Precision Environmental Sensors
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For Sales & Service Contact
2650 E. 40th Ave. • Denver, CO 80205
Phone 303-320-4764 • Fax 303-322-7242
1-800-833-7958
www.geotechenv.com
An ON
I
CON Brand
PT12
Pressure/Temperature Sensor
Instructions
For PSIG
sensors, refer
to page 16
regarding
desiccant
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PROUDLY
MADE
IN THE
USA
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C
ISO
9001:2008
a
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y
use!
TABLE OF CONTENTS
General Information
General Information ...................................................................................................................................................Page 3
Dimensions ....................................................................................................................................................................Page 3
Specications ................................................................................................................................................................Page 4
How Pressure Sensors Work....................................................................................................................................Page 5
Initial Inspection and Handling ..............................................................................................................................Page 6
Do’s and Don’ts ............................................................................................................................................................Page 6
Installation
Cable Wiring ..................................................................................................................................................................Page 7
Installing the Sensor ...................................................................................................................................................Page 7
Desiccant Use ................................................................................................................................................................Page 7
Grounding Issues .........................................................................................................................................................Page 8
Sensor/Data Logger Conguration ......................................................................................................................Page 8
Operation/Modbus RTU
Power Consideration ..................................................................................................................................................Page 9
Communication Settings ..........................................................................................................................................Page 9
Modbus Functions.......................................................................................................................................................Page 9
Register Denitions .....................................................................................................................................................Page 9
Sensor Conguration/Control ................................................................................................................................Page 10
Readings and the Auto-Enable Setting ...............................................................................................................Page 10
Calibration and Conversion Constants ................................................................................................................Page 10
PT12 INSTRUCTIONS
Operation/SDI-12
Reading via SDI-12 ......................................................................................................................................................Page 11
Calibration Register Denitions .............................................................................................................................Page 15
Maintenance
Removing Debris from End Cone ..........................................................................................................................Page 16
Desiccant Tubes ...........................................................................................................................................................Page 16
Sensor/Cable/End Connections .............................................................................................................................Page 17
Troubleshooting
Problems/Probable Causes/Things to Try ..........................................................................................................Page 18
Seametrics • 253.872.0284 Page 2 seametrics.com
GENERAL INFORMATION
PT12 INSTRUCTIONS
The Seametrics PT12 Pressure/Temperature Sensor
has been designed to provide trouble-free submersible
operation in liquid environments. This sensor communicates
via SDI-12 (v1.3) or Modbus® RTU (RS485)protocol.
Pressure/level is measured with an extremely rugged and
stable piezo-electric, media isolated pressure element
and compensated for temperature using Seametrics’
proprietary calibration methodology. Temperature is
measured using an on-board digital chip.
Dimensions
8.44” (21.4 cm)
Seametrics also carries a special version of the PT12
designed to measure barometric pressure in reference
to absolute pressure. If you are using an absolute PT12,
contact your representative for details on how our PT12-BV
can facilitate obtaining barometrically compensated
pressure/level.
0.28” (0.7 cm)
Water inlets
Diameter
0.75” (1.9cm)
Seametrics • 253.872.0284 Page 3 inwusa.com
GENERAL INFORMATION
PT12 INSTRUCTIONS
Specications*
Housing & Cable Weight 0.8 lb. (0.4 kg)
Body Material 316 stainless or titanium
Wire Seal
Material
Cable Submersible: polyurethane, polyethylene, or ETFE; 4 lb./100 ft., 1.8 kg/30 m; 2000 ft max for Modbus®
Desiccant 1-3 mm indicating silica gel
Field Connector Available as an option
Temperature Operating Range Recommended: -15˚ to 55˚C (5˚ to 131˚F) Requires freeze protection kit if using pressure option in water
Storage Range -40˚ to 80˚C (-40˚ to 176˚F)
Power Voltage 9-16Vdc, 24Vdc over voltage protection, electromagnetic & transient protection IEC-61000 - 4-3, 4-4,
Supply Current Active 3mA average/ 10mA peak; sleep 150 µA
Communication Modbus® RS485 Modbus® RTU, output=32bit IEEE oating point
SDI-12 SDI-12 (ver. 1.3) - ASCII
Output Channels Temperature Depth/Level¹
Element Digital IC on board Silicon strain gauge transducer, 316 stainless or Hastelloy
Accuracy ±0.5°C — 0° to 55°C (32˚ to 131˚F)
Resolution 0.06˚C 0.0034% FS (typical)
Range -15˚ to 55˚C (5˚ to 131˚F) Gauge
Compensated --- 0˚ to 40˚C (32˚ to 104˚F)
Max operating pressure 1.1 x full scale
Over pressure protection 3x full scale up to 300psi - for > 300psi (650 ft or 200 m) contact factory
Burst pressure 1000 psi (approx. 2000 ft or 600 m)
Environmental IP68, NEMA 6P
*Specications subject to change. Please consult out web site for the most current data (seametrics.com). Modbus is a registered trademark of Schneider Electric.
1 Higher pressure ranges available upon request
2 ±0.25% accuracy FSO (max) at this range
3 Depth range for absolute sensors has 14.7 PSI subtracted to give actual depth allowed.
Fluoropolymer and PTFE
below freezing.
4-5, 4-6
±2.0°C — below 0°C (32˚F)
±0.05% FSO (typical, static)
±0.1% FSO (maximum, static)
(B.F.S.L. 20˚C)
PSI: 12, 5, 7, 15, 30, 50, 100, 300
FtH₂O: 2.32, 12, 35, 69, 115, 231, 692
mH₂O: 0.72, 3.5, 5, 10.5, 21, 35, 70, 210
Absolute
3
PSI: 30, 50, 100, 300
FtH₂O: 35, 81, 196, 658
mH₂O: 10, 24, 59, 200
Seametrics • 253.872.0284 Page 4 seametrics.com
GENERAL INFORMATION
PT12 INSTRUCTIONS
How Pressure Sensors Work
Liquids and gasses do not retain a xed shape. Both
have the ability to ow and are often referred to as
uids. One fundamental law for a uid is that the uid
exerts an equal pressure in all directions at a given level.
Further, this pressure increases with an increasing depth of
“submergence”. If the density of a uid remains constant
(noncompressible...a generally good assumption for water
at “normal” pressures and temperatures), this pressure
increases linearly with the depth of “submergence”.
We are all “submerged” in the atmosphere. As we increase
our elevation, the pressure exerted on our bodies decreases
as there is less of this uid above us. It should be noted
that atmospheric pressure at a given level does vary
with changes in the weather. One standard atmosphere
(pressure at sea level at 20º C) is dened to be 14.7 PSI
(pounds per square inch).
There are several methods to reference a pressure
measurement. Absolute pressure is measured with respect
to an ideal vacuum (no pressure). Gauge pressure is the
most common way we express pressure in every day life
and is the pressure exerted over and above atmospheric
pressure. With this in mind, gauge pressure (Pg) can be
expressed as the dierence between the absolute pressure
(Pa) and atmospheric pressure (Patm):
Water Line
P = Patm + kd
A
Patm
d
“A”
Pressure Diagram: See Detail A.
Pg = Pa - Patm.
To measure gauge pressure, atmospheric pressure is
subjected to one side of the system and the pressure to be
measured is subjected to the other. The result is that the
dierential (gauge pressure) is measured. A tire pressure
gauge is a common example of this type of device.
Recall that as the level of submergence increases (in a
noncompressible uid), the pressure increases linearly.
Also, recall that changes in weather cause the absolute
atmospheric pressure to change. In water, the absolute
pressure (Pa) at some level of depth (d) is given as follows:
Pa = Patm + kd
where k is simply a constant
(i.e.: 2.307 feet of water = 1 PSI)
Seametrics’ standard gauge submersible pressure
devices utilize a vent tube in the cable to allow the
device to reference atmospheric pressure. The resulting
gauge pressure measurement reects only the depth of
submergence. That is, the net pressure on the diaphragm
is due entirely to the depth of submergence.
Absolute pressure is given as Pa = Patm + kd
(where k is 2.307 feet of water)
Seametrics • 253.872.0284 Page 5 inwusa.com
GENERAL INFORMATION
PT12 INSTRUCTIONS
Initial Inspection and Handling
Upon receipt of your sensor, inspect the shipping package for damage. If any damage is apparent, note the signs of
damage on the appropriate shipping form. After opening the carton, look for concealed damage, such as a cut cable. If
concealed damage is found, immediately le a claim with the carrier.
Check the etched label on the sensor to be sure that the proper range and type were provided. Also check the label
attached to the cable at the connector end for the proper cable length.
Do’s and Don’ts
Do handle sensor with
care
Do store sensor in a
dry, inside area when
not in use
Do install a desiccant
tube if using a gauge
sensor
Do not disassemble—
will void warranty!
Don’t drop into well
Lower gently to prevent
damage
Seametrics • 253.872.0284 Page 6 seametrics.com
Don’t scrape cable
over edge of well
May nick or fray the
cable
Don’t bend cable sharply
May close o vent tube
and/or weaken internal
wires
Don’t support sensor
with the connector
Use a strain relief device
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