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In our latest articles we extensively discussed ESD, its implications, ways to avoid, and indicators to tell if an object has an electrostatic charge. Our key takeaway is that ESD is common and can cause a lot of damage if no precautions are taken, especially in industries where static-sensitive devices are assembled and manufactured. While it is common, it can be managed to mitigate the impact it has on the business and its finances by implementing static control measures such as using anti static equipment.
In this article, we shall explore another dimension of ESD: surfaces. Objects do not inadvertently get ESD out of nowhere. There is a source and, most often than not, these are the work desks and other surfaces that the product has undergone as part of the production cycle. Checking the objects and removing the static discharge from it is reactive. Proactively looking at the source of the ESD by checking the surfaces is quite another. It will not just save time but also resources.
In understanding surface resistance, it is crucial to explain what resistivity is. Also known as electrical resistance, it is the characteristic of a material to resist the flow of electrical currents. The higher the resistivity of a material is, it becomes a poor conductor of electricity.
As not all objects are created equal, others are more susceptible to electric currents, while others are more resistant. If a material has higher electric currents, static electricity will stay in it. In a sense, measuring an object or surface resistance meter is the capacity of the object or surface to repel any electric current, prohibiting static electricity.
Resistivity factor then is defined as the specific electrical resistance value of an object. Normally, these are tested on different types of conductor to compare their electrical resistance to various temperatures and environmental elements, without due regard to its physical properties.
Meanwhile, the resistivity of insulators are measured based on the amount of voltage they can carry. Devices allow you to measure this accurately, but should you opt to fo it manually you can use the Ohm’s Law to calculate the resistance of an insulator.
The resistivity of a surface and object is dependent on a contingent of factors such as: applied voltage, electrification time, and environmental factors. Variations on these three factors will yield different results as well. For instance, if an object or surface has been exposed to a certain level of voltage in a prolonged period, the result would differ for other tests which might have a different length of time and amount of voltage. Same goes for the relative humidity of the area where the test was conducted. This could impact the resistivity of objects. It is widely known that the more humid an area is, conductors will be less resistive. This is the reason parameters must be set as clearly as possible to avoid dubious results and ensure resources and efforts are not wasted.
Now that you have a clear understanding of resistivity, let us dive into surface resistivity. Defined as the electrical resistance of an insulating material’s surface, surface resistivity looks at the electrode to electrode reaction of the insulator’s surface. The more resistance the surface has, the better.
Based on universal standards, surface resistance meters should measure at 100v. These are usually portable and lightweight allowing for it to be used anywhere and anytime. Readings and calculations using these devices are usually accurate.
Using these devices is easy and straightforward. The meter is placed on the surface of the area to be tested, then the button is pressed allowing for the device to read the electric resistance of the object. If the object to be tested is the ground, the lead must be placed to the earth leakage socket. This should be connected using a crocodile clip to the area to be tested. Pressing the button will then read the electronic resistance.
The test will measure the surface’s conductivity, static dissipativity and the insulation capacity of the surfaces. The readings will be read and measured using Ohm per square.
Traditionally, Megohmmeters are used to measure the resistivity of insulators and other objects. By injecting a huge amount of voltage, it is the easiest way to check the efficiency of these objects. However, ESD insulating kits offer a more advantageous feature. It can keep records of all the readings, reducing errors and retesting of the objects, allowing you to save time, resources and effort.
In testing, you should be mindful of the red and green colours. Red indicates that your setup is incorrect and you might need to adjust the positioning of your surface to the crocodile clip or something else is amiss. You better check it out. On the contrary, a green light indicates that all conditions are met and it is ready to measure the resistivity of the object.
As we all know static energy is energy at rest. Given the right conditions and environment, it can become active and create harmful effects to the people and other objects. This is the reason surface resistivity tests are made – to identify and prevent the build up of static electricity. There are various test kits available out in the market, but we recommend using the Half Decade Surface Resistivity Meter (SRM100). This equipment does not just tell the resistivity of the surfaces but also their point-to-point resistance giving an accurate calculation. Another selling point of this equipment is it can store data and be of use for more than five years. It is a worthy investment to make for your business.
Accuracy is important across all test kits to ensure calculations are at par with international standards and acceptable to various markets. Bondline issues certificates of calibration across all its product lines. You can be assured that it meets the stringent guidelines of the EU. Calibrations are made annually to ensure customer satisfaction and deliver the promise of excellence in the ESD industry.
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