Specifications

1
APPLICATION NOTE NO. 84 July 2006
Using Instruments with Druck Pressure Sensors in
Muddy or Biologically Productive Environments
This Application Note applies to Sea-Bird instruments with Druck pressure sensors, for moored applications or other long
deployments that meet either of the following conditions:
used in a high-sediment (muddy) environment, in a pressure sensor end up orientation
used in a biologically productive environment, in any orientation
At Sea-Bird, a pressure port plug with a small (0.042-inch diameter)
vent hole in the center is inserted in the pressure sensor port. The vent hole
allows hydrostatic pressure to be transmitted to the pressure sensor inside
the instrument.
If the instrument is deployed in a high-sediment (muddy) environment
with the pressure sensor end up, the pressure port may partially fill
with sediment (through the vent hole) over time, causing a delay in the
pressure response.
If the instrument is deployed in a biologically productive environment,
the vent hole may be covered with biological growth over time, causing a
delay in the pressure response, or in extreme cases completely blocking
the pressure signal.
Note: Photo is for an SBE 37-SM. Pressure port details are similar for all instruments included in this application note.
Sea-Bird has developed a high-head pressure port plug for deployment in muddy and/or
biologically productive environments. The high-head plug extends beyond the surface of
the instrument end cap, and has four horizontal vent holes connecting internally to a vertical
vent hole.
The horizontal orientation of the external holes prevents the deposit of sediment inside
the pressure port.
Each of the four vent holes is larger (0.062-inch vs. 0.042-inch diameter) than the
single vent hole in the standard pressure port plug, significantly reducing the possibility
that biological growth will cover all of the hole(s).
To purchase the high-head pressure port plug, Part Number 233186, contact Sea-Bird.
High-Head Pressure Port Plug Installation
1. Unscrew the standard pressure port plug from the pressure port.
2. Rinse the pressure port with warm, de-ionized water to remove any particles, debris, etc. Do not put a brush or any
object in the pressure port; doing so may damage or break the pressure sensor.
3. Install the high-head pressure port plug in the pressure port.
Note: Until several years ago, Sea-Bird filled the pressure port with silicon oil at the factory. For Druck pressure sensors,
we determined that this was unnecessary, and no longer do so. It is not necessary to refill the oil in the field. However, for
Paine or Paroscientific Digiquartz pressure sensors, the pressure port does need to be refilled with silicon oil. Please
contact Sea-Bird with the serial number of your instrument if you are unsure of the type of pressure sensor installed in
your instrument.
Sea-Bird Electronics, Inc.
1808 136th Place NE
Bellevue, WA 98005
US
A
Phone: [phone]
Fax: [phone]
E-mail: [e-mail]
Web: www.seabird.com
High-Head
Pressure Port Plug,
Part Number 233186
Vent hole
(typical)
Standard pressure sensor port plug
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