OHAUS DISCOVERY BALANCE Service Manual

Contents

CHAPTER 4 TESTING4.2.2 Adjusting Off Center Load6. Adjust as shown until the reading is two to three times the the specifications inTable 1-2. Then re-test as shown in Section 4.2.1.6.1. Use small adjustments, no more than a quarter-turn at a time.6.2. As you get close to the tolerance you have to reduce the amount of the turn.7. Work front-to-back first, then side-to-side.8. This process is complete when all four edges of the Pan are within tolerancespecifications.4.2.3 Repeatability TestRepeatability is a word used in balance specifications meaning the Standard Deviation of a setof similar weight readings. To determine whether a balance meets the calculated StandardDeviation value in the Specification Table 1-2, perform the following test:1. Tare the balance. The reading on the display should be 0g.2. Select a mass weighing near the maximum capacity of the balance and place themass on the center of the Pan. Observe and record the reading.3. Remove the mass. Reading should return to 0g ± 1 count.4. Repeat the test for ten readings. If the standard deviation of the readings is withinthe specifications in Table 1-2 (Discovery Balance Model Specifications, page 1-3),the balance passes the Repeatability Test.4.2.2 RemediationIf the deviation for any set of readings (using the same mass placed on the center of the Pan) isgreater than the specifications in Table 1-2, the balance does not meet the Repeatability Testspecification. Inspect and correct the following areas:1. Check for mechanical obstructions. Any foreign object touching any part of themoving Pan can cause a balance to fail the Repeatability Test specification. Inspectand correct if necessary.2. An error in the Off-Center Load Test can affect the results of the Repeatability Test.Inspect and correct if necessary. See Section 4.2.3 - Off-Center Load Test.3. Foreign material or debris located in the balance between the Pan, and the DraftShield Bottom can cause the balance to fail the test.4. Environmental influences such as vibrations, drafts or a non-level surface can alsocause failures.Ohaus Corporation www.ohaus.com 4-4 Discovery Balance Service Manual