HOBO MX pH and Temperature Logger (MX2501) Manual
U.S. and International Sales: 1-508-759-9500 9
www.onsetcomp.com
•
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-END-
CAP) 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 O-
rings on the sensor end cap shown below. Using your
finger, spread a small dot of grease along both outer O-
rings.
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.)
Use this hole for
mounting the logger
Outer O-rings on
sensor end cap
Use cable ties around these
grooves for mounting the logger
First, unscrew this closure cap
Then, pull this
sensor end cap
straight out
Gently and slowly
remove the pH electrode
from the end cap
