ANSI ESD STM11.12:2000 pdf free download – for Protection of Electrostatic Discharge Susceptible Items- Volume Resistance Measurements qf Static Dissipative Planar Materials
7.1.1 Top Electrode
The top electrode assembly consists of two concentric rings which make contact with the material under test. See Figure 2. The contact surface material of the electrode assembly shall be conductive rubber having a hardness of 50 to 70 on the Shore-A Durometer scale and a volume resistivity of less than 10 ohm-cm per ASTM D-991. The inner electrode shall be a solid disk 1.2+ 0.025 inches (30.48 + 0.64mm) in diameter. The inner electrode shall be flat and make total contact with the test sample. The outer electrode shall be a ring having an inner diameter of 2.25 + 0.025 inches (57.15 + 0.64mm). The width of the outer ring shall be 0.125 + 0.010 inches (3.18 + 0.025mm). The total weight of the top electrode assembly shall be five (5) pounds, + 2 ounces (2.27 kg, + 56.7 grams).
7.1.2 Bottom Electrode Support
The bottom electrode shall be a flat conductive metal plate sufficiently large to support the sample under test. The plate should be supported by an insulative material having a surface resistivity greater than 1 x 1012 ohm/square per ASTM D-257. See Figure 3.
7.3 System Verification Fixtures System verification is accomplished by testing the equipment setup as shown in Figure 6. Low and high value (certified/verified) resistors are inserted in series with the system to verify that the test set up will correctly read in the specified resistance ranges of this standard. The low resistance verification fixture shall be a 499 +1% Kohm resistor. See Figure 4. The high resistance verification fixture shall be a 1 tera ohm (1 x 101) +5% resistor. See Figure 5.
NOTE: The high and low value resistors used for system verification should have their exact values certified at the time of purchase and periodically thereafter as required (Recommended annually). 8.0 Sample Preparation and Conditioning The samples shall not be marked nor handled on the surface area to be tested. A minimum of six (6) representative specimens of the sample material shall be prepared. Minimum sample size shall be 3.0 x 5.0 inches (76 x 127mm). Each sample shall be clearly identified in such a way that the markings will not interfere with the area to be tested. Specimens shall be conditioned and tested in an environment of 12 + 3% relative humidity and 72 degrees + 5 F (23 + 3 degrees C). The conditioning period shall be a minimum of 48 hours but not greater than 72 hours. Do not remove specimens from the controlled environment until the measurements are completed.
10.0 Upper Resistance Range System Verification Procedure: The following procedure is used to determine the maximum electrification time and the ability of the system to measure resistances up to 1 x 101 ohms. This is done at 12% RH and 72 degrees F.
A) Connect the electrode assembly to the instrument according to Figure 6.
B) Insert the high resistance verification fixture into the electrode assembly.
C) Apply a voltage of 100 volts to the electrode assembly and wait for the reading to stabilize. Record the stabilized resistance value and the time required to stabilize. This value should be within + 5% of the certified resistance value of high resistance verification fixture. Turn off the applied voltage.
D) Repeat step C for a total of five (5) times and record the time required for the instrumentation to indicate the resistance.
E) The Electrification Period shall be the average of the five readings recorded in steps C and D plus 5 seconds.