Gravitational effects – Snap-On 5000-3 User Manual
Page 57
CALIBRATION
CHAPTER 5
Gravitational Effects
Correction Factors on Test Weights
Weights used in torque calibration are affected by their acceleration due to:
•
Altitude above or below sea level, and
•
Latitude on earth between the equator and the poles.
Test bars are not affected by these conditions. The accuracy of torque wrenches and testers does
not change due to changes in geographic location. Only when using weights must correction
factors be considered. After an analysis is made for a given location, it is often found that the
correction factor is insignificant.
Two methods of correction are provided. They are:
•
Correction Factor For Check Point Readings adjusts the calibration readings without changing
the applied weight.
•
Correction Factor For Weights adjusts the weight applied without changing check point readings.
For additional information refer to Gravitational Charts in this chapter.
Correction Factor for Check Point Readings
1.
Determine latitude and altitude. Obtain information from local geological survey office or library.
2.
Find the acceleration due to gravity for sea level from its chart.
3.
Subtract the free air correction for altitude from its chart.
4.
Divide the result calculated in step 3 by the standard gravitational factor 980.665cm/sec/sec.
5.
Multiply the check point in the calibration charts by the factor calculated in step 4 to obtain the
corrected check point readings while using the original weight.
Correction Factor for Weights
1.
Determine latitude and altitude. Obtain information from local geological survey office or library.
2.
Find the acceleration due to gravity for sea level from its chart.
3.
Subtract the free air correction for altitude from its chart.
4.
Divide the result, calculated in step 3, by the standard gravitational factor 980.665 cm/sec/sec.
5.
Calculate the reverse of the calculation in step 4 by dividing it into 1.
6.
Multiply the weight given for each checkpoint in the calibration charts by the inverse factor,
calculated in step 5, and use this corrected weight with the original check point readings.
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