Pipette leak testing units
Discover the PLT unit – the BRAND pipette leak testing unit for testing your Transferpette® S air displacement pipettes.
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Crucial improvement of process reliability of air displacement pipettes
The PLT unit cannot replace regular gravimetric testing; however, daily pipette checks secure the phases between calibration. The smallest leaks are detected! As a result, the process security of the pipettes is substantially improved.
Regular checking intervals
To monitor measuring instruments according to ISO 8655, air-displacement pipettes must be checked at regular intervals and the results must be compared with the error limits contained in ISO 8655-2. However, a calibration certificate only reflects the performance of the instrument at the time of testing. The time between calibrations is crucial, since leaks can occur at any time, even immediately after testing. Well over 80% of pipettes sent in for repair have leaks and are outside their volume tolerances, even if they don’t drip.
System leaks are the most common cause for the lack of accuracy in piston-stroke pipettes
These arise through damage to the seals, pistons or tip sampling cones. Often invisible to the eye, these faults can lead to significant volumetric errors. The PLT unit from BRAND, the leak-checking device for air cushion pipettes, detects the smallest of leaks with seconds!
Frequently Asked Questions (Pipette leak testing units)
Leak rates and their detection
The leak rate is a measure of the quantity of material that flows through a leak per time unit. 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.
PLT unit software
The optional PLT unit software, also called PLTconnect, is a program to facilitate the documentation of leak tests, which are carried out with the PLT unit from BRAND. Measured values from the test result of the PLT unit will be automatically transferred to the program. The result is displayed as a test certificate and stored in the program. Thus, the documentation of your test results will be significantly facilitated.
Complex determinations
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 time unit, pipette volume and type, etc.
The leak rate QL
The leak rate QL is the ratio of the pV value and the period of time during which the gas flows through a path cross-section.
The pV value
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 volume loss
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 means a volume loss of about 1 μl/s.
