Repeatability Test - OHAUS NV212 Service Manual

CHAPTER 4 TESTING
4. Repeat this test three times. The readings should be within tolerances. If so, the balance
passes the Precision Test.
5. If the deviation for any set of readings (using the same mass placed on the center of the Pan)
is greater than the tolerance listed in Table 4-2, the balance does not meet the precision
specification. Inspect and correct the following areas:
–
Check for mechanical obstructions. Any foreign object touching any part of the moving
assemblies will cause a balance to fail the Precision Test. Inspect and correct as
necessary.
–
If the scale 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, perform a service calibration, and
try again. (See Appendix B for Service Calibration.)
–
If the scale does not pass this test, the Load Cell may need to be replaced.

4.5.2 Repeatability Test

The repeatability specification is defined as the Standard Deviation value derived from a set of
weight readings. This test uses more weight data than the Precision Test and will allow for
occasional weight deviations due to testing variations.
Requirements:
– To perform this test a single mass must be used for all readings.
– The test mass should be approximately ½ of the capacity of the instrument.
– Wear gloves when handling the mass.
Set Up:
Before starting a repeatability test, set up the instrument as follows.
Enter the service menu (see appendix B.1) and adjust and record the following settings:
A. Set the Stability setting to 0.5d (its lowest setting).
B. Set the Filter level to L2 (close to mid range).
C. Set the AZT (Auto Zero Tracking) to .5d (its lowest setting). Do not turn it off.
Enter the User Menu (see 1.8.1) and adjust the following settings:
A. Set the instrument to display the same units as the performance specifications.
(Usually kg, g, or mg)
Record Settings:
Stability Setting =
Filter Level Setting =
Auto Zero Tracking Setting =
Displayed Units =
Mass Used =
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28 Navigator Series Service Manual