pH Troubleshooting Chart
Symptom
Cause
Recommended Solution
Clogged Junction
Soak in 4.07 M KCL @ 60
o
C for 30
minutes
Strong Alkaline measurement
Deteriorated Gel layer
Soak in 0.1 M HCL overnight
Protein coating on electrode
surface
Soak in 1 gm Pepsin dissolved in
100ml of 0.1 m HCL for 30 minutes or
as needed
Oil, paint, dyes, suspended solids
on sensor
Rinse electrode alternately with
materials solvent then buffer 7.00
Organic solvents are coating
sensor
Long response
time or reading
drift
Dehydrated membrane
Organic mole fraction has to be less
than 50% to assure reasonable
readings. Limit time of measurement.
Keep probe in the 7.0 buffer between
readings.
Dry Bulb
Long term storage without wetting Soak electrode tip in wetting cap filled
with 1ml 7.00 buffer for 24 to 48 hours
Static Charge
Wiping electrodes
Rinse electrode in 7.0 buffer and blot.
Do no wipe electrode.
Same readings in
different buffers
and samples
Cracked or broken bulb
Replace electrode. Use bulb guard.
Avoid plunging electrode to bottom of
container and spinning bars. A
wetting cap will protect bulb between
measurements.
Erratic LCD
display
Samples have low ionic strength
(lacks salt); e.g. distilled, de-
ionized, boiled, lake water (high
pressure)
For each 50 ml of sample add 1 drop
(50uL) of SAT.KCL No alteration in
pH will occur by inert KCL.
MAINTENANCE
Conductivity Cell Simulator
The meter is supplied with a cell simulator which can be used in place of the conductivity
cell to provide a means to verify the operation of the meter. The simulator will produce a
reading of approximately 800 - 1200uS (~1mS). The simulator should not be used as a
calibration device.
This device is helpful in determining if the cause of calibration difficulties is related to the
meter or (more likely) an aged or defective conductivity cell.
Battery Replacement
Install a new battery when the LOW BATTERY indication appears on the LCD. Remove
the battery cover (refer to Fig. 1 for location), install new battery, and replace cover.
Calibration / Repair Services
Extech offers complete repair and calibration services for all of the products we sell. For
periodic calibration, NIST certification or repair of any Extech product, call customer
service for details on services available. Extech recommends that calibration be performed
on an annual basis to insure calibration integrity.
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
FAX 781.665.0780 - TestEquipmentDepot.com
