Omega Speaker Systems PH-2720-PA - Manual (Page 6)

With simulator
connected
Ok with
simulator
connected but
fails with
electrode
Error Condition
A) mV output stuck at
zero
B) mV output erratic
C) mV output stuck at
1.4 VDC
A) mV output stuck
near zero
B) mV output erratic
C) Output stuck at
1.4 VDC
Possible Cause
A) Shorted input signal
B) Faulty preamplifier or wiring
C) Faulty preamplifier
A) Cracked electrode glass
B1) Poor contact between
electrode and preamplifier
connectors
B2) Fouled electrode
reference or aged electrode
B3) Ground loop
C) Faulty preamplifier
Possible Remedy
A) Check preamplifier cable connections and shielding.
B) Verify preamplifier shield connections. Verify cable shield
wire has been maintained through each cable splice.
C) Replace preamplifier
A) Replace electrode
B1) Check contacts between electrode and preamplifier.
Contacts must be clean and dry.
B2) Clean electrode, see electrode manual
B3) Isolate electrode in test beaker. If output is stable, ground
loops may exist causing erratic behavior; isolate instrument
outputs (i.e. 4 to 20 mA, 0 to 5 VDC).
C) Replace preamplifier
8. Electrode Maintenance and Cleaning
8.1 Maintenance
Variables can affect long term pH or ORP electrode life. For this
reason, a maintenance log is recommended for trend analysis. When
storing boxed sensors, lay the sensor flat to maximize hydration of the
glass surface. Keep the glass surface wet at all times. Soak the sensor
tip in pH 4.0 buffer during system maintenance intervals. In-line
applications should be plumbed with a depression (trap) which ensures
liquid is maintained around the sensor tip. If sensor dehydration has
occurred, soak the sensor tip in pH 4 buffer for 24 to 48 hours, then
visually inspect the electrode for surface cracks, swelling, or
discoloration.
8.2 Cleaning
Cleaning techniques vary depending on the type of coating present on
the glass electrode surface or reference junction.
• Soft coatings: can be removed by vigorous stirring, or with
directed spray of an applicable detergent or solvent onto the glass
electrode surface. Chlorine bleach or mild detergent may be used
to remove soft coatings. Always rinse electrode tip in clean water
after cleaning.
• Hard coatings: can be chemically removed. Always use the least
harsh chemical which will remove the contaminant within two (2)
minutes without attacking the materials of construction. e.g. calcium
carbonate may be removed with a 5% HCL (muriatic acid) solution.
• Oily or Organic Coatings: can be removed with detergents or an
appropriate solvent that does not attack the materials of
construction e.g. isopropyl alcohol may be used but acetone must
be avoided to prevent damage to the CPVC sensor body.
• ORP electrode surface (platinum rod): can be gently sanded with
600 grit wet and dry silicone or carbide sandpaper, jewelers
rouge, crocus cloth, or very fine steel wool.
WARNING!
When using chemicals or solvents care should be taken and
appropriate eye, face, hand, body, and/or respiratory
protection should be used.