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Frequently Asked Questions
Leak Tester and Pipette Accuracy Testers

 

Question

Leak Tester


 

Pipette Accuracy Testers


 

 

Answer

Leak Tester

Q1.   Is the pressure display of the leak tester accurate?        Top

  • Since the leak tester was developed as a pipette inspection tool, the pressure display is output for reference.*1  Since leaks are detected by changes in pressure, the absolute accuracy of the pressure is not important for judgment. If a pressure inspection record or traceability diagram is required, one can be published for a fee.
    *1 Decompression: -20 kPa±20% (mentioned in the product specifications) is guaranteed as accurate.

Q2.   What is the validity of the pressure setting (decompression: -20.0 kPa) and leak detection conditions (leak volume: 1.0 kPa, detection time: 3 seconds)?        Top

  • The values have been determined from past results of pipette leak testing. Specifically, it has been determined that the pressure and detection conditions are sufficient to detect leakage and do not damage pipettes from 2 to 10,000 µL.
    If a test is failed very close to the limit of the leak detection conditions, the pipette might have a minute leak or temperature changes after adiabatic expansion of the equipment may have caused a pressure change. In such cases, use a pipette accuracy tester to check if the output volume is correct and then judge whether the pipette is acceptable or not.

 

Pipette Accuracy Testers

Q1.   What are the merits of using a pipette accuracy tester? (How is it different from managing the output volume as a mass (in grams) using a regular balance?)        Top

  • A balance outputs a mass (mg) while a pipette is managed by volume (µL). Since the pipette accuracy tester converts mass to volume, it can check the volume required for the pipette. Furthermore, it can accurately measure without concern for evaporation because of its evaporation trap. Finally, it can confirm that the specified volume and the output volume match (accuracy and repeatability).

Q2.   Is it necessary to enter humidity and atmospheric pressure into the WinCT-Pipette software?        Top

  • Humidity: This entry is a record of the measurement environment. In cases where an evaporation trap is not used, it is important to record the humidity because the evaporation volume rises as the surrounding humidity decreases. However, if an evaporation trap is used, the evaporation volume is minimized and measurement can be performed without worrying about the surrounding humidity. Since entering the humidity does not affect the conversion of mass to volume, the humidity value does not have to be entered.
    Atmospheric pressure: The range of atmospheric pressure change in a single location is generally ±15 hPa. Therefore, even though an average (fixed value) is used, the pressure fluctuation can be locked in easily between ±30 hPa. The effect of pressure changes on volume conversion in this case is ±0.003%. Consequently, it is acceptable to enter a representative value for the atmospheric pressure of the location.

Q3.   Can 2 µL pipettes be inspected?        Top

  • A volume of 2 µL is about 2 mg and the balance requires a resolution of 1 µg (0.001 mg). The AD4212B-PT can display mass at a resolution of 0.001 mg up to 5 g so 2 µL pipettes can be inspected. One µg is about 1,000,000th of a one yen coin (about 2,500,000th of an American penny). As you can imagine, measuring at 1 µg is not a simple task and the measuring environment is extremely important. When setting up the tester, ensure that the following conditions are met.
      - Avoid measuring on a weak foundation, on the second floor or higher, in the center of a floor away from the support pillars, in earthquake-proof structures, near tall structures, along heavily traveled roadways, etc.
      - Place the balance on a stand.
      - Prevent direct contact with air blown from air conditioners, etc.
      - Perform tests in a temperature and humidity controlled room.
    If these conditions are met and measurement values are still not stable, it is necessary to take further countermeasures, such as decreasing the precision level of the values displayed by the balance. (For example, by pressing SAMPLE to select a resolution of 0.01 mg.)

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