HOBO MX Water Level Logger Instruction Manual
a close up of a device

HOBO MX Water Level Logger

Models:

  • MX2001-01 or MX2001-01-Ti (Titanium), 9-meter/30-foot depth)
  • MX2001-02, 30-meter/100-foot depth
  • MX2001-03, 76-meter/250-foot depth
  • MX2001-04 or MX2001-04-Ti (Titanium), 4-meter/13-foot depth
    Note: Each model consists of a sensor end (MX2001-0x-S or MX2001-0x-Ti-S) and a top end (MX2001-TOP).

Included Items:

  • Two AA 1.5 V Batteries
  • Logger consisting of a top end and sensor end connected by a cable in desired length (ordered separately)

Required Items:

  • HOBOconnect app
  • Mobile device with Bluetooth and iOS, iPadOS®, or Android™
  • Cable (CABLE-DR-xxx)

Accessory:

  • Well cap (WELL-CAP-01)

The HOBO MX water level logger is used for monitoring changing water levels in a wide range of applications, including streams, lakes, wetlands, tidal areas, and groundwater. This Bluetooth® Low Energy-enabled logger is designed for wireless communication with a mobile device. Using the HOBOconnect™ app, you can easily configure the logger and read it out—all from its deployed location—to your phone or tablet where you can view the logged data or share it for further analysis. With the app, you can also set a reference water level and water density, configure up to 8 logging intervals, log statistics, configure an alarm to trip at thresholds you specify, or set up burst logging in which data is logged at a different interval when sensor readings are above or below certain limits. This logger features a ceramic pressure sensor, durable housing, and an integrated barometric pressure sensor for barometric compensation in the logger, which allows for direct water level readout without needing to do any post processing. An optional cap is also available for deployment in existing wells or stilling wells. Without cumbersome vent tubes or desiccants to maintain and convenient data retrieval to a phone or tablet, this easy-to-use logger is an ideal solution for water level studies and research.

Specifications

  Pressure (Absolute) and Water Level Measurements MX2001-01-S and MX2001-01-Ti-S
  Operation Range   0  to 207 kPa (0 to 30 psia); approximately 0 to 9 m (0 to 30 ft) of water depth     at sea level, or 0 to 12 m (0 to 40 ft) of water at 3,000 m (10,000 ft) of altitude
  Factory Calibrated Range  69 to 207 kPa (10 to 30 psia), 0° to 40°C (32° to 104°F)
  Burst Pressure   310 kPa (45 psia) or 18 m (60 ft) depth
  Water Level Accuracy*  Typical error: ±0.05% FS, 0.5 cm (0.015 ft) water

Maximum error: ±0.1% FS, 1.0 cm (0.03 ft) water

  Raw Pressure Accuracy**  ±0.3% FS, 0.62 kPa (0.09 psi) maximum error
  Resolution  <0.02 kPa (0.003 psi), 0.21 cm (0.007 ft) water
  Pressure Response Time (90%)***   <1 second at a stable temperature
  Pressure (Absolute) and Water Level Measurements MX2001-02-S
  Operation Range   0 to 400 kPa (0 to 58 psia); approximately 0 to 30.6 m (0 to 100 ft) of water   depth at sea level, or 0 to 33.6 m (0 to 111 ft) of water at 3,000 m (10,000 ft) of     altitude
  Factory Calibrated Range   69 to 400 kPa (10 to 58 psia), 0° to 40°C (32° to 104°F)
  Burst Pressure   500 kPa (72.5 psia) or 40.8 m (134 ft) depth
  Water Level Accuracy*   Typical error: ±0.05% FS, 1.5 cm (0.05 ft) water

Maximum error: ±0.1% FS, 3.0 cm (0.1 ft) water

  Raw Pressure Accuracy**   ±0.3% FS, 1.20 kPa (0.17 psi) maximum error
  Resolution   <0.04 kPa (0.006 psi), 0.41 cm (0.013 ft) water
  Pressure Response Time (90%)***   <1 second at a stable temperature
Pressure (Absolute) and Water Level Measurements MX2001-03-S
  Operation Range   0 to 850 kPa (0 to 123.3 psia); approximately 0 to 76.5 m (0 to 251 ft) of water     depth at sea level, or 0 to 79.5 m (0 to 262 ft) of water at 3,000 m (10,000 ft) of   altitude
  Factory Calibrated Range   69 to 850 kPa (10 to 123.3 psia), 0° to 40°C (32° to 104°F)
  Burst Pressure   1,200 kPa (174 psia) or 112 m (368 ft) depth
  Water Level Accuracy*   Typical error: ±0.05% FS, 3.8 cm (0.125 ft) water

Maximum error: ±0.1% FS, 7.6 cm (0.25 ft) water

  Raw Pressure Accuracy**   ±0.3% FS, 2.55 kPa (0.37 psi) maximum error
  Resolution   <0.085 kPa (0.012 psi), 0.87 cm (0.028 ft) water
  Pressure Response Time (90%)***   <1 second at a stable temperature

Specifications (continued)

  Pressure (Absolute) and Water Level Measurements MX2001-04-S and MX2001-04-Ti-S
  Operation Range   0 to 145 kPa (0 to 21 psia); approximately 0 to 4 m (0 to 13 ft) of water depth at sea level, or 0     to 7 m (0 to 23 ft) of water at 3,000 m (10,000 ft) of altitude
  Factory Calibrated Range   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
  Water Level Accuracy*   Typical error: ±0.075% FS, 0.3 cm (0.01 ft) water

Maximum error: ±0.15% FS, 0.6 cm (0.02 ft) water

  Raw Pressure Accuracy**   ±0.3% FS, 0.43 kPa (0.063 psi) maximum error
  Resolution   <0.014 kPa (0.002 psi), 0.14 cm (0.005 ft) water
  Pressure Response Time   (90%)***   <1 second at a stable temperature
  Barometric Pressure (MX2001-    TOP)  
  Operation Range   66 to 107 kPa (9.57 to 15.52 psia)
  Temperature Calibrated Range   -20 to 50°C (-4 to 122°C)
  Accuracy   ±0.2 kPa (±0.029 psi) over full temperature range at fixed pressure; maximum error ±0.5% FS
  Water Level Accuracy*   Typical error: ±0.075% FS, 0.3 cm (0.01 ft) water

Maximum error: ±0.15% FS, 0.6 cm (0.02 ft) water

  Resolution   <0.01 kPa (0.0015 psi)
  Response Time   <1 second at stable temperature
  Stability (Drift)   <0.01 kPa (0.0015 psi) per year
  Temperature Measurements (All Sensor End Models MX2001-0x-S and MX2001-0x-Ti-S)
Operation Range   -20° to 50°C (-4° to 122°F)
  Accuracy   ±0.44°C from 0° to 50°C (±0.79°F from 32° to 122°F), see Plot A
  Resolution   0.1°C at 25°C (0.18°F at 77°F), see Plot A
  Response Time (90%)   5 minutes in water (typical)
  Stability (Drift)   0.1°C (0.18°F) per year
  Logger  
  Operating Range     -20° to 50°C (-4° to 122°F)
  Radio Power   1 mW (0 dBm)
  Transmission Range   Approximately 30.5 m (100 ft) line-of-sight
  Wireless Data Standard   Bluetooth Low Energy (Bluetooth Smart®)
  Logging Rate   1 second to 18 hours
  Logging Modes   Fixed interval, multiple intervals with up to 8 user-defined logging intervals and durations, or     burst
  Memory Modes   Wrap when full or stop when full
  Start Modes   Immediate, date & time, or next interval
  Stop Modes   When memory full, date & time, or after a set logging period
  Time Accuracy   ±1 minute per month 0° to 50°C (32° to 122°F)
Battery   Two AA, 1.5 V alkaline batteries, user replaceable
Battery Life   1 year, typical with logging interval of 1 minute. Faster logging and/or statistics sampling   intervals, entering burst logging mode, excessive readouts, checking of Full Status Details, and   remaining connected with the app will impact battery life.
  Memory   256 KB memory (30,000 sets of measurements)
  Full Memory Download Time   Approximately 2 minutes; may take longer the further the device is from the top end of the   logger
Dimensions   Top end (MX2001-TOP): 2.54 cm (1.0 inches) diameter, 28.9 cm (11.4 inches) length;   mounting   hole 7.6 mm (0.3 inches) diameter

Sensor end (MX2001-0x-S and MX2001-0x-Ti-S: 2.54 cm (1.0 inches) diameter, 9.91 cm (3.9   inches) length

  Note: The length of the water level logger cable (CABLE-DR-xxx) can vary -0% to +3% +10    cm (3.9 inches) from the length ordered. The logger adds 38.8 cm (15.3) inches to the length of   the cable ordered.

  Weight   Top end (MX2001-TOP): Approximately 136 g (4.78 oz) in air

Stainless sensor end (MX2001-0x-S): Approximately 106 g (3.74 oz) in air; approximately 53.9 g (1.9 oz)    in fresh water

Titanium sensor end (MX2001-0x-Ti-S): Approximately 80 g (2.83 oz) in air; approximately 37 g (1.3 oz)   in fresh water

  Wetted Materials   Top end (MX2001-TOP): PVC housing, Polycarbonate end cap, Viton O-ring

Stainless sensor end (MX2001-0x-S): Acetal housing, Viton and Buna-N O-rings, ceramic sensor in   stainless steel end cap

Titanium sensor end (MX2001-0x-Ti-S): Acetal housing, Viton and Buna-N O-rings, ceramic sensor in     Titanium end cap

Cable (CABLE-DR-XXX): Polycarbonate end cap, PVC end cap, nylon collar nut, Viton O-rings,   polyurethane jacket

  Environmental Rating   Top end: NEMA 6, IP67

Sensor end: IP68

    The CE Marking identifies this product as complying with all relevant directives in the European Union    (  EU).
    See last page

* Water Level Accuracy: With accurate reference water level measurement, known water density, and a stable temperature environment. System Water Level Accuracy equals thesum of the Barometric Water Level Accuracy plus the selected sensor end Water Level Accuracy.
** 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. There can be up to 0.5% of additional error due to rapid temperature changes. Measurement accuracy also depends on temperature response time.
chart

Logger Components and Operation

diagram

Disassembled top end

The MX water level logger consists of a top end and a sensor end that is connected by a water level logger cable. The three components work together to allow for wireless transfer of data to the app on a mobile phone or tablet. This is an overview of each main component and the internal components in the top end:

  • Top end. This contains the Bluetooth wireless communication and two AA batteries. This top end unit is suspended from the top of the well using the mounting hole in the end cap (see Deploying the Logger).
  • Sensor end. This measures the pressure and temperature in the water. The nose cone on the sensor end houses the pressure sensors and the body of the sensor end houses the temperature sensor.
  • Water level logger cable. This is the cable that connects the top end to the sensor end. Data measured by the sensor is transmitted through the cable to the top end where it is logged for later upload to a mobile phone or tablet (see Configuring the Logger).
  • Battery holders. Two AA batteries are installed in the battery holders in the top end (see Battery Information).
  • Password reset button. Press the button between the two batteries in the top end to reset the logger password to the factory default (see Setting a Logger Password).
  • LED. Remove the end cap from the top end to view the red LED below the top edge of the circuit board. This LED blinks every second while logging and every 8 seconds

when the logger is configured to start on a specific date/time or on the next logging interval. The LED will also blink once when you press the password reset button and blink quickly multiple times when the batteries are installed.
When the three components are deployed together, you can then configure the logger or offload data to your mobile device without having to pull the logger up to the surface.

Factory Calibration

The pressure sensors in the sensor end are individually calibrated. During calibration, raw pressure sensor data is collected at multiple pressures and temperatures over the calibrated range of the logger (see Specifications). This data is used to generate calibration coefficients that are stored in the sensor end’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!

Configuring the Logger

Follow these steps to begin using the logger. After completing steps 1–4, it is recommended that you perform a trial run of steps 5 through 12 before deploying the logger.
Important: When assembling the logger or attaching the cable, make sure the O-rings and mating housing surfaces are clear of any debris. Any contamination of these surfaces can cause leaks that will lead to logger failure.

  1.  Install the batteries in the top end. See Battery Information for details.
  2. Connect the logger components. Connect the top end to the sensor end with the water level logger cable as shown below. The end of the cable with the longer housing connects to the top end as shown below.
    diagram
  3. Download the app. Go to the App Store® or Google Play™ and download HOBOconnect to your phone or tablet.
  4. Open the app. Enable Bluetooth in your device settings if prompted.
  5.  Determine the logger is within range. Tap Devices. The logger should appear in the list of devices (note that the serial number shown in the app is for the top end of the logger). If the logger does not appear, make sure it is within range of your device. Note that sensor readings are displayed as “–“ when the logger is stopped.
  6. Deploy the logger if ready. If you are ready to deploy the logger, place it in the deployment location (see Deploying the Logger for deployment guidelines). Otherwise, skip deployment and complete the following steps as a test.
  7. Connect to the logger. Tap the logger in the app to connect to it. Tips for connecting:
    • Make sure the top end of the logger is within range of your mobile device. The range for successful wireless communication is approximately 30.5 m (100 ft) with full line-of-sight.
    • If your device can connect to the logger intermittently or loses its connection, move closer to the top end of the logger, within sight if possible
    • If the logger appears in the app, but you cannot connect to it or if you are experiencing persistent connection problems, close the app and power cycle the mobile device (turn it off, wait a minute, and turn it back on). This forces the previous Bluetooth connection to close.
  8. Configure the logger. Once connected to the logger, tap icon to set up the logger.
  9. Set the Reference Water Level and Water Density.
    a. Under Deployment Information, tap Reference Water Level and enter the current water level as the reference level in meters or feet. Water levels that are below the reference point should be entered as negative values. The reference water level entered will be associated with the first data point once logging begins to determine the correction factor to be used for water level data.
    b. Tap water density and select one from the list for the deployment or enter your own value under Manual Input.
    c. Tap Save to return to the Configuration screen.
  10. Enable the desired sensors. Scroll down in the Configuration screen to select the measurement parameters to be logged. Differential pressure must be enabled to calculate water level. Temperature must be enabled to log absolute pressure. Temperature must also be enabled if you selected the water density option “Fresh Water adjusted for Temp” because the temperature values are used to calculate the water density.
  11. Finish configuring the logger. Select any of the following logger settings as desired. The following table provides an overview of the settings. For complete details, see the app user’s guide at www.onsetcomp.com/hoboconnect.
  Logger

  Setting

 

Action

  Name   Enter a name for the logger (optional). If no name is entered, the logger serial number    is used.
  Group   Tap Group to add the logger to a group (optional). Tap Save.
   

 

  Logger Setting

 

 

 

  Action

    Logging Intervals Tap Logging Intervals and select how often the logger will record data. When selecting a logging interval, keep in mind that data offload time is proportional to the amount of data logged. The faster the logging interval, the more data that will need to be offloaded and the longer it will take.

Multi-Rate Logging

You can set a total of 8 logging intervals. After tapping Logging Intervals and entering a rate for Interval 1, tap Add to set up additional logging intervals. For each interval, enter the rate and select the number of samples that will be recorded for the selected rate. Tap Save.

    Start Logging Options Tap Start Logging and choose one of the following:

·   Now. Logging will begin immediately after the configuration settings are saved to the logger.

·   On Next Logging Interval. Logging will begin at the next even interval as determined by the selected logging interval.

·   On Date/Time. Logging will begin at a date and time you specify.

Tap Save.

    Stop Logging Options   Tap Stop Logging and choose a memory option:

·   When Memory Fills. The logger will continue recording data until the memory is full.

·   Never (Wrap When Full). The logger will continue recording data indefinitely, with   newest data overwriting the oldest. This option is not available if the Logging Mode is set    to Burst (see Burst Logging) or if you set up multiple logging intervals.

Select one of the following time options for when to stop logging:

·   Never. Select this if you do not want the logger to stop at any predetermined time   frame.

·   On Date/Time. Select this if you want the logger to stop logging on a specific date     and   time. Select the date and time.

·   After. Select this if you want to control how long the logger should continue logging   once it starts. Choose the amount of time you want the logger to log data. For example,   select 30 days if you want the logger to log data for 30 days after logging begins.

Tap Save.

    Logging Mode and       Statistics   Tap Logging Mode. Choose the logging mode (note that you cannot change the logging     mode if you have multiple logging intervals configured):

·   Fixed Logging. Select Normal to record the current reading for each enabled sensor at   each logging interval. Note that this is also the mode you need to select for multi-rate     logging. You must select Normal if you want to log water level and barometric pressure     data. If you deselect Normal, the logger will only record statistics series for the enabled   series. It will not be able to calculate water level or barometric pressure.

                            · Statistics. Select any statistics you want to                    

  Logger

  Setting

 

  Action

    record (maximum, minimum, average, and standard deviation) and set the statistics sampling     interval. Statistics are not available for water level and barometric pressure data. See Statistics     Logging for more information.

·   Burst Logging. Select this to enable burst mode in which logging can occur at a faster rate   when a specified trigger level is exceeded. See Burst Logging for more information.

·

  Sensors & Alarm Setup   After enabling the sensors as described in step 10, set up any alarms. See Setting up Alarms for    details.

12. Save the configuration settings. Tap to save the configuration settings The logger will begin logging data based on the settings you selected. After logging begins, you can read out the logger at any time (see Reading Out the Logger for details). You can update the reference water level or water density during the deployment if necessary (see Updating the Reference Water Level and Water Density).

Notes:

  • When the logger is stopped, the water level reading shown while connected to the logger does not reflect any reference water level and water density values you have entered (it reverts to a reference water level of zero and a water density of “Fresh Water adjusted for Temperature”). Once logging begins, the readings shown in the app will be based on the reference water level and water density you entered.
  • If the logger is logging and you start a new deployment, the logger will take a current water level reading and use that as the default reference reading for the new deployment.
  • These are the options available when the logger is connected to the app:
  Tap this:   To do this:

  icon

 Select logger settings and save them onto the logger to start logging. See Configuring the Logger.
icon   Read out (offload) logger data. See Reading Out the Logger.
 

graphical user interface

  Start or restart logging depending on the configuration settings selected in Configuring the Logger.
graphical user interface   Set a password for the logger that will be required if another mobile device attempts to connect     to it. To reset a password, press the reset button between the batteries inside the

logger or tap and tap Reset.

shape   Mark the logger as a favorite. You can then filter the list of devices to only show loggers marked    as favorites.

graphical user interface, diagram, application Update the firmware on the logger. A logger readout will be completed automatically at the beginning of the firmware update process
Important: Before updating the firmware on the logger, check the remaining battery level and make sure it is no less than 30%. Make sure you have the time to complete the entire update process, which requires that the logger remains connected to the device during the upgrade.

Deploying the Logger

The logger is designed to be easy to deploy in many environments. The logger includes an absolute pressure sensor and a barometric pressure sensor so no vent tube is required. Follow these guidelines when deploying the logger:

  • The absolute pressure sensor is temperature compensated over the range of 0° to 40°C (32° to 104°F). The barometric pressure sensor is temperature compensated over the range of -20° to 50°C (-4° to 122°F). To obtain the highest level of accuracy, both the sensor end and top end units of the logger should be allowed to come to full temperature equilibrium (approximately 20 minutes) before the reference level is entered.
  • Sudden temperature changes should be avoided.
  • When deploying the logger in a well, make sure the well is vented to the atmosphere. Typically, a small hole can be drilled in the side of the well cap to ensure that the pressure inside and outside the well is at equilibrium. You can also use the Onset well cap (WELL-CAP-01).
  • The sensor face located in the nose cone of the sensor end needs to be in the water to measure water level.
  • There is a vent for the barometric sensor at the top of the logger (in the top end). This vent must not collect water or it will block proper barometric pressure readings. To avoid collecting water, the logger should be hung vertically and the vent hole in the well cap should not be oriented directly above the vent in the top end of the logger. If the logger must be mounted at an angle, the vent in the top end should point down so that any water will drain out of it.
  • Consider using slots for a mounting bolt at the top of the well rather than holes so that the logger can be pulled up easily for well access without having to remove nuts in the field. This can reduce the chances for small parts falling into the water and being lost.
  • Any change in length of the logger cable 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.
  • The top of the logger must be close to the surface and not shielded in metal so that your phone or tablet can connect to it. The maximum range for communication is 30.5 m (100 ft) with full line-of-sight.
  • If you are deploying the logger in a lake, river, or stream, you must first build a stilling well to protect the logger, sensor, and cable. A simple stilling well can be constructed with PVC or ABS pipe. A properly constructed stilling well holds the sensor in position and protects the logger components from currents, wave action, and debris. Suspend the sensor end 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
  • To prevent the sensor 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 just above the sensor or hang a weight below the sensor. In some cases, you may need to both add a weight and use a stilling well.
  • Be very careful not to exceed the burst pressure for the sensor. The pressure sensor will burst if the maximum depth is exceeded (see Specifications). The sensor should be positioned at a depth where it will remain in the water for the duration of the deployment, but not exceed the rated bursting depth.

To deploy the logger:

  1. Make sure the top end is connected to the sensor end with the water level logger cable as described in Getting Started with the Logger.
  2. Attach any small parts, such as bolts with nuts, before you go into the field so you don’t risk losing them in the field.
  3. Lower the logger into the well or stilling well.
  4. Use the Onset well cap if it is a 5 cm (2 inch) well. Otherwise, use a 1/4-inch bolt of sufficient length to span the well top or washer. Mount the logger as follows:
    • The top end must be above any metal well to ensure good wireless transmission.
    • Make sure there is access for measuring the water level in the well. In some cases, such as when using the Onset well cap, it will be necessary to pull the top end of the logger out of the well to get a water level meter sensor into the well.
    • Make sure the logger cannot accidentally fall in the well.
    • If the cable is too long, loop the cable and secure the cable with multiple zip ties to ensure the loop does not slip. The looped cable should be tight enough that the cable can be easily pulled out of the well if necessary, but it must not bend the cable any tighter than a 1.25 cm (0.5 inch) radius to prevent damage to the cable.
  5. Measure the water level from the desired reference point (top of pipe, ground level, or sea level) and enter it in the app. Note that you may need to pull the top end out of the well to gain access for measuring the water level within the well. Follow these guidelines for determining the reference level:
  • 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.
  • If the well is too small in diameter to measure the water depth while the logger is deployed, measure the water depth before deployment, then deploy the logger immediately.
  • If the water level surface is below the reference point as shown below, enter the reference water level in the app as a negative number.
    diagram
  • If the water level surface is above the reference point as shown below, enter the reference water level in the app as a positive number.
    diagram
  • If you are using the sensor as the reference point as shown below, enter the reference water level in the app as zero and start the logger before the sensor is in the water. The logged water level readings will represent the height above the sensor.
    diagram

Setting up Alarms

You can set an alarm to trip on the logger when a sensor reading rises above or falls below a specified value. This can alert you to problems so you can take corrective action. To set an alarm:

  1. Tap Devices. Tap the logger in the app to connect to it and tap .
  2. If you are going to set up a water level alarm, you must enter the reference water level and water density before setting the alarm levels.
  3. Tap the Differential Pressure sensor if you want to set a water level alarm. Tap the Temperature sensor to set a temperature alarm. You cannot configure alarms for absolute pressure. Note: The fixed logging mode must be set to normal to configure a water level alarm.
  4. Select High if you want an alarm to trip when the sensor reading rises above the high alarm value. Drag the slider or type a value to set the high alarm value. If you are configuring a water level alarm, enter the limit value for water level and app will show the differential pressure level that will be used to trigger the alarm in the logger.
  5. Select Low if you want an alarm to trip when the sensor reading falls below the low alarm value. Drag the slider or type a value to set the low alarm value.
  6. For the Duration, select how much time should elapse before the alarm trips and select one of the following:
  7. Cumulative. The alarm will trip once the sensor reading is out of the acceptable range for the selected duration any time during logging. For example, if the high alarm is set to 85°F and the duration is set to 30 minutes, then the alarm will trip once the sensor readings have been above 85°F for a total of 30 minutes since the logger was configured.
  8.  Consecutive. The alarm will trip once the sensor reading is out of the acceptable range continuously for the selected duration. For example, the high alarm is set to 85°F and the duration is set to 30 minutes, then the alarm will only trip if all sensor readings are 85°F or above for a continuous 30-minute period.
  9.  Tap Save and repeat steps 3–8 for the other sensor if desired.
  10. Back in the Configuration settings, the Sensor in Limits alarm option should be enabled. This indicates the alarm icon will remain visible in the app until the sensor reading returns to the normal range between any configured high and low alarm limits. icon

Notes:

  • The actual values for the high and low alarm limits are set to the closest value supported by the logger. In addition, alarms can trip or clear when the sensor reading is within the resolution specifications. This means the value that triggers the alarm may differ slightly than the value entered.
  • When setting water level alarm limits, make sure that the water level remains constant from the time alarm limits are set until the time the logger is started.
  • If you need to change the reference water level during the deployment, you will also need to re-enter the alarm limits based on the new reference water level.
  • The alarm icon will appear in the app next to the logger name or serial number when the alarm trips if the device is within range of the logger.
  • Once an alarm condition clears, the alarm icon in the app will go away. There is no option to keep the alarm icon visible until the logger is reconfigured.
  • When you read out the logger, alarm events can be displayed on the plot or in the data file. See Logger

Burst Logging

Burst logging is a logging mode that allows you to set up more frequent logging when a specified condition is met. For example, a logger is recording data at a 5-minute logging interval and burst logging can be configured to log every 30 seconds when the water temperature rises above 85°F (the high limit) or falls below 32°F (the low limit). This means the logger will record data every 5 minutes as long as the water temperature remains between 85°F and 32°F. Once the water temperature rises above 85°F, the logger will switch to the faster logging rate and record data every 30 seconds until the temperature falls back to 85°F. At that time, logging then resumes every 5 minutes at the normal logging interval. Similarly, if the temperature falls below 32°F, then the logger would switch to burst logging mode again and record data every 30 seconds. Once the water temperature rises back to 32°F, the logger will then return to normal mode, logging every 5 minutes. Note: Sensor alarms, statistics, and the Stop Logging option “Wrap When Full” are not available in burst logging mode.

To set up burst logging:

  1. Tap Devices. Tap the logger in the app to connect to it and tap icon .
  2. If you are going to set up burst logging for water level, you must enter the reference water level and water density before setting the burst limits.
  3. Tap Logging Mode and then tap Burst Logging.
  4. Select Low and/or High and either type or drag the slider to set the low and/or high values. If you are configuring burst logging for water level, enter the limit value for water level and the app will show the differential pressure level that will be used to trigger burst logging in the logger.
  5. Repeat step 4 for the other sensor if desired.
  6. Set the burst logging interval, which must be faster than the logging interval. Keep in mind that the more frequent the burst logging rate, the greater the impact on battery life and the shorter the logging duration.
  7. Tap Save.
  8. Tap .icon

Notes:

  • Once the logger is configured, the high and low burst limits are checked once every 15 seconds. Therefore, if you set the logging interval to less than 15 seconds and the sensor reading falls outside the levels, the burst logging will not begin until the next 15-second refresh cycle.
  • If high and/or low limits have been configured for more than one sensor, then burst logging will begin when any high or low condition goes out of range. Burst logging will not end until all conditions on all sensors are back within normal range.
  • The actual values for the burst logging limits are set to the closest value supported by the logger.
  • When setting water level limits for burst logging mode, make sure the water level remains constant from when the burst limits are set until when the logger is started.
  • If you need to change the reference water level during the deployment, you will also need to re-enter the burst limits based on the new reference water level.
  • Burst logging mode can begin or end when the sensor reading is within the resolution specifications. This means the value that triggers burst logging may differ slightly than the value entered.
  • Once the high or low condition clears, the logging interval time will be calculated using the last recorded data point in burst logging mode, not the last data point recorded in normal mode. For example, let’s assume the logger has a 10-minute logging interval and logged a data point at 9:05. Then, the high limit was surpassed and burst logging began at 9:06. Burst logging then continued until 9:12 when the sensor reading fell back below the high limit. Now back in normal mode, the next logging interval will be 10 minutes from the last burst logging point, or 9:22 in this case. If burst logging had not occurred, the next data point would have been at 9:15.
  • A New Interval event is created each time the logger enters or exits burst logging mode. See Logger Events for details on plotting and viewing the event.

Statistics Logging

During fixed logging, the logger records data for enabled sensors and/or selected statistics at the logging interval selected. Statistics are calculated at a sampling rate you specify with the results for the sampling period recorded at each logging interval. The following statistics can be logged for each sensor:

  • The maximum, or highest, sampled value,
  • The minimum, or lowest, sampled value,
  • An average of all sampled values, and
  • The standard deviation from the average for all sampled values.

For example, a logger is configured with the absolute pressure, differential pressure, and water temperature sensors enabled, and the logging interval set to 5 minutes. The logging mode is set to fixed interval logging with Normal and all four statistics enabled and with a statistics sampling interval of 30 seconds. Once logging begins, the logger will measure and record the actual absolute pressure, differential pressure, and water temperature sensor values every 5 minutes as well as calculate the water level and barometric pressure. In addition, the logger will take readings for the enabled sensors every 30 seconds and temporarily store them in memory. The logger will then calculate the maximum, minimum, average, and standard deviation using the samples gathered over the previous 5-minute period and log the resulting values. When reading out the logger, this would result in 17 data series: 5 sensor-related series (differential pressure, absolute pressure, barometric pressure, temperature, and water level with data logged every 5 minutes) plus 12 maximum, minimum, average, and standard deviation series (four for differential pressure, four for absolute pressure, and four for temperature with values calculated and logged every 5 minutes based on the 30-second sampling). Statistics are not available for barometric pressure and water level data.
To log statistics:

  1. Tap Devices. Tap the logger in the app to connect to it and tap icon .
  2. Tap Logging Mode and then select Fixed Logging.
  3. Select Normal to record the current reading for each enabled sensor at the selected logging interval.
    Important: You must select Normal if you want to log water level and barometric pressure data. If you deselect Normal, the logger will not be able to calculate water level or barometric pressure.
  4. Select the statistics you want the logger to record at each logging interval: Maximum, Minimum, Average, and Standard Deviation (average is automatically enabled when selecting Standard Deviation). Statistics will be logged for all enabled sensors. In addition, the more statistics you record, the shorter the logger duration and the more memory is required.
  5. Tap Statistics Sampling Interval and select the rate to use for calculating statistics. The rate must be less than, and a factor of, the logging interval. For example, if the logging interval is 1 minute and you select 5 seconds for the sampling rate, then the logger will take 12 sample readings between each logging interval (one sample every 5 seconds for a minute) and use the 12 samples to record the resulting statistics at each 1-minute logging interval. Note that the more frequent the sampling rate, the greater the impact on battery life.
  6. Tap Save.
  7.  Tap icon

You can plot the statistics series once you read out the logger. Note that the logger will always display the current sensor readings in the app even if they are not being logged.

Updating the Reference Water Level and Water Density

The logger calculates data based on the reference water level and water density settings in the app. You may need to update these settings during deployment. These are guidelines for when to update reference water level or water density.

  • The reference water level may need to be adjusted to compensate for drift (see Compensating for Drift) or for cable stretch in water level logger cables longer than 30 meters (100 feet). Check the reference reading in the first couple of months of deployment when using a long cable and update the reference water level as necessary. Once stabilized, you should not need to reset the reference water level for several months.
  • If you realize during a deployment that the reference water level and water density you entered are not as accurate as needed, then you will need to update them.
  • If you update the water density, you will also need to enter a new reference water level reading. Once the new values are entered and saved, a reading is taken and will be used to calculate a new calibration constant that will be applied to all data for the current deployment (both before and after the new values are entered).
  • If you only want to change future data, then stop the current deployment, offload the data, and start a new deployment with the new water parameters.

To change the reference water level or water density:

  1. Tap Devices. Tap the logger in the app to connect to it and tap  .
  2. Enter the current water level as the new reference water level, making sure you have selected the proper units.
  3. Change the water density if needed, making sure you have selected the proper units.
  4. Tap Save. The changes will take effect immediately. This will result in reference water level and water density events in the data file (see Logger Events).

Reading Out the Logger

To read out the logger:

  1.  Tap Devices. Tap the logger in the app to connect to it.
  2. Tap .icon The logger will read out the data to the phone or tablet.
  3. Once the readout is complete, tap HOBO Files and select the file to view it.
  4.  Tap icon and then icon to export and share the data.
    Data can also be uploaded automatically to HOBOlink, Onset’s web-based software, via the app or the MX gateway. For details, see the app user’s guide and see the HOBOlink help for details on working with data in HOBOlink.
    You can also change the reference water level, reference time, and water density in the data file as needed.

Important: Editing the water parameters permanently changes the data file. If you need the original data, share the data file as described above before making the changes.
To change the water parameters:

  1. Tap HOBO Files and select the file.
  2. Tap icon and  iconthen .
  3.  Tap Reference Water Level or Water Density.
  4. In the Water Parameters screen:
    • Enter a new reference water level value and/or change the water level units.
    • Tap Reference Time and select a time associated with a logged data point for when the reference reading was taken. Tap Save to return to the Water Parameters screen.
    • Change the water density used for the file and/or the units.
  5.  Tap Save to apply these new settings to the HOBO file and graph.

Logger Events

The logger records the following internal events to track logger operation and status. You can view events in exported files or plot events in the app.
To plot events, tap HOBO Files and select a file to open.
Tap icon and then tap icon . Select the events you want to plot
and tap OK.

  Internal Event Name   Definition
  Host Connected   The logger was connected to a mobile device.
  Started   The logger received a command to start recording data from the software.
  Stopped   The logger received a command to stop recording data from the software.
 

 

  Internal Event Name

 

 

  Definition

 
  Reference Water Level   The reference water level for the logger has been updated. The new   reference water level is listed with the event.  
  Water Density   The water density for the logger has been updated. The new water density   value is listed with the event.  
  Chan <#> Alarm Tripped   A sensor alarm has tripped; <#> is the sensor number, where 1 is   differential pressure (water level) and 2 is temperature.  
  Chan <#> Alarm Cleared   A sensor alarm has cleared; <#> is the sensor number, where 1 is   differential pressure (water level) and 2 is temperature.  
  New Interval   The logger has entered or exited burst logging mode.  
  Safe Shutdown   The battery level dropped below 1.85 V; the logger performs a safe     shutdown.  

Setting a Logger Password

You can assign the logger a password to prevent other devices from connecting to it. To set a password:
1. Tap Devices. Tap the logger to connect to it.
2. Tap icon and then .
3. Type a password and then tap Set.

Only the phone or tablet used to set the password can then connect to the logger without entering a password; all other mobile devices will be required to enter the password. For example, if you set the password for the logger with your tablet and then try to connect to the device later with your phone, you will be required to enter the password on the phone but not with your tablet. Similarly, if anyone else attempts to connect to the logger with a different device, then they would also be required to enter the password.
To reset a password, press the reset button on the logger located between the two batteries in the top end as shown below or connect to the logger and tap icon , then , and tap Reset.

Maintenance
The logger requires the following periodic maintenance to ensure optimal operation:

  • Protect the logger. This logger can be damaged by shock. Always handle the top end and sensor end with care. The sensors may lose their calibrated accuracy or can be damaged if dropped. Use proper packaging when transporting or shipping the logger.

Important: Do not attempt to open the sensor end housing! Unscrewing the nose cone of the sensor end will cause serious damage to the pressure sensor and logger electronics. There are no user serviceable parts inside the sensor end. Contact Onset Technical Support if the sensor end requires servicing.

  • Periodically inspect the logger for biofouling. Biological growth on the face of the pressure sensor will impact 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.
  • 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 acetal end cap. Acetal is resistant to most solvents, fuels, and lubricants.

Compensating for Drift

All pressure sensors drift over time. The drift for the pressure sensors and electronics in the 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 enter the reference water level in the app at the beginning of each deployment. In effect, you are re-zeroing the sensor each time you apply a reference reading to the data file.
Pressure sensor drift matters more 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). See Reading Out the Logger for changing the reference water level in the data file.

Verifying Accuracy

You can check the differential accuracy of the logger for water level measurements by deploying the logger’s sensor end at two depths and comparing the difference in level readings in the data files. When verifying the accuracy this way, be sure to allow the sensor’s temperature to stabilize at each depth.

You can check the absolute pressure accuracy by using the two pressure sensors in the logger. Pull up the sensor end that is in the water so that both the absolute and differential sensors are in the air. Check the differential pressure with the app. The differential pressure should be zero or less than the sum of the error for the two sensors.

Battery Information

The logger requires two user-replaceable AA 1.5 V alkaline batteries for operation at the extreme ends of the logger operating range. Expected battery life varies based on the ambient temperature where the logger is deployed, the logging or sampling interval, frequency of offloading and connection to the mobile device, number of channels that are active, alarm duration, use of burst mode or statistics logging, and battery performance. New batteries typically last 1 year with logging intervals greater than 1 minute. Deployments in extremely cold or hot temperatures, a logging interval faster than 1 minute, or a sampling interval faster than 15 seconds can impact battery life. Estimates are not guaranteed due to uncertainties in initial battery conditions and operating environment.
To install or replace the batteries:

  1. Before changing the batteries, stop the logger and offload any data.
  2. Disconnect the cable.
  3. Unscrew the end cap on the top end. Push the board out from the cable end and then pull out the printed circuit board.
  4. Insert two AA batteries observing polarity as shown on the board. A slight curvature in the printed circuit board is normal when the batteries are installed. Reinsert the board and place the desiccant back on the end of the board as shown. It is recommended that you replace the desiccant (DESICCANT2) when replacing the batteries.
    a close up of a device
  5. Screw the cap back on until hand tight.

Federal Communication Commission Interference Statement
This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates uses and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications. However, there is no guarantee that interference will not occur in a particular installation. If this equipment does cause harmful interference to radio or television reception, which can be determined by turning the equipment off and on, the user is encouraged to try to correct the interference by one of the following measures:

  • Reorient or relocate the receiving antenna
  • Increase the separation between the equipment and receiver
  • Connect the equipment into an outlet on a circuit different from that to which the receiver is connected
  • Consult the dealer or an experienced radio/TV technician for help

This device complies with Part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation.
FCC Caution: Any changes or modifications not expressly approved by the party responsible for compliance could void the user’s authority to operate this equipment.
Industry Canada Statements
This device complies with Industry Canada license-exempt RSS standard(s). Operation is subject to the following two conditions: (1) this device may not cause interference, and (2) this device must accept any interference, including interference that may cause undesired operation of the device.

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