About Indicators

Indicators: vary in size and type. The two main types are lever and plunger/probe. They can be mechanical with dial and pointer readout, or electronic with digital readout. The most common indicator used by industries is the Plunger type ANSI/AGD Group 2. This is the type that Check-It-Gauge uses.

Mounting: Check-It-Gauge takes advantage of the 3/8" diameter mounting stem of the ADG Group 2 indicators.

Points/tips: The thread standard for an ADG style indicator is #4-48. Tips normally interchange between most brands of indicators.

Accuracy: The American Gage Design(AGD) standards specify that dial indicators be accurate to within +/- one graduation in the first 2 1/2 revolutions of the dial. Most manufactures exceed this specification. You should check with the individual indicator manufactures for their accuracy specifications.

Range and Graduations: For most applications, Check-It-Gauge paired with 1" travel indicator works best . Dial Graduations for this type of indicator generally are .0010" or .0005".

Dial Indicator Advantages: The use of a dial indicator with Check-It-Gauge has the advantage of displaying the changing variation of a surface more visually. It is also easier to preset the gauge to a given number. Also, they have no batteries that need to be replaced and are more economical to purchase.

Digital Indicator Advantages: The use of a digital indicator with Check-It-Gauge provides for ease of readings while being more definitive. This and its ability to output data make the digital indicator the best choice for some applications. The option to switch between inch and metric is also another important feature. When used with Check-It-Gauge, the ability to zero out at a reference point and take measurements above and below that point is of benefit. Some models now come with an analog scale to help visualize surface variance.

Enhancing Accuracy: To verify an indicator's reading, a comparative method of measurement can be done by using gauge blocks stacked to the correct height and then compare the numbers read on the indicator.

Errors: Plunger type indicators with long travels can have small errors due to gear train or manufacturing flaws. The higher the quality of indictor used, the better the accuracy. Another error source can be amplified from the use of long extensions with long travels. This is called cosine error and is due to axial misalignment of tip to the body mounting. The method of gauge block stacking as described above can help to verify readings.

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