Teledyne 4250, Инструкция по установке и эксплуатации, Страница: 130 / 204

4250 Flow Meter
Section 4 Options and Accessories
4-20
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 Teledyne Isco recommends facing upstream, as there is a
stop on the sensor carrier that is not effective when the probe is
facing downstream. 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.
The Isco amplifier box extends the allowable distance between
the probe and the flow meter. The probe has a 25-foot cable, so
you must mount the amplifier within this distance. The
maximum distance between the amplifier box and the flow meter
is 1,000 feet.
4.10.3 Storage and
Maintenance of pH
Probes
If you remove the pH probe from operation, be careful to keep the
glass sensor bulb wet. Always store the probe with the rubber
cover screwed completely over the threaded end of the sensor.
Exposure to air causes the glass membrane on the sensor bulb to
dry out. This makes it very slow to respond in solution.
Pro-
longed or repeated dehydration of the bulb will ruin the
probe.
Table 4-3 pH Probe Specifications
Description Submersible, horizontal-mounting probe with combination-type
electrodes. Porous Teflon
®
liquid junction to resist fouling and coat-
ing. Steam-sterilized glass hemi-bulb for long- term stability.
Size 6" long

3

4
NPT.
Body Material Stainless Steel.
pH Range 0 to 14 pH units.
Temperature 32° to 176° F (0° to 80°C).
pH Accuracy ±0.1 pH units over the full range.
pH Electrode Junctions Double porous junction
Temperature Compensation Performed by software inside the flow meter. The standard pH
Probe contains an integral temperature sensor.