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2.5.1
Sizing of PVDF Probe
Null Zone
Overall
Length
Deadband
Clearance
Figure 2-6
PVDF Probe
Insertion Length: The actual height of the tank from the
mounting point to the bottom of the tank.
Clearance: The distance from the bottom of the tank required
for probe expansion at higher temperatures.
Dead Band: Inactive area at the bottom of the probe. The
spacer used at the bottom of the tank to insure the float will be
in the active range during contraction of the probe.
Null Zone: The inactive area at the top of the probe where the
electronics are located.
Active Range: Is the Insertion Length minus the Clearance
+ Deadband plus 5" (127mm) for the Null Zone. See Table 2-1
below to determine the variable dimensions.
PVDF Probes Without a Weight Kit are usually those less
than 10 feet (3.1m) in length. They have a Float Kit that comes
with a special spacer and pin that must be used to prevent float
from entering the deadband at the end of the probe.
"C" version PVDF probes are for limited temperature ranges
of -4°F to 120°F (-20°C to 49°C ). They come with a spacer and
upper level float collar. They have a 3" (76mm) deadband at the
bottom of the probe because of less need for expansion room at
those temperatures. The Null Zone on the "C" version is 9".
PVDF Probes Requiring a Weight Kit, come with the
weight and retainer pin along with the float made of either
316SS or PVDF, depending upon the application requirements.
Deadband is variable, See Table 2-1.
Length
0-144 in
(0 - 3660 mm)
145-288 in
Active
(368 - 7320
Span
mm)
289-432 in
(7.34 - 11 m)
433-600 in
(11 - 15.2 m)
Clearance
Dead Band
1 in
6 in
(25 mm)
(152 mm)
2 in
8 in
(51 mm)
(203 mm)
3 in
12 in
(76 mm)
(305 mm)
4 in
14 in
(102 mm)
(356 mm)
Table 2-1
Variable Dimensions for PVDF Probe
15
Installation
Null Zone
Spacer
12 in
5 in
(305 mm)
(127 mm)
12 in
7 in
(305 mm)
(178 mm)
12 in
11 in
(305 mm)
(279 mm)
12 in
13 in
(305 mm)
(330 mm)
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