# A22 Auto Zero Offset
### Definition
Recalibrates the flowmeter zero point, resetting the output to zero. Recommended for ultra-low flow measurement to correct zero-flow offset errors and improve measurement accuracy.
Starts only after pressing **Start** and automatically updates the **Z04 (Auto Zero Flow)** settings.
It is recommended to perform **Z04** when measuring ultra-low flow (below 10% of the maximum range), as small zero-point offsets can cause significant errors at low flow.
**Example:** With a zero-point offset of 0.2 L/min:
* At an actual flow of 100 L/min, the error is approximately 0.2%.
* At an actual flow of 0.5 L/min, the error can reach nearly 40%.
{% hint style="info" %}
Currently, **A22** does not support Modbus read/write command operation.
{% endhint %}
### Notes
1. Perform **A22** when the pipeline is **fully filled with liquid and the liquid is completely stationary**. Performing Z04 when the pipe is not full may cause flow measurement errors and unstable readings; if this occurs, repeat Z04 under full-pipe conditions.
2. **Repeat this procedure after every reinstallation or when changing pipe size or material.**
3. The **A22** function is equivalent to **Z04**; users can choose either.\
(Z-series parameters are designed for quick setup, consolidating multiple essential settings to streamline installation.)
### Operation Procedure
Button Functions (Click to Expand)
The main unit has **four buttons**. The **bottom line (Line 3)** of the LCD displays the current function of each button. Under normal operation, the button functions are as follows:
* **Blue Button -** Leftmost button: Return, exit, or save settings.
Gray Arrow Buttons:
* **Left Gray Button:** Page up, increase value, or select item
* **Right Gray Button:** Page down, decrease value, or select item
* **Orange Button:** 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 %}
```
A22 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 start Automatic Zero Offset
• Device shows “Start auto Z04” when automatic zero-flow begins.
• After ~30 seconds, it displays “Set zero offset to ____”.
• Then it returns to Z04 Auto Zero Flow, indicating completion.
```
