EVOM
device or power line or are connected to a computer with an unshielded power
supply. Moving the system to a different area or removing the connection to the
computer, will eliminate that problem
c.
The electrode is broken and needs to be replaced.
5. Voltage reading drifts
Possible causes include:
a.
The electrode is not equilibrated. See the “Electrode Preparation” Section of the
manual.
b.
The electrode is dirty. Clean the electrode (see the section on Cleaning the
Electrode).
c.
The electrode and its cable are too close to a strong electromagnetic radiation
device or power line or are connected to a computer with an unshielded power
supply. Moving the system to a different area or removing the connection to the
computer, will eliminate that problem.
d.
The electrode is broken and needs to be replaced.
6. Meter is not reading within 1% of 1000 ohm during Meter Self-Test
Possible causes include:
a.
Low batteries: Check and change the batteries as necessary.
b.
“Zero
Ω
” is not adjusted correctly. See INSTRUMENT SELF-TESTS: Testing the
Electrode for Resistance Measurements.
c.
System requires calibration: as the meter ages, the test reading is expected to drift
slightly downward. However, this drift is normal within 1% accuracy at 1000 ohm.
If the error is more than 1% (>10
Ω
), then, the accuracy of your measurement
will have a error that is larger than 1%. In that case, it is recommended that WPI
recalibrate the instrument.
7. Resistance reading is lower than expected
If the resistance reading of the “blank” is close to the normal value and the tissue
resistance reading is stable and repeatable, perform the Instrument Self-Test to confirm
that the meter is functioning appropriately. If the reading continues to be lower than
expected and the meter has satisfactorily met the Instrument Self-Testing criteria, the
likely cause is a problem with the cell culture,
e.g.
, the cells are contaminated with
something that is affecting their ability to grow to confluence. Electrode failure will not
cause a lower than expected yet stable reading.
WORLD PRECISION INSTRUMENTS 17
