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HOBO MX pH and Temperature Logger (MX2501) Manual 

6

at different temperatures. HOBOmobile will automatically 
compensate for temperature variances from 25°C (77°F) 
based on the actual temperature-dependent pH value 
(from the chart below) of buffers and samples. 

Temperature 

°C °F 

pH 4.01 

Buffer 

pH 7.00 

Buffer 

pH 10.00 

Buffer 

0 32  4.01 

7.12 

10.31 

5 41  4.00 

7.09 

10.24 

10 50 

4.00 

7.06 

10.17 

15 59 

4.00 

7.04 

10.11 

20 68 

4.00 

7.02 

10.05 

25 77 

4.01 

7.00 

10.00 

30 86 

4.01 

6.99 

9.95 

35 95 

4.02 

6.98 

9.92 

40 104 

4.03 

6.97 

9.88 

45 113 

4.04 

6.97 

9.85 

Configuring the Logger 

Use HOBOmobile 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 

HOBOmobile User’s Guide

1. Open HOBOmobile and tap the HOBOs icon.

2. Find the logger in the list and tap it to connect to it. If the

logger was previously configured with Bluetooth Always Off,
press the switch on the logger to wake it up. If the logger
was previously configured with Bluetooth Off Water Detect
and it is deployed in water, remove it from water. If you are
working with multiple loggers, pressing the button also
brings the logger to the top of the list (and the logger name
will turn green). Note that the current sensor readings are
displayed even when the logger is not logging. 

3. Once connected, tap Configure.

4. Tap Name and type a name for the logger up to 20

characters (optional). Tap Done. If no name is selected, the
logger serial number is used as the name. 

5. Tap Group to add the logger to the Favorites group, an

existing custom group, or create a new group name with up
to 20 characters (optional). Tap Done. 

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

will use 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 will begin:

Now.

 Logging will begin immediately after tapping Start

in the Configure screen. 

On Next Logging Interval. 

Logging will begin at the next

even interval as determined by the selected logging
interval.

On Button Push.

 Logging will begin once you press the

switch on the logger for 3 seconds.

On Date/Time.

 Logging will begin on a date and time you

specify. Select the date and time and tap Done. 

Tap Done in the Start Logging screen. 

8. Tap Stop Logging and select the options for when logging

will end.

a. Choose one of two memory options:

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

).

b. Select On Button Push if you want to be able to stop

logging by pushing the switch on the logger for 3
seconds. Note that if you also choose On Button Push for
the Start Logging option, then you will not be able to stop
logging until 30 seconds after logging begins. 

c. 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 and then tap Done. 

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
and then tap Done. For example, select 30 days if you
want the logger to log data for 30 days after logging
begins. 

d. Tap Done in the Stop Logging screen. 

9. 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.

10. Tap Logging Mode. Select either fixed interval logging or

burst logging. With fixed interval logging, the logger records
data for all sensors and/or selected statistics at the logging
interval selected (see 

Statistics Logging

 for details on

Summary of Contents for MX series

Page 1: ...ately 30 5 m 100 ft line of sight in air Wireless Data Standard Bluetooth Low Energy Bluetooth Smart Logging Rate 1 second to 18 hours Logging Modes Fixed interval normal statistics or burst Memory Modes Wrap when full or stop when full Start Modes Immediate push button date time or next interval Stop Modes When memory is full push button date time or after a set logging period Time Accuracy 1 min...

Page 2: ...cap can detect the presence of water This allows you to configure the logger in a power saving mode in which Bluetooth advertising is active only when the logger is removed from water See Configuring the Logger for details Note The logger will check for the presence of water every 15 seconds when the Bluetooth Off Water Detect power saving mode is selected pH Electrode This is the electrode that i...

Page 3: ...ut from the logger without twisting it 2 If this is the first time you re installing a pH electrode skip to step 3 If a pH electrode is currently installed gently remove it from the sensor end cap Use a foam swab dipped in water to clean the internal O rings 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...

Page 4: ... Configure Select logger settings and load them onto the logger to start logging See Configuring the Logger Readout Download logger data See Reading Out the Logger pH Calibration Calibrate the logger following the instructions in HOBOmobile The logger should be calibrated after replacing or cleaning the electrode See Calibrating the Logger Full Status Details Check the battery level and view the c...

Page 5: ... as prompted making sure the sensor end cap temperature sensor and closure cap are submerged in the solution Follow the instructions on the screen Once the pH reading is stable tap Confirm Buffer 10 If you selected three point calibration repeat steps 8 9 11 Tap Save Calibration 12 Rinse the pH sensor with deionized or distilled water again If you will not be deploying the logger immediately attac...

Page 6: ...e Setting up Alarms for more details 7 Tap Start Logging and select when logging will begin Now Logging will begin immediately after tapping Start in the Configure screen On Next Logging Interval Logging will begin at the next even interval as determined by the selected logging interval On Button Push Logging will begin once you press the switch on the logger for 3 seconds On Date Time Logging wil...

Page 7: ...the High Alarm if you want an alarm to trip when the sensor reading rises above the high alarm value Drag the slider to the reading that will trip the alarm or tap the value field and type a specific reading In the example an alarm will trip when the temperature rises above 85 F 5 Enable the Low Alarm if you want an alarm to trip when the sensor reading falls below the low alarm value Drag the sli...

Page 8: ...ensor Limits 5 Enable High Limit if you want burst logging to occur when the sensor reading rises above a specific reading Drag the slider to the reading that will trigger burst logging or tap the value field and type a specific reading In this example the logger will switch to burst logging when the temperature rises above 85 F 6 Enable Low Limit if you want burst logging to occur when the sensor...

Page 9: ...n select Fixed Interval Logging 4 Select Normal to record the current reading for each enabled sensor at the logging interval shown at the top of the screen Do not select this if you only want to log statistics 5 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 Deviat...

Page 10: ...ed because the reading was outside the alarm limits or back within range Note Although the reading may have returned to a normal range during logging an alarm cleared event will not be logged if the logger was set up to maintain alarms until reconfigured New Interval The logger has switched to logging at the burst logging rate or back to the normal rate Water Detect The logger has been placed in w...

Page 11: ...s on the sensor end cap shown above Using your finger spread a small dot of grease along both outer O rings 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 2 years with Bluetooth Off Water Detect selected and 3 years with Bluetooth Always O...

Page 12: ...nto position 9 Screw the closure cap back on the logger WARNING Do not cut open incinerate heat above 85 C 185 F or recharge the lithium battery The battery may explode if the logger is exposed to extreme heat or conditions that could damage or destroy the battery case Do not dispose of the logger or battery in fire Do not expose the contents of the battery to water Dispose of the battery accordin...

Page 13: ...dustry 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 Avis de conformité pour l Industrie Canada Le présent appareil est conforme aux CNR d Industrie Canada applicables aux appareils radio exempts ...

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