Drawing Number: 21106
Revision: NR
OPERATION MANUAL FOR
MINIATURE ICP
PRESSURE SENSOR
105A AND 105C SERIES
2
3.3
MODELS 105C03, C13, 23, C33,
C43
This style is the largest and is supplied in five models
with full-scale ranges to 100, 1000, 5000, 10,000 and
30,000 psi.
The electrical connection to this style sensor is made
via a 10-32 coaxial connector.
3.4
FLASH TEMPERATURE
PROTECTION
It is good practice to protect the diaphragm against
flash thermal effects, especially when flush-mounted,
to minimize spurious outputs generated by high heat
influx due to blasts, high compression heating, etc.
One or more layers of black vinyl electrical tape on
the diaphragm can be useful for this purpose in many
cases. RTV-type silicone rubber has also proven
effective.
Experimentation is the best method for determination
of effectiveness of protective material for each sensor
application.
3.5
RECESSED INSTALLATION
If ultra-high frequency response is not needed, it is
good practice to use a recessed diaphragm
installation.
.060 Dia. Passage
Passage Length
.010 Gap
Typical Recessed Installation
Because of its one-piece machined diaphragm
construction, the 105A series is sensitive over its
entire frontal area. Use extreme care when preparing
recessed installation port to ensure that no particles,
burrs or other residue are entrapped in the .010
”
gap
ahead of the diaphragm. Force on the diaphragm due
to such entrapped particles may change the
calibration of the sensor.
Recessed mounting protects the sensor diaphragm
from the effects of high-flash temperatures and
particle impingement due to blast effects, thereby
prolonging sensor life.
The limitation is that this type of installation lies in
the high-frequency limiting effects of the passage, due
to its length.
The passage behaves like an underdamped second
order
system,
the
resonant
frequency being
determined by the passage length. This can have a
limiting effect on pressure pulse rise time while
causing passage ringing in cases where the passage is
too long with respect to pulse rise time. (See chart
below.)
The following relationship determines this resonant
frequency (f
r
):
(Hz)
L
4
V
fr
(Eq. 1)
Where: f
r
= Resonant frequency of passage (Hz)
V = Velocity of sound in air (ft/sec)
L = Length of column (ft)
For air at room temperature, (Eq. 1) becomes:
L
3300
f
r
Where L = Passage length (in.)
