Measurements Verify Static Control Performance
- Published: June 09, 2025
By Dr. Kelly Robinson, Founder, Electrostatic Answers
One can verify that static dissipaters are functioning properly by making verification measurements.
How can we be sure that a newly installed static dissipater is doing the job? Our eyes cannot see static charges, so we must rely upon instruments. These instruments are part of a complete static control system, which has three elements illustrated in Figure 1.
- Passive static dissipaters (tinsel, ionizing cords, static brushes, needle bars);
- Powered static dissipaters (static bars, ionizing fans);
- Instruments (fieldmeters and electrostatic voltmeters) either handheld or inline.
Passive and powered static dissipaters accomplish two goals. First, they suppress static sparks that can injure operators, ignite flammable atmospheres or damage products. Second, static dissipaters maintain low static charge levels to prevent material handling problems like sticking and jamming of cut sheets and pouches.
Static instruments also accomplish two goals. First, they help diagnose static problems. They tell us the static charge levels. And, more importantly, they help us find static charging sources. Neutralizing charges at the source is key to solving static problems.
Second, once the static problems are solved by installing dissipaters in the right locations, our instruments tell us if the dissipaters are functioning properly and help us see that static charges are well controlled.
I use two instruments to measure static charge levels:
- Electrostatic fieldmeter (ESFM);
- Electrostatic voltmeter (ESVM).
Use the electrostatic fieldmeter (ESFM) in Figure 2 on a free web span away from metal objects like idler rollers, metal wires and conduits and machine frame elements. The web in Figure 2 has two sides; the top side and the bottom side. Static charges may be on either side or both sides. Charge density Top is the charge per unit area on the top surface, which is analogous to the paint thickness on a wall. Similarly, charge density Bot is the charge per unit area on the bottom surface. The ESFM in Figure 2 measures electric field E in (1) that is proportional to the sum of these charge densities.
An ESFM measures the total charge density or "net charge" on the web, Ih Is good because net charge causes sparks. An ESFM tells us the risk of a spark.
An ESFM is our workhorse instrument for solving static problems because using it is quick and easy. Just follow the GeeZE rules to collect reliable, repeatable readings.1
The ESFM in Figure 2 measures the net charge over a relatively large area, which is approximately halfway to the idler rollers on either side of the meter. Averaging over a large area reduces variability that steadies the readings.
To verify static control, choose several key locations to take ESFM readings. For example, on a coater, take readings on the (1) unwinding roll, (2) exiting the unwinding roll, (3) entering the coater, (4) exiting the dryer/oven, (6) entering the winding roll and (7) on the winding roll. Tracking these readings over time will tell us if the static control system on the coater has been working properly.
One problem with the ESFM in Figure 2 is that it reads zero when there is positive charge on one side of the web and an equal amount of negative charge on the other side of the web. “Balanced charges,” which are very common, can cause coating defects and high static levels on winding rolls. These problems are often “mysterious” because our ESFM says that the charge on the web is zero.
Use the electrostatic voltmeter (ESVM) in Figure 3 where the web is wrapped on a grounded, metal idler roller. ESVM reading VTop in Figure 3 is proportional to the charge density Top in (2).
Similarly, ESVM reading VBot measures the charge density Bot only on the bottom surface of the web.
An ESVM can detect balanced charges, which is very important for diagnosing static problems. An ESVM reading has high spatial resolution meaning that it detects the charge density along a "pencil line." While this can be helpful, ESVM readings are often more variable than ESFM readings. So, it is helpful to capture ESVM readings and average them.
Balanced charges are very persistent. Once formed, balance charges persist through web cleaning, corona treatment, coating, drying and pretty much every process in a manufacturing line. To verify the static control system, take an ESVM reading at the beginning and at the end of the process. I usually take a first ESVM reading on the web exiting the unwinding roll and a second reading on the web entering the winding roll. The measured voltages should be similar when the charge control system is working well.
An ESFM is the primary instrument for diagnosing static problems and monitoring static control because it is easy to use and tells us the risk of a spark. Take ESFM readings at a few key locations to verify that the static control system is working properly. An ESVM is a specialty instrument that is sometimes useful especially to detect balanced charges.
1 https://www.pffc-online.com/static-beat/14478-static-beat-geeze-rules-for-static-readings
About the Author
Dr. Kelly Robinson writes on static issues occurring in converting processes. Robinson founded Electrostatic Answers, has 40-plus years experience in industrial problem solving and was named Top Manufacturing Consulting Services Provider 2023 by Managing MFG. He can be reached at Kelly.Robinson@ElectrostaticAnswers.com.
