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Issue: When should I use the external temperature probe?
Action:
We recommend always using the external temperature probe as your
first choice. Because it is isolated, its temperature response is faster
than the sensor inside your Alicat's flow stream. Keep the tip of the
probe in a bit of shade or inside a radiation shield for best results.
Issue: The internal temperature sensor doesn't match the external probe.
Action:
The temperature sensor inside the flow body is the same kind as the
one at the end of the external probe. However, the internal probe has
the larger mass of the aluminum flow body around it, and this takes
longer to equilibrate than the tip of the external probe. Your FP-25
always references the external probe temperature to provide flow
readings whenever it is connected. If you are not using the external
probe, do be sure to allow time for the flow body to equilibrate to
ambient temperature.
Issue: Do I need to sheath the shaft of the probe in direct sunlight?
Action:
Nope! The temperature sensor at the tip of the probe is thermally
isolated from the rest of the shaft. The tip will temporarily heat up
in response to direct sunlight, but your readings will quickly settle
to ambient temperature once you insert the probe into a radiation
shield or place its tip in the shade. Do not sheath the metal shaft in
an attempt to insulate it; this makes the probe's response slower and
can lead to poor performance.
Issue: Can I immerse the external probe in a temperature bath?
Action:
Yes, we do this at Alicat, too. The internal electronics of the probe are
not exposed, so you can immerse it up to an inch shy of its handle.
Pressure Readings
Issue: How can I see pressure in different units?
Action:
From Standard Mode, push the button above the pressure reading
twice, and then choose Set button eng units. Use the UP/DOWN keys to
move the > cursor to the desired unit, and then press SET.
Issue: How do I know which pressure reading the Alicat is displaying?
Action:
Above the pressure reading in Standard Mode, or to its right in Direct
Mode, the FP-25 displays BARO when the pressure reading is from
the barometer. If you have set your FP-25 to display internal pressure,
the pressure unit will end with A for absolute pressure (
e.g.
mmHgA) or
G for gauge pressure (
e.g.
mmHgG).
Troubleshooting Your FP-25