A3586
Stray voltage
check sheet
Steady state 60 hertz AC spot check
by D. J. Reinemann
Adapted from materials developed by the Public Service Commission of
Wisconsin and the Department of Agriculture, Trade and Consumer Protection
Scope
This form should be used by farm
operators, electricians, power suppliers
or others measuring stray voltage. The
procedures outlined are designed to
indicate approximate stray voltage and
current levels. The tests are simple,
requiring a minimum of equipment.
The tests are intended to help
identify steady state 60 hertz AC stray
voltage problems. These tests are not
conclusive, and additional procedures
may be required if stray current levels
greater than 1.0 milliampere AC
(approximately 0.5 VAC) are recorded
at potential cow contact points.
Farm operator:
Address:____________________________________________________________
Township, city: __________________________________________________
Phone number: __________________________________________________
Electric power supplier: ______________________________________________
Contact person: _________________________________________________
Phone number: __________________________________________________
Electrician:__________________________________________________________
Phone number: __________________________________________________
Investigator: ________________________________________________________
Phone number: __________________________________________________
General information
Date: _______________________________________________________________
Weather conditions during visit: _______________________________________
____________________________________________________________________
Describe concerns of farm operator: ____________________________________
____________________________________________________________________
____________________________________________________________________
____________________________________________________________________
Has a previous investigation been performed at this location?
Yes ■
No ■
Is the farm currently using stray voltage corrective devices?
Yes ■
No ■
_________ If yes, list devices: for example, neutral isolator, equipotential
plane, active voltage suppression device. ___________________________
________________________________________________________________
________________________________________________________________
Measurement technique
Cows react to electrical current
flowing through their bodies. A 500
ohm resistor simulates the body
resistance of a cow. Measuring the
voltage across such a Òcow resistorÓ
will indicate the level of current flow
that a cow would experience (see Figure
1). If 0.5 volts AC is measured across a
500 ohm resistor the current flow
through the resistor will be 1.0
milliampere. The Public Service
Commission of Wisconsin has defined 1
milliampere (0.5 volts) or greater
measured in this way as a level of
concern for cow contact locations.
Determine the location of cow
contact measurements through
discussions with the farm operator.
Measurements may include milking
area, feeding lots and watering areas.
Indicate the location of your measurement points on the farm layout sketch
on page 3.
Pre-test equipment
checks
Note the make and model number
of meter being used for
testing:______________________
Cow resistor value check
(Assumes a simple digital meter is
being used for the test.)
a. Place meter on the ohmÕs scale
b. Touch leads together and
measure: R = __________ ohms
c. With leads apart, insert nominal
500-ohm resistor and measure:
R = _____ ohms
d. Return to the AC volts range.
Part b of this check verifies that the
meter ohm scale is zeroed and ready to
measure the cow resistor. Part c
measures the value of the cow resistor.
DC blocking check
Perform the DC blocking check as
shown in Figure 2. This test verifies that
the meter, when set to the AC position,
will not erroneously read the DC
component of any measured voltage.
Make a farm sketch on the next
page. Show location of transformer(s),
building locations, approximate size
and length of service drops, meter test
points, and remote reference rod
location. Show location of all electrical
measurement points.
Is the water line metallic?
Yes ■ No ■
Is the water cup metallic?
Yes ■ No ■
Is the stanchion metallic?
Yes ■ No ■
Is the stanchion bonded to the
water line?
Yes ■ No ■
Figure 1. Cow contact area measurement, mouth to rear hooves (for long term monitoring).
Notes:
1. Locate floor plate in rear
hoove area at least 12' from
stanchion and building
supports.
2. Clean floor surface.
3. Add salt water to metallic
plate area.
Figure 2. Testing your meter for DC blocking when set to AC range
Show farm layout below.
Summary notes:
Stray voltage checks
All cow contact measurements should be taken both with (WR) and without (WOR) a cow resistor. Identify the highest
steady state readings that can be obtained, noting the time of day and the equipment in operation (normal electrical loads
during milking operations). Use the test set-up illustrated in Figure 1. Alternate floor contact methods are shown in Figure 3.
In the last column, identify and list farm equipment and lighting that is energized during measurements. Use an additional
sheet if necessary.
Time of day __________ a.m./p.m.
Measurement
surfaces
AC volts
WR/WOR
Equipment
energized
stanchion
to
floor
_____ _____
___________________________
water cup
to
floor
_____ _____
___________________________
_________
to
____
_____ _____
___________________________
_________
to
____
_____ _____
___________________________
_________
to
____
_____ _____
___________________________
_________
to
____
_____ _____
___________________________
_________
to
____
_____ _____
___________________________
_________
to
____
_____ _____
___________________________
_________
to
____
_____ _____
___________________________
_________
to
____
_____ _____
___________________________
_________
to
____
_____ _____
___________________________
Figure 3. Alternate rear hoof contact plate.
NOTE: For spot voltage checks, stand on plate at each checkpoint.
This completes spot check
electrical test procedures. If herd
problems persist, further electrical
testing and continued investigation
into non-electrical factors is needed.
Author: D. J. Reinemann is an associate professor of biological systems engineering at the University of WisconsinÐMadison and the
University of WisconsinÐExtension.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of
Agriculture, University of WisconsinÐExtension, Cooperative Extension. University of WisconsinÐExtension provides equal opportunities in
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You can obtain copies of this publication from your Wisconsin county Extension office or from Cooperative Extension Publications, Room 170,
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Stray voltage check sheet: steady state 60 hertz AC spot
RP-02-99-2M-50