1x/2x/4x, CW/CCW) to match the encoder type and the resolution required by the application — dual-phase 4x multiplication quadruples effective resolution but requires both A and B phase signals to be connected. Keep encoder cable runs physically separated from motor power cables and inverter output cables by at least 200 mm to prevent EMI-induced false counts.
Frequently Asked Questions
Q: What is the difference between QD62 and QD62E?
A: The QD62E is an enhanced variant that adds an external preset input and extended coincidence output functions compared to the standard QD62. The QD62E also supports a wider range of input signal types. For new designs requiring external hardware preset triggering, specify the QD62E. The QD62 is suitable for applications where preset is software-initiated via buffer memory only.
Q: Can the QD62 be used with absolute encoders?
A: No. The QD62 accepts incremental pulse signals only — it has no serial communication interface for SSI, BiSS, or EnDat absolute encoder protocols. For absolute encoder interfaces, Mitsubishi offers dedicated absolute encoder input modules or the use of servo amplifier encoder interfaces via the MELSEC-Q motion CPU.
Q: How does the CPU read the QD62 counter value?
A: The current counter value is stored in the QD62 buffer memory (BFM #2 and #3 for the 32-bit value of channel 1). The CPU reads it using the FROM instruction in GX Works2 ladder, or via auto-refresh assignment in the intelligent function module parameters, which automatically transfers the counter value to a specified CPU data register at every scan without explicit FROM instructions in the ladder program.
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