# Z04 Auto Zero Offset
### Definition
This function recalibrates the flow meter zero point (0 flow) by resetting the output to zero.\
For ultra-low flow measurements, zero calibration helps correct zero-offset errors and improves accuracy.
The function starts after pressing **Start** and automatically updates **A22 (Auto Zero Offset)** upon completion.
**Recommendation**\
It is strongly recommended to execute **Z04** when measuring flow rates below **10% of full scale**, as small zero offsets can cause significant errors at low flow.
**Example**
* Zero offset: **0.2 L/min**
* Actual flow **100 L/min** → error ≈ **0.2%**
* Actual flow **0.5 L/min** → error ≈ **40%**
{% hint style="info" %}
Parameter Z is not supported for Modbus read/write operations in the current version.
{% endhint %}
### Notes
1. This step **must be performed when the pipe is completely full and the liquid is fully stationary**. Running **Z04** under non-full or moving-liquid conditions may cause **flow detection errors and unstable readings**. If this occurs, repeat **Z04** under full-pipe conditions.
2. **Re-execute this function whenever the device is reinstalled, or when the pipe size or material changes and the flow reading is below 10% of the maximum range.**
3. **A22** has the same function as **Z04**; users may run either one.
(**Z-series parameters** are for **quick setup during installation**, combining multiple required settings for faster configuration.)
### Operation Procedure
Button Functions(Click to Expand)
When the main screen is displayed in **green backlight**, the four buttons function as follows:
* **Blue Button (leftmost):** Return, exit, or save settings.
* Gray Direction Buttons:
* **Left Gray:** Previous Page, decrease value, or select item
* **Right Gray:** Next Page, increase value, or select item
* **Orange Button (rightmost):** Rightmost button: Enter settings, edit, or confirm selection
{% hint style="danger" %}
**Do not hold buttons for extended periods to avoid damage.**
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{% hint style="info" %}
Button functions may change depending on the operation context to improve usability or prevent accidental presses.
{% endhint %}
```
Z04 Automatic Zero Offset Setting Steps
• From the main screen (green backlight),
press Orange Button (Setup) to enter settings (orange backlight).
• Use Gray Arrow Buttons to select Z. Easy Setup , press Orange Button (Enter).
• Use Gray Arrow Buttons to select Z04. Auto Zero Offset , press Orange Button (Enter).
• Press Right Gray Button to start Auto Zero Offset.
• Device shows “Start auto Zero Offset” when automatic zero-flow begins.
• After ~30 seconds, it displays “Set zero offset to ____”.
• Then it returns to Z04 Auto Zero Flow, indicating completion.
```
**Orange Button (rightmost):** Rightmost button: Enter settings, edit, or confirm selection
{% hint style="danger" %}
**Do not hold buttons for extended periods to avoid damage.**
{% endhint %}
{% hint style="info" %}
Button functions may change depending on the operation context to improve usability or prevent accidental presses.
{% endhint %}
