gauge: a standard dimension, quantity, or capacity

查一下字典，gauge含义如下，我认为这里是第4、5点的含义：
n.
1. a measuring instrument for measuring and indicating a quantity such as the thickness of wire or the amount of rain etc.
2. accepted or approved instance or example of a quantity or quality against which others are judged or measured or compared
3. the distance between the rails of a railway or between the wheels of a train
4. the thickness of wire
5. diameter of a tube or gun barrel


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Note added at 1 hr (2011-09-02 07:56:42 GMT)
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因为直径是基板的一个很重要的参数，我认为这里直径的含义可能性较大。

测量仪, 测量表为最普遍说法。

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Note added at 52 mins (2011-09-02 07:33:17 GMT)
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http://dcf0135.plastic.com.cn/sell/itemid-1965116.shtml

This is an example of the link between 基板产品 and 测量仪. Hope that clarifies! :)

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Note added at 1 hr (2011-09-02 08:05:18 GMT)
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Hmm would you be able to provide a longer text to confirm the context of the word "gauge"? Proposed answers by others below could also fit the bill depending on the context. Thanks!