CHAPTER 4 – FINAL TESTING
MB90 MB120 Series Service Manual
57
Ohaus Corporation www.ohaus.com
4.4.3 Repeatability Test
8. Calculate the Delta for each reading and record it in the work sheet.
Delta = Reading – Mean
9. Calculate the Delta x Delta for each reading and record in worksheet.
10. Add the ten Delta x Delta values and divide by 9
11.
Calculate the Standard Deviation by applying the square root of the result from step 8.
Standard Deviation
=___________
Note:
If the Analyzer does not meet specifications, move it to a suitable location, ensure
that it is level, and try again. If it still does not meet specifications, calibrate the unit and
try again. (See Appendix A for Calibration.)
4.4.4 Linearity Test
This test is used to determine the linearity of the unit throughout its operating range.
The masses used to perform this test can be utility masses.
Note:
Due to the use of relative weighing and limited use of the weighing range in moisture
analysis, linearity performance is not critical.
Linearity Test Mass
– Reference Mass: 10g
PERFORMANCE
TEST
MB90
MB120
Load 1
10g
10g
Load 2
40g
40g
Load 3
80g
100g
NOTE:
All masses are nominal values. Be certain to use the same reference mass throughout
the procedure.
1. Place the reference mass on the pan, record the weight and remove.
2. Place Load 1 on the pan and press TARE.
3. Place the test mass on the pan, record the weight and remove.
4. Place Load 2 on the pan and press TARE.
5. Place the test mass on the pan, record the weight and remove.
6. Place Load 3 on the pan and press TARE.
7. Place the test mass on the pan and record the weight.
8. The difference in the weights of the test mass should be within the Linearity
tolerance in Table 1-1. If not, calibrate (see Appendix A.1) and repeat the test.
9. If the unit remains out of tolerance, the Load Cell may need to be replaced.
