> For the complete documentation index, see [llms.txt](https://docs.lorric.com/qr/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.lorric.com/qr/fu-tx310-ultrasonic-flowmeter-manual-en-v2/1-product-introduction/1.5-measuring-principle.md).

# 1.5 Measuring principle

![](/files/-LrDMY4NUUQIR7lq9vl5)

Fluid flow rate = V​; sound wave velocity during transmission through the fluid = c​; interior pipe diameter = D,​ interior pipe cross section = A​. When ultrasonic waves are transmitted through water between probes A​ and B​, the forward and reverse flow directions produce a time differential that is proportional to the flow rate.

![](/files/-LrDMjz4SU7oPneYwB9t)

Flow rate is Q = v \* A. If the interior pipe cross section is a circle, then Q= v＊(d² π/ 4). Therefore, the size of the pipe diameter and the flow accuracy have a great relationship.


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.lorric.com/qr/fu-tx310-ultrasonic-flowmeter-manual-en-v2/1-product-introduction/1.5-measuring-principle.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.