Drawing Number: 21102
Revision: A
OPERATION MANUAL FOR
2
Series 138
Some models of the Series 138 feature a tygon tube
closed at one end with conical-shaped delrin plug.
The plug features a small hole for attachment of a
weight. Other models feature a one-piece molded
closed tube.
2.0
INSTALLATION, CABLE
ATTACHMENT, AND SEALING
THE CABLE/CONNECTOR
ASSEMBLY
Various methods are used to mount the 138 sensors
for use in liquids. Care should be taken to prevent
conductive liquids from entering the cable or
connector assemblies, where they could cause
corrosion,
short-circuiting
or
degradation
of
insulation resistance.
For low-pressure (<500psi) dynamic measurements, a
standard low-noise coaxial cable with an extruded
teflon jacket and a 10-32 connector can be used.
Heat shrink tubing, RTV silicon rubber or sometimes
silicone grease can make an adequate seal in an
environment with low static pressure.
For high static pressures due to deep submersion or
use in a pressure vessel, alternate methods of sealing
the cable/connector may be required. A method of
waterproofing the cable/connector assembly of a 138
which also provides protection to the cable is to put a
flexible tube (plastic, tygon, etc.) around the cable
and cable/connector assembly. Tie the tube at the
metal housing with monofilament or fine steel wire.
The opposite end of the tube must be above the level
of the liquid or sealed around the cable to prevent
liquid from entering the protective tubing. Filling the
protective tube with a non-conducting liquid such as
Dow Coming silicone oil can be done to prevent the
tube from collapsing. This will also equalize pressure
inside and outside the tubing, helping to prevent a
conductive liquid (such as water) from entering.
In some blast applications, when using a standard 10-
32 micro cable/connector, the high shock can flex the
cable/connector joint enough to move the center pin
of the 10-32 cable connector. This can cause noise
on the output signal. Protecting the connection from
shock may be required.
PCB Model 070A03 adaptor can be used to adapt the
10-32 micro jack on the 138 to a BNC jack. A
heavier coaxial cable (eg. RG-58/U) can now be used
in place of the micro cable. Because of the large
mass of the 070A03 compared to the 10-32 jack, this
connection should be sealed and protected from
shock and turbulence. Putting a two to three inch
diameter of duct seal, wrapped with a waterproof
tape, will seal the connection and provide shock
protection at the cable/connector/ amplifier assembly.
PCB Model 070A09 Solder Connector Adaptor can
also be used to attach a short length (~two to three
inches) of ribbon cable to a 138. The ribbon cable
can then be soldered to an extension cable. The
ribbon cable and both solder connections should be
sealed with a suitable waterproofing material.
Various types of sealing materials such as
polyethylene and flexane have been shown to be
effective for sealing cables, connectors, etc.
2.1
MOUNTING OR SUSPENDING
THE SENSOR
After the cable/connector assembly is sealed, the
sensor can be suspended in the liquid where the
measurement is to take place. For low dynamic
pressure measurements (less than 500 psi), models
featuring a small hole in the conical end piece of the
tube allow attachment of a light weight (~two lb.) to
suspend the sensor in a vertical position.
The line should be of light material (monofilament,
15 lb. test) to enable it to break easily. This way, the
sensor does not pull apart in the turbulence caused by
the collapse of gas bubbles resulting from a shock
wave.
For higher pressure dynamic measurements, alternate
methods of suspending the sensor should be used to
minimize damage from turbulence. Taping or
attaching (with cable ties) the sensor amplifier
housing to a braided steel wire is a method that is
suited for use in higher dynamic pressure
measurements.
Summary of Contents for ICP 138A50
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