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导致活塞式移液器精准度下降最常见的原因是泄漏。而泄漏可能来自于密封圈，活塞或者吸头锥的损坏。许多时候这种导致显著体积误差的泄漏无法用裸眼识别。 inaccuracy in piston-operated pipettes is leakage. This arises from damage either to the seals'' pistons'' or tip cones.Often not detectable by the naked eye'' leaks lead to significant volume errors.The BRAND pipette leak tester (PLT unit) for air displacement pipettes finds even the smallest leaks within seconds.

Air-displacement pipettes must be checked at regular intervals and the results must be compared with the ISO 8655-2 error limits. However'' a calibration certificate only reflects the results at the time of testing. The time between these calibrations is crucial'' since leaks can occur at any time. Well over 80% of pipettes sent in for repair have leaks and are outside their volume tolerances'' even if they don’t drip.

While the PLT unit cannot replace regular gravimetric testing'' daily pipette checks can provide a safeguard during the periods between calibrations. Even the smallest leaks are detected! Process reliability for the pipettes is thus significantly improved.

Leak rates'' their detection and quantification
The leak rate is a measure of the quantity of material that flows through a leak per unit time. For air-displacement pipettes the PLT unit determines the rate through a differential pressure measurement'' i.e.'' after creating a negative pressure'' the pressure rise over a given time is measured.

• The leak rate is determined by considering complex physical relationships. Calculation of the limit values resident in the PLT must include factors such as the dead volume of the pipette/tip system'' flow cross section of the pipette tip'' pressure rise per unit time'' pipette volume and type'' etc.
• The pV value is the product of the pressure and the volume of a certain quantity of a gas at the prevailing temperature. This is a measure of the quantity of material or the mass of the gas.
• The leak rate QLis the ratio of the pV value and the period of time during which the gas flows through a path
  cross-section.
• For the pipette test'' hPa ml/s is a suitable unit for the leak rate. A leak rate of e.g.'' 1 hPa ml/s at an air pressure of 1000 hPa (approx.atmospheric pressure) means a volume loss of about 1 μl/s.

Easy To Use
Menu-driven software'' combined with a jog wheel and affirmative/negative buttons make it easy to select the correct test parameters'' pressure units or language (English'' Spanish or German)

A Diagnostic Tool
To check the overall pipette system'' the test is conducted with mounted'' unused tip. When a leak has been identified'' the test can be repeated without a tip to determine whether the leak arises from the tip cone/tip coupling region.Additionally static or dynamic (piston operated during test procedure) testing can also help localize source of leaks when detected.  The ability to test multichannel pipettes four channels at a time'' or individually increases the throughput of testing'' and assisting in the diagnosis of faulty channels.

Pass/Fail Determination
The limit values referenced during testing represent a warning limit'' from which significantly lower volume values can also be determined gravimetrically. This is one quarter of the volume tolerances'' according to ISO 8655-2.
The limit value for the leak volume of a given pipette allows the leak rate to be calculated. These calculations'' which are based on over 35 years of experience in the development and production of pipettes'' include the dead volume and the intake characteristics'' among other things. If the pipette is mechanically defect-free'' clean'' and the test is carried out properly with the BRAND PLT unit'' then the instrument is within the ISO 8655-2 tolerances.

根据计量仪器监测要求，空气活塞移液器需要定期检查并将结果与ISO 8655-2规定的误差极限相比较。 然而，校准证书仅反映了测试当时的结果。 两次测试之间的时间非常关键，因为在这段时间内随时可能发生泄漏。即便看不出明显的滴漏，超过80%的送修移液器有泄漏现象并且超出了他们的容差范围。

BRANDTech针对空气活塞移液器的PLT泄漏测试仪不能替代常规的重力法测试，但可以作为两次校准间的日常移液器检查提供保障。即便最小的泄漏也可被检出！使用移液器的可靠性因此可以得到显著提升。

产品特点

• 预设市售量程范围自1 μl至 10 ml的单通道与多通道移液器的极限值；
• 可带吸头或不带吸头检测；
• 测试结果数秒显现；
• 专利注册 ；
The most frequent cause of