HOBO MX pH and Temperature Logger MX2501 Instruction Manual

HOBO MX pH and Temperature Logger MX2501

MX2501

Included Items

• pH electrode installed and submerged in storage solution
• Extra electrode storage solution
• Anti-biofouling copper guard
• Silicone-based O-ring grease and foam swab

Required Items:

• HOBOconnect app
• Mobile device with Bluetooth and iOS, iPadOS®, or Android™, or a Windows computer with a native BLE adapter or supported BLE dongle
• Deionized or distilled water and squirt bottle
• Calibration solutions

Accessories:

• Replacement pH electrode (MX2500-ELECTRODE)
• Calibration kit with three bottles: pH 4.01, 7.00, and 10.00 calibration solution (MX2500-CAL-KIT) and calibration beakers (MX2500-CAL-BKR)
• Maintenance kit with calibration kit plus storage solution (MX2500-MAINTKIT)
• pH 4.01 calibration solution (MX2500-CAL-4)
• pH 7.00 calibration solution (MX2500-CAL-7)
• pH 10.00 calibration solution (MX2500-CAL-10)
• Electrode storage solution (MX2500-STORE-SOLN)
• Replacement sensor end cap (MX2500-END-CAP)
• Replacement anti-biofouling copper guard (MX2500- GUARD)
• Replacement clear storage cap (MX2500-STORAGE-CAP)

The HOBO MX pH and Temperature logger is designed for long-term monitoring of pH in aquatic systems. With a replaceable pH electrode and anti-biofouling copper guard, this durable logger can be deployed in both fresh and salt water environments. This logger is Bluetooth® Low Energy (BLE)-enabled for wireless communication with a mobile device or computer. Using the HOBOconnect® app, you can easily calibrate and configure the logger, download logged data to your phone, tablet, or computer, or automatically upload the data to HOBOlink® for further analysis. You can also configure the logger to calculate statistics, set up alarms to trip at specific thresholds, or enable burst logging in which sensor readings are logged at a faster interval when the pH or temperature rises above or falls below certain limits.

Specifications

Logger Components and Operation

Anti-Biofouling Copper Guard: Use this guard to protect the pH electrode when deploying the logger in water prone to biofouling (see Deploying and Mounting the Logger).

Closure Caps: These caps are screwed onto the sensor end and the mounting end (or top end) of the logger.

Sensor End Cap: This is the bottom end of the logger where the pH electrode is installed, and the temperature sensor and water detection screws are located.

Temperature Sensor: The temperature sensor is located at the base of the sensor end cap.

Water Detection Screws: These two screws on the sensor end cap can detect the presence of water.

pH Electrode: This is the electrode that is plugged into the logger. The clear plastic end houses a glass pH sensor bulb that must always be placed in storage solution when not deployed
in water. See Installing the pH Electrode for details.

Logger Housing: This is the main body of the logger.

Battery Holder: This is where one AA battery is installed under a battery strap (see Battery Information).

Reed Switch: This is used in conjunction with the magnetic switch on the mounting end cap.

LEDs: The blue LED blinks every 4 seconds when the logger is logging (unless Show LED is disabled as described in Configuring the Logger). The blue LED blinks every 8 seconds if the logger is waiting to start logging because it was configured to start On Button Push or with a delayed start. The blue LED blinks every 4 seconds when an alarm is tripped (unless the Show LED option is disabled). The blue and red LEDs blink once when you press the magnetic switch to wake up the logger or blink four times when you press the switch to start or stop logging. If you select Illuminate Logger in the app, the red LED is illuminated for 5 seconds.

Mounting Hole: Use the hole on the mounting end of the logger to attach it to a cable or cord for deployment (see Deploying and Mounting the Logger).

Switch: This magnetic switch on the mounting end of the logger works in conjunction with the reed switch. Press this switch into the gap beneath the mounting lanyard for 3 seconds to start or stop the logger when it is configured to start or stop On Button Push (see Configuring the Logger). Press this switch for 1 second to wake up the logger (if configured with Bluetooth Always Off as described in Configuring the Logger).

Downloading the App and Connecting to a Logger

Install the app to connect to and work with the logger.

1. Download HOBOconnect to a phone or tablet from the App Store® or Google Play™.
   Download the app to a Windows computer from www.onsetcomp.com/products/software/hoboconnect.

2. Open the app and enable Bluetooth in the device settings if prompted.

3. Wake up the logger by pushing the switch on the mounting end of the logger into the gap beneath the mounting lanyard.

4. Tap Devices and then tap the logger tile in the app to connect to the logger.
   If the logger does not appear in the list or if it is having trouble connecting, follow these tips:

   • If the logger was configured with Bluetooth Always Off (see Configuring the Logger), make sure the logger is awake by pressing the switch for 1 second. This brings the logger to the top of the list if you are working with multiple loggers.
   • Make sure the logger is within range of your mobile device or computer. The range for successful wireless communication is approximately 30.5 m (100 ft) in air with full line-of-sight.
   • Change the orientation of your device to ensure the antenna is pointed toward the logger. Obstacles between the antenna in the device and the logger may result in intermittent connections.
   • If your device can connect to the logger intermittently or loses its connection, move closer to the logger, within sight if possible. If the logger is in water, the connection can be unreliable. Remove it from water for a consistent connection.
   • If the logger appears in the app, but you cannot connect to it, close the app and then power down your device to force the previous Bluetooth connection to close.

Once the logger is connected, you can:

Configuring the Logger.
| Tap to view live data.
| Mark the logger as a favorite. You can then filter the list of devices to show only loggers marked as favorites.
| Calibrate the logger. See Calibrating the Logger.
| Start logging if the logger was configured to start with a button push. See Configuring the Logger.
| Stop logging data (this overrides any Stop Logging settings described in Configuring the Logger ).
| Download logger data. See Downloading Data From the Logger.
| Lock the logger. Set a password for the logger so that it is not mistakenly stopped or reconfigured. Tap the icon, enter a password, and then tap Set. Once a password is entered on a phone or tablet, that mobile device is the only one to “remember” it. This means you can connect to the logger without entering a password on that mobile device, but you must enter a password on all other mobile devices. 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 must enter the password on the phone but not with your tablet. Similarly, if others attempt to connect to the logger with different devices, they are also required to enter the password.

To reset a password:

·    Press the Start/Stop button for 10 seconds, or

·    Tap Manage Password and then tap Reset.

| Manage Password. Reset your existing password or set a new password for the logger.
| Illuminate the logger LEDs for 5 seconds.
| 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.|

Calibrating the Logger

If the logger is new or if you have installed a new pH electrode, you must calibrate the logger with the app before configuring and deploying it. The app prompts you to calibrate the logger if
the pH electrode has never been calibrated, the last calibration is more than seven days old, or the logger firmware was updated.

Important: The pH sensor must be kept in storage solution when not being calibrated or deployed in water. The hydration layer surrounding the sensor starts to break down after 10 minutes if the pH sensor is not submerged in storage solution or calibration solution, or deployed in water.

You will need:

• Deionized or distilled water and a squirt bottle to rinse the pH sensor.
• The logger with the pH electrode installed and the copper guard removed.
• Calibration solution (also called buffer solution) poured into beakers. All three buffers are available in a kit
  (MX2500-CAL-KIT) or individually (MX2500-CAL-4,MX2500-CAL-7, or MX2500-CAL-10).

Important: The logger should be calibrated based on the conditions at the location where it will be deployed.

Specifically, if the water temperature is expected to be different than 25°C (77°F), it is important for the calibration buffers to be close to the expected temperature of the analyte (see the chart at the end of this section for the effect of temperature on buffers). Similarly, if the logger will be deployed at an altitude other than sea level, perform the calibration at or near the deployment altitude.

To calibrate the logger:

1. If the sensor is in the storage solution, unscrew the clear storage cap and remove it from the logger.
2. If you removed the clear storage cap, screw the closure cap onto the logger.
3. In the HOBOconnect app, tap Devices.
4. Remove the logger from water. If the logger was previously configured with Bluetooth Always Off, press the switch on the logger to wake it up.
5. Tap the logger in the app to connect to it.
6. Tap Calibrate if you are not automatically prompted to calibrate the logger.
7. Use a squirt bottle to rinse the pH sensor with deionized or distilled water.
8. Place the sensor end of the logger in the pH 7 solution and tap Start. Make sure the sensor end cap, temperature sensor, and closure cap are submerged in the solution as shown in the illustration. Once the pH reading is stable, tap Confirm.
9. Rinse the pH sensor with deionized or distilled water.
10. If you are using the pH 4 buffer, place the sensor end in the pH 4 solution and tap Start. If you are not using the pH 4 buffer, tap Skip and go to step 12.
11. Once the pH reading is stable, tap Confirm. Rinse the pH sensor with deionized or distilled water.
12. If you are using the 10 buffer, place the sensor end in the pH 10 solution and then tap Start. Once the pH reading is stable, tap Confirm. If you are not using the pH 10 buffer, tap Skip.
13. Verify that the slope and offset are acceptable and tap Save. If the slope and offset are not acceptable, tap the back arrow and repeat the calibration steps in this section as needed.
14. Rinse the pH sensor with deionized or distilled water again.

If you are not deploying the logger immediately, place the pH electrode in storage solution. Unscrew the sensor end cap installed on the sensor end of the logger. If the clear storage cap is empty, pour in storage solution to the marked fill line.
Carefully screw the clear cap with storage solution onto the logger. Only use storage solution in the clear cap; do not use water. Do not use the copper guard when the pH electrode is in storage solution.

Notes:

• The date of the last calibration, the slope and offset values, and the buffers used for the calibration are listed under the Deployment Information in the Configuration screen for reference.
• Once a logger is connected to the app, a notice appears if the last calibration is more than seven days old prompting you to recalibrate the logger. Although you can postpone the calibration, we recommended you recalibrate the logger before configuring it.
• If the status message during calibration indicates the reading is invalid or it never stabilizes, try the following:
  • Make sure the sensor is in the correct buffer solution or try rinsing the sensor and restarting the calibration. If the problem persists, clean the sensor (see Maintaining the Logger) and inspect it to make sure it is not damaged. Note: There could be microcracks on the glass bulb of the electrode that may not be visible to the human eye.
  • Remove the sensor from the calibration solution and clean it (see Maintaining the Logger). Restart the entire calibration process.
  • Wait longer to see if it stabilizes, keeping in mind that a pH electrode has a 6-month typical maximum life and may produce unstable readings if it is older than 6 months. The slope and offset values that are provided are the best indication for the condition of the electrode. A healthy electrode has a slope between 85% and 100% and an offset between ±30 mv.
  • If the reading reported in app is acceptable for your deployment even though it is reported as unstable, you can tap Stop and then Confirm and proceed with the calibration.
• You can calibrate the logger while it is logging. After the\ calibration is saved, any new data logged uses the new calibration. Data logged before the new calibration was saved uses the old calibration data. If you do not want data in a single file to be based on more than one calibration, then stop the logger and read it out. You can then calibrate it and reconfigure it.
• pH values of calibration buffers and samples vary depending on their temperature. It is important that the logger is calibrated in buffers that have the same temperature as that of the sample. To do this, you must use buffers that have known values at different temperatures. The app automatically compensates for temperature variances from 25°C (77°F) based on the actual temperature-dependent pH value (from the chart below) of buffers and samples.

Configuring the Logger

Use the app to set up the logger, including selecting the logging options, configuring alarms, and other settings. These steps provide an overview of setting up the logger. For complete details, see the HOBOconnect User’s Guide.

1. Remove the logger from water. If the logger was previously configured with Bluetooth Always Off, press the switch on the logger to wake it up. If you are working with multiple loggers, pressing the button also brings the logger to the top of the list in the app.
2. Tap Devices and then tap the logger tile in the app to connect to the logger.
3. Tap Configure & Start to configure the logger.
4. Tap Name and type a name for the logger (optional). If you do not enter a name, the app uses logger serial number as the name.
5. Tap Group to add the logger to a group (optional).
6. Tap Logging Interval and choose how frequently the logger will record data unless operating in burst logging mode (see Burst Logging). Note: If you configure an alarm, the logger uses the logging interval you selected as the rate to check for alarm conditions (alarms are not available if burst logging is configured). See Setting up Alarms for more details.
7. Tap Start Logging and select when logging begins:
   • On Save. Logging begins immediately after configuration settings are saved.
   • On Next Interval. Logging begins at the next even interval as determined by the selected logging interval.
   • On Button Push. Logging begins when you press either the Start/Stop logging button on the logger for 3 seconds or start logging with the app.
   • On Date/Time. Logging begins at a date and time you specify. Select the Date and Time.
8. Tap Stop Logging and select the options for when logging ends:
   • Never Stop (Overwrites Old Data). The logger does not stop at any predetermined time. The logger continues recording data indefinitely, with newest data overwriting the oldest.
   • On Date/Time. The logger stops logging on a specific date and time that you specify.
   • 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.
   • Stop When Memory Fills. The logger continues recording data until the memory is full.
9. Tap Pause Options, then select Pause On Button Push to specify that you can pause the logger by pressing its switch for 3 seconds.
10. Tap Logging Mode. Select either Fixed Logging Mode or Burst Logging. With fixed logging, the logger records data for all sensors and/or selected statistics at the logging interval selected (see Statistics Logging for details on choosing statistics options). In burst mode, logging occurs at a different interval when a specified condition is met. See Burst Logging for more information.
11. Enable or disable Show LED. If Show LED is disabled, the alarm and status LEDs on the logger are not illuminated while logging (the alarm LED does not blink if an alarm trips). You can temporarily turn on LEDs when Show LED is disabled by pressing the button on the logger for 1 second.
12. Select the power saving mode, which determines when the logger advertises or regularly sends out a Bluetooth signal for the mobile device or computer to find via the app.
    • Bluetooth Always Off. The logger advertises only during logging when you push the switch on the logger. This wakes up the logger when you need to connect to it. This option uses the least battery power.
    • Bluetooth Always On. The logger always advertises. You never need to push a switch to wake up the logger. This option uses the most battery power.
13. Set up an optional alarm to trip when the pH and/or temperature sensor reading rises above or falls below a specified value. See Setting up Alarms for details on enabling sensor alarms.
14. Tap Start to save the configuration settings.
    Logging begins based on the settings you selected. See Deploying and Mounting the Logger for details on mounting and see Reading Out the Logger for details on downloading.

Setting up Alarms
You can set up alarms for the logger so that if a sensor reading rises above or falls below a specified value, the red logger LED blinks and an alarm icon appears in the app. Alarms alert you to problems so you can take corrective action.
To set an alarm:

1. Tap Devices. If the logger was configured with Bluetooth Always Off enabled, push the switch on the logger to wake it up.
2. Tap the logger tile to connect to the logger and tap Configure & Start.
3. Tap a Sensor/Channel.
4. Tap Enable Logging, if necessary.
5. Tap Alarms to open that area of the screen.
6. Select Low if you want an alarm to trip when the sensor reading falls below the low alarm value. Enter a value to set the low alarm value.
7. Select High if you want an alarm to trip when the sensor reading rises above the high alarm value. Enter a value to set the high alarm value.
8. For the Duration, select how much time should elapse before the alarm trips and select one of the following:
   • Cumulative. The alarm trips 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, the alarm trips once the sensor readings have been above 85°F for a total of 30 minutes since the logger was configured.
   • Consecutive. The alarm trips 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, the alarm trips only if all sensor readings are 85°F or above for a continuous 30- minute period.

When an alarm trips, the red logger LED blinks every 4 seconds (unless Show LED is disabled), an alarm icon appears in the app, and an Alarm Tripped event is logged. The alarm state clears when the readings return to normal if you selected Sensor in Limits in step 9. Otherwise, the alarm state remains in place until the logger is reconfigured.

Notes:

• Alarm limits are checked at every logging interval unless burst logging is configured. For example, if the logging interval is set to 5 minutes, the logger checks the sensor readings against your configured high and low alarm setting every 5 minutes.
• The actual values for the high and low alarm limits are set to the closest value supported by the logger. For example, the closest value to 85°F that the logger can record is 84.990°F. In addition, alarms can trip or clear when the sensor reading is within the specified resolution specifications.
• When you read out the logger, alarm events can be displayed on the plot or in the data file. See Logger Events.

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 is configured to log every 30 seconds when the temperature rises above 85°F (the high limit) or falls below 32°F (the low limit). This means the logger records data every 5 minutes as long as the temperature remains between 85°F and 32°F. Once the temperature rises above 85°F, the logger switches to the faster logging rate and records data every 30 seconds until the temperature falls back to 85°F. At that time, logging then resumes every 5 minutes at the fixed logging interval. Similarly, if the temperature falls below 32°F, then the logger switches to burst logging mode again and record data every 30 seconds. Once the temperature rises back to 32°F, the logger then returns to fixed mode, logging every 5 minutes. Note: Sensor alarms, statistics, and the Stop Logging option Never Stop (Overwrites Old Data) are not available in burst logging mode.

To set up burst logging:

1. Tap Devices. Remove the logger from water. If the logger is configured with Bluetooth Always Off enabled, press the button on the logger to wake it up.
2. Tap the logger tile to connect to the logger and tap Configure & Sta
3. Tap Logging Mode and then tap Burst Logging.
4. Set the burst logging interval, which must be faster than the logging interval. Keep in mind that the faster the burst logging rate, the greater the impact on battery life and the shorter the logging duration. Because measurements are being taken at the burst logging interval throughout the deployment, the battery usage is similar to what it would be if you had selected this rate for the normal logging interval.
5. Select Low and/or High and type a value to set the low and/or high values. Select Low and/or High and either type or drag the slider to set the low and/or high values.

Notes:

• The high and low burst limits are checked at the burst logging interval rate whether the logger is in normal or burst condition. For example, if the logging interval is set to 1 hour and the burst logging interval is set to 10 minutes, the logger always checks for burst limits every 10 minutes.
• If high and/or low limits have been configured for more than one sensor, then burst logging begins when any high or low condition goes out of range. Burst logging does 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. In addition, burst logging can begin or end when the sensor reading is within the specified resolution. 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 is calculated using the last recorded data point in burst logging mode, not the last data point recorded at the fixed logging rate. For example, the logger has a 10-minute logging interval and logged a data point at 9:05. Then, the high limit is surpassed and burst logging begins at 9:06. Burst logging then continues until 9:12 when the sensor reading falls back below the high limit. Now back in fixed mode, the next logging interval is 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. In addition, if the logger is stopped with a button push while in burst logging mode, a New Interval event is automatically logged and the burst condition is cleared, even if the actual high or low condition has not cleared.

Statistics Logging
During fixed interval 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
• The standard deviation from the average for all sampled values

For example, a logger is configured with the logging interval set  to 5 minutes and Fixed Logging Mode. In addition, all fourstatistics are enabled with a statistics sampling interval of 30 seconds. Once logging begins, the logger measures and records the actual temperature and pH sensor values every 5 minutes.
In addition, the logger takes a temperature and pH sample every 30 seconds and temporarily store them in memory. The logger then calculates the maximum, minimum, average, and standard deviation using the samples gathered over the previous 5-minute period and log the resulting values. When downloading data from the logger, this results in 10 data series (not including the mV series): two sensor series (with temperature and pH data logged every 5 minutes) plus eight maximum, minimum, average, and standard deviation series (four for temperature and four for pH with values calculated and logged every 5 minutes based on the 30-second sampling).

To log statistics:

1. Tap Devices. Remove the logger from water. If the logger was configured with Bluetooth Always Off enabled, press the button on the logger to wake it up.
2. Tap the logger tile in the app to connect to the logger and tap Configure & Start.
3. Tap Logging Mode and then select Fixed Logging Mode.
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 are 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, the logger takes 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 faster the sampling rate, the greater the effect on battery life. Because measurements are being taken at the statistics sampling interval throughout the deployment, the battery usage is similar to what it would be if you had selected this rate for the normal logging interval.

Setting a Password

You can create an encrypted password for the logger that is required if another device attempts to connect to it. This is recommended to ensure that a deployed logger is not mistakenly stopped or purposely altered by others. This password uses a proprietary encryption algorithm that changes with every connection.

To set a password:

1. Tap Devices. Press the switch on the logger to wake it up, if necessary. Tap the logger tile in the app to connect to it.
2. Tap Lock Logger.
3. Type a password and then tap Set.
   Only the device used to set the password can then connect to the logger without entering a password; all other devices are 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 logger later with your phone, you must enter the password on the phone but not with your tablet. Similarly,if others attempt to connect to the logger with different devices, they are also required to enter the password. To reset a password, press the switch on the logger for 10 seconds or connect to the logger and tap Manage Password and tap Reset.

Downloading Data From the Logger

To download data from the logger:

1. Tap Devices.
2. Tap Download Data. The logger downloads data to the phone, tablet, or computer.
3. Once the download is complete, tap Done to return to the previous page or tap Export and Share to save the file in the specified format.
4. When the export file has successfully been created, tap Done to return to the previous page or tap Share to use your device’s usual modes of sharing.

You can also upload data automatically to HOBOlink, Onset’s web-based software, using the app or the MX gateway. For details, see the HOBOconnect User Guide and see the HOBOlink help for details on working with data in HOBOlink.

Logger Events
The logger records the following events to track logger operation and status. You can view events in exported files or plot events in the app.

To plot events, tap Data and select a file to open.

Tap (if applicable) and then tap . Select the events you want to plot and tap OK.

Deploying and Mounting the Logger

Important: The pH sensor must be kept in storage solution when not being calibrated or deployed in water.

Follow these guidelines when deploying the logger:

• If the logger is in storage solution, remove the clear storage cap from the logger and replace it with a closure cap as shown in the next diagram before deploying it.
• If your water sample is prone to biofouling, insert the optional copper anti-biofouling guard over the pH sensor as shown. Gently twist the copper guard so that the holes line up with the holes in the sensor end cap and pH electrode. Do not use the copper guard when the pH sensor is being calibrated or in storage solution, or if the sensor is placed in a very small container with still water or in water where copper can affect the environment.
• There are two mounting options:
  • Attach a nylon cord or other strong cable to the mounting hole to deploy the logger.
  • Alternatively, secure the logger to a pipe or similar surface using cable ties wrapped around the two large grooves in the logger housing.
• The logger should be appropriately secured and protected depending on water conditions and desired measurement location.

Maintaining the Logger

• The pH sensor must be kept in storage solution when not being calibrated or deployed in water. Additional storage solution (MX2500-STORE-SOLN), clear storage caps (MX2500-STORAGE-CAP), and a maintenance kit containing pH 4.01, 7.00, and 10.00 calibration solution and storage solution (MX2500-MAINT-KIT) are available.
  See www.onsetcomp.com.

• Periodically inspect the logger for biofouling. To clean the logger housing, rinse the logger in warm water. Use mild dishwashing soap if necessary on the logger housing only, taking care not to touch the glass bulb in the pH electrode. Do not use harsh chemicals, solvents, or abrasives. Replacement sensor end caps (MX2500-ENDCAP) and copper guards (MX2500-GUARD) are available if they cannot be cleaned effectively. See www.onsetcomp.com for replacement parts.

• Periodically uninstall the pH electrode from the logger to inspect it for deposits. Clean and recondition it as follows depending on the type of deposits found. To remove a build-up of scale or other dissolve salts, briefly soak the pH sensor in 5% hydrochloric acid. To remove oil deposits, soak the pH sensor in a solution with mild dishwashing soap. Never touch the glass bulb inside the clear plastic end of the probe. Always calibrate the logger after cleaning the pH electrode with anything other than distilled or deionized water.

• The hydration layer surrounding the glass pH sensor bulb in the electrode naturally breaks down over time.
  Cleaning and reconditioning the electrode as described in in the previous bullet can help to extend its life. It is recommended that you replace the pH electrode after 6 months of continuous use or when the slope and offset readings reported during calibration are consistently not within an acceptable range, even after cleaning. The ideal range for slope is 85% to 100% and for offset is ±30 mv.
  See Installing the pH Electrode for steps on replacing the electrode (MX2500-ELECTRODE).

• Periodically add silicone-based grease to the outer Orings on the sensor end cap shown below. Using your finger, spread a small dot of grease along both outer Orings.

Installing the pH Electrode

Important: New pH electrodes are uncalibrated. Once a pH electrode is installed in the logger for the first time, it must be calibrated before configuring and deploying the logger (see Calibrating the Logger).

To install the pH electrode in the logger:

1. Unscrew the closure cap over the sensor end cap of the logger. Pull the sensor end cap straight out from the logger without twisting it.

2. Gently and slowly remove the pH electrode from the sensor end cap. ( Note: Removing the electrode too quickly could result in unseating the internal O-rings.)

3. Use a foam swab dipped in water to clean the internal Orings.
   Use the foam swab to spread a small dot of silicone-based grease along both the O-rings inside the sensor end cap. Do not use a cotton swab as the fibers on the swab can interfere with the operation of the electrode.

4. Remove the replacement pH electrode from the shipping bottle and wipe the outer plastic body dry with a soft paper or cloth towel. Never touch the glass bulb inside the clear plastic end of the probe.

5.  Remembering not to touch the glass bulb, push the pHelectrode gently and slowly into the sensor end cap. You will feel the pH electrode pause as it passes through two internal O-rings inside the sensor end cap (shown with step 3). Make sure the internal O-rings are still in place as the probe is pushed into the sensor end cap. Note: If done too quickly, this process can unseat the internal O-rings.
   Gently twist the electrode so that the holes in the clear electrode body line up with the holes in the end cap.

6. Continue to gently push the electrode into place until the clear plastic is fully seated in the end cap as shown.

7. Push the sensor end cap back into the logger, making sure the small tab in the end cap fits in the small groove in the logger housing. Use the large tab on the end cap and the arrow on the logger housing to help with proper alignment.
   Do not twist or turn the end cap as you push it straight into position.

8. If you will be calibrating the logger immediately: screw the closure cap back on the logger and follow the instructions in
   Calibrating the Logger.
   If you will not be calibrating or deploying the logger immediately:
   a. Pour storage solution into the clear storage cap to the marked fill line.
   b. Carefully screw the cap with storage solution onto the logger.

Important: Keep the sensor in storage solution unless you are calibrating the logger or deploying it in water. Only use storage solution in the cap; do not use water. Do not use the copper guard while the sensor is in the cap.

Battery Information
The logger requires one user-replaceable AA 1.5 V alkaline or lithium battery. With a logging interval of 1 minute and at 25°C (77°F), battery life is 1 year with Bluetooth Always On selected and 3 years with Bluetooth Always Off selected. Expected battery life varies based on the ambient temperature where the logger is deployed, the logging interval, the frequency of connections, downloads, and paging, and the use of burst mode or statistics logging. Deployments in extremely cold or hot temperatures or a logging interval faster than 1 minute can impact battery life.
Estimates are not guaranteed due to uncertainties in initial battery conditions and operating environment.

To install or replace the battery:

1. Wipe the logger clean and dry it completely.

2. Unscrew the closure cap on the mounting end of the logger.

3. Pull the mounting end cap and attached battery holder straight out from the logger body without twisting. Insert a screwdriver through the mounting hole if you need additional leverage for removing the mounting end cap from the logger.
   Pull the mounting end cap and attached battery holder straight out from the logger body without twisting. Insert a screwdriver through the mounting hole if you need additional leverage for removing the mounting end cap from the logger.
   Screw the closure cap back on the logger.

4. Remove the battery strap. Insert a flat-head screwdriver into the hole on the strap to lift it off the battery.

5. Remove the battery and install a new one, observing polarity.

6. Using your finger, spread a small dot of silicone-based grease along both O-rings (shown in step 4) on the mounting end cap.

7. Place the battery strap back in place, using the notches on both sides of the holder (shown in step 4) to align it and guide it into place until you hear a click.

WARNING: Do not cut open, incinerate, heat above 85°C (185°F), or recharge the lithium battery. The battery mayexplode 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.

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.
To comply with FCC and Industry Canada RF radiation exposure limits for general population, the logger must be installed to provide a separation distance of at least 20cm from all persons and must not be co-located or operating in conjunction with any other antenna or transmitter.

NCC Statement

Translation:

Article 12
Without permission granted by the NCC, any company, enterprise, or user is not allowed to change frequency, enhance transmitting power or alter original characteristic as well as performance to an approved low power radio-frequency device.

Article 14
The low power radio-frequency devices shall not influence aircraft security and interfere with legal communications. If found, the user shall cease operating immediately until no interference is achieved. The said legal communications means radio communications is operated in compliance with the Telecommunications Act. The low power radiofrequency devices must be susceptible with the interference from legal communications or ISM radio wave radiated devices.

KC Statement

Translation:
The service related to human safety is not allowed because this device may have the possibility of the radio interference.

2018–2022 Onset Computer Corporation. All rights reserved. Onset, HOBO, HOBOconnect, and HOBOlink are registered trademarks of Onset Computer Corporation. App Store, iPhone, iPad, and iPadOS are service marks or registered trademarks of Apple Inc. Android and Google Play are trademarks of Google LLC. Windows is a registered trademark of Microsoft Corporation. Bluetooth and Bluetooth Smart are registered trademarks of Bluetooth SIG, Inc. All other trademarks are the property of their respective companies.
Patent #: 8,860,569

U.S. and International Sales: 1-508-759-9500
www.onsetcomp.com/support/contact

References

• Onset HOBO and InTemp Data Loggers
• HOBOconnect | Onset's HOBO and InTemp Data Loggers
• Technical Support | Onset's HOBO and InTemp Data Loggers

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