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Campbell Scientific AVW200 AVW200-series Vibrating Wire Interfaces - Page 15

Measurements, 2.1 Vibrating Wire

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CR10X CR5000 CR23X CR800, CR850 CR1000 CR3000 SDI-12 AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules AVW200 0 AM16/32B 1 2 3 Datalogger MUST Control Multiplexers in SDI-12 Mode FIGURE 1-3. 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) 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. 7

Section	Page
Revision and Copyright Information	1
Warranty	3
Assistance	4
Table of Contents	5
1. Overview	9
1.1 Design Features	9
1.2 Specifications	11
1.3 Communication	11
1.3.1 Datalogger	11
1.3.1.1 PakBus Protocol/Direct RS-232 Connection	12
1.3.1.2 PakBus Protocol/Wireless Connection	12
1.3.1.3 PakBus Protocol/MD485 Communication	12
1.3.1.4 SDI-12 Communication Mode	12
1.3.2 Computer	13
1.3.2.1 Device Configuration Utility	13
1.3.2.2 LoggerNet	13
1.3.2.3 Terminal Commands	13
1.4 Use with Multiplexers	13
2. Measurements	15
2.1 Vibrating Wire	15
2.2 Temperature	18
3. Quick Start Guides	19
3.1 One or Two Sensors (no multiplexers)	19
3.1.1 Direct RS-232 Connection	19
3.1.2 Wireless Connection	20
3.2 Multiplexers Controlled by AVW200	22
3.2.1 Direct RS-232 Connection	22
3.2.2 Wireless Connection	23
3.3 Multiplexers Controlled by Datalogger	25
3.3.1 SDI-12 Communication	25
4. Connections	26
4.1 Sensor Wiring (no multiplexers)	26
4.2 Power and Ground	27
4.3 Datalogger Wiring (Direct Connection)	28
4.4 Wireless Connections (AVW206, AVW211, AVW216)	29
4.5 Multiplexer Wiring	30
4.5.1 AVW200 Controlling the Multiplexer	30
4.5.2 Datalogger Controlling the Multiplexer	31
5. Device Configuration (DevConfig) Utility	33
5.1 Connecting to DevConfig	33
5.2 Deployment Tab	34
5.2.1 Communications	34
5.2.2 Measurement	37
5.3 Data Monitor	38
5.4 Send OS	40
5.5 Troubleshoot	41
5.6 Settings Editor	44
5.7 Terminal	44
6. Programming	45
6.1 AVW200 Instruction	45
6.1.1 Pipeline Mode	49
6.1.2 Sequential Mode	49
6.2 SDI-12 Measurements	50
6.2.1 SDI12 Recorder() Instruction	50
6.2.2 Extended SDI-12 Commands	52
6.2.3 Use with Multiplexers	52
7. Example Programs	53
7.1 AVW200() Instruction (no multiplexers)	53
7.1.1 Direct RS-232 Connection (two sensors)	53
7.1.2 Wireless/One Sensor/Resistance Converted to Temperature	54
7.2 AVW200() Instruction Controlling Two Multiplexers	55
7.3 AVW200( ) Instruction Running in the Pipeline Mode	56
7.4 AVW200( ) Instruction Running in the Sequential Mode	57
7.4.1 AVW200 Controlling Two Multiplexers in Sequential Mode	58
7.4.2 Datalogger Controlling Two Multiplexers in Sequential Mode	58
7.5 SDI-12 Example	59
8. Troubleshooting Communication Problems	62
8.1 Unable to Communicate with DevConfig or Terminal Emulator	62
8.2 Datalogger to AVW200 Communication	62
8.3 Wireless Communications	62
Appendix A. Conversion from Hertz	65
A.1 Displacement Example	65
Appendix B. Thermistor Information	67
B.1 Converting Resistance to Temperature	67
B.1.1 Resistance Conversion Example – Geokon Sensor	67
B.2 Accuracy and Resolution	67
Appendix C. Antennas, Antenna Cables, and Surge Protectors for the AVW206, AVW211, and AVW216	71
C.1 Antennas	71
C.2 Antenna Cables	75
C.3 Surge Protectors	75
C.3.1 Electrostatic Issues	75
C.3.2 Antenna Surge Protector Kit	76
C.4 Part 15 FCC Compliance Warning	76
Appendix D. The Public Table	79
D.1 Forced Measurement Program	82
Appendix E. Status Table	83
Appendix F. Time Series and Spectrum Graph Information	87
F.1 Good Sensor Examples	87
F.2 Good Sensors with Noise	89
Appendix G. CR10X Programming Example	91
Appendix H. Additional Programming Examples	93
H.1 AVW200-Controlled Multiplexer	93
H.1.1 Direct RS-232 Connection	93
H.1.2 Wireless/Sensors with Different Frequencies	96
H.2 Datalogger-Controlled Multiplexer	99
Appendix I. Using MD485 Multidrop Modems with AVW200 Interfaces	105
I.1 Required Settings	105
I.2 Connections	106
I.2.1 Datalogger to MD485	107
I.2.2 MD485 to MD485	107
I.2.3 MD485 to AVW200	108
I.2.4 Multiplexer Connections	108
I.3 Programming	108
I.3.1 Example Program	108