Mitsubishi FX5U PID Instruction Guide

Mitsubishi FX5U PID instruction setup explained with full parameter configuration, auto-tuning, ladder logic, and error code guide using GX Works3.

💡 Related: If you’re looking for a quick overview of the FX5U’s built-in PID function, which allows configuration directly through parameters (no programming required), check out our separate post: Built-in PID Function of FX5U – Overview & Setup Guide.

Mitsubishi FX5U PID Instruction Contains

Before diving into ladder logic or programming, let’s break down the key elements of a PID (Proportional‑Integral‑Derivative) control setup:(Download Link For Ladder Logic at the END)

• PV – Process Variable
  The input reading (e.g., a sensor’s analog temperature value).
• SP – Setpoint
  Your desired target value.
• MV – Manipulated Variable
  The control output (e.g., analog signal to a heater or valve).
• Kₚ (Proportional Gain)
  Determines the output’s immediate response to error (SP – PV).
• Kᵢ (Integral Gain)
  Corrects accumulated past error over time.
• K𝒹 (Derivative Gain)
  Predicts and dampens future error based on PV’s rate of change.
• Sample Time
  How often the PID loop recalculates (PLC scan or update interval).
• Upper/Lower MV Limits
  Prevents overdriving actuators by bounding the output.

In Mitsubishi’s FX5U series, the PID instruction involves four elements:

• S1 – Set Value (SP)
• S2 – Present Value (PV)
• S3 – Parameter block (up to 29 words)
• D – Output register where MV is stored

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Step‑by‑Step: Setting It Up in GX Works3 for FX5U

1. Open GX Works3
2. Create a New Project targeting the FX5U CPU
3. Go to the Navigation Window → Global Label section
4. Define labels such as:
   • Set_Value (S1)
   • Present_Value (S2)
   • PID_Parameters (S3)
   • Output_MV (D)
5. Insert the PID instruction into your ladder or structured program.

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Configuring the PID Parameter Block

Create PID_Parameters as an array of 29 words, starting at, for example, D0 (covers D0–D28). Here’s how to set key elements:

• D0 – Sampling Time: e.g., 500 ms
• D1 – Operation Settings (bit flags):
  • b0 (D1.0) = 1 → Backward action (heating mode)
  • b5 (D1.5) = 1 → Enable upper/lower MV limits
  • b7 (D1.7) = 1 → Enable overshoot suppression
• D2 – Input filter constant (if needed)
• D3 – Proportional gain (KP): e.g., 3000
• D4 – Integral time (TI): e.g., 2000 (×100 ms units)
• D5 – Differential gain (KD): adjust based on smoothness needs
• D6 – Differential time (TD): e.g., 5000 (×10 ms units)

For MV limiting:

• D22 – MV upper limit: e.g., 2000
• D23 – MV lower limit: e.g., 0 (or another safe min)

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You can either manually tune KP, TI, and TD or utilize Mitsubishi’s Auto‑Tuning feature by setting the appropriate bits in D1 and adding required parameters (like hysteresis, wait times, or limits) starting at D25—depending on your tuning strategy.

Finally, your MV is output via another designated register, typically labelled Output_MV.

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Operation Bit b8 Behavior

Status	Description
ON	Twenty-eight devices are occupied from the device specified in (s3).
OFF	Twenty-five devices are occupied from the device specified in (s3).

Note: (1): Latched data register number is specified to (d).

PID Instruction Error Codes

Error Code	System Register	Description
2820H	SD0 / SD8067	Invalid connection number in (s1). Must be between 1 and 8.
2822H	SD0 / SD8067	Device number in (s2), (d), or (n) is out of range.
3500H	SD0 / SD8067	Sampling time (TS) is less than or equal to 0.
3502H	SD0 / SD8067	Invalid input filter constant (α < 0 or α ≥ 100).
3503H	SD0 / SD8067	Invalid proportional gain (KP ≤ 0).
3504H	SD0 / SD8067	Invalid integral time (TI < 0).
3505H	SD0 / SD8067	Invalid derivative gain (KD < 0 or KD ≥ 100).
3506H	SD0 / SD8067	Invalid derivative time (TD < 0).
350AH	SD0 / SD8067	Sampling time (TS) is less than or equal to the scan time.
350CH	SD0 / SD8067	Measured value variation exceeds limit (∆PV < -32768 or > 32767).
350DH	SD0 / SD8067	Deviation exceeds limit (EV out of range).
350EH	SD0 / SD8067	Integral result exceeds range (-32768 to 32767).
350FH	SD0 / SD8067	Excessive derivative value due to derivative gain (KD).
3510H	SD0 / SD8067	Derivative result exceeds range (-32768 to 32767).
3511H	SD0 / SD8067	PID operation result exceeds allowable range.
3512H	SD0 / SD8067	Upper MV limit is lower than the lower MV limit.
3513H	SD0 / SD8067	Invalid alarm setting (set value < 0).
3514H	SD0 / SD8067	Step response method: Improper auto-tuning result.
3515H	SD0 / SD8067	Step response method: Auto-tuning direction mismatch.
3516H	SD0 / SD8067	Step response method: Improper auto-tuning operation.
3517H	SD0 / SD8067	Limit cycle method: Upper limit (ULV) ≤ lower limit (LLV).
3518H	SD0 / SD8067	Limit cycle method: Hysteresis (SHPV) set below 0.
3519H	SD0 / SD8067	Limit cycle method: Auto-tuning transfer status error.
351AH	SD0 / SD8067	Limit cycle method: Excessive auto-tuning time (τon > τ or τon/τ < 0).

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