OHAUS Pioneer PJX Series, Service Manual

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CHAPTER 4 - TESTING
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5. Add the ten readings and divide the total by 10 to find the Mean (average).
Mean = (Reading 1 + Reading 2 + Reading 3 + Reading 4 + Reading 5+ Reading 6 + Reading
7+ Reading 8 + Reading 9 + Reading 10) / 10
Mean =________
6. Calculate the Delta for each reading and record in the work sheet.
Delta = Reading – Mean
7. Calculate the Delta x Delta for each reading and record in worksheet.
8. Add the ten Delta x Delta values and divide by 9
9. Calculate the Standard Deviation by applying the square root of the result from step 8.
Standard Deviation
=___________
Note: If the balance does not meet specifications, check environmental conditions, ensure that
the balance is level, and try again. If it still does not meet specifications, perform a service
calibration, and try again. (See
Appendix B for Service Calibration)
Repeatability Test – Approved models
This test is a variation of the test above. Rather than determining acceptance based on the
standard deviation of the errors, MPE is used. The other variation is that 2 series of weighings are
used, one near 50% of max and the other near 100% of maximum capacity.
1. See Table 4-1 to determine the two weight values that must be used.
2. Record 10 reading using each weight value. Zero the balance between each reading if
necessary.
3. The difference between the results of the 10 readings must be less than the twice value of
the Maximum Permissible Error (MPE) for the load. The MPE for each load in grams is
given in Table 4-3.
TABLE 4-3 MPE - MAXIMUM PERMISSIBLE ERROR
MPE
For loads (m) in verified units (e)
Class I Class II
± 0.5 e 0
≤m≤50,000
0
≤m≤5000
± 1 e
50,000<m≤200,000 5000<m≤20,000
± 1.5 e 200,000<m
20,000<m≤1000,000
Maximum errors for balances in usage are twice the acceptable errors for initial verification.