Proper measurement is a complex but necessary process.
An oft-asked question is, “Does my process generate an electrostatic charge, and if so, how much?” If the ESD program manager is looking for a simple “yes or no,” the answer may be disappointing. If, however, the ESD program manager is making an argument for the complexity of ESD, then the answer proves the point.
Static control would be much easier if a “yes or no” question led to a successful ESD control program. However, oversimplification often creates more problems than it solves. In ESD control situations, this is more the rule than the exception. While ESDA standards and other documents such as ANSI/ESD S20.20 and ESD Handbook TR20.20 can provide guidance and starting points, each process and facility is unique. Therefore, the rule to successful ESD control is not guessing, but measuring.
Why measure? Why take the time to measure the processes or materials? Several reasons. Measurements will aid in ESD control from beginning an ESD control program through to program maintenance.
First, measurement defines the problem accurately. From an ESD perspective, most environments are unique. What might cause an ESD problem in one environment may not cause a problem in another. Measurement helps identify whether a problem exists in a given environment. Then, those measurements provide concrete documentation for obtaining the financial and personnel resources needed to solve the problem.
One can arrive at more accurate solutions through measurement. For example, if the insulators in the environment are not producing electrostatic fields, why purchase ionizers to solve a problem that doesn’t exist?
Once measurement has accurately identified the problem, prioritize those areas that require the most attention and select the appropriate solutions. The more specific the knowledge of the problem, the more successful the solution will be. For example, knowing that a material has a resistance of 106-109 helps prevent confusion that can occur with the imprecise use of terms such as conductive or dissipative.
Once ESD control measures have been selected and put in place, assess progress and results through measurements. If the solution reduces electrostatic potentials on personnel from 1,000V to 50V, the solution has been effective and can be checked regularly to ensure that it continues to work.
Where to start. What gets measured in the facility? Generally, those processes and materials suspected of generating electrostatic potentials or charge: personnel moving in the area, conveyor systems, display monitors, insulators, carts, etc. After ESD control processes and materials have been selected, they should also be measured to ensure the items function properly and that they continue to function properly.
Measurement equipment. Generally, two types of measurements should be considered: electrostatic fields or potentials and resistance or resistivity. Some relatively inexpensive equipment options are resistivity meters, resistance test kits, and electrostatic field meters. For process and facility evaluation, what’s of primary interest is an indication of whether a material or process generates high or low levels of electrostatic charge. Frequently, what is wanted is an indication of whether a material has ESD properties, and will remove electrostatic charge when connected to ground.
Material evaluation and qualification may merit laboratory level tests, which may require more precise instrumentation.
ESD control doesn’t often fit into a simple “yes or no” framework. When observations and intuition are supported with data, surprises and guesswork can be eliminated. By making a practice of measuring, the implemented ESD control measures have an increased chance of effectiveness and success.