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as indicated by the dashed and solid lines. A 60 Hz steady 2-Volt peak recording would elicit a behavioral reaction in about 5% of cows according to Figure 2. If the same voltage were recorded as a step potential about 10% of cows would be expected to show some type of behavioral response. More voltage and current would be required to produce an avoidance response as discussed below.

Motor Starts

Motor starts are generated by motors on the farm being investigated. The starting current of the motor and the resistance of the farm neutral determine the magnitude of a motor starting transient for 120 V motors and the primary neutral for 240 V motors. Motor starts typically produce multiple cycle 60 Hz transients. A typical motor starting transient is shown in Figure 1b. The phase duration can be estimated by noting that there are about 9 ½ zero crossings in 4 time divisions (80 milliseconds).

80 ms / 9.5 phases = 8.4 ms phase duration

This again corresponds to the 8.3 ms phase duration expected for a frequency of 60 Hz. The peak voltage during the motor start is 1.5 V (3 volts peak to peak). Referring to Figure 2 we see that about 20 % of cows would show a behavioral response to this voltage.

Controlled experiments have shown that the current ratio between aversive Reponses such as reduced water consumption and the first behavioral response and is about 0.7:1. To determine the number of cows that would show an aversive response to this 3 V pulse, multiply the peak voltage by 0.7 and plot on Figure 2 (3V x 0.7 = 2.1 V, about 5 % of animals showing an aversive response).


Most electric fencers and cow trainers produce a single mono-phasic pulse once per second (Figure 1c). These pulses typically have phase durations of 10 to 50 microseconds with a peak output voltage from 2000 volts to 10,000 Volts (shaded area in Figure 3). It has been known for almost 100 years that as the phase duration of a voltage/current pulse gets shorter, much more voltage and current is required to produced nerve stimulation and perception or pain. This knowledge has been used to design electric fencers that produce a very high voltage/current pulse that is of very short duration. The vast field experience with these devices suggests that these levels produce a painful shock but do not do physical harm to the animal.

Part of this high voltage fencer pulse can appear on grounded objects if fencers or trainers are improperly installed. An example of such a case is shown in Figure 1c. This is an example of a fencer pulse that was recorded using an oscilloscope at a cow contact location using a 500-Ohm shunt resistor. It is important to use a shunt resistor for all cow contact measurements to eliminate erroneous measurement of induced voltages.

The time scale of the oscilloscope is set to 50 microseconds per division and the voltage scale set to 10 Volts per division. The phase duration of this pulse is estimated as 20 microseconds. The peak voltage is estimated as 38 Volts. The ability of this pulse to be perceived by animals can be estimated using Figure 3.


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