HOBO® MX pH and Temperature Logger (MX2501) Manual
22511-B
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-enabled for wireless communication with a mobile device. Using the
HOBOmobile® app, you can easily calibrate and configure the logger, download logged data to
your phone or tablet, 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
pH Sensor
in
pH in mV
Range 2.00 to 12.00 pH -512 to 512 mV
Accuracy ±0.10 pH units within ±10°C of
temperature at calibration
±0.20 mV
Resolution 0.01 pH 0.02 mV
Response Time 1 minute typical to 90% at constant temperature in stirred water
Temperature Sensor
Range -2° to 50°C (28.4° to 122°F)
Accuracy ±0.2°C (±0.36°F)
Resolution 0.04°C (0.072°F)
Response Time 7 minutes typical to 90% in stirred water
Logger
Operating Range -2° to 50°C (28.4° to 122°F) — non-freezing
Buoyancy Fresh water: 13.6 g (0.48 oz) negative
Salt water: 19.6 g (0.69 oz) negative
Waterproof To 40 m (131.2 ft)
Water Detection Water conductivity level of 100 µS/cm or greater is necessary for
reliable detection of water. Deionized water or water below 100 µS/cm
may not be detected.
The water conductivity circuit may not reliably detect water that has
frozen around the electrodes, i.e. below 0°C (32°F).
Radio Power 1 mW (0 dBm)
Transmission Range Approximately 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 minute per month 0° to 50°C (32° to 122°F)
Battery Type One AA 1.5 Volt, user-replaceable
Battery Life 1 year typical at 25°C (77°F) with logging interval of 1 minute and
Bluetooth Always On selected in software.
2 years typical at 25°C (77°F) with logging interval of 1 minute and
Bluetooth Off Water Detect enabled in software.
3 years typical at 25°C (77°F) with logging interval of 1 minute and
Bluetooth Always Off selected in software.
Faster logging intervals and statistics sampling intervals, burst logging,
remaining connected with the app, excessive downloads, and paging
may impact battery life.
HOBO MX pH and
Temperature Logger
MX2501
Included Items:
• pH electrode in storage
solution
• Electrode storage solution
bottle and cap
• Anti-biofouling copper
guard
• Silicone-based O-ring
grease and foam swab
Required Items:
• HOBOmobile app
• Device with iOS and
Bluetooth
• 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 beaker
(MX2500-CAL-BKR)
• Maintenance kit with
calibration kit plus storage
solution (MX2500-MAINT-
KIT)
• 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)
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176 - TestEquipmentDepot.com
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