ESD Systems - Questions And Answers

I need to understand readings I was receiving from our digital LCD megohmeter. I was tryingto determine if a shelving system and the storage containers were ESDprotected.I first measured the ESD floor (RTT) and it fell into the conductive range. I then measured the shelf material (it looked like pressed fiberboard) andreceived a measurement that fell into the dissipative range. I placed oneweight on the floor and placed the other weight on the shelf. I was tryingto measure the RTG I was expecting a resistivity reading telling me theshelving was either dissipative or insulative. The measurement I receivedwas "P". Tech Brief PS-2060 tells me there was noise or a "high openresistance." Does this reading mean that that the shelving system wasextremely insulative, higher than our megohmeter attaches values?I did not think to measure the shelving material (RTT). I was told it wasan ESD protected rack with dissipative paint.Do I need to measure the shelf (RTT) to confirm its resistivity.? Is myreasoning correct? Charlie, Dallas, TX

Shelving, according to ANSI/ESD-20.20 should be under 1x10⁹ ohms referenced to ESD ADV 53.1. RTT is the measurement between two 5 pound electrodes (not RTG which is the measurement from one 5 lb electrode [on the measured surface] to ground). For measuring shelves in accordance to ESD ADV53.1, you place one lead of the test apparatus to the Common Point Ground and connect the other lead to an electrode. Set meter output to 100 volts. Place the electrode 2” from a corner and apply test voltage and record the resistance after 15 seconds of electrification. Repeat procedure with the electrode placed in the center of the shelf. This way you are ensuring not only that the shelf complies, but also that it is coupled to ground as well.

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