7792

• UCREFRP Catalog Number: 7792
• Author: Kolz, A. L.
• Title: In-water Electrical Measurements for Evaluating Electrofishing Systems.
• USFW Year: 1993.
• USFW - Doc Type: \
• Copyright Material: NO

IN-WATER ELECTRICAL MEASUREMENTS 17
Fig. 17. Voltage profiles for three vertical
plates measured along a transect nor-
mal to their surface.
E
So'
D
50
45
40
35
30
25
20
15
10
5
Immersion depth = 15.2 cm - o
=30.5cm-x
=45.7 cm-•
Plates measure 122 cm wide x 0.32 cm thick
0 1
0
50 100 150
Distance (centimeters)
Fig. 18. Profiles of voltage gradient (E)
and the squared value of voltage gra-
dient (E) for two spheres having di-
ameters of 15.2 and 27.7 cm.
200
Spheres
E - 27.7 cm
???` E-16.2 cm
E2 -27.7 cm
E2-15.2 cm ~???•.__
0
50 100 150 200
Distance (centimeters)
ardous position for fish in an electric field is always
next to the electrodes, and the fish should not be
allowed to touch the electrodes.
Figures 18 through 23 show two additional
curves that are calculated by taking the square of
each value for voltage gradient (E). These curves
are provided to emphasize that power density is
actually proportional to E2 (equation 11), and the
steep slope of these E2 curves demonstrates how
quickly power density diminishes with distance.
102
q
d
101
d
10°
10-1
10-2
m 10-'
m
10-4
Discussion of the Voltage Gradient Vector
Voltage gradient is defined as a vector quantity
that has magnitude and direction (Rogers 1954).
However, the voltage gradient profiles shown in
Figs. 18 through 23 were developed without em-
phasizing any vector relation for the gradient;
only the magnitudes of the gradient are pre
sented. For these figures, two of the three direc-
tional components are justifiably ignored be-