UFC 3-570-06
JANUARY 31 2003
and should be disregarded. The second blink is the instant-OFF
measurement, which should be recorded. Since this number is only
displayed for about of a second, watching the display through several
interruption cycles may be required to assure the correct value is
recorded. The value recorded using this technique will have from about
1/8 of a second to just under of a second of depolarization.
Some digital meters have a memory function that will remember the
minimum and maximum (ON and instant-OFF) readings and the meter
can toggle between the two readings. Using this type of digital meter with
the interrupter(s) on a short off cycle (usually 1 second), the meter can be
reset, then the ON and instant-OFF displayed and recorded. The value
recorded using this technique will have from about to just less than 1
second of depolarization (with a 1 second OFF cycle). Some interrupters
are available which have the capability of a second OFF cycle, which
could be used to obtain approximately the same accuracy as the previous
method (1/8 of a second to just under of a second of depolarization).
There are occasions where a significant depolarization may occur in the
time required for these methods to obtain an instant-OFF reading. The
speed of depolarization depends on the type of coating, the condition of
the coating, the dielectric strength of the coating, the current density, and
the type of electrolyte.
Figure 7-8. Readings Recorded by Digital Voltmeter with Minimum/Maximum
Function (Reference Cell to Meter Negative, Structure to Meter Positive)
Neg1.025
ative
1.025
Minimum
Volts
1.2 .025
1
1.025
1
1
0.865
0.8 .855
0
0.845
1.02
0.6
1.022
Maximum Recorded (most positive)
1.025
0.4
1.025
Interupter Set at 1 Second Off and 4 Seconds On
1.025
0.2
1.025
1.025
Number of Readings at 1/4 Second Intervals
0 .025
1
1.1 25
5
9
13
17
21
25
29
33
37
41
45
49
0
1 025
7-3.7.2
Using a Data Logger with Current Interrupters. As with digital meters,
7-15
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