- 15 -
Trouble
Reason
How to fix
Cannot
calibrate
Incorrect standard
solutions
Power on the meter, calibrate pH 7 first, then pH 4.
After pH 4 is calibrated, if you want to calibratepH 7
again, you need to reboot the tester.
Poor quality standard
solutions
Replace with fresh and clean standard calibration
solutions made by legitimate scientific instrument
manufacturers.
Contaminated probe
Clean the probe with Apera probe cleaning solution
or detergent water.
Aged probe
Replace the probe.
Dried-out probe
Soak the probe in 3M KCL solution for at least 15
minutes.
Probe is not fully
submerged in the solution
Make sure the probe is fully immersed in the
solution at least 1 inch deep.
Air bubbles around the
sensor
Make a quick stir in the solution to remove air
bubbles.
Reading is
always slowly
changing, won’t
stabilize
Contaminated probe
Clean the probe with Aprea’s cleaning solution or
detergent water.
Clogged junction
Clean the probe with Aprea’s cleaning solution,
then soak it in 3M KCL soaking solution overnight.
Aged probe
Replace the probe.
Testing pH of low iconic
strength solutions like tap
water, drinking water, RO
water
Be patient, wait for 1-5 minutes to reach a fully
stabilized reading. If still not stabilizing, add 1ml of
3M KCL solution to 1000ml of test solution (or 1
teaspoon to 1 gallon).
Display similar
readings in any
solutions or
always display
7.0 pH
Broken probe
If you don’t find any visible damage of the probe,
contact us for warranty fulfillment; If there is visible
damage, replace the probe.
Reading keeps
jumping
Probe is not fully
submerged in the solution
Make sure the probe is fully immersed in the
solution at least 1 inch deep.
Air bubbles around the
sensor
Make a quick stir in the solution to remove air
bubbles.
Probe is not properly
connected, or the pin
connector is broken.
Check the probe’s connector, make sure it’s not
broken and is correctly connected. Align the probe
and instrument correctly before plugging in. Never
force it. Ensure that the probe connector is not
exposed to air too long.
Calibration is
successful, but
reading is not
accurate
Aged probe
Replace the probe.
Air bubbles around the
sensor
Make a quick stir in the solution to remove air
bubbles.
Clogged junction
Clean the probe with cleaning solution, then soak it
in 3M KCL soaking solution overnight.
Comparison with other
testers, test strips, or
drop tests
To compare with other testers, make sure to
perform a 2-point calibration for all testers in the
same standard, then test a 3rd point. Whichever
gives more accurate reading is the more accurate
one. Test strips or drop tests’ accuracy is not
comparable to pH meters ‘.
