CHAPTER 4 TESTINGPioneer™ Balances Service Manual 4-3 Ohaus Corporation www.ohaus.com4.4.1 Precision Test – Precision and Analytical Balances5. If the deviation for any set of readings (using the same mass placed on the center ofthe Pan) is greater than the tolerance listed in Table 4-1 or 4-2, the balance does notmeet the precision specification. Inspect and correct the following areas:5.1. 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.5.2. An error in the Off-Center Load Adjustment can affect the results of thePrecision Test. Inspect and correct if necessary. See the next section.4.4.2 Off-Center Load TestThe Off-Center Load Test is used to determine whether displayed weight values are affected bymoving the sample to different areas of the Pan. See Figure 4-2.Figure 4-2. Mass Placement Locationsfor Off-Center Load Test.1. Place a mass weighing half of the balance’s capacity in the center of the Pan.2. Press the On/Off button to return the reading to zero.3. Move the mass halfway to the rear of the Pan and note the reading.4. Move the mass halfway between the center and the left edge of the Pan and note thereading.5. Repeat this test for the right and front edges and note the readings.Note any differences in the displayed weight reading at all positions. See Tables 4-2and 4-3 for maximum allowable variance for each of the four positions.Mass Locations
