Geokon 8020-59 User manual

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 © 2006 – 2018 by Geokon, Inc.
(Doc Rev J, 05/18/2018
Instruction Manual
Model 8020-59
Vibrating Wire to Analog Converter

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. INSTALLING AND CONFIGURING THE 8020-59 SOFTWARE APPLICATION ..................................... 2
2.1 CONFIGURING THE COM PORT ........................................................................................................................... 5
3. QUICK START (SINGLE CHANNEL)............................................................................................................... 7
4. SINGLE AND MULTI-CHANNEL OPERATION............................................................................................10
4.1 THEORY OF OPERATION.....................................................................................................................................10
4.2 OPERATING MODES ...........................................................................................................................................11
4.2.1 Single Channel Mode................................................................................................................................11
4.2.2 16-Channel Multiplexed Mode..................................................................................................................12
4.2.3 32-Channel Multiplexed Mode..................................................................................................................13
4.3 CONVERSION TO “DIGITS” .................................................................................................................................14
4.4CONNECTION TO A VOLTAGE INPUT DAS..........................................................................................................15
4.5 CONNECTION TO A CURRENT INPUT DAS..........................................................................................................15
4.6 TEMPERATURE MEASUREMENT .........................................................................................................................16
5. COMMUNICATIONS ..........................................................................................................................................17
5.1 COMMAND LINE INTERFACE..............................................................................................................................17
6. 8020-59 WINDOWS APPLICATION..................................................................................................................20
6.1 SOFTWARE INSTALLATION.................................................................................................................................20
6.2 STARTING THE 8020-59 APPLICATION ...............................................................................................................20
6.3 COMMUNICATIONS TIMEOUT ERROR .................................................................................................................20
6.4 SINGLE CHANNEL CONFIGURATION...................................................................................................................21
6.5 16-CHANNEL CONFIGURATION ..........................................................................................................................22
6.6 32-CHANNEL CONFIGURATION ..........................................................................................................................25
APPENDIX A. SPECIFICATIONS.........................................................................................................................26
A.18020-59 SPECIFICATIONS ..................................................................................................................................26
A.2 MULTIPLEXER TIMING SPECIFICATIONS............................................................................................................27
APPENDIX B. THERMISTOR TEMPERATURE DERIVATION.....................................................................28
APPENDIX C. WIRING CONFIGURATIONS.....................................................................................................29
C.1 VOLTAGE OUTPUT –SINGLE CHANNEL MODE (DIGITAL I/O DAS) ..................................................................29
C.2 VOLTAGE OUTPUT –16-CHANNEL MODE (DIGITAL I/O DAS) .........................................................................30
C.3 VOLTAGE OUTPUT –32-CHANNEL MODE (DIGITAL I/O DAS) .........................................................................31
C.4 CURRENT OUTPUT –SINGLE CHANNEL MODE (DIGITAL I/O DAS) ..................................................................32
C.5 CURRENT OUTPUT –16-CHANNEL MODE (DIGITAL I/O DAS): ........................................................................33
C.6 CURRENT OUTPUT –32-CHANNEL MODE (DIGITAL DAS)................................................................................34
C.7 VOLTAGE OUTPUT –SINGLE CHANNEL MODE (PLC DAS) ..............................................................................35
C.8 VOLTAGE OUTPUT –16-CHANNEL MODE (PLC DAS)......................................................................................36
C.9 VOLTAGE OUTPUT –32-CHANNEL MODE (PLC DAS)......................................................................................37
C.10 CURRENT OUTPUT –SINGLE CHANNEL MODE (PLC DAS).............................................................................38
C.11 CURRENT OUTPUT –16-CHANNEL MODE (PLC DAS)....................................................................................39
C.12 CURRENT OUTPUT –32-CHANNEL MODE (PLC DAS)....................................................................................40
APPENDIX D. DATA REDUCTION ......................................................................................................................41
D.1 PRESSURE CALCULATION..................................................................................................................................41
D.2 TEMPERATURE CORRECTION.............................................................................................................................42
D.3 BAROMETRIC CORRECTION (REQUIRED ONLY ON NON-VENTED TRANSDUCERS)...............................................43
APPENDIX E. SAMPLE CALIBRATION REPORT ...........................................................................................44
APPENDIX F. IMPROVING THE ACCURACY OF CALCULATED PRESSURES.......................................45
APPENDIX G. BAROMETRIC CORRECTION (NON-VENTED TRANSDUCERS ONLY).........................46

FIGURES
FIGURE 1-EXTRACTING THE 8020-59 INSTALLER .........................................................................................................2
FIGURE 2-SELECT DESTINATION FOLDER .....................................................................................................................2
FIGURE 3-EXTRACTED 8020-59 INSTALLER .................................................................................................................3
FIGURE 4-INSTALL WIZARD,START SCREEN................................................................................................................3
FIGURE 5-INSTALL WIZARD,CHOOSE USERS ...............................................................................................................3
FIGURE 6-INSTALL WIZARD,CHOOSE START MENU FOLDER.......................................................................................4
FIGURE 7-INSTALL WIZARD,INSTALLATION COMPLETE ..............................................................................................4
FIGURE 8-INSTALL WIZARD,LAUNCH 8020-59 APPLICATION......................................................................................5
FIGURE 9-8020-59 SOFTWARE APPLICATION,STARTUP DIALOG..................................................................................5
FIGURE 10 -COMMUNICATIONS PARAMETERS DIALOG .................................................................................................6
FIGURE 11 -SINGLE CHANNEL CONFIGURATION SCREEN ..............................................................................................8
FIGURE 12 -SINGLE CHANNEL MONITOR.......................................................................................................................8
FIGURE 13 -CONTROL SIGNAL SEQUENCE:SINGLE CHANNEL MODE ..........................................................................11
FIGURE 14 -CONTROL SIGNAL SEQUENCE:16-CHANNEL MODE (CHANNELS ONE AND TWO ONLY) ..........................12
FIGURE 15 -CONTROL SIGNAL SEQUENCE:32-CHANNEL MODE (CHANNELS ONE THROUGH FOUR ONLY) ................13
FIGURE 16 -COMMUNICATION TIMEOUT WARNING MESSAGE ....................................................................................20
FIGURE 17 -16-CHANNEL CONFIGURATION SCREEN ...................................................................................................22
FIGURE 18 -16-CHANNEL MONITOR SCREEN...............................................................................................................23
FIGURE 19 -CHANNEL ONE MONITOR .........................................................................................................................24
FIGURE 20 -32-CHANNEL MONITOR SCREEN...............................................................................................................25
FIGURE 21 -CHANNEL THREE MONITOR......................................................................................................................25
FIGURE 22 -16-CHANNEL MULTIPLEXER TIMING REQUIREMENTS ..............................................................................27
FIGURE 23 -32-CHANNEL MULTIPLEXER TIMING REQUIREMENTS ..............................................................................27
FIGURE 24 -CONNECTION EXAMPLE FOR ONE CHANNEL 8020-59 WITH VOLTAGE OUTPUT TO DIGITAL I/O DAS.....29
FIGURE 25 -CONNECTION EXAMPLE FOR 16-CHANNEL MULTIPLEXER,8020-59 WITH VOLTAGE OUTPUT AND DIGITAL
I/O DAS .............................................................................................................................................................30
FIGURE 26 -CONNECTION EXAMPLE FOR 32-CHANNEL MULTIPLEXER,8020-59 WITH VOLTAGE OUTPUT AND DIGITAL
I/O DAS .............................................................................................................................................................31
FIGURE 27 -CONNECTION EXAMPLE FOR ONE CHANNEL 8020-59 WITH CURRENT OUTPUT TO DIGITAL I/O DAS .....32
FIGURE 28 -CONNECTION EXAMPLE FOR 16-CHANNEL MULTIPLEXER,8020-59 WITH CURRENT OUTPUT AND DIGITAL
I/O DAS .............................................................................................................................................................33
FIGURE 29 -CONNECTION EXAMPLE FOR 32-CHANNEL MULTIPLEXER,8020-59 WITH CURRENT OUTPUT AND DIGITAL
I/O DAS .............................................................................................................................................................34
FIGURE 30 -CONNECTION EXAMPLE FOR ONE CHANNEL.8020-59 WITH VOLTAGE OUTPUT,8020-59 PLC AND PLC
DAS ...................................................................................................................................................................35
FIGURE 31 -CONNECTION EXAMPLE FOR 16-CHANNEL MULTIPLEXER,8020-59 W/VOLTAGE OUTPUT,8020-59 PLC
AND PLC DAS....................................................................................................................................................36
FIGURE 32 -CONNECTION EXAMPLE FOR 32-CHANNEL MULTIPLEXER,8020-59 W/VOLTAGE OUTPUT,8020-59 PLC
AND PLC DAS....................................................................................................................................................37
FIGURE 33 -CONNECTION EXAMPLE FOR ONE CHANNEL 8020-59 WITH CURRENT OUTPUT,8020-59 PLC AND PLC
DAS ...................................................................................................................................................................38
FIGURE 34 -CONNECTION EXAMPLE FOR 16-CHANNEL MULTIPLEXER,8020-59 W/CURRENT OUTPUT,8020-59 PLC
AND PLC DAS....................................................................................................................................................39
FIGURE 35 -CONNECTION EXAMPLE FOR 32-CHANNEL MULTIPLEXER,8020-59 W/CURRENT OUTPUT,8020-59 PLC
AND PLC DAS....................................................................................................................................................40
FIGURE 36 -VIBRATING WIRE PRESSURE TRANSDUCER CALIBRATION REPORT..........................................................44

TABLES
TABLE 1-CONNECTOR PINOUT AND SIGNAL DESCRIPTION .......................................................................................... 1
TABLE 2-THERMISTOR RESISTANCE VERSUS TEMPERATURE .....................................................................................28
TABLE 3-ENGINEERING UNITS MULTIPLICATION FACTORS ........................................................................................42
EQUATIONS
EQUATION 1-VIBRATING WIRE FREQUENCY TO DIGITS CONVERSION........................................................................14
EQUATION 2-ANALOG VOLTAGE OUTPUT ..................................................................................................................14
EQUATION 3-ANALOG CURRENT OUTPUT ..................................................................................................................14
EQUATION 4-ANALOG VOLTAGE OUTPUT ..................................................................................................................14
EQUATION 5-ANALOG CURRENT OUTPUT ..................................................................................................................14
EQUATION 6-TEMPERATURE DERIVED FROM VOLTAGE OUTPUT................................................................................16
EQUATION 7-TEMPERATURE DERIVED FROM CURRENT OUTPUT................................................................................16
EQUATION 8-RESISTANCE TO TEMPERATURE .............................................................................................................28
EQUATION 9-DIGITS CALCULATION............................................................................................................................41
EQUATION 10 -CONVERT DIGITS TO PRESSURE ...........................................................................................................41
EQUATION 11 -TEMPERATURE CORRECTION ...............................................................................................................42
EQUATION 12 -BAROMETRIC CORRECTION..................................................................................................................43
EQUATION 13 -CORRECTED PRESSURE CALCULATION ................................................................................................43
EQUATION 14 -SECOND ORDER POLYNOMIAL EXPRESSION.........................................................................................45
EQUATION 15 -LINEARITY CALCULATION ...................................................................................................................45

1
1. INTRODUCTION
The Model 8020-59 Vibrating Wire (VW) to Analog Converter is a low cost module that
provides a simple way to connect Geokon’s vibrating wire transducers to data acquisition
systems that are not capable of reading frequency signals nor able to generate the proper signals
required to excite VW transducers. The converter can operate with single transducers, as a stand-
alone device, or with multiple transducers in conjunction with the Geokon Model 8032
Multiplexer. The converter is powered using either a 12V or a 24V supply.
The 8020-59 interface is capable of outputting a 0-5V or 4-20mA signal that is directly
proportional to “digits”, a vibrating wire sensor’s native units. These outputs are easily converted
to digits via several simple formulas (see Section 4.3). The analog outputs are automatically
scaled to minimum and maximum parameters (defaults are 0 and 25,000) and sloped to provide
their complete 0-5V or 4-20mA range for each individual transducer. These analog outputs offer
20-bit resolution (one part in 1,048,576) with an accuracy of better than 0.1% of full scale span
(0-5V output) throughout the operating temperature range (-20 ºC min, +80 ºC max). In a similar
fashion, the temperature reading from the transducer’s thermistor is available with 10-bit
resolution (one part in 1024). When configured for single-channel operation, the 8020-59
updates the reading approximately once every second.
Pin
Number
Signal
Name
Signal Description
1
GND
Analog Signal Ground
2
V OUT
Conversion Voltage Output, 0 to 5 Volts
3
+24V
24 Volt Power In
4
+24V GND
Ground for 24V Power
5
I-RET
Return for Conversion Current Output
6
+12V
12 Volt Power Supply In OR +12V Output, if powered by 24V
7
GND
Ground for 12 Volt Power
8
TH+
Thermistor Positive Lead
9
TH-
Thermistor Negative Lead
10
C+
Vibrating Wire Positive Lead
11
C-
Vibrating Wire Negative Lead
12
VALID
Valid Output:
5V indicates conversion complete
0V indicates conversion not done
13
ENABLE
Enable Input:
Single Channel Mode: 0V = VW output (digits)
5V = Temperature output (˚C)
16/32-Channel Mode: 0V = Conversion Disabled
5V = Conversion Enabled
14
CLOCK
Clock Input:
Single Channel Mode: 0V = 8020-59 ON
5V = 8020-59 OFF
16-Channel Mode: 0 → 5V transition =
increment channel and select VW Analog or Temperature Analog
32-Channel Mode: 0 → 5V transition = increment channel
15
I-OUT
VW and Thermistor Conversion Current Output
Table 1 - Connector Pinout and Signal Description

2
2. INSTALLING AND CONFIGURING THE 8020-59 SOFTWARE
APPLICATION
A free setup and configuration application is available for download on Geokon’s website,
providing a user-friendly way to set up the 8020-59 VW to Analog Converter. Follow the steps
below to install the software:
1) After downloading the installer from the Geokon website, right-click on the zip file, “8020-
59_setup.zip”, and select “Extract All…” from the resulting popup menu (see Figure 1).
Figure 1 - Extracting the 8020-59 Installer
2) Another dialog will be displayed showing the editable default destination folder for the
extracted contents (see Figure 2). When satisfied with the destination folder, click on the
Extract button to extract the contents of the zipped installer (see Figure 2).
Figure 2 - Select Destination Folder
3) Figure 3 on the following page shows the extracted installer in the destination folder. Double
click on the file, “setup.exe”, to start the install process.

3
Figure 3 - Extracted 8020-59 Installer
4) After a few moments, the dialog shown in Figure 4 will be displayed.
Figure 4 - Install Wizard, Start Screen
5) After clicking on the “Next >” button, the dialog shown in Figure 5 is displayed.
Figure 5 - Install Wizard, Choose Users

4
6) Choose whether to install the 8020-59 Software Application for all users or just for the
current user (see Figure 5). NOTE: Without administrative privileges on the PC, the only
option allowed will be “Install just for me”. After making a selection, click “Next >”; this
will bring up the dialog shown in Figure 6.
Figure 6 - Install Wizard, Choose Start Menu Folder
7) The dialog shown in Figure 6 allows the installer to choose where the “shortcut” to launch
the application will be located – the default is the “Geokon” folder. A “shortcut” will also be
located on the desktop. Clicking on “Install” begins the process of copying files and causes
the dialog box shown in Figure 7 to be displayed:
Figure 7 - Install Wizard, Installation Complete

5
8) The installation process is now complete. Clicking “Next >” allows the opportunity to launch
the 8020-59 application when finished by checking the box next to “Launch 8020-59
Application” (see Figure 8). Click on “Finish” (see below) to close the install wizard.
Figure 8 - Install Wizard, Launch 8020-59 Application
2.1 Configuring the COM Port
After launching the 8020-59 Software Application, the first thing that must be done is to
configure the COM Port. Click on the “Com Setup” (or press the “Alt” and the “c” key at the
same time) to select a COM port for communication with the 8020-59 VW to Analog Converter
(See Figure 9).
Figure 9 - 8020-59 Software Application, Startup Dialog

6
Select a COM port that corresponds to an available RS-232 communication port, whether it is
built-in (such as COM1) or an external one via a USB to Serial Converter (see Figure 10). Some
newer PCs are so fast that a small delay between characters is needed to give the 8020-59 time to
process the characters. The “Inter-character Delay” is specified in milliseconds.
Figure 10 - Communications Parameters Dialog

7
3. QUICK START (SINGLE CHANNEL)
In order to properly set up and use the 8020-59 VW to Analog Converter, a field “Zero Reading”
will need to be taken. This is required so that the 0-5V and 4-20mA outputs are scaled correctly
for the transducer being monitored. This section will allow the user to quickly set up and obtain
valid readings from the 8020-59 Converter:
Equipment Required:
Personal Computer (PC) with RS-232 COM port
8020-59 Software Application
RS-232 Cable (supplied)
VW Transducer
VW Transducer Calibration Report
1) Install the 8020-59 software on the PC that will be used to interface to the 8020-59 unit (see
Section 2).
2) Connect the 8020-59 to the computer’s serial port (typically COM1). If using an external
USB to Serial converter, drivers for this device will need to be installed before this step (see
Section 2.1).
3) Connect +12VDC to connector pin six OR +24VDC to connector pin three (see Table 1 in
Section 1).
4) Connect the power supply return (or Ground) to connector pin seven OR, if using a 24V
supply, connector pin four, 24V GND (see Table 1).
5) Connect the un-pressurized VW transducer to the 8020-59 (see Table 1):
RED wire to connector pin 10 (C+).
BLACK wire to connector pin 11 (C-).
WHITE wire to connector pin 8 (TH+).
GREEN wire to connector pin 7 (TH-)
SHIELD wire to connector pin 1 (GND).
6) Start the 8020-59 program.
7) Click the “Single Channel” button (or press the “Alt” and “s” keys) from the program’s
Startup Dialog (see Section 2.1).
8) The Single Channel Configuration screen should now be displayed (see Figure 11 on the
following page). This screen is used to define the parameters that the 8020-59 uses to read
the attached transducer.

8
Figure 11 - Single Channel Configuration Screen
9) Ensure that the Transducer Model drop-down control is correctly set to the proper VW model
and that the “Use Defaults” checkbox is checked.
10)Click “Activate/Monitor” (or press the “Alt” and “m” keys). The “Upload Confirmation”
dialog will be displayed with the prompt: “Do you want to upload the current settings to the
8020-59?”. Click the “Yes” button. The Single Channel Monitor screen should now appear
(see Figure 12), and after several seconds should update with a reading.
Figure 12 - Single Channel Monitor

9
11)Note the digits that are displayed. Record the VW reading, barometric pressure, and
temperature. This is what is known as the “initial zero” reading. The “initial zero” reading
will be used in future calculations. For example, the VW zero reading will be the R0value in
the pressure calculations equation: P = (R1 – R0) x GF, where R1equals the “Current
Reading” and GF is the Gage Factor obtained from the calibration report for the sensor being
measured. See Appendix D for further information on Data Reduction.
12)Click “Exit” (or press the “Alt” and “e” keys) to return to the Setup Screen.
After setup is complete, the PC is disconnected from the 8020-59 and the sensor is in a
pressurized state, the “Current Reading” (R1) “Digits” will need to be calculated from the value
read from the analog voltage (V OUT, in volts) or current (I-OUT, in milliamperes) output. See
Section 4.3 for more information on how to convert from an analog voltage or current value into
digits. Once a “Digits” value has been obtained, translation into other engineering units is
accomplished by multiplying the “Digits” value by the Gage Factor for the particular sensor
read.

10
4. SINGLE AND MULTI-CHANNEL OPERATION
In addition to working as a stand-alone device to interface a single transducer to a Data
Acquisition System (DAS), multiple channels may be configured in similar fashion to the Single
Channel. The 8020-59 works in conjunction with the 8032 Multiplexer and the user’s Data
Acquisition System to select either 1 of 16 or 1 of 32 transducers.
The 8020-59 was developed with multiplexing in mind and uses the same control signals as the
Geokon model 8032 Vibrating Wire Multiplexer (for control signal timing requirements, refer to
the model 8032 Multiplexer Instruction Manual). With a simple control program executing on
the host DAS, it is capable of working with 16 vibrating wire transducers (with thermistors), or
32 transducers (without thermistors). All setup parameters for each channel are stored in internal
EEPROM memory, requiring no backup battery and can be retained for years.
The 8020-59 is powered from either a 12V or 24V supply (nominal), and draws approximately
70mA when taking readings. When it is “shut-off”, or between scans when multiplexing, the
total current consumption of the 8020-59 is less than 10μA (12V) or 16.5mA (24V).
The 8020-59 setup and configuration utility runs on a PC operating under the Windows operating
system and communicates to the 8020-59 via the 8020-59’s RS-232 port. A “Command Line”
interface is provided in the 8020-59 internal firmware, with a command set that allows all
functions to be easily set up and calibrated.
4.1 Theory of Operation
The 8020-59 provides excitation for a VW transducer using a swept frequency pluck that is
optimized for the selected gage type. The period of the resulting VW signal is measured using a
25 MHz clock. This measurement is performed 512 times, resulting in an average period being
stored in internal memory. The microprocessor then converts the average period into digits and
scales the output accordingly, for the specific transducer being read. This information is then sent
to a 20-bit D/A converter, which outputs a voltage (0-5V) that is directly proportional to the
average digits. Post-processing circuitry converts this voltage to a non-isolated 4-20mA current
signal. In addition, the 20-bit D/A is put through a self-calibration routine at the start of each
measurement cycle to minimize errors due to temperature and power supply variations. The
resulting 0-5V and 4-20mA signals are brought to the output connector for connection to the
input(s) of the host DAS.

11
4.2 Operating Modes
The 8020-59 has three modes of operation: single channel mode, 16-Channel mode, and 32-
Channel mode. Each operation mode is detailed in the subsections below.
4.2.1 Single Channel Mode
In this mode (Figure 13), the 8020-59 will maintain continuous excitation of the VW
transducer and provide a continuous 0-5V and 4-20mA output to the host DAS, updated
approximately every second.
By controlling the ENABLE input to the 8020-59, the 8020-59 voltage and current
outputs (VOUT and IOUT) will either be proportional to the transducer’s digits
(ENABLE=0V – or disconnected) or the transducer’s temperature in degrees Centigrade
(ENABLE=5V).
By controlling the CLOCK input to the 8020-59, the 8020-59 will either be ON
(CLOCK=0V − or disconnected) or OFF (CLOCK=5V).
Figure 13 - Control Signal Sequence: Single Channel Mode

12
4.2.2 16-Channel Multiplexed Mode
In this mode (Figure 14), the 8020-59 will excite and provide output only when told to do
so from the host DAS. As soon as the 8020-59 is powered, if ENABLE and CLOCK are
low (0V), the 8020-59 will go to “sleep” and will wait for commands from the host DAS,
drawing less than 10μA from the +12V system power supply (16.5mA if using a +24V
system power supply).
When a reading is to be taken, the host system first brings ENABLE high (5V) to enable
the 8020-59 and then CLOCK high (5V) to activate channel 1 of 16 (for control signal
timing requirements, refer to the model 8032 Multiplexer Instruction Manual). The 8020-
59 will “wake up” and read the transducer connected to channel one of the multiplexer.
When the reading is ready (approximately one to two seconds later), the 8020-59 will
bring the VALID output high (5V), indicating to the host DAS that the voltage and
current outputs (proportional to the digits) are at VOUT and IOUT and are ready to be
acquired.
Once the reading is acquired, the host system brings CLOCK low (0V) and then high
(5V) again to read the temperature of the transducer. When this reading is ready (<100ms
later), the VALID output will again go high (5V), indicating that the voltage and current
outputs (now proportional to temperature) are at VOUT and IOUT and are ready to be
acquired. When the host DAS again brings CLOCK low (0V) and then HIGH (5V), the
8020-59 and multiplexer increment to channel 2 of 16 and this reading sequence starts
over again. This reading sequence may be used for up to 16 transducers.
When the final transducer has been read, the host DAS brings CLOCK and ENABLE
both low (0V) to reset the system. The 8020-59 will go back to sleep until it is time for
the next reading. Using this feature, up to 16 Vibrating Wire transducers with thermistors
may be multiplexed into a single DAS.
Figure 14 - Control Signal Sequence: 16-Channel Mode (Channels One and Two Only)

13
4.2.3 32-Channel Multiplexed Mode
In this mode (Figure 15), the 8020-59 will also excite and provide output only when told
to do so from the host DAS. As soon as the 8020-59 is powered, if ENABLE and
CLOCK are low (0V), the 8020-59 will go to “sleep” and will wait for commands from
the host DAS, drawing less than 10μA from the +12V system power supply (16.5mA if
using a +24V system power supply).
When a reading is to be taken, the host system first brings ENABLE high (5V) to enable
the 8020-59 and then CLOCK high (5V) to activate channel 1 of 32 (for control signal
timing requirements, refer to the model 8032 Multiplexer Instruction Manual). The 8020-
59 will “wake up” and read the transducer connected to channel one of the multiplexer.
When the reading is ready (approximately one to two seconds later (typ)), the 8020-59
will bring the VALID output high (5V), indicating to the host DAS that the voltage and
current outputs (proportional to the digits of transducer number one) are at VOUT and
IOUT and are ready to be acquired.
Once the reading is acquired, the host system brings CLOCK low (0V), and then high
(5V) again to increment the 8020-59 and multiplexer to the next transducer. When this
reading is ready ( approximately one to two seconds later), the VALID output will again
go high (5V), indicating that the voltage and current outputs (proportional to the digits of
transducer number two) are at VOUT and IOUT and are ready to be acquired. This
reading sequence may be used for up to 32 transducers.
When the final transducer has been read, the host DAS brings CLOCK and ENABLE
both low (0V) to reset the system. The 8020-59 will go back to sleep until it is time for
the next reading. Using this feature, up to 32 Vibrating Wire transducers may be
multiplexed into a single DAS.
Figure 15 - Control Signal Sequence: 32-Channel Mode (Channels One through Four Only)

14
4.3 Conversion to “Digits”
A useful frequency related unit that is directly proportional to pressure is the “digit”. These units
are related to vibrating wire frequency as:
Digits = [Frequency (Hz)]² x 0.001
Equation 1 - Vibrating Wire Frequency to Digits Conversion
The 8020-59 provides analog outputs that are directly proportional to digits.
Referring to the sample calibration in Figure 36 of Appendix E, a value in digits can be derived
from the voltage and current outputs as described below.
For the following “positive slope” transducers: 4000, 4100, 4150, 4200, 4210, 4300, 4350, 4360,
4400, 4420, 4425, 4450, 4650 and 4700; use Equation 2 for Analog Voltage Output (assumes
Vout is in volts (V)), or Equation 3 for Analog Current (4-20mA) Output (assumes Iout is in
milliamperes (mA).
Digits = (Vout * (Digits Span/5V)) + Minimum Limit
Equation 2 - Analog Voltage Output
Digits = ((Iout - 4mA) * (Digits Span/16mA)) + Minimum Limit
Equation 3 - Analog Current Output
For the following “negative slope” transducers: 4500, 4600, 4675, 4800 and 4900; use Equation
4 for Analog Voltage Output (assumes Vout is in Volts (V)), or Equation 5 for Analog Current
(4-20mA) Output (assumes Iout is in milliamperes (mA)).
Digits = Maximum Limit – (Vout * (Digits Span/5V))
Equation 4 - Analog Voltage Output
Digits = Maximum Limit – ((Iout - 4mA) * (Digits Span/16mA))
Equation 5 - Analog Current Output
Where:
Minimum Limit = Minimum limit parameter set in the channel specific setup screen of the
8020-59 configuration utility (default is zero)
Maximum Limit = maximum limit parameter set in the channel specific setup screen of the
8020-59 configuration utility (default is 25,000)
Digits Span = Maximum Limit - Minimum Limit