Geokon 4500HT User manual

Instruction Manual
Model 4500HT
High Temperature
Vibrating Wire Piezometer
No part of this instruction manual may be reproduced, by any means, without the written consent of Geokon, Inc.
The information contained herein is believed to be accurate and reliable. However, Geokon, Inc. assumes no responsibility for
errors, omissions or misinterpretation. The information herein is subject to change without notification.
Copyright © 2012, 2013 by Geokon, Inc.
(Doc Rev A 6/13)

Warranty Statement
Geokon, Inc. warrants its products to be free of defects in materials and workmanship, under normal
use and service for a period of 13 months from date of purchase. If the unit should malfunction, it must
be returned to the factory for evaluation, freight prepaid. Upon examination by Geokon, if the unit is
found to be defective, it will be repaired or replaced at no charge. However, the WARRANTY is VOID
if the unit shows evidence of having been tampered with or shows evidence of being damaged as a
result of excessive corrosion or current, heat, moisture or vibration, improper specification,
misapplication, misuse or other operating conditions outside of Geokon's control. Components which
wear or which are damaged by misuse are not warranted. This includes fuses and batteries.
Geokon manufactures scientific instruments whose misuse is potentially dangerous. The instruments
are intended to be installed and used only by qualified personnel. There are no warranties except as
stated herein. There are no other warranties, expressed or implied, including but not limited to the
implied warranties of merchantability and of fitness for a particular purpose. Geokon, Inc. is not
responsible for any damages or losses caused to other equipment, whether direct, indirect, incidental,
special or consequential which the purchaser may experience as a result of the installation or use of the
product. The buyer's sole remedy for any breach of this agreement by Geokon, Inc. or any breach of any
warranty by Geokon, Inc. shall not exceed the purchase price paid by the purchaser to Geokon, Inc. for
the unit or units, or equipment directly affected by such breach. Under no circumstances will Geokon
reimburse the claimant for loss incurred in removing and/or reinstalling equipment.
Every precaution for accuracy has been taken in the preparation of manuals and/or software, however,
Geokon, Inc. neither assumes responsibility for any omissions or errors that may appear nor assumes
liability for any damages or losses that result from the use of the products in accordance with the
information contained in the manual or software.

TABLE of CONTENTS
1. INTRODUCTION....................................................................................................................................1
2. PRINCIPLE OF OPERATION ..............................................................................................................1
3 INSTALLATION ......................................................................................................................................2
3.1 PRELIMINARY TESTS ..............................................................................................................................2
3.2 CABLES ............................................................................................................................................3
3.3 INSTALLATION IN BOREHOLES .............................................................................................................4
4TAKING READINGS ...........................................................................................................................4
4.1WIRING DIAGRAM .................................................................................................................................4
4.2 OPERATION OF THE GK-403 READOUT BOX......................................................................................4
4.3 OPERATION OF THE GK-404 READOUT BOX......................................................................................5
4.4 OPERATION OF THE GK-405 READOUT BOX......................................................................................6
4.5 MEASURING TEMPERATURES..............................................................................................................7
5. DATA REDUCTION ...............................................................................................................................7
LIST of FIGURES, TABLES and EQUATIONS
FIGURE 1MODEL 4500HT HIGH TEMPERATURE PRESSURE TRANSDUCER .................................................1
FIGURE 24500HT PRESSURE TRANSDUCER ATTACHED TO COILED CABLE.................................................3
FIGURE 3GK405 READOUT BOX..................................................................................................................6
FIGURE 4MODEL 4700 VW TEMP SENSORTYPICAL CALIIBRATION SHEET.................................................9
FIGURE 5MODEL 4500 VW PRESSURE SENSORTYPICAL CALIIBRATION SHEET AT ROOM TEMP............10
FIGURE 6MODEL 4500 VW PRESSURE SENSORTYPICAL CALIIBRATION SHEET AT 100C……...………11
FIGURE 7MODEL 4500 VW PRESSURE SENSORTYPICAL CALIIBRATION SHEET AT 150C…………...…12
FIGURE 8MODEL 4500 VW PRESSURE SENSORTYPICAL CALIIBRATION SHEET AT 200C.......................13
FIGURE 9MODEL 4500 VW PRESSURE SENSORTYPICAL CALIIBRATION SHEET AT 250C……………....14

1. INTRODUCTION
Geokon’s 4500HT Series High Temperature Piezometers and Pressure Transducers are
designed for monitoring downhole pressures and temperatures in oil recovery systems
and geothermal applications.
These sensors are capable of operation under extreme conditions and at temperatures
up to 250°C. In thermal recovery applications (steam assisted gravity drainage (SAGD)
or cyclic steam stimulation (CSS)), they can provide accurate, real-time, continuous
monitoring of pressures in production and injection wells thereby optimizing the recovery
rate and reducing the costs of the steam injection process. In geothermal applications,
they offer a means for in situ and continuous monitoring of pressures and temperatures
over extended periods of time.
Figure 1 Model 4500HT high temperature pressure transducer
2. PRINCIPLE OF OPERATION
The sensor utilizes a sensitive stainless steel diaphragm to which a vibrating wire
element is connected. See Figure 2. In use, changing pressures on the diaphragm
cause it to deflect, and this deflection is measured as a change in tension and frequency
of vibration of the vibrating wire element. The square of the vibration frequency is

2
directly proportional to the pressure applied to the diaphragm. Two coils, one with a
magnet, another with a pole piece, are located close to the wire. In use, a pulse of
varying frequency (swept frequency) is applied to the coils and this causes the wire to
vibrate primarily at its resonant frequency. When excitation ends the wire continues to
vibrate and a sinusoidal AC electrical signal, at the resonant frequency, is induced in the
coils and transmitted to the readout box where it is conditioned and displayed.
To prevent damage to the sensitive diaphragm a filter is used to keep out solid particles.
. Standard filters are 50 micron stainless steel; high air entry value tips are available on
request.
All exposed components are made of corrosion resistant stainless steel and, if proper
installation techniques are used, the device should have an unlimited life. In salt water it
may be necessary to use special materials for the diaphragm and housing.
Portable readout units are available to provide the excitation, signal conditioning and
readout of the instrument. Datalogging systems are also available for remote
unattended data collection of multiple sensors. Contact Geokon for additional
information.
Calibration data are supplied with each piezometer for conversion of gage readings to
engineering units and for temperature corrections see Section 5.
3 INSTALLATION
3.1 Preliminary Tests
Upon receipt of the piezometer the zero reading should be checked and noted (see
Sections 3.1 to 3.3 for readout instructions). A Model 4700 VW Temperature Sensor is
included inside the body of the sensor for the measurement of temperature (see Section
5 for instructions).
Calibration data are supplied with each gage and zero readings at six different
temperatures and barometric pressure, is included. Zero readings at the site should
coincide with the calibration zero readings within +/- 50 digits after barometric and
temperature corrections are made. The factory elevation is +580 ft. Before March 21,
1995 factory barometric pressure readings were corrected to sea level; readings after
this date represent absolute pressure. (Barometric pressure changes with elevation at a
rate of

½ psi per 1,000 ft.) See Section 5 for sample calibration sheets.

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3.2 Cables
The 4500HT Series are delivered with either mineral insulated cables (4 solid, 22 gage
copper conductors in magnesium oxide inside a 316 stainless steel tube), or with Teflon®
insulated cables inside stainless steel tubing with couplings or Teflon insulated
conductors in a continuous stainless steel tube. The Tubing is delivered in coils and can
be terminated with a connector, a transition to a regular instrumentation cable, or other
as determined by the customer.
Figure2 4500HT pressure transducer attached to coiled cable
Cable lengths of several kilometers are possible and the frequency output signal is not
affected by changing cable resistances (caused by splicing, changes of length, terminal
contact resistances, etc.), nor by penetration of moisture into the electronic circuitry.
These sensors are designed for static measurements only and at least one second is
required to excite and read the sensor.

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3.3 Installation in Boreholes
Before installing make sure both pressure and temperature sensors are working and
record initial readings with a portable readout box (GK-403 or GK 404).
Push the sensor into the borehole by whatever means are chosen. This may include
attachment to grout pipes, special installation rods or other apparatuses being
inserted into the borehole at the same time.
4 TAKING READINGS
The 4500HT is usually connected to a datalogger. But for initial set up it is often
convenient to use a portable readout box. In the case of dataloggers the pluck voltage
setting to use is 12Volts..
4.1 Wiring Diagram
For the 4500HT pressure transducer the red and black leads are connected to the
pressure transducer and the green and white leads are connected to the vibrating wire
temperature sensor.
4.2 Operation of the GK-403 Readout Box
The GK-403 can store gage readings and also apply calibration factors to convert
readings to engineering units. Special GK 403 units can be provided that have a 12Volt
pluck. Consult the GK-403 Instruction Manual for additional information on Mode "G" of
the Readout. The following instructions will explain taking gage measurements using
Modes "B" and "F"
Connect the Readout using the flying leads, the red and black clips are for taking both
the pressure reading, and the temperature reading. [The white and green leads of the
flying leads are not used].
1. Turn the display selector to position "B" (or "F"). Readout is in digits

5
2. Turn the unit on and a reading will appear in the front display window. The last digit
may change one or two digits while reading. Press the "Store" button to record the
value displayed. If the no reading displays or the reading is unstable see section 5
for troubleshooting suggestions. The thermistor will be read and output directly in
degrees centigrade.
3. The unit will automatically turn itself off after approximately 2 minutes to conserve
power.
4.3 Operation of the GK-404 Readout Box
The GK404 is a palm sized readout box which displays the Vibrating wire value and the
temperature in degrees centigrade.
The GK-404 Vibrating Wire Readout arrives with a patch cord for connecting to the
vibrating wire gages. One end will consist of a 5-pin plug for connecting to the socket on
the bottom of the GK-404 enclosure. The other end will consist of 5 leads terminated
with alligator clips. Note the colors of the alligator clips are red, black, green, white and
blue. Only the red and black clips are used. Connect first to the red and black leads of
the 4500HT cable (pressure) and then to the green and white leads (temperature).
Use the POS (Position) button to select position Band the MODE button to select Dg
(digits).
Other functions can be selected as described in the GK404 Manual.
The GK-404 will continue to take measurements and display the readings until the OFF
button is pushed, or if enabled, when the automatic Power-Off timer shuts the GK-404
off.
The GK-404 continuously monitors the status of the (2) 1.5V AA cells, and when their
combined voltage drops to 2V, the message Batteries Low is displayed on the screen.
A fresh set of 1.5V AA batteries should be installed at this point

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4.4 Operation of the GK-405 Readout Box
The GK-405 Vibrating Wire Readout is made up of two components:
the Readout Unit, consisting of a Windows Mobile handheld PC running the GK-405
Vibrating Wire Readout Application
the GK-405 Remote Module which is housed in a weather-proof enclosure and
connects to the vibrating wire sensor by means of:
1) Flying leads with alligator type clips when the sensor cable terminates in bare wires
or,
2) by means of a 10 pin connector..
The two components communicate wirelessly using Bluetooth®, a reliable digital
communications protocol. The Readout Unit can operate from the cradle of the Remote
Module (see Figure 3) or, if more convenient, can be removed and operated up to 20
meters from the Remote Module
Figure 3 GK405 Readout Unit
For further details consult the GK405 Instruction Manual.

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4.5Measuring Temperatures
Each 4500HT pressure transducer is equipped with a Model 4700 vibrating wire
temperature sensor connected to the white and green leads.
A Typical Calibration Sheet is Shown on page 9
5. DATA REDUCTION
The Model 4500HT pressure transducer incorporates a Model 4700 thermometer –both
sensors operating on the vibrating wire principle. The Model 4700 thermometer output
will yield the operating temperature directly using a second order polynomial. Calculation
of the pressure from the Model 4500HT pressure transducer readings is not quite so
direct because the effect of temperature on both the zero reading and gage factor on the
sensors must be taken into account.
Each Model 4500HT pressure transducer/thermometer combination is supplied with a
calibration sheet from the Model 4700 thermometer (see Figure 4) showing the output of
the temperature sensor at 5 different temperatures ranging from room temperature to
250 degrees C. Also supplied are six calibration sheets from the pressure transducer
showing the output readings versus pressure change at each one of these six
temperature intervals. ( Typical Calibration Sheets for the 4500HT transducer are shown
in Figures 5 thru 9).In essence the data interpretation proceeds as follows, using second
order polynomials for greater accuracy:
To calculate the pressure, P, from any current reading, R1, on the pressure transducer.
1. Calculate the temperature, T, from the VW temperature sensor using the output
reading, RTfrom the temperature sensor and the polynomial expression shown on the
temperature gage calibration sheet.
2. Use the temperature values and the zero pressure readings shown on the six
calibration sheets in an Excel spreadsheet to develop a polynomial that describes how
the zero reading, R0, varies with the temperature. (This polynomial will be supplied
along with the cal sheets).

8
3. Use temperature values and the linear gage factors shown on the six calibration
sheets in an Excel spreadsheet to develop a polynomial that describes how the gage
factor, G, varies with the temperature. (This polynomial will be supplied along with the
cal sheets).
Fourth, Using these developed polynomials calculated values of R0 and G at the
measured temperature, T, and with the current reading R1 find the pressure P from the
equation P = (R1- R0) G
An example follows. From the one Model 4700 temperature calibration sheet, and the
five pressure calibration sheets at five different temperatures. Using an Excel
Spreadsheet and the Chart Wizard Trendlines.
T = 3.7511E-07 RT2 + 0.03484 RT-124.98
Equation 1
R0 = -0.00193T2+ 1.885T + 8367
Equation 2
G = -8.61E-11T2–2.038E-09T - 0,0002246
Equation 3
For example: suppose that the reading, RT, on the temperature sensor is 8400 and the
reading on the pressure transducer, R1, is 6500,
then: from Equation 1 T = 194.1°C
and from Equation 2 R0 = 8660
and from Equation 3 G = -0.0002282
From which P = (6500 –8660) (-0.002282) = 0.493MPa

9

10
Figure 4 A Typical Model 4700 VW Temperature Sensor Calibration Sheet
Figure 5 Typical Calibration Sheet at 25°C

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Figure 6 Typical Calibration Sheet at100°C

12
Figure 7 Typical Calibration Sheet at 150°C

13
Figure 8 Typical Calibration Sheet at 200°C

14
Figure 9 Typical Calibration Sheet at 250°C