Teledyne 4220 - Manual (Page 124)

4220 Flow Meter
Section 5 Options and Accessories
5-16
Figure 5-4 pH Parameter Module
Note
When installing the pH probe and its sensor carrier, make sure
the mounting slots on the carrier are completely pressed into
the mating tabs on the ring. The probe relies on a full engage-
ment between tabs and slots for secure mounting. If the slots
are loose against the tabs, the probe may be swept away by
the force of the stream.
Always mount the probe in an easily-accessible location, because
you will need to clean it from time to time. Also, all pH probes are
consumable items, meaning that they will eventually fail and
have to be replaced. The probe is due for replacement when you
can no longer calibrate it (after cleaning) to ±0.2 pH with the
standard buffers of 4, 7, and/or 10. Another indication of
end-of-life is when the probe calibrates satisfactorily, but takes
too long to stabilize (more than 10 minutes). Such a probe could
not possibly respond to rapidly-changing pH. If your situation
requires fast response, you should consider replacement when
stabilization time reaches 5 minutes.
You can mount the probe facing either upstream or downstream,
but Isco recommends facing upstream, as there is a stop on the
sensor carrier that is not effective when the probe is facing down-
stream. Remember to unscrew the rubber guard cap from the
sensing end of the probe when you install it, or the probe will be
unable to sense the flow stream.
The guard cap is to protect the probe during shipment and
storage and to keep the glass membrane and liquid junction from
drying out. If you remove the probe for any reason, clean it and
replace the cap after filling with 4.0 buffer solution. Never store
the probe dry or without the cap in place.