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Weighing performance test on Explorer Semi-Micro balance and Ductless Filtering Fume Hood



Introduction

Weighing requires accuracy, especially when the readability of a balance reaches 0,01mg or more. However, in many applications the samples being weighed might be harmful or dangerous for the operator and the use of a fume hood is required in order to protect the laboratory personnel. Air flow, drafts and vibrations can adversely affect the weighing performance of any balance and eventually cause errors to the measurement. Such errors can further have negative effect on analysis performed with the use of a balance as well as processes in which weighed samples are required.


Protection of the operator is made possible with the use of ERLAB Ductless Filtering Fume Hood Captair 391 Smart. This unit is specially designed to protect users against inhalation of chemicals. It can embed molecular filters and particulate filters depending on the needs of the application. This protection device complies to safety international standard, such as NFX 15211. To achieve this efficiency and a high level of containment, face velocities of the units must be maintained above 0,4 m/s which requires a total airflow higher almost equal to 220 m3/h. Despite this airflow, the unit is design in order to minimize turbulent

airflows in the enclosure and to absorb vibration that could be generated by the fan. The tested Captair 391 was also equipped with an optional Trespa Toplab benchtop in order to minimize conduction of vibration to the balance.


Weighing with high accuracy is made possible with an OHAUS Explorer Semi-Micro balance, a modular model that can be easily fitted in to the fume hood. In addition, a set of four infrared touchless sensors combined with an Ionizer and automatic doors as well as a grid pan bring the level of vibrations to the minimum. The display can be separated from the base of the balance to a distance of up to 1,5m with a standard cable included. The automatic doors as well as the ionizer, tare and a number of other commands can be actioned with the use of four touchless infrared sensors. This way there is no need for the operator

to touch the balance during the weighing procedure which both adds to the protection of the operator as well as minimizes disturbances influencing the balance’s performance. An accessory grid pan helps the balance to stabilize up to 1s faster.


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