# 1.5 量測原理

![supersonic-flowmeter-principle](/files/-Lk23WEgWNIZxyYFzN9M)

流體流速為V，聲波在流體中傳遞速度為c，內管徑為D，內管截面為A。當超聲波在水中於探頭A與探頭B之間傳遞時，順流與逆流的方向會產生一個與流速成正比的時間差。

![](/files/-LkbbPm3KWt01yX2hCWa)

流量為Q= v  A， 若內管截面是一個圓，則Q= v＊(d² π/ 4)，故管徑尺寸與流量準確度有很大關係。

##


---

# Agent Instructions: 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-chinese-v2/1.-chan-pin-jie-shao-1/1.5-liang-ce-yuan-li.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.