AquiStar PS98i Bedienungsanleitung
For PSIG
sensors, refer
to page 6
regarding
desiccant
use!
AquiStar®
PS98i/PS9800
Submersible Pressure Transmier
INSTRUCTION MANUAL
1
Information in this document is subject to change without notice and does not
represent a commitment on the part of the manufacturer. No part of this manual may
be reproduced or transmitted in any form or by any means, electronic or mechanical,
including photocopying and recording, for any purpose without the express written
permission of the manufacturer.
©1997 - 2013 Instrumentation Northwest, Inc.
Registered trademarks and trademarks belong to their respective owners.
Table of Contents
Introduction - PS98i & PS9800 4-20 mATransmitters...................................................2
Initial Inspection and Handling.........................................................................................2
Do’s and Don’ts ................................................................................................................2
General Information..........................................................................................................3
Installation.........................................................................................................................5
Monitoring Wells.......................................................................................................5
Other Installations......................................................................................................6
Maintenance......................................................................................................................6
Desiccant Tubes.........................................................................................................6
Miscellaneous............................................................................................................7
Troubleshooting................................................................................................................7
Erratic Readings.........................................................................................................7
Oscillating Readings Over Time................................................................................7
Zero Readings When Pressurized.............................................................................8
Technical Specifications....................................................................................................8
Component and Wiring Information..........................................................................9
Mechanical Specifications ......................................................................................10
Electrical Specifications ..........................................................................................10
Adaptors...................................................................................................................11
Reordering Information ..................................................................................................11
Accessories .....................................................................................................................11
LIMITED WARRANTY/DISCLAIMER - PS98i/PS9800 ...........................................12
2
Introduction - PS98i & PS9800 4-20 mA Transmitters
These pressure transmitters represent the latest state-of-the-art technology and have
been designed to provide trouble-free submersible operation in liquid environments,
when properly installed and operated. Please take the time to read through this manual
if you are not familiar with this product.
Initial Inspection and Handling
Upon receipt of your transmitter, 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 dam-
age is found, immediately file a claim with the carrier.
Check the etched label on the transmitter 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 the device with care.
Do store the device in a dry, inside area when not in use.
Do install a desiccant tube if you are doing long-term outdoor monitoring.
Don’t install the device so that the connector end is submerged.
Don’t support the device with the connector or with the connectors of an extension
cable. Use a strain relief device to take the tension off the connectors.
Don’t allow the device to free-fall down a well at high velocities as impact damage
can occur.
Don’t bang or drop the device on hard objects.
Don’t disassemble the device. (The warranty is void if transmitter is disassembled.)
3
General Information
The following paragraphs outline the basics of how pressure is measured using sub-
mersible pressure transmitters:
Liquids and gasses do not retain a fixed shape. Both have the ability to flow and are
often referred to as fluids. One fundamental law for a fluid is that the fluid 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 fluid 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 fluid 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 on a “normal” day) is defined 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 difference between the absolute pressure (Pa) and atmospheric pressure (Patm):
Pg = Pa - Patm
Pressure Diagram
4
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 dif-
ferential (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 an incompressible fluid), the pres-
sure increases linearly. Also, recall that changes in weather cause the absolute atmo-
spheric 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 ft of water = 1 PSI)
Pressure Diagram, Detail “A”
INW’s 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 reflects only the depth of submergence. That is, the net pressure on the
diaphragm is due entirely to the depth of submergence.
5
Installation
The PS98i & PS9800 measure pressure. The most common application is measuring
liquid levels in wells and tanks. In order to do this, the transmitter must be installed
below the water level at a fixed depth. The installation depth depends on the range of
the transmitter. One (1) PSI is equal to approximately 2.31 feet of water. If you have
a 5 PSI transmitter, the range is 11.55 feet of water and the transmitter should not be
installed at a depth below 11.55 feet. If the transmitter is installed below its maximum
range, damage may result to the transmitter and the output reading will not be correct.
Monitoring Wells
Lower the transmitter to the desired depth. Fasten the cable to the well head using tie
wraps or a weather proof strain-relief system. When securing the cable, make sure not
to pinch the cable too tightly or the vent tube inside the cable jacket may be sealed off.
Take a measurement to insure the transmitter is not installed below its maximum range.
It is recommended that several readings be taken to insure proper operation after instal-
lation.
Important Note: If the transmitter is to be left in the well for a long-term
monitoring application and the connector end is not in a dry, thermally-stable
environment, a desiccant tube must be installed in line with the cable to pre-
vent condensation in the cable vent tube. Water in the vent tube will cause
inaccurate readings and, in time, will work its way into the transmitter and
damage it.
Installation
6
Other Installations
The transmitter can be installed in any position; however, when it leaves the factory it is
tested in the vertical position. Strapping the transmitter body with tie wraps or tape will
not hurt it. If the transmitter is being installed in a fluid environment other than water,
be sure to check the compatibility of the fluid with the wetted parts of the transmitter.
INW can provide a variety of seal materials if you are planning to install the transmitter
in an environment other than water.
Maintenance
Desiccant Tubes
On vented sensors, inspect the desiccant tube at least once every two months. The des-
iccant tube prevents moisture in the air from being sucked into the vent tube, which can
cause erratic readings and sensor damage.
The desiccant tube is filled with blue silica gel beads. A locking barb and a hydrophobic
water filter are attached to the end of the desiccant tube. This filter prolongs the life of
the desiccant as much as three times over a desiccant tube without the filter.
Install the sensor so that the desiccant tube will not flood or lie in water.
The desiccant is a bright blue color when active and dry. As moisture is absorbed the
color will begin to fade, becoming a light pink, which indicates full saturation and time
to replace. Replacement desiccant and hydrophobic filters can be purchased from INW;
please contact an INW sales engineer for more information.
The desiccant tube prevents water intrusion through the vent tube. Be sure to
replace the desiccant when it turns pink, as that indicates it is saturated.
Vent tube
Cable
Desiccant tube Hydrophobic filter
7
Miscellaneous
Sensor: There are no user-serviceable parts, other than the batteries. If problems
develop with sensor stability or accuracey, contact INW. If the transducers have been
exposed to hazardous materials, do not return them without notification and authoriza-
tion.
Cable: Cable can be damaged by abrasion, sharp objects, twisting, crimping, crushing,
or pulling. Take care during installation and use to avoid cable damage. If a section
of cable is damaged, it is recommended that you send your sensor back to replace the
cable harness assembly.
End Connections: The contact areas (pins & sockets) of the connectors will wear out
with extensive use. If your application requires repeated connections other types of
connectors can be provided. The connectors used by INW are not submersible, but are
designed to be splash-resistant.
Troubleshooting
Erratic Readings
Erratic readings can be caused by a damaged transmitter, damaged cable, poor connec-
tions or improper operation of readout equipment. In most cases, erratic readings are
due to moisture getting into the system. Assuming that the readout equipment is work-
ing correctly, the first thing to check is the connection. Look for moisture between
contacts or a loose or broken wire. If the connection appears OK, pull the transmitter
up a known distance while monitoring its output. If the transmitter responds approxi-
mately as it should, but the reading is still erratic, most likely the cable is damaged. If
the transmitter does not respond approximately as it should, it is most likely that the
sensor is damaged. In either case, consult the factory.
Oscillating Readings Over Time
If, after time, your transmitter is functioning normally but your data is showing a
cyclic effect in the absence of water level changes, you are probably seeing baromet-
ric changes. The amount is usually .5 to 1.5 feet of water. This can be caused by a
plugged vent tube in the cable or actual water level changes in the aquifer itself in re-
sponse to barometric pressure changes. This effect can occur in tight formations where
the transmitter will immediately pick up barometric changes but the aquifer will not. If
you think you are having this type of problem you will have to record the barometric
pressure as well as the water level pressure and compensate the data. If it appears that
the vent tube is plugged, consult the factory.
8
If a desiccant tube is not installed in line with the cable, water may have condensed in
your vent tube causing it to plug. After you are finished installing the desiccant tube
you can test the vent tube by applying a small amount of pressure to the end of the
desiccant tube and seeing if this affects the transmitter reading.
Zero Readings When Pressurized
Continuous zero readings are caused by an open circuit which usually indicates broken
cable, a bad connection, or possibly a damaged transmitter. Check the connector to see
if a wire has become loose, or if the cable has been cut. If neither of these appears to
cause the problem, the transmitter needs factory repair.
Technical Specifications
The PS98i submersible pressure transmitter represents the latest in state-of-the-art level
measurement technology. This industry standard two-wire, 4-20 mA device offers
improved noise immunity, thermal performance and transient protection. In addition
to reverse polarity protection, under-current and over-current limitation are featured on
both transmitter channels.
As mentioned above, the PS98i & PS9800 transmitters are current loop devices. This
means that changes in pressure imposed on the stainless steel diaphragm result in
proportional changes in current. The excitation source (DC supply or data logger) sup-
plies the power but the transmitter actually controls how much current flows as long as
the excitation specifications (e.g., voltage level) are met.
For a standard gauge pressure device, there is zero pressure on the diaphragm when
above the surface of the liquid. This zero pressure is converted to a current flow of
4 mA. As the transmitter is lowered into the liquid, the amount of current that flows
increases linearly (with increasing depth) to 20 mA when the maximum rated pressure
(thus depth) is reached. That is, there is a straight line relationship between pressure
(thus depth of submergence) and the amount of current that flows. Adata logger there-
fore can apply power, measure the amount of current that is flowing and convert that to
the depth of submergence using a multiplier and offset (m and b, respectively, for a y =
mx + b straight line) which are preset in the logger by the user.
Compute these m and b values as follows:
m = (Total range of measurement in your units) / 16 / 1000
For example: if you want to measure 0 – 15 psi:
15 / 16 / 1000 = .0009375
b = m * 4000 * (–1)
Using our 0 – 15 psi example above, this would be
.0009375 * 4000 * (–1) = –3.75
9
Component and Wiring Information
Wiring Information
Cable Type: 9-conductor, vented
PS9800
4-20 mA pressure only
Shield = ground
White = (V+) pressure
Blue = pressure signal return
4-20 mA pressure and temperature
Shield = ground
White = (V+) pressure
Blue = pressure signal return
Yellow = (V+) temperature
Purple = temperature signal return
PS98i
4-20 mA pressure only
Shield = ground
White = (V+) pressure
Blue = pressure signal return
4-20 mA pressure and 30K thermistor
Shield = ground
White = (V+) pressure
Blue = pressure signal return
Yellow = resistance
Purple = resistance
Transmitter Components
Transmitter Components
0.28”
(0.7 cm) Cable
Water
Inlets
Diameter 0.75” (1.9 cm)
8.30”
(21.081 cm)
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