HOBO U20L Water Level Logger (U20L-0x) Manual
Contents
1. 310 kPa 45 psia or 18 m 60 ft depth Typical error 0 1 FS 1 0 cm 0 03 ft water Water Level Accuracy Maximum error 0 2 FS 2 0 cm 0 06 ft water 0 3 FS 0 62 kPa 0 09 psi maximum error Raw Pressure Accuracy Resolution Pressure Response Time 90 lt 0 02 kPa 0 003 psi 0 21 cm 0 007 ft water lt 1 second at a stable temperature measurement accuracy also depends on temperature response time Pressure Absolute and Water Level Measurements U20L 02 O to 400 kPa 0 to 58 psia approximately O to 30 6 m 0 to 100 ft Operation Range of water depth at sea level or O to 33 6 m 0 to 111 ft of water at 3 000 m 10 000 ft of altitude 69 to 400 kPa 10 to 58 psia 0 to 40 C 32 to 104 F Factory Calibrated Range Burst Pressure 500 kPa 72 5 psia or 40 8 m 134 ft depth Typical error 0 1 FS 3 0 cm 0 1 ft water Water Level Accuracy Maximum error 0 2 FS 6 0 cm 0 2 ft water Raw Pressure Accuracy Resolution 0 3 FS 1 20 kPa 0 17 psi maximum error lt 0 04 kPa 0 006 psi 0 41 cm 0 013 ft water Pressure Response Time 90 lt 1 second at a stable temperature measurement accuracy also depends on temperature response time Pressure Absolute and Water Level Measurements U20L 04 O to 145 kPa 0 to 21 psia approximately O to 4 m 0 to 13 ft of Operation Range Factory Calibrated Range water depth at sea level or O to 7 m 0 to 23 f2. 1 800 LOGGERS www onsetcomp com Distributed by MicroDAQ com Ltd _www MicroDAQ com 603 746 5524 HOBO U20L Water Level Logger U20L Ox Manual Logger Operation HOBOware Pro software is required for logger operation Using a reference water level HOBOware Pro automatically converts pressure readings into water level readings see Barometric Compensation for more detail The software also supports compensation for temperature fluid density and barometric pressure An LED in the communications window of the logger confirms logger operation When the logger is logging the LED blinks once every one to four seconds the shorter the logging interval the faster the LED blinks The LED also blinks when the logger is recording a sample When the logger is awaiting a start because it was configured to start At Interval On Date Time or Using Coupler the LED blinks once every eight seconds until logging begins Mounting hole Removable end cap covering communications window Groove for alignment with coupler Sensor face make sure sensor face is in the water when deploying the logger the sensor is located inside the logger case as represented by dashed lines in this diagram The logger can record two types of data samples and events Samples are the sensor measurements recorded at each logging interval for example the pressure every minute Events are independent occurrences triggered by a logge
3. compare the calculated water level at the end of the plot with the water level measured just before you removed the water level logger Barometric Data from Other Sources If you choose to use barometric pressure from a third party weather station or barometric logger you need to convert the date time and pressure data to a text file with special header requirements For information on how to set up the text file see the HOBOware Help or User Guide It is easiest to do this work in Microsoft Excel and then save it as a text file If you choose to use barometric pressure from an online weather station such as the National Weather Service the measured barometric pressure is modified to be at sea level This sea level pressure is useable since all pressure offsets are zeroed when you enter the reference measurement When you select the barometric data file in the Barometric Pressure Assistant see previous section select the text file that you generated Select tab or comma for the data format and data separation characters and then import the barometric data Maintenance The logger requires the following periodic maintenance to ensure optimal operation e Protect the logger This logger can be damaged by shock Always handle the logger with care The logger may lose its calibrated accuracy or be damaged if it is dropped Use proper packaging when transporting or shipping the logger Important Do not attempt to open the log
4. HOBO U20L Water Level Logger U20L 0x Manual HOBO Water Level Logger Models e U20L 01 30 foot depth e U20L 02 100 foot depth e U20L 04 13 foot depth Required Items e Coupler COUPLER2 C with USB Optic Base Station BASE U 4 or HOBO Waterproof Shuttle U DTW 1 e HOBOware Pro version 3 5 or higher Accessories e Cable CABLE 1 300 or CABLE 1 50 and Cable Crimp CABLE 1 CRIMP e Replacement Coupler COUPLER2 C Distributed by MicroDAQ com Ltd www MicroDAQ com 603 746 5524 The HOBO U20L Water Level Logger is used for monitoring changing water levels in a wide range of applications including streams lakes wetlands tidal areas and groundwater Using HOBOware Pro you can easily configure this logger to record absolute pressure and temperature data This logger features a ceramic pressure sensor durable housing and a protective end cap for deployment in existing wells or stilling wells Without cumbersome vent tubes or desiccants to maintain this easy to use logger is an ideal solution for water level studies and research Specifications Pressure Absolute and Water Level Measurements U20L 01 O to 207 kPa 0 to 30 psia approximately O to 9 m 0 to 30 ft of Operation Range water depth at sea level or O to 12 m 0 to 40 ft of water at 3 000 m 10 000 ft of altitude 69 to 207 kPa 10 to 30 psia 0 to 40 C 32 to 104 F Factory Calibrated Range Burst Pressure
5. as a positive number 6 Record the reference measurement date and time Deploying a Water Level Logger for Barometric Pressure Data Optional If you are using a U20 or U20L logger to record barometric pressure data install one logger in one of the wells as follows 1 Cut wire for suspending the logger a Measure the physical depth to the surface of the water from the suspension point b Cut a piece of stranded stainless steel wire Teflon coated is best so that the logger will hang about 2 feet below the ground surface but always above the water surface 2 Attach the wire to the suspension point and to the logger Cap 3 Relaunch the logger if desired if a laptop or a HOBO U Shuttle is available 4 Lower the logger into the well or stilling well Make sure the logger does not go below the water surface See the diagram in the previous section 5 Record the deployment time Reading Out the Logger To read out the logger for water level data see later in this section for steps to read out a water level logger used for barometric pressure data 1 Measure the water depth using the original reference point with the correct sign 2 Record depth and date and time 3 Pull the logger out of the well 4 Remove the logger from its cap leaving the suspension undisturbed 5 Read out the data using a laptop or shuttle 6 Save the data in a test folder location 7 Redeploy the logger optional as desc
6. ature samples Approximately 154 g 5 43 oz in air Approximately 53 9 g 1 9 oz in fresh water 3 18 cm 1 25 inches diameter 15 24 cm 6 0 inches length mounting hole 6 3 mm 0 25 inches diameter Polypropylene housing and lanyard Viton and Buna N O rings ceramic sensor in acetyl end cap stainless steel screws suitable for saltwater Fixed rate or multiple logging intervals with up to 8 user defined logging intervals and durations logging intervals from 1 second to 18 hours Refer to the HOBOware User s Guide for details Immediate start and delayed start Offload while logging stop and offload Battery voltage can be viewed in status screen and optionally logged in datafile Low battery indication in datafile The CE Marking identifies this product as complying with all relevant directives in the European Union EU Water Level Accuracy With accurate reference water level measurement known water density accurate Barometric Compensation Assistant data and a stable temperature environment K K Raw Pressure Accuracy Absolute pressure sensor accuracy includes all sensor drift temperature and hysteresis induced errors Changes in Temperature Allow 20 minutes in water to achieve full temperature compensation of the pressure sensor Maximum error due to rapid thermal changes is approximately 0 5 Accuracy Resolution C Accuracy eResolution Temperature C Plot A
7. et below that level 2 Attach the wire to the suspension point and to the logger Cap 3 Relaunch the logger if desired if a laptop or a HOBO U Shuttle is available 4 Lower the logger into the well or stilling well GROUND LEVEL OPTIONAL BAROMETRIC PRESSURE LOGGER WATER LEVEL WATER LEVEL LOGGER 5 Measure the water depth from the desired reference point top of pipe ground level or sea level e To maximize accuracy allow 20 minutes after deploying the logger before measuring water depth to allow the logger to reach temperature equilibrium with the water e If the well is too small in diameter to measure the water depth after deployment measure the water depth before deployment then deploy the logger immediately and record deployment time e For well deployments If the water level surface is below the reference point such as referencing groundwater measurements to the top of the well record the water level as a negative number If the water level surface is above the reference point such as height above sea level record the water level as a positive number e For lake stream and river deployments If the water level is being referenced to some point above the logger such as the top of the stilling well record the water level as a negative number If the water depth is being referenced to a point below the water surface such as the bottom of the stream record the water level
8. etcomp com To base station or shuttle Distributed by MicroDAQ com Ltd _www MicroDAQ com 603 746 5524 HOBO U20L Water Level Logger U20L Ox Manual 1 Follow the instructions that came with your base station or shuttle to attach it to a USB port on the computer 2 Unscrew the black plastic end cap from the logger by turning it counter clockwise 3 Attach the coupler to the base station or shuttle 4 Insert the logger into the coupler aligning the bump on the coupler with the groove on the logger Be sure it is properly seated in the coupler It may take a few seconds for the new hardware to be detected by the computer NOTE If you are using the Waterproof Shuttle briefly press the coupler lever to put the shuttle into base station mode Align bump on the coupler Logger with the groove on the logger EB Coupler P Coupler lever for use with HOBO Waterproof Shuttle If the logger has never been connected to the computer before it may take a few seconds for the new hardware to be detected by the computer WARNING Do not leave the logger in the coupler for extended periods of time When connected to a coupler the logger is awake and consumes significantly more power than when it is disconnected and considered asleep Always remove the logger from the Optic Base Station or HOBO Waterproof Shuttle as soon as possible after launching reading out or checking the status to avoid draining the batte
9. evel measurements by deploying the loggers at two depths and comparing the difference in level readings When verifying the accuracy this way be sure to allow the loggers temperature to stabilize at each depth Use the logger software to convert the readings from pressure to level The level readings should be taken close enough together that the barometric pressure does not change You can check the absolute pressure accuracy of your HOBO U20L Water Level Logger by comparing its ambient pressure readings to a second HOBO logger Their readings should be within each other s specified accuracy Alternatively you can check the pressure reading against an accurate local barometer If you use a non local source of barometric information such as the NOAA website adjust for altitude Battery Guidelines The battery in the HOBO U20L Water Level Logger is a 3 6 Volt lithium battery e Battery Life The battery life of the logger should be about five years or more Actual battery life is a function of the number of deployments logging interval and operation storage temperature of the logger Frequent deployments with logging intervals of less than one minute and continuous storage operation at temperatures above 35 C will result in significantly lower battery life For example continuous logging at a one second logging interval will result in a battery life of approximately one month To obtain a five year battery life a logging inte
10. ger housing Unscrewing the nose cone of the logger will cause serious damage to the pressure sensor and logger electronics There are no user serviceable parts inside the case Contact Onset Technical Support if your logger requires servicing e Periodically inspect the logger for biofouling Biological growth on the face of the pressure sensor will throw off the pressure sensor s accuracy Organisms that grow inside the sensor nose cone and on the sensor itself can interfere with the sensor s operation and eventually make the sensor unusable If the deployment area is prone to biofouling check the logger periodically for marine growth e Be careful of solvents Check a materials compatibility chart against the wetted materials listed in the Specifications table before deploying the logger in locations where untested solvents are present The logger has Viton and Buna N O rings which are sensitive to polar solvents acetone ketone ammonia chlorine and brake fluids The sensor is housed in an acetyl end cap Acetyl is resistant to most solvents fuels and lubricants The black polypropylene cap is provided to help protect the communications window The polypropylene communications window is sealed as an additional barrier to prevent water and dirt from entering the logger housing 1 800 LOGGERS www onsetcomp com Distributed by MicroDAQ com Ltd _www MicroDAQ com 603 746 5524 HOBO U20L Water Level Logger U20L Ox Man
11. o their smaller range and temperature compensated accuracy HOBOware Pro includes a Barometric Compensation Assistant for easy and accurate barometric compensation See Processing Water Level Data using Barometric Pressure Data for more details Calibration The pressure sensor in each HOBO U20L Water Level logger is individually calibrated During calibration raw pressure sensor data is collected at multiple pressures and temperatures over the calibrated range of the logger see the specifications table This data is used to generate calibration coefficients that are stored in the logger s non volatile memory The calibration coefficients are then checked to be sure that the logger meets its stated accuracy over the calibrated range The pressure sensor can be used at pressures and temperatures that are outside of the calibrated range but the accuracy cannot be guaranteed Important Never exceed the burst pressure of the sensor Connecting the Logger to a Computer The HOBO Water Level Logger requires a coupler COUPLER2 C and Optic Base Station BASE U 4 or HOBO Waterproof Shuttle U DTW 1 to connect to the computer The optical interface allows the logger to be offloaded without breaking the integrity of the seals The USB compatibility allows for easy setup and fast downloads Important USB communications may not function properly at temperatures below 0 C 32 F or above 50 C 122 F 1 800 LOGGERS www ons
12. ps to protect the logger from currents wave action and debris Suspend the logger in the stilling well so it is always underwater but not on the bottom to be buried by silt For more information see the Technical Application Note for Constructing a Stilling Well at http www onsetcomp com water_level_ stilling well html e To prevent the logger from moving in currents and to ensure the support cable is kept straight during deployment you may need to add a weight to the suspension cable or hang a weight below the logger Alternatively you could deploy the logger in a stilling well as described above 1 800 LOGGERS www onsetcomp com Distributed by MicroDAQ com Ltd _www MicroDAQ com 603 746 5524 HOBO U20L Water Level Logger U20L Ox Manual e Be very careful not to exceed the burst pressure for the logger The pressure sensor will burst if the maximum depth is exceeded see specifications table The logger should be positioned at a depth where the logger will remain in the water for the duration of the deployment but not exceed the rated bursting depth To deploy the logger 1 Cut wire to suspend logger a Measure the physical depth to the surface of the water from the suspension point b Cuta piece of stranded stainless steel wire Teflon coated is best so that the logger will be deep enough to always be in the water Estimate the low water level and make the cable length such that the logger will be about 2 fe
13. r activity such as Bad Battery or Host Connected Events help you determine what was happening while the logger was logging Barometric Compensation The logger records absolute pressure which is later converted to water level readings by HOBOware Pro software In this application absolute pressure includes atmospheric pressure and water head Atmospheric pressure is nominally 100 kPa 14 5 psi at sea level but it changes with weather and altitude Left uncompensated barometric variations could result in errors of 0 6 m 2 ft or more To compensate for barometric pressure changes you can use another HOBO U20L Water Level logger as a barometric reference The barometric reference is typically deployed in the same well or at the same location as the water level of interest but rather than being placed in the water column it is deployed above the water in air Barometric pressure readings are consistent across a region except during fast moving weather events so you can generally use barometric pressure readings that are taken within 15 km 10 miles of the logger or more without significantly degrading the accuracy of the compensation Therefore one HOBO U20L or U20 Water Level logger or weather station HOBO U30 recommended can be used to compensate all the water level loggers in an area The U20L 01 model with its O 9m 0 30 ft range or the U20L 04 with its 0 4 m 0 13 ft range are both good barometric references due t
14. reference level is recorded e Sudden temperature changes should be avoided When deploying a HOBO U20L Water Level Logger for barometric pressure reference some consideration should be made to minimize the rate of temperature fluctuations Ideally the barometric pressure reference logger should be hung several feet below ground level in an observation well where ground temperatures are stable while making sure the logger remains above the water level If that is not possible or if a well is not used try to put the logger ina location where it will not be subject to rapid daily temperature cycles e When deploying a HOBO Water Level logger in a well make sure the well is vented to the atmosphere Typically a small hole can be drilled in the well cap to ensure that the pressure inside and outside the well is at equilibrium If this is not possible the barometric pressure reference logger should be used inside the same well e Use ano stretch wire to hang the water level logger Any change in length of the wire will result in a 1 to 1 corresponding error in the depth measurement Always pull test a cable prior to deploying a logger in a well to make sure it does not stretch e If you are deploying the logger in a lake river or stream you must first build a stilling well to protect the logger from vibration shock and movement A simple stilling well can be constructed with PVC or ABS pipe A properly constructed stilling well hel
15. ribed later in this section To read out a U20L logger used for barometric pressure data 1 Remove the logger from the well 2 Read out the data using a laptop or shuttle 1 800 LOGGERS www onsetcomp com Distributed by MicroDAQ com Ltd _www MicroDAQ com 603 746 5524 HOBO U20L Water Level Logger U20L Ox Manual 3 Save the data in a test folder location 4 Redeploy the logger optional as described below If you are redeploying the logger you must first make sure that it is launched If you used the HOBO Waterproof Shuttle to offload data the shuttle automatically performs a synchronized relaunch of the logger so that data is logged on the same measurement intervals If you wish to change the launch settings you must launch the logger using HOBOware Pro The existing suspension can be reused as long as the water level logger remained in the water and the barometric logger remained out of the water for the entire test interval Take a new reference reading with the date and time as described in this section Record this information in your field notebook to use later to calibrate the data which will zero out any drift error Processing Water Level Data using Barometric Pressure Data To determine water level using barometric pressure data use the Barometric Compensation Assistant in HOBOware Pro as described below If you are using barometric pressure data from a HOBO weather station you can use the data file a
16. rval of one minute or greater should be used and the logger should be operated and stored at temperatures between 0 and 25 C 32 and 77 F e Battery Voltage The logger can report and log its battery voltage If the battery falls below 3 1 V the logger will record a bad battery event in the datafile If the datafile contains bad battery events or if logged battery voltage repeatedly falls below 3 3 V the battery is failing and the logger should be returned to Onset for battery replacement e Replace the Battery To have your logger s battery replaced contact Onset or your place of purchase for return arrangements Do not attempt to replace the battery yourself Severe damage to the logger will result if the case is opened without special tools and the warranty will be voided perenne Do not cut open incinerate heat above 100 C 212 F or recharge the lithium battery The battery may explode if the logger is exposed to extreme heat or conditions that could damage or destroy the battery case Do not dispose of the logger or battery in fire Do not expose the contents of the battery to water Dispose of the battery according to local regulations for lithium batteries 2014 Onset Computer Corporation All rights reserved Onset HOBO and HOBOware are trademarks or 1 800 LOGGERS 564 4377 508 759 9500 registered trademarks of Onset Computer Corporation All other trademarks are the property of their ww
17. ry To wake up the logger remove it from the coupler wait a moment and then re insert the logger Launching the Logger Before deploying the HOBO U20 Water Level Logger in the field perform the following steps in the office 1 Open HOBOware 2 Connect the logger to the computer as described in the previous section 3 From the Device menu select Launch 4 Inthe Launch Logger window make sure both the Abs Pressure and Temperature sensors are selected temperature is required for temperature compensation of pressure 5 Select any other launch settings as desired including when to start logging and the logging interval Click the Start button in the lower right corner of the Launch Logger window to send the launch settings to the logger note that the Start button text changes based on the Start Logging selection Deploying the Logger The HOBO Water Level Logger is designed to be easy to deploy in many environments The logger uses an absolute pressure sensor so no vent tube is required The small size of the logger is convenient for use in small wells and allows the logger to be mounted and or hidden in the field Follow these guidelines when deploying the logger e The pressure sensor is temperature compensated over the range of 0 to 40 C 32 to 104 F To obtain the highest level of accuracy the logger should be allowed to come to full temperature equilibrium approximately 20 minutes before the
18. s if it were U20L barometric data For data from sources other than Onset products see Barometric Data from Other Sources below 1 In HOBOware Pro open the water depth data file The Plot Setup window appears 2 Uncheck all boxes except Abs Pressure 3 Run the Barometric Compensation Assistant a Select the assistant and click the Process button b Select the water density box that best describes the water that you are measuring or enter the actual water density c Check the Use a Reference Water Level box and enter the reference water level that you measured at the beginning of the deployment d Select the date and time from the pull down menu that is closest to the recorded date time for the measurement If you measured the depth before deployment because of pipe size then select a date time after the start of the deployment e Check Use Barometric Data file f Click the Choose button This will allow you to select the data file to use for barometric pressure compensation g Select and open the data file h Click the Create New Series button A new Plot Setup window appears 4 Select the Water Level checkbox and any other series that you want plotted Click the Plot button to obtain a plot of the resulting water level data Measurement error can be caused by manual measurement error sensor drift or change in the suspension cable length To quantify measurement error which is ideally zero
19. t of water at 3 000 m 10 000 ft of altitude 69 to 145 kPa 10 to 21 psia 0 to 40 C 32 to 104 F Burst Pressure 310 kPa 45 psia or 18 m 60 ft depth Typical error 0 1 FS 0 4 cm 0 013 ft water Water Level Accuracy Maximum error 0 2 FS 0 8 cm 0 026 ft water 0 3 FS 0 43 kPa 0 063 psi maximum error Raw Pressure Accuracy Resolution Pressure Response Time 90 lt 0 014 kPa 0 002 psi 0 14 cm 0 005 ft water lt 1 second at a stable temperature measurement accuracy also depends on temperature response time 17153 B Distributed by MicroDAQ com Ltd _www MicroDAQ com 603 746 5524 HOBO U20L Water Level Logger U20L Ox Manual Specifications continued Operation Range Accuracy Resolution Response Time 90 Stability Drift Logger Real time Clock Battery Battery Life Typical Use Memory Non volatile Weight Dimensions Wetted Materials Logging Interval Launch Modes Offload Modes Battery Indication ce Temperature Measurements All Models 20 to 50 C 4 to 122 F 0 44 C from 0 to 50 C 0 79 F from 32 to 122 F see Plot A 0 10 C at 25 C 0 18 F at 77 F see Plot A 10 minutes in water typical 0 1 C 0 18 F per year 1 minute per month 0 to 50 C 32 to 122 F 2 3 AA 3 6 Volt lithium factory replaceable 5 years with 1 minute or greater logging interval 64K bytes memory approx 21 700 pressure and temper
20. ual Compensating for Drift All pressure sensors drift over time The drift for the pressure sensor and electronics in the HOBO U20L Water Level logger is less than 0 5 FS worst case per year In most applications drift is not a significant source of error because the offset created by any drift is zeroed out when you take a manual reference level measurement and use the logger software to automatically calculate the level readings relative to the reference measurement In effect you are re zeroing the sensor each time you apply a reference reading to the data file Pressure sensor drift matters only when absolute pressure values are needed or if there are no recent reference level or depth measurements available For example if the logger is deployed for one year and no new reference level readings are taken during the deployment it is possible that the sensor could have drifted as much as 0 5 FS by the end of the deployment It is possible to determine the actual amount of drift during a deployment if a reference level is taken at the beginning and the end of a long term deployment The results of applying the two different reference levels once at the beginning of the data file and again at the end of the data file can be compared Any difference between the files indicates the amount of sensor drift assuming accurate reference levels Verifying Accuracy You can check the differential accuracy of your loggers for water l
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