CHAPTER 4 TESTINGPioneer™ Balances Service Manual 4-9 Ohaus Corporation www.ohaus.com4.4.7 Linearity TestThis test is used to determine the linearity of the unit throughout its operating range.The displayed readings are compared with the tolerances listed in the specifications for theinstrument. (See Specifications Tables, Chapter 1.) Tolerance values are expressed in counts.A one-count change is equal to the last digit shown on the scale display.The masses used to perform this test can be utility masses.NOTE:The balance must be warmed up prior to performing these tests, and must pass thePrecision, Off-Center Load Test and Repeatability Tests, and be calibrated beforethe Linearity Test may be performed.The Reference Mass should be approximately 1/8 of the full capacity of the balance.USE THE SAME REFERENCE MASS THROUGHOUT THE LINEARITY TEST.1. Press ZERO to zero the display.2. Place the Reference Mass in the center of the pan and record the exact value (alldecimal places) displayed.3. Remove the Reference Mass and verify that the display returns to zero. If it does not,disregard the reading, press ZERO to re-zero the display, and repeat the process.4. Place a mass equal to ¼ of the full scale capacity on the platform and press ZERO.5. Add the Reference Mass to the center of the platform and record the value.6. Remove the Reference Mass and verify that the display returns to zero. If it does not,disregard the reading, press ZERO to re-zero the display, and repeat the process.7. Place a mass equal to ½ of the full-scale capacity on the platform and press ZERO.8. Add the Reference Mass to the center of the platform and record the value.9. Remove the Reference Mass and verify that the display returns to zero. If it does not,disregard the reading, press ZERO to re-zero the display, and repeat the process.10. Place a mass equal to ¾ of the full scale capacity on the platform and press ZERO.11. Add the Reference Mass to the center of the platform and record the value.12. Remove the Reference Mass and verify that the display returns to zero. If it does not,disregard the reading, press ZERO to re-zero the display, and repeat the process.13. Calculate the weight differences between the readings as shown below.14. The maximum difference should be less than or equal to the Linearity specificationfor the instrument. (See Specification Tables, Chapter 1.)
