X hits on this document

# Stray Voltage Field Guide - page 4 / 8

22 views

0 shares

4 / 8

Note that there are 3 lines on Figure 3. The lower dashed line is for multiple cycle sine waves, as shown in Figure 1a. The upper dashed line is for a single cycle, biphasic wave. A biphasic wave goes from zero to some peak positive value, back through zero to some peak negative value and then back to zero (two phases, + and -). The middle line is for mono-phasic sine waves. The fencer pulse in Figure 1c is a mono-phasic wave. The voltage goes from zero to some peak positive value and back to zero (one phase, +).

From Figure 3 we can see that the fencer pulse (1c) falls below the sensitivity threshold for mono-phasic waves. This means that it would elicit a behavioral response for less than 5% of cows and a smaller percentage would show an aversive response.

# Switching transients

Switching of electrical equipment produces the third category of electrical pulses found on farms. Switching transients are typically multiple cycle events that decay very quickly. An example of a switching transient recorded in a cow contact location with an oscilloscope and 500-Ohm shunt resistor is shown in Figure 1d. The time scale is set for 100 nanoseconds per division and the voltage scale to 1 Volt per division. The phase duration of this switching transient (1d) is estimated at 17 nanoseconds (6 zero crossings in 100 ns). The peak voltage (zero to peak) of the maximum single cycle is 3.3 Volts. The average peak voltage for the entire event is about 1.5 volts. From Figure 3 we can see that these levels are more than 1000 times below the reaction threshold for both the multiple cycle or single cycle biphasic behavioral response and is not of concern for animal welfare.

III.

# Contact Resistance

With proper measurement technique and using the information presented in figures 2 and 3 we can determine if to potential exists for causing annoyance to dairy cows. The next step is to determine if the exposure conditions are such that adverse effects could occur. In all of the previous figures and calculations, it has been assumed that the body resistance of a cow plus the contact resistance is approximately equal to 500 Ohms. This is a conservative estimate and approximates the conditions if a cow is standing on a clean, wet surface. If a cow is standing on a dry surface or is standing on bedding the contact resistance is greatly increased and a value of 1000 or more is an appropriate estimate of the cow and contact resistance.

# Location

The only studies which have documented adverse effects of voltage and current on cows had BOTH sufficient current applied to cause aversion AND forced exposures, (animals could not eat or drink without being exposed to voltage/current). It is typical for voltage levels to vary considerably at different locations on a farm. Decreased water and/or feed intake or undesired behaviors will result only if current levels are sufficient to produce aversion at locations that are critical to critical daily animal activity. These locations include feeders, waterers and milking areas.

4

 Document views 22 Page views 22 Page last viewed Fri Dec 09 14:12:41 UTC 2016 Pages 8 Paragraphs 189 Words 2450