Sequoia LISST-AOBS User Manual

Super-turbidity sensor

Hide thumbs

Table Of Contents

Table of Contents

Quick Links

Download this manual

LISST-AOBS

Super-Turbidity Sensor

Version 2

User's Manual

Version 2.2

November, 2021

Describes LISST-AOBS Version 2, serial numbers 6246 and higher.

For earlier Version 1 LISST-AOBS models, see manual version 1

Sequoia Scientific, Inc.

2700 Richards Road Suite 107

Bellevue, WA, 98005, USA

Phone: +1 855-753-3313

support@SequoiaSci.com; www.SequoiaSci.com

Table of Contents

Need help?

Do you have a question about the LISST-AOBS and is the answer not in the manual?

Questions and answers

Summary of Contents for Sequoia LISST-AOBS

Page 1 User’s Manual Version 2.2 November, 2021 Describes LISST-AOBS Version 2, serial numbers 6246 and higher. For earlier Version 1 LISST-AOBS models, see manual version 1 Sequoia Scientific, Inc. 2700 Richards Road Suite 107 Bellevue, WA, 98005, USA Phone: +1 855-753-3313...
Page 3 FOR TECHNICAL ASSISTANCE please contact your local Distributor, or Sequoia if the instrument was purchased directly from Sequoia. Please be sure to include the instrument serial number with any correspondence. A list of local Sequoia distributors can be found at our website http://www.sequoiasci.com/about/contact/distributors...
Page 4 This page intentionally blank...
Page 5: Table Of Contents
Table of Contents INTRODUCTION ............................1 LISST-AOBS system parts ........................1 Data outputs ............................1 Data interface and logging options ......................1 Anti-fouling wiper...........................2 Sampling modes and start-up sequence ....................2 Wi ing ..............................2 General Use and Care ..........................3 OPERATION WITH THE NEXSENS X2 LOGGER ....................4 About the X2 and X2-SDL ........................4...
Page 6 Interpreting LISST-AOBS Data ......................23 CONNECTION DETAILS ..........................24 Pin functions ............................24 Male connector numbering ........................24 Female mating connector numbering ....................24 Cables ..............................24 SPECIFICATIONS ............................25 APPENDIX: HOW THE LISST-ABS WORKS ....................26 ............................28 EVISION HISTORY...
Page 7: Introduction
Any logger that supports SDI-12 version 1.3 or higher can use the SDI-12 interface. Sequoia has teamed with NexSens Technology to integrate the LISST-AOBS with the NexSens X2 logger family, using SDI-12. The X2 can automatically detect a LISST-AOBS and deliver its data, with data from other connected sensors, through Wi-Fi, cellular, radio, or satellite channels.
Page 8: Anti-Fouling Wiper
GO command), every 10* minutes. *These are the default factory settings, but can be changed via RS- 232 with the OBSSET command (see Set automatic wiping on page The LISST-AOBS RS-232 interface can operate in either polled or free- Sampling modes running mode.
Page 9: General Use And Care
LISST-ABS. Damage to the transducer can severely affect accuracy. • Be sure water flows freely through the area directly in front of the LISST-AOBS, and within 10 cm of the ABS face. Any solid object within 10 cm can interfere with the measurements.
Page 10: Operation With The Nexsens X2 Logger
The factory-default sample period is 10 minutes, but can be changed through the X2’s Wi-Fi interface, or through the CONNECT software. The logging of LISST-AOBS data on an X2 is controlled by a script provided Data storage & with the X2. The standard script transmission 1.
Page 11: Connect Software
If you purchased the complete X2-LISST-AOBS system as a package, the X2 logger will already be set up to with knowledge of the LISST-AOBS that is connected. If you add sensors or otherwise change the configuration of the system, you must run the X2’s process for detecting which sensors are connected.
Page 12 4. Now you should see a list of all the parameters measured by the logger, including the LISST-AOBS parameters. You can edit the names as you see fit. We recommend “ABS Concentration”,...
Page 13: Sdi-12 Operation Details
SDI-12 methods. In this document, we use a to represent the LISST-ABS address. The ABS and turbidity sensors in the LISST-AOBS can be sampled every 2 Sampling and to 3 seconds, using the SDI-12 M command. However, we recommend...
Page 14: Sdi-12 Command Reference
SDI-12 COMMAND REFERENCE The following commands comply with the SDI-12 standard version 1.3. The address of the LISST-AOBS is represented by a. Command Function SDI-12 Action Command Address query Request address (requires that only one device is connected to the SDI-12 bus)
Page 15: Rs-232 Operation
10 seconds, then send data, once per second, via RS-232. NOTE: the LISST-AOBS will not respond to RS-232 commands when an SDI- 12 command is in progress. The 2-meter adapter cable from Sequoia, part number SEQ-AC-ABS- USB-powered CBL02, provides both power and communication through a USB port.
Page 16: Rs-232 Command Reference
RS-232 COMMAND REFERENCE Display Status Syntax: DS or status Description: Display the identity and status of the LISST-AOBS. NOTE: future firmware versions may include more information in the response. LISST-AOBS>DS Example: Serial number: 6260 SDI-12 address: 0 Version 2.10 Apr 13 2021 22:59:53 Input voltage is 12.46...
Page 17 WI command or an SDI-12 command. LISST-AOBS>OBSSET OBSI Example: OBS wipe interval (obsi)= 10 min [the factory default] LISST-AOBS>OBSSET OBSI 60 OBS wipe interval (obsi)= 60 min LISST-AOBS>OBSSET OBSI 0 OBS wipe interval (obsi)= 0 min [automatic wiping is off]...
Page 18 Syntax: SL or sendlast Description: Transmits the last sample collected by the issuing of a GetSample or HoldSample command. This can be called multiple times and will return the same result each time until a new sample is collected. LISST-AOBS>SL Example: +4.66e+01,+1.004,+8.78e+02 LISST-AOBS>...
Page 19: Lisst-Abs Windows Software
LISST-ABS WINDOWS SOFTWARE The LISST-AOBS is shipped with a Windows application for basic data viewing and logging. The software is called ‘LISST-ABS’, but works with both LISST-ABS and LISST-AOBS sensors. Using this software requires a USB or RS-232 connection to a computer. You...
Page 20: Software Configuration Options
Within a few seconds the software will find the instrument and begin displaying concentration values. The software will automatically start plotting the concentration as function of sample number. The instrument serial number will also be displayed at the top left of the screen. Should you have more than one AOBS instrument plugged into your computer, the software will interface with the first instrument it finds while searching your computer’s ports.
Page 21 Y-Axis Scale Scaling of the y-axis is handled automatically by default. However, if you wish to lock the y-axis limits at a specific value, enter a number in the text box below ‘Y- Min’ or ‘Y-Max’. You can switch back to auto scaling by deleting the values in the text boxes.
Page 22 Or they can be docked in any orientation by dragging and hovering over the main window:...
Page 23: Logging Data
Clearing or Data currently shown in the plots can be cleared by pressing the ‘Clear Plot’ Stopping Data button. This will only clear the display and will have no effect on data logging. If Plotting the software is left to run for a long period of time, the plots will show a maximum of 900 data points (15 minutes of data).
Page 24: Settings/Tools
The log file header contains instrument specific information, the computers current time zone, and the measurement average selected in the software. The header is followed by five columns of data: date, time, ABS standardized concentration, optical backscatter (volts), and total concentration (mg/L). Program settings and tools are accessed by clicking the gear icon in the lower Settings/Tools right corner.
Page 25 About LISST- The ‘About LISST-AOBS’ option will display instrument specific information, which AOBS is useful for viewing instrument settings or for troubleshooting purposes. Terminal The terminal window allows you to communicate directly with the instrument. This can be useful for retrieving information about your sensor or exploring the instruments serial communication features.
Page 26 Communication Communication settings allows you to disable the automatic port searching Settings feature. If you know what port your LISST-ABS is connected to, you can specify the port in this window. This can be useful if you are on a computer with many ports, or have multiple LISST-ABS’s connected to one computer.
Page 27: How Super-Turbidity Measurement Works
HOW SUPER-TURBIDITY MEASUREMENT WORKS The LISST-AOBS combines two measurement techniques: acoustic (ultrasonic) and optical, to measure suspended sediment concentration. The two techniques have different strengths, and combining them provides data superior to either one alone. The acoustic measurement is provided by the LISST-ABS, which measures Acoustic backscattering with 8 MHz ultrasonic pulses.
Page 28: Pairing Abs With Turbidity
Pairing By combining the complementary characteristics of the optical and acoustic measurements, the LISST-AOBS provides better tracking of total sediment ABS with concentration than either measurement alone. We can define a combined turbidity concentration measurement, C , as follows: AOBS + P * (V –...
Page 29: Interpreting Lisst-Aobs Data
Interpreting Although the AOBS or Super-Turbidity value is optimum in terms of estimating total concentration across a wide range of particle sizes, the LISST-AOBS separate ABS and OBS data have value beyond their contribution to the Data AOBS quantity. Because they have different responses to particle size, the ABS and OBS data can also provide insight into the particle size distribution (PSD).
Page 30: Connection Details
CONNECTION DETAILS The connector on the LISST-AOBS Y-adapter is a Subconn MCBH8M, wired as shown below. Mating connector is Subconn MCIL8F. functions 1. Common* 2. Supply voltage, 10 to 15 V 3. Common* 4. RS232 transmit (from AOBS to computer) 5.
Page 31: Specifications
SPECIFICATIONS NOTE: these specifications apply to version 2 of the LISST-AOBS (starting with serial number 6246) and are significantly different from the previous version. • Power Consumption (typical, 12 V input): o Idle: 60 mA o Sampling: 75 mA o Wiper running (sampling pauses): 68 mA •...
Page 32: Appendix: How The Lisst-Abs Works
APPENDIX: HOW THE LISST-ABS WORKS Basics The LISST-Acoustic Backscatter Sensor, LISST-ABS operates in a manner similar to radar. A short pulse of high-frequency sound is transmitted by a ceramic transducer, and the same transducer receives signals reflected by particles. The pulse travels outward, and its location at any time is at a distance equal to the product of speed of sound in water c, and time t after transmission, ct.
Page 33 noise floor, it is small]. Thus, the two-point backscatter determines the quantity in square bracket. Any increase in the difference determines water attenuation term. Knowing the terms in Eq.(2), we simply project the measurement to a small distance from the transducer, i.e. at R ~0 in Eq.(1), yielding the concentration term log ().
Page 34: Revision History
Added LISST-ABS software section and how LISST-ABS works appendix Version 2.1 Add note about USB-powered operation on page 9. Version 2.0 Major revision to describe new LISST-AOBS version 2 (Manual version 1.3 still applies to older LISST-AOBS). Version 1.3 Remove incorrect warranty statement. For warranty information see www.sequoiasci.com/support/warranty...