Labconco 3940200 User Manual - Requirements
7
Chapter 2: Prerequisites
Humidity and Static Electricity
Requirements
Electrostatics can be troublesome in a balance enclosure. It is
important to understand and, to the extent possible, control static
charges. An electrostatic charged vessel, sample or enclosure can
apply forces and lead to errors in weighing. The repulsion or
attraction can be detected with micro, semi micro and analytical
balances. Static charges can also lead to particulates being
attracted to surfaces within the balance enclosure. Containment of
harmful powders, prevention of cross-contamination and clean up
are enhanced when static attraction of powders is minimized. The
construction of the XPert Filtered Balance System and XPert
Filtered Balance Station avoid the use of plastics, which are highly
insulative. The advantages to the glass and epoxy-coated metal
construction are twofold:
1. The enclosure does not contribute high electrostatic forces
affecting the precision of the balance.
2. The attraction and ultimate accumulation of powders,
(hazardous or nuisance), are minimized on the inside of the
enclosure.
To correct or ensure against electrostatic issues, the following
additional measures may be prescribed to improve weighing
operations.
•
Maintain a humidity level between 45 and 60%. The ability to
sustain this humidity range can be challenging depending
upon the regional climate and HVAC system.
•
Ionizers in various forms (guns, bars and blowers) are
effective ways to flood an area with ions and essentially
“neutralize” electrostatic electricity.
Background on Electrostatics or
Static Electricity
Electrostatic charges on a surface such as the wall of a balance
enclosure are not created by moving air. Gases do not cause the
charge. Impurities within the air impinging upon surfaces dictate
the polarity and magnitude of the charge. The process,
triboelectrification, occurs when the dust particles contact the
surface, creating friction and electrons move across the interface.