It's All About the Math

This formula is a fundamental law of physics and is represented by a linear equation v = i x r, where v is volts, i is current measured in amperes (and frequently expressed in milliamperes, or thousandths of amperes), and r is resistance measured in ohms. When testing for stray voltage, using the accurate data matters immensely. Utilities always use 500 ohms to represent the cow's resistance. They will also use 1 or 2 mA (0.001 or 0.002 Amps) in their equation to determine what level of Voltage they need to find before they believe there may be a problem on your farm.

.002 Amps x 500 Ohms = 1 Volt OR

.001 Amps x 500 Ohms = 0.5 Volts

Therefore, utilities require 0.5 - 1 volts to be found using a 500 ohm resistor on their meter before they would say there was a problem for the cows that requires a fix. Using these figures is the primary reason very few farms get the fixes to their stray voltage problems.

Research shows a cow's resistance in real world applications is in the low 200's for healthy cows. Cows with sore feet can test much lower in resistance, even below 100 Ohms. For this example, we will use 200 Ohms for all practical purposes. (However, with many cows testing much lower, we support the use of a 125-ohm resistor in testing. We will also use 0.25 milliAmps as the level at which cows show a physical reaction to the current. (Check out the other pages on this website to see the proof in these numbers)

.00025 Amps x 200 Ohms = 0.05 Volts

**This is 10 - 20 times lower than the standard set by the utility industry. **

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