CHAPTER 4 TESTING
Adven
turer ™ Balances Service Manual 51 Ohaus Corporation www.ohaus.com
Table 4-3. Tolerances
– Analytical Models
Performance Test
TOLERANCE
– COUNTS
AX124
AX224
AX324
Precision (counts)
±1
±1
±1
Off Center Load (mg)
±0.4
±0.4
±0.4
Repeatability (mg)
±0.1
±0.1
±0.1
Linearity (mg)
±0.2
±0.2
±0.2
NOTE:
The following performance tests are used to evaluate balance operation before and
after repairs. The balance must meet the requirements specified in each test as
well as the specifications listed in Tables 1-1
– 1-4.
Before proceeding with the following tests, the balance should be warmed up for at
least five minutes, and calibrated. (See Appendix A.)
4.4.1 Precision Test
– Precision & Analytical Balances
The Precision Test measures the Standard Deviation of a set of similar weight readings, which
should match the specification for each model, listed in Tolerance Tables 4-1 and 4-2.
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 it on the
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 reading
recorded. 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 4-1 or 4-2, the balance does not
meet the precision specification. Inspect and correct the following areas:
5.1. 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.
5.2. An error in the Off-Center Load Adjustment can affect the results of the Precision
Test. Inspect and correct if necessary. See the next section.
