Testing for Excessive Zero Drift vs. Temperature

If a system is experiencing small zero shifts over temperature that exceed the accepted normal limits shown in the following table (for example, if the temp changes by 10 C, the maximum allowed shift on a 2 1/8 system is 34kg), a test must be conducted to determine which of the bars is causing the excessive zero shift. NOTE: IF THE SYSTEM SHIFTS LESS THAN THE AMOUNT SHOWN IN THE TABLE, THERE IS NO NEED TO RUN THE TEST. THE SYSTEM IS FUNCTIONING PROPERLY AND SOME SHIFT IS TO BE EXPECTED.

The test can be accomplished in one night. When the customer is done with the system for the evening, and won’t be using it (not adding or subtracting any weight from it and not moving it) until morning, follow the steps below. DO NOT ZERO THE INDICATOR AT ANY POINT.

1. Label the cables near the connector or j-box in some manner so that they can be identified (A, B, C, D or 1, 2, 3, 4).
2. Record the outside temperature, if possible.
3. With the indicator turned on, record the number on the indicator.
4. Disconnect all bars except the one labeled A.
5. Record the number from the display. Do not be concerned at this number, as with only one bar connected, this number by itself is somewhat meaningless.
6. Disconnect bar A, and connect bar B. (It does not matter which port)
7. Record the number from the display.
8. Disconnect bar B, and connect bar C.
9. Record the number from the display.
10. Disconnect bar C, and connect bar D.
11. Record the number from the display.
12. Connect all bars, and wait until morning. The indicator can be left on or turned off.
13. In the morning, repeat steps 2 through 11.

Subtract the Evening reading from the Morning reading. The difference should be no more than the values listed in the table above (the values are valid for a full system and also for data taken with only one bar connected to a 4-bar system). If the value for any bar is larger than the specified value in the table above for the listed temperature change, that bar should be replaced.