CDI Torque MULTITEST Government - Manual (Page 78)

5-14
Calibration
Free Air Correction for Altitude
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 980.665 cm/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 inverse of the calculation in step 4 by
dividing it into 1.
6. Multiply the weight given for each check point in the
calibration charts by the inverse factor, calculated in step
5, and use this corrected weight with the original check
point readings.
Altitude Correction
Meters cm/sec2
200 -.0617
300 -.0926
400 -.1234
500 -.1543
600 -.1852
700 -.2160
800 -.2469
900 -.2777