Campbell AVW200 series User manual

AVW200-series 2-Channel
Vibrating Wire Spectrum
Analyzer Modules
Revision: 2/12
Copyright © 2008-2012
Campbell Scientific, Inc.

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AVW200-series Table of Contents
PDF viewers: These page numbers refer to the printed version of this document. Use the
PDF reader bookmarks tab for links to specific sections.
1. Overview.......................................................................1
1.1 Design Features ........................................................................................1
1.2 Specifications............................................................................................3
1.3 Communication.........................................................................................3
1.3.1 Datalogger.......................................................................................3
1.3.1.1 PakBus Protocol/Direct RS-232 Connection ........................4
1.3.1.2 PakBus Protocol/Wireless Connection..................................4
1.3.1.3 PakBus Protocol/MD485 Communication............................4
1.3.1.4 SDI-12 Communication Mode ..............................................4
1.3.2 Computer ........................................................................................5
1.3.2.1 Device Configuration Utility.................................................5
1.3.2.2 LoggerNet .............................................................................5
1.3.2.3 Terminal Commands .............................................................5
1.4 Use with Multiplexers...............................................................................5
2. Measurements..............................................................7
2.1 Vibrating Wire..........................................................................................7
2.2 Temperature............................................................................................10
3. Quick Start Guides ....................................................11
3.1 One or Two Sensors (no multiplexers)...................................................11
3.1.1 Direct RS-232 Connection............................................................11
3.1.2 Wireless Connection .....................................................................12
3.2 Multiplexers Controlled by AVW200 ....................................................14
3.2.1 Direct RS-232 Connection............................................................14
3.2.2 Wireless Connection .....................................................................15
3.3 Multiplexers Controlled by Datalogger ..................................................17
3.3.1 SDI-12 Communication ................................................................17
4. Connections ...............................................................18
4.1 Sensor Wiring (no multiplexers) ............................................................18
4.2 Power and Ground ..................................................................................19
4.3 Datalogger Wiring (Direct Connection) .................................................20
4.4 Wireless Connections (AVW206, AVW211, AVW216) .......................21
4.5 Multiplexer Wiring .................................................................................22
4.5.1 AVW200 Controlling the Multiplexer..........................................22
4.5.2 Datalogger Controlling the Multiplexer........................................23
5. Device Configuration (DevConfig) Utility ................25
5.1 Connecting to DevConfig .......................................................................25
5.2 Deployment Tab .....................................................................................26
5.2.1 Communications ...........................................................................26
5.2.2 Measurement.................................................................................29
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AVW200-series Table of Contents
5.3 Data Monitor.......................................................................................... 30
5.4 Send OS ................................................................................................. 32
5.5 Troubleshoot .......................................................................................... 33
5.6 Settings Editor........................................................................................ 36
5.7 Terminal................................................................................................. 36
6. Programming..............................................................37
6.1 AVW200 Instruction.............................................................................. 37
6.1.1 Pipeline Mode .............................................................................. 41
6.1.2 Sequential Mode........................................................................... 41
6.2 SDI-12 Measurements ........................................................................... 42
6.2.1 SDI12 Recorder() Instruction....................................................... 42
6.2.2 Extended SDI-12 Commands....................................................... 44
6.2.3 Use with Multiplexers .................................................................. 44
7. Example Programs ....................................................45
7.1 AVW200() Instruction (no multiplexers) .............................................. 45
7.1.1 Direct RS-232 Connection (two sensors)..................................... 45
7.1.2 Wireless/One Sensor/Resistance Converted to Temperature ....... 46
7.2 AVW200() Instruction Controlling Two Multiplexers .......................... 47
7.3 AVW200( ) Instruction Running in the Pipeline Mode ......................... 48
7.4 AVW200( ) Instruction Running in the Sequential Mode ..................... 49
7.4.1 AVW200 Controlling Two Multiplexers in Sequential Mode ..... 50
7.4.2 Datalogger Controlling Two Multiplexers in Sequential Mode... 50
7.5 SDI-12 Example..................................................................................... 51
8. Troubleshooting Communication Problems ...........54
8.1 Unable to Communicate with DevConfig or Terminal Emulator .......... 54
8.2 Datalogger to AVW200 Communication............................................... 54
8.3 Wireless Communications ..................................................................... 54
Appendices
A. Conversion from Hertz............................................ A-1
A.1 Displacement Example........................................................................ A-1
B. Thermistor Information........................................... B-1
B.1 Converting Resistance to Temperature ............................................... B-1
B.1.1 Resistance Conversion Example................................................ B-1
B.2 Accuracy and Resolution..................................................................... B-1
C. Antennas, Antenna Cables, and Surge
Protectors for the AVW206, AVW211, and
AVW216 .................................................................C-1
C.1 Antennas.............................................................................................. C-1
C.2 Antenna Cables ................................................................................... C-5
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AVW200-series Table of Contents
C.3 Surge Protectors ...................................................................................C-5
C.3.1 Electrostatic Issues .....................................................................C-5
C.3.2 Antenna Surge Protector Kit ......................................................C-6
C.4 Part 15 FCC Compliance Warning ......................................................C-6
D. The Public Table...................................................... D-1
D.1 Forced Measurement Program............................................................ D-4
E. Status Table ............................................................. E-1
F. Time Series and Spectrum Graph Information ..... F-1
F.1 Good Sensor Examples......................................................................... F-1
F.2 Good Sensors with Noise ..................................................................... F-3
G. CR10X Programming Example ..............................G-1
H. Additional Programming Examples ...................... H-1
H.1 AVW200-Controlled Multiplexer....................................................... H-1
H.1.1 Direct RS-232 Connection ........................................................ H-1
H.1.2 Wireless/Sensors with Different Frequencies ........................... H-4
H.2 Datalogger-Controlled Multiplexer .................................................... H-7
I. Using MD485 Multidrop Modems with AVW200
Interfaces.................................................................I-1
I.1 Required Settings ......................................................................................1
I.2 Connections...............................................................................................2
I.2.1 Datalogger to MD485......................................................................3
I.2.2 MD485 to MD485 ...........................................................................3
I.2.3 MD485 to AVW200 ........................................................................4
I.2.4 Multiplexer Connections .................................................................4
I.3 Programming.............................................................................................4
I.3.1 Example Program ............................................................................4
Figures
1.4-1. Network of AVW200s and AM16/32Bs (using a direct RS-232
connection)....................................................................................6
1.4-2. Network of AVW206s and AM16/32s (wireless)................................6
1.4-3. Network of AVW200 Interfaces (SDI-12)...........................................7
2.1-1. Cutaway of Vibrating Wire Sensor ......................................................8
2.1-2. DevConfig plots showing the AVW200 measurement approach.......10
4.1-1. Wiring for Sensor Connections ..........................................................19
4.2-1. Ground Lug and Power Connectors on the AVW200........................20
4.4-1. AVW206 with Whip Antenna............................................................21
4.5.1-1. Example AM16/32-series to AVW200 Hookup (multiplexers
controlled by AVW200) .............................................................23
4.5.2-1. AM16/32B to AVW200 Hookup (AM16/32Bs controlled by
datalogger and using SDI-12) .....................................................24
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AVW200-series Table of Contents
iv
4.5.2-2. Multiplexer to Datalogger Power/Control Hookup (multiplexer
controlled by datalogger) ........................................................... 24
5.1-1. Opening Page in DevConfig.............................................................. 26
5.2.1-1. Deployment Communications Editor in DevConfig....................... 27
5.2.2-1. Deployment/Measurement Tab in DevConfig................................ 29
5.3-1. Data Display/Public Table in DevConfig .......................................... 30
5.3-2. Data Display/Status Table in DevConfig........................................... 31
5.4-1. Sending an Operating System using DevConfig ............................... 32
5.5-1. Opening Page of the Troubleshoot Tool............................................ 33
5.5-2. Options Tab of the Troubleshoot Tool .............................................. 34
5.5-3. Graphs for Evaluating Spectral Analysis of a Sensor........................ 35
A.1-1. Geokon Calibration Report............................................................. A-2
B.2-1. Temperature Measurement Error at Three Temperatures as
a Function of Lead Length. . ................................................... B-2
B.2-2. Temperature Measurement Error on a 1000 foot Lead................... B-3
B.2-3. Temperature Measurement Error on a 3000 foot Lead................... B-3
B.2-4. Temperature Measurement Error on a 5000 foot Lead................... B-4
C.1-1. Some FCC Approved Antennas...................................................... C-4
C.1-2. Example COAX RPSMA-L Cable for Yagi or Omni Colinear ...... C-5
C.1-3. Antenna Surge Protector ................................................................. C-5
F.1-1. Good Sensor with a Narrower Range (200 to 2200 Hz) ..................F-2
F.1-2. Good Sensor with a Wider Range (200 to 6500 Hz)........................F-2
F.2-1. Good Sensor with Noise (600 to 1800 Hz) ......................................F-3
F.2-2. Good Sensor with Noise (450 to 6500 Hz) ......................................F-4
I-1. Deployment tab in DevConfig with proper MD485 configuration .......I-1
I-2. Point-to-Point MD485-to-AVW200 Network ......................................I-2
I-3. Point-to-Multipoint MD485-to-AVW200 Network..............................I-2
I-4. MD485 and its connectors.....................................................................I-3
I-5. MD485-to-MD485 Connections and Grounding ..................................I-4
Tables
2.1-1. Cutaway of Vibrating Wire Sensor...................................................... 8
2.1-2. AVW200 Measurement Outputs ......................................................... 9
4.3-1. Datalogger to AVW200 Cable Options............................................. 20
4.3-2. 17855 or SC110’s DTE Cable Wiring............................................... 21
4.4-1. Datalogger to Spread Spectrum Radio Connections.......................... 22
5.2.1-1. AVW206 Power Modes and the Recommended Corresponding
RF401 Power Modes.................................................................. 28
5.4-1. Terminal Mode Commands ............................................................... 36
6.2.1. SDI-12 Command Codes ................................................................... 43
7.1-1. Wiring for Example 7.1.1 .................................................................. 45
7.2-1. Wiring for Example 7.2 ..................................................................... 47
7.3-1. Wiring for Example 7.3 ..................................................................... 48
7.4-1. Wiring for Sequential Mode Examples ............................................. 50
7.5-1. SDI-12 Command Codes................................................................... 52
D-1. Description of the Public Table ......................................................... D-1
E-1. Status Fields and Descriptions ............................................................E-1

AVW200-series 2-Channel Vibrating
Wire Spectrum Analyzer Modules
The AVW200 series consist of a base model (AVW200) and three wireless models
(AVW206, AVW211, AVW216). The wireless models combine the AVW200 with a spread
spectrum radio. The different model numbers of the wireless versions are for different
spread spectrum frequency ranges.
Compatible Radios
•AVW206—910 to 918 MHz (US/Canada) RF401
•AVW211—920 to 928 MHz (Australia/Israel) RF411
•AVW216—2.4 GHz (worldwide) RF416
Throughout this manual AVW200 will refer to all models unless specified otherwise.
Likewise, AVW206 typically refers to all wireless models, and RF401 refers to the
corresponding spread spectrum radio.
1. Overview
The AVW200 module allows the measurement of vibrating-wire strain gauges,
pressure transducers, piezometers, tiltmeters, crackmeters, and load cells.
These sensors are used in a wide variety of structural, hydrological, and
geotechnical applications because of their stability, accuracy, and durability.
Up to two vibrating wire or vibrating strip transducers can be connected to the
AVW200. More sensors can be measured by using multiplexers (see Section
1.4).
1.1 Design Features
Historically, vibrating-wire sensors suffered from one major problem—
external noise. The AVW200 significantly reduces and, in most cases,
eliminates the problem of incorrect readings due to noise sources. The noise
problems were overcome by advancement in technology and mathematical
processing1, resulting in frequency based measurements—a complete departure
from previous time-domain based measurements.
Read more! Vibrating Wire Measurements are discussed in detail in
Section 2.
To simplify programming of the AVW200, engineers implemented firmware to
eliminate several parameters that were necessary in programming the older
Campbell Scientific interfaces (i.e., AVW1, AVW4, AVW100).
1U.S. Patent No. 7,779,690
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AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
The eliminated parameters are:
•Number of steps
•Number of cycles
•Time of Swept Frequency
These parameters are now part of the AVW200 internal operating system and
require no user input. The user only needs to input the lower frequency range,
upper frequency range, and excitation voltage of the sensor.
Read more! Detailed programming information is provided in Section 6.
The AVW200 returns five or six values per measurement. The first value is
the vibrating wire frequency in Hz. The sixth value is the optional thermistor
measurement on Ohms. Values two through five are diagnostic information
giving an indication or validation of the measurement.
(1) = Frequency in Hertz
(2) = SignalStrength in mV_RMS
(3) = Signal/Noise Ratio (unitless)
(4) = Noise Frequency Hz
(5) = DecayRatio (unitless)
(6) = Thermistor output in Ohms of resistance (see Section 2.2)
The on-board diagnostics should be monitored to determine faulty wiring,
incorrect frequency range, sensor degradation over time, or to determine faulty
sensors.
Read more! Information on how to use the on-board diagnostics is
provided in Appendix F.
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AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
1.2 Specifications
1.3 Communication
1.3.1 Datalogger
The AVW200 module is designed to work with and complement Campbell
Scientific dataloggers, as well as data acquisition products from other
manufacturers.
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AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
1.3.1.1 PakBus Protocol/Direct RS-232 Connection
When using the PakBus protocol, the AVW200() instruction in CRBasic
supports an AVW200 connected to a datalogger via a cable attached to the
AVW200’s RS-232 port. You can run the datalogger AVW200() instruction in
either the pipeline or sequential mode. This instruction is contained in the
following datalogger operating systems:
•CR800std.06 or greater
•CR1000std.15 or greater
•CR3000std.08 or greater
Multiplexers can be controlled by either the AVW200 or the datalogger.
Read more! You can find Quick Start Guides in Section 3, AVW200()
instruction description in Section 6.1, and programming examples in
Section 7.
1.3.1.2 PakBus Protocol/Wireless Connection
An AVW206, AVW211, or AVW216 interface can transmit data to a
corresponding spread spectrum radio that is attached to the datalogger. The
AVW200() instruction in CRBasic supports these wireless interfaces. You can
run the AVW200() instruction in either the pipeline or sequential mode. This
instruction is contained in the following datalogger operating systems:
•CR800std.06 or greater
•CR1000std.15 or greater
•CR3000std.08 or greater
Multiplexers can be controlled by the wireless AVW200.
Read more! You can find Quick Start Guides in Section 3, AVW200()
instruction description in Section 6.1, and a programming example in
Section 7.1.2.
1.3.1.3 PakBus Protocol/MD485 Communication
For situations where wireless communication is impractical, MD485 multidrop
modems may extend the distance between the AVW200 interfaces.
Multiplexers must be controlled by the AVW200.
Read more! Appendix I describes using MD485 modems with AVW200s.
1.3.1.4 SDI-12 Communication Mode
SDI-12 is the only option available for our CR5000, CR10X, and CR23X
dataloggers and non-Campbell Scientific dataloggers. Our CRBasic
dataloggers use the SDI12Recorder instruction and Edlog dataloggers (i.e.,
CR10X, CR23X) use Instruction 105. The SDI12Recorder instruction should
only be run in the sequential mode. When using SDI-12, multiplexers must be
controlled by the datalogger.
Read more! You can find a Quick Start Guide in Section 3.3.1,
SDI12Recorder instruction description in Section 6.2, and a programming
example in Section 7.5.
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AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
1.3.2 Computer
1.3.2.1 Device Configuration Utility
The Device Configuration (DevConfig) Utility supports AVW200
configuration, operating system download, and vibrating wire spectrum
analysis troubleshooting. To use DevConfig, the AVW200 must be connected
to a PC and a power source. DevConfig is bundled in Campbell Scientific’s
datalogger support software and can also be acquired, at no cost, from
Campbell Scientific’s website. DevConfig 1.10 or greater is required.
Read more! DevConfig is described in detail in Section 5.
1.3.2.2 LoggerNet
LoggerNet supports datalogger programming, accesses the status and public
tables, and displays network routing. Please ensure that the AVW200 CRBasic
instruction is included. If using LoggerNet 3.4.1 or lower, the user needs to
download the most recent OS for the datalogger. This installation installs the
required CRBasic files on the user’s computer so that the AVW200 instruction
shows up in the editor.
Read more! Programming information is provided in Section 6. Also,
refer to the LoggerNet manual and help.
1.3.2.3 Terminal Commands
You can monitor the AVW200 by entering terminal commands in the terminal
emulator of DevConfig or LoggerNet. HyperTerminal or ProComm can also
be used. The AVW200 needs to be connected to a computer with a standard
RS-232 cable (CSI model 10873).
Read more! Terminal Mode Commands are discussed in Section 5.6.
1.4 Use with Multiplexers
For the AVW200 interfaces, the AM16/32B multiplexer is recommended over
its predecessors (i.e., AM16/32, AM16/32A). The AM16/32B has a clocking
mode that can use relay addressing to go directly to a specific channel—
reducing power consumption and wear on the relay switches.
Up to 32 vibrating wire sensors without thermistors or 16 vibrating wire
sensors with thermistors can be connected to one multiplexer. Two
multiplexers can be connected to one AVW200. Using a direct RS-232
connection, up to four AVW200 interfaces can be connected to one CR1000 or
CR3000; up to two AVW200 interfaces can be connected to one CR800 or
CR850. This allows up to 256 vibrating wire sensors (128 with temperature) to
be measured by one CR1000 or CR3000 (see Figure 1.4-1) or 128 vibrating
wire sensors (64 with temperature) to be measured with one CR800 or CR850.
Figures 1.4-2 and 1.4-3 indicate the number of interfaces that can be connected
to one datalogger when using wireless interfaces or the SDI-12 protocol.
Read more! You can find Quick Start Guides in Section 3.2 and 3.3,
wiring information in 4.5, programming information in Section 6, and
programming examples in Section 7.
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AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
AM16/32B
AVW200
CR3000
FIGURE 1.4-1. Network of AVW200s and AM16/32Bs (using a direct RS-232 connection)
FIGURE 1.4-2. Network of AVW206s and AM16/32Bs (wireless)
COM1 (C1/C2)
CR1000
COM3 (C5/C6)
COM4 (C7/C8)
COM2 (C3/C4)
CR3000
CR800, CR850
128 – Vibrating Wire Sensors in 4x16 configuration
256 – Vibrating Wire Sensors in 2x32 configuration
CR1000
128 – Vibrating Wire Sensors in 4x16 configuration
256 – Vibrating Wire Sensors in 2x32 configuration
PakAddr = 200
PakAddr = 201
PakAddr = 202
PakAddr = 203
AVW206
A
M16/32B
RF401
6

AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
CR10X
CR5000
CR23X
CR800, CR850
CR1000
CR3000
AVW200
FIGURE 1.4-3. Network of AVW200 Interfaces (SDI-12)
2. Measurements
2.1 Vibrating Wire
The spectral approach implemented by the AVW200 offers significantly
improved noise immunity when compared to older period-averaging techniques
implemented by other vibrating-wire interfaces (AVW1, AVW4, and
AVW100). Testing revealed more than two to three orders of magnitude better
noise immunity with the AVW200. In addition, the spectral analysis gives
improved frequency resolution (0.001 Hz rms) during quiet conditions.
The AVW200 measures the resonant frequency of the taut wire in a vibrating
wire sensor (see Figure 2.1-1) with the following procedure. First, the
AVW200 excites the wire with a swept-frequency excitation signal. Next, the
AVW200 records the response from the vibrating wire. Finally, the AVW200
Fourier transforms the recorded response and analyzes the resulting spectrum
to determine the wire’s resonant frequency. This analysis also provides
diagnostic information indicating the quality of the resonant-frequency
measurement.
SDI-12
AM16/32B
Datalogger MUST Control
Multiplexers in SDI-12 Mode
0
1
2
3
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AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
FIGURE 2.1-1. Cutaway of Vibrating Wire Sensor
There are three user-determined inputs to the AVW200 measurement process
and five outputs from the measurement process. The input parameters control
the excitation frequency range (BeginFreq and EndFreq) and the excitation
amplitude (ExVolt); see Table 2.1-1. The frequency range supported spans
from 100 Hz to 6500 Hz.
TABLE 2.1-1. AVW200 Measurement Inputs
Input Units Description
BeginFreq Hz Minimum excitation and analysis frequency
EndFreq Hz Maximum excitation and analysis frequency
ExVolt Unitless Excitation voltage
1: 5 Volts peak to peak
2: 12 Volts peak to peak
Therm50_60Hz
(see Section 2.2)
Unitless Thermistor measurement parameter
0: No thermistor measurement
_60Hz Use 60 Hz noise rejection
_50Hz: Use 50 Hz noise rejection
The measurement outputs are resonant frequency, response amplitude, signal-
to-noise ratio, noise frequency, and decay ratio; see Table 2.1-2. The raw
frequency measurement output of the AVW200 is in Hertz unlike our previous
interfaces, which output kHz2or 1/T2(where T is the period in milliseconds).
The Hertz output is converted to the appropriate units of measurement (e.g.,
pressure, strain, displacement) by using information provided on the sensor’s
calibration report.
Read more! You can find an example of converting Hertz to displacement
in Appendix A, and an example program that converts Hertz to
displacement in Section 7.1.2.
Vibrating
Wire
Plucking/
Pickup Coil
Diaphragm
8

AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
TABLE 2.1-2. AVW200 Measurement Outputs
Output Units Description
Resonant Frequency Hz Frequency of the peak response
Response Amplitude mV rms Amplitude of the peak response1
Signal-to-Noise Ratio unitless Response amplitude divided by
amplitude of largest noise candidate1
Noise Frequency Hz Frequency of largest noise candidate1
Decay Ratio unitless Ending time-series amplitude divided
by the beginning time-series
amplitude1
Thermistor Resistance
(see Section 2.2)
Ohms On-gage thermistor resistance2
Notes:
1. Use for measurement diagnostics.
2. Optional output, not measured if Therm50_60Hz is set to 0.
When using firmware version Std.04 (or higher) and the Response Amplitude
diagnostic is measured as less than 0.01 mV rms (10 microvolts), the Resonant
Frequency reading will be modified to warn the user about the occurrence of
low signal strength amplitudes. If SDI-12 is used to communicate with the
AVW200-series device, the frequency will be given as -9,999,999 under those
conditions. For all other communication methods, the frequency will be given
as NAN (not-a-number) when experiencing this low signal strength condition.
If the user desires the frequency to be returned as NAN for a higher (i.e., more
pessimistic) threshold than 0.01 mV, this can be done by using an optional
parameter in the AVW200 CRBasic Instruction. See Section 6.1 for details
about how this can be done.
The Resonant Frequency reading is also used to warn the user when there is an
invalid voltage supply in the hardware of the device (firmware Std.04 and
higher). If an internal calibration factor is outside of the expected range, then
the value of -555,555 is returned for the frequency measurement. This
indicates to the user that there is a hardware issue on the device which requires
a factory examination and/or repair. Contact Campbell Scientific for
instructions when this value is given as the Resonant Frequency reading.
Figure 2.1-2 (a representative output from the Device Configurator’s
Troubleshooter) illustrates the AVW200 measurements. The bottom graph
shows the raw time series data recorded from a vibrating sensor after the sensor
has been excited with the frequency-swept voltage signal, and the top graph
shows the spectrum after the AVW200 has applied the fast Fourier transform
(FFT). In addition to the wire’s resonant frequency, the spectrum shows the
response amplitude, noise amplitude, and noise frequency. The AVW200
computes the signal-to-noise ratio diagnostic by dividing the response
amplitude by the noise amplitude. The AVW200 computes the decay ratio
diagnostic from the time series ending amplitude divided by the beginning
amplitude shown on the bottom graph in Figure 2.1-2.
9

AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
Response
Amplitude Noise Amplitude
Resonant Frequency Noise Frequency
Beginning Amplitude
Ending Amplitude
FIGURE 2.1-2. DevConfig plots showing the AVW200 measurement approach.
Please note that the use of the special FFT algorithm to achieve better noise
immunity does require time for computation, which limits the maximum
vibrating wire measurement rate to 2 seconds per sensor. Running a program
at rates faster than this will result in compile/download errors.
Read more! You can find Troubleshoot tool information in Section 5.5 and
Appendix F; and detailed programming information in Section 6.
2.2 Temperature
The AVW200 contains a completion resistor for measuring the internal
thermistor contained in many vibrating wire sensors. The thermistor’s
resistance changes with the internal temperature of the sensor. This
temperature can be used to correct errors in the vibrating wire measurement
due to thermal expansion/contraction of the sensor body. The temperature
correction is often used when the temperature of the medium that the sensor is
measuring is changing (e.g. water temperature in a river or shallow lake).
Temperature is calculated by applying the resistance to a known equation such
as the Steinhart-Hart equation. The Steinhart-Hart coefficients for your sensor
are found in the sensor’s user manual.
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AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
Read more! You can find an example program that converts resistance to
temperature in Section 7.1.2 and detailed information about the
thermistors in Appendix B.
3. Quick Start Guides
The AVW200 can be used in many types of systems—from simple to complex.
The following quick start guides provide steps used to set up a system for some
example configurations.
3.1 One or Two Sensors (no multiplexers)
3.1.1 Direct RS-232 Connection
Cable that Comes with Sensor
17855 Pigtailed Cable or
18663 Null Modem Cable
19246 Power Cable
Sensors AVW200
Sensors
Datalogger
Power
Supply
For this simple configuration, the AVW200 can be used straight from the box
(i.e., settings do not need to be changed in DevConfig). The sensor(s) are
attached directly to the AVW200. The AVW200 is connected directly with the
datalogger via the 17855 cable or 18663 cable. The 17855 cable terminates in
pigtails for connection to datalogger control port pairs (C1/C2…C7/C8). The
18663 Null Modem Cable has a DB9 connector for attachment to the
datalogger’s RS-232 port.
The following steps are used to measure the sensor(s):
1. Attach the vibrating wire sensor(s) to the AVW200 as shown in
Figure 4.1-1.
2. Use the 17855 cable to attach the AVW200 to a control port pair on the
datalogger (i.e., C1/C2, C3/C4, C5/C6, C7/C8), or use the 18663 Null
Modem cable to attach the AVW200 to the RS-232 port on the datalogger.
3. Connect one end of the 19246 power cable to the 12V and G terminals on
the AVW200 and the other end to the 12V and G terminals on the
datalogger or external power supply.
Read more! You can find power connection information in Section 4.2,
and datalogger connection information in Section 4.3.
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AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
4. Create a CRBasic program that includes an AVW200() instruction for each
of the sensors.
Check the manufacturer’s specification for the sensors frequency
and excitation range before picking the begin/end frequencies
and excitation voltage.
NOTE
For example, the following AVW200() instructions can be used to
measure two sensors:
AVW200(Result,Com1,200,200,Dst(1,1),1,1,1,1000,3500,2,_60HZ,1,0)
AVW200(Result,Com1,200,200,Dst(2,1),2,1,1,1000,3500,2,_60HZ,1,0)
Where,
AVW200 connects to datalogger control ports 1 & 2 via 17855 cable
(option Com1)
Begin Frequency = 1000
End frequency = 3500
Excitation voltage = 12 V peak to peak (option 2)
Read more! A thorough description of the AVW200() instruction and its
parameters is provided in Section 6.1. A complete example program that
measures two vibrating wire sensors (no multiplexer) is included in
Section 7.1.1.
3.1.2 Wireless Connection
Cable that Comes with Sensor
19246 Power Cable
SC12 CS I/O Cable
Wireless Connection
Sensors AVW206
Sensors
Power
Supply
DataloggerRF401
Onsite
Office
For this example configuration, the sensor(s) are attached directly to the
AVW206. The AVW206 interface transmits the data to an RF401 spread
spectrum radio that is connected to the datalogger.
At the AVW206 site, do the following steps:
1. Configure the AVW206 for RF communications as described in Sections
5.1 and 5.2.1.
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