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Maximum Touch Current Measurement
Protocol being tested to measure the maximum touch current possible at a selected location. The keys to this protocol are assuring enough moisture in the ground at the test point, and using a special disk probe on the ground. The disk (12 in.) is covered with bentonite clay on the side contacting earth. Bentonite fills gaps between the rigid disk and the irregular terrain surface, to reduce contact resistance. For the theory beyond this read the related 1998 paper "Methodology for Measuring Maximum Touch Current Near Grounded Systems at Industrial and Power Facilities" in Publications.
	Commercially available bentonite powder is mixed with water to form a clay mix that is then applied to the probe disk.
	The disk is laid over reference test point using pressure to ensure good contact with earth. Gently stepping on disk and letting clay ooze out of sides assures good contact.
	Disk ready for testing.
	The maximum touch current can be measured between an object, such as the pipeline in this case, and the probe disk that simulates the feet of a as person touching the pipeline.
	The oozed out bentonite is trimmed from the edge of the disk to control the surface contact area.
	The exercise demonstrated that the protocol is practical and easy. On the other hand, controlling the moisture in the ground is more problematic. Raining assured adequate moisture in the groundd during this test.

Touch Potential Measurement Pogo Stick
	The pogo stick was developed to conduct touch potential probing and measurements quickly and effortlessly. The operator walks around with a pole that has a special probe disk at the lower end. A meter, mounted on top of the pole for convenience, is connected to the structure being probed, a telephone pedestal in this case, and the probe disk.
	The probe disk is rugged and mounted in a pivoting assembly below a foot rest. By stepping on the foot rest the operator makes solid contact with the earth quickly and effortlessly, and tests various points walking around the structure.

Step Potential Measurement Shoe Accessories and Other Tools
	A variety of shoe accessories that an operator wears to make walk-around step potential probing.
	Small disk probe attached to rubber shoes; the easiest probe to wear.
	Simulating a large foot, this probe has a flexible screen that conforms to irregular and rigid surfaces, such as roads and sidewalks.
	A similar probe with fangs at the edge of a flat, rectangular surface that works better on soft earth.
A frame with disk probes mounted exactly one meter from each other. While controlling the separation distance, this set does not resolve all the variabilities associated with this type of probes. Read a related 1994 paper "Resistance Characterization for Step-Voltage and Body-Current Testing" in Publications for further information.

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` Last updated: June 5, 1998.