4230 Flow Meter
Section 4 Optional Equipment
4-22
from contact with certain gases) or plated with silver
(which can result from extended use with a loose or
wrinkled membrane), you need to restore its surface.
You can return it to Isco or clean it yourself with a probe
reconditioning kit. (This kit is available from Isco.)
Never use chemicals or any abrasive not supplied with
this kit. It is also possible for the silver anode to become
contaminated, which will prevent successful calibration.
Try soaking the probe overnight in a 3% ammonia
solution; then rinse with deionized water, recharge with
electrolyte, and install a new membrane. If you are still
unable to recalibrate the probe after several hours,
return the probe to Isco for service.
• If the sensor O-ring is worn or loose, you should replace
it. The probe comes with a kit of O-rings and
replacement membranes. Additional replacement
O-rings are available from Isco in an O-ring replacement
pack.
• If the probe will not be in constant use, you should store
it in the plastic bottle provided in shipping. To keep the
electrolyte from drying out, place a small piece of moist
towel or sponge in the bottle and insert the probe into
the open end. If you need service for your D.O. probe,
Isco recommends returning the unit for evaluation. In
addition to servicing the probe, we can also provide
advice on product applications, and you can also
purchase other accessories for use with the D.O. probe.
Use only 2-mil membranes with D.O. probes connected
to Isco flow meters.
Table 4-4 D.O. Probe Technical Specifications
Cathode Gold
Anode Silver
Membrane FEP Teflon; 2 mil standard
Electrolyte Half-saturated KCl (Potassium Chloride)
Temp. Range 0° to +45° C
Polarizing
Voltage
0.8 Volts (Nominal)
Probe Current in Air at
30
o
C
19 microamps (nominal)
Probe Current in Nitro-
gen at 30
o
C
0.15 microamps or less
Connection 12 ft. (3.2 m) cable with 5-pin male M/S
connector
Response time Typical response for dissolved oxy-
gen, using supplied membranes, is 90% in 20 sec-
onds. Response at low dissolved oxygen levels is
typically 90% in 60 seconds.
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