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Dial Test Indicator Standard B7533-1990 (Extract from JIS/Japanese Industrial Standards)
No. Item Calibration method Diagram of calibration setup Tools for calibration
1 Wide-range (1) For an indicator of 0.01 mm graduation: Displace the contact point so as to move the pointer Dial test indicator
accuracy clockwise in increments of 0.1 mm with reference to the graduations from the zero point to Supporting stand
the end point of the measuring range while taking readings of the calibration tool at each
2 Adjacent error point and determine this accuracy from the error curve drawn by plotting the differences of Micrometer head or mea-
each "indicator reading - calibration tool reading". suring unit (graduation:
Micrometer head or 1 µm or less, instrumental
(2) For an indicator of 0.002 mm graduation: Displace the contact point so as to move the pointer length measuring unit error: within ±1 µm),
clockwise in increment of 0.02 mm with reference to the graduations from the zero point to supporting stand
the end point of the measuring range while taking readings of the calibration tool at each
3 Retrace error point and determine this accuracy from the error curve drawn by plotting the differences of
each "indicator reading - calibration tool reading". The instrumental error of the calibration
tool shall be compensated prior to this measurement.
After the completion of the wide-range accuracy measurement, reverse the contact point from
the last point of measurement while taking readings at the same scale graduations as for the
wide-range accuracy measurement and determine the retrace error from the error curve plotted.
Holding the dial test indicator with its stylus parallel with the top face of the measuring stage, Measuring stage Dial test indicator
a displace the contact point quickly and slowly five times at a desired position within the measuring
Supporting stand
range and determine the maximum difference in indication.
Measuring stage,
4 Repeatability Supporting stand, and
Gauge block of grade 1
Holding the stylus parallel to a gauge block placed on the measuring stage, move the gauge block as stipulated by JIS B7506
b to and fro and left to right under the contact point within the measuring range and determine the (Gauge block)
maximum difference in indication.
Gauge block Measuring stage
Holding an indicator by the case or stem, displace the contact point gradually and continuously Top pan type spring scale F
in the forward and backward directions respectively and take a reading of measuring force at the (graduation: 2 gf or less) or
5 Measuring force zero, middle and end points of the measuring range in each direction. Dial test indicator force gage (sensitivity:
• Performance Top pan type spring scale 0.02 N or less)
The maximum measuring force in the forward direction shall not exceed 0.5 N. The difference
between the maximum and minimum measuring forces in one direction shall not exceed 0.2 N
(20 gf). Note that the smallest possible measuring force is desirable for indicators.
Notes: There are no JIS standards applicable to models with a graduation of 0.001 mm. Therefore, referring to JIS B 7533-1990 for inspecting the wide-range accuracy and adjacent error, the accuracy is measured
by moving the contact point 0.01 mm clockwise from the start point of the measuring range to the end point with reference to the graduations.
Accuracy of indication
Permissible indication errors of dial test indicators are as per the table below.
Graduation (mm) Measuring range (mm) Wide range accuracy Adjacent error Repeatability Retrace error
0.01 0.5 5 5 3 3
0.002 0.8 8 2 1 4*1
10 2
1.0
3
0.2
0.28
*1: Applies to indicators with a stylus over 35 mm long.
Remarks: Values in the table above apply at 20°C.
Dial Test Indicators and the Cosine Effect
Always minimize the angle between movement directions during use.
The reading of any indicator will not represent an accurate measurement if its
measuring direction is misaligned with the intended direction of measurement
(cosine effect). Because the measuring direction of a dial test indicator is at right
angles to a line drawn through the contact point and the stylus pivot, this effect
can be minimized by setting the stylus to minimize angle (as shown in the
figures). If necessary, the dial reading can be compensated for the actual value by
using the table below to give the true value of a measurement.
True value = indicated value x compensation factor
Compensating for a non-zero angle
Angle Compensation factor Examples
If a 0.200 mm measurement is indicated on the dial at
10 0.98 various values of , the true values are:
20 0.94 For = 10, 0.200 mm x .98 = 0.196 mm
30 0.86 For = 20, 0.200 mm x .94 = 0.188 mm
40 0.76 For = 30, 0.200 mm x .86 = 0.172 mm
50 0.64
60 0.50
Note: A special contact point of involute form can be used to apply compensation automatically and allow
measurement to be performed without manual compensation for any angle from 0 to 30. (This type of
contact point is custom-made.)
F-78
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