OHAUS Valor 1000W Service Manual

CHAPTER 4 TESTINGOhaus Corporation www.ohaus.com 4-2 Valor™ 1000W Series Service Manual4.4 Performance TestsAccurate performance of the Valor 1000W scales is determined by a series of four performancetests. The displayed readings are compared with the tolerances listed for each test in Table1-2. Tolerance values are expressed in counts. A one-count difference is shown in the last digiton the scale display.NOTE:The following performance tests are used to evaluate scale operation before andafter repairs. The scale must meet the requirements specified in each test aswell as the other specifications listed in Table 1-1. Before proceeding with thefollowing tests, the scale should be calibrated. (See Appendix A and B.)4.4.1 Precision TestThe Precision Test measures the Standard Deviation of a set of similar weight readings, whichshould match the specification for each model, listed in Table 1-1.1. Power on the balance. The reading on the display should be 0g.2. Select a mass weighing near the maximum capacity of the balance, and place it onthe center of the Pan. Observe and record the reading.3. Remove the mass. The reading should return to 0g ±1 count.4. Repeat this test three times. The reading should be within ±1 count of the readingrecorded. 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 ofthe Pan) is greater than ±1 d, 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 themoving assemblies will cause a balance to fail the Precision Test. Inspect andcorrect as necessary.– If the scale does not meet specifications, move it to a suitable location, ensurethat it is level, and try again. If it still does not meet specifications, perform aservice calibration, and try again. (See Appendix B for Service Calibration.)