TSI Incorporated VELOCICALC Plus 8360, Operation And Service Manual

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Chapter 3
6
switching to temperature mode. This is necessary because the velocity
sensor is heated during velocity mode, and some heat is conducted down to
the temperature sensor.
Measuring Pressure
Press the
PRESSURE
key to measure differential pressure. To measure
pressure, tubing must be connected to the pressure ports on the top back of
the unit. When the pressure source is connected the same way the pressure
ports are marked, the meter will display a positive number.
Zeroing Pressure
If the zero reading of pressure has drifted, the pressure function can be
easily re-zeroed. To reset the zero, make sure that the pressure ports
are exposed to the exact same pressure. The easiest way to do this is to
remove the pressure hoses and leave both ports exposed to ambient
pressure.
Press and hold the
PRESSURE key down for at least three seconds.
The V
ELOCI
C
ALC
will give a double beep and the display will show “0
in. H
2
O” (or whatever units have been selected). When the key is
released the display will be re-zeroed.
Measuring Humidity (Model 8360 and 8388 Only)
Press the
HUMIDITY
key to display humidity readings. The readings will
be in units of percent relative humidity (%RH). The reading may need time
to stabilize if the ambient conditions have recently changed.
In order to see if the humidity reading has stabilized, extend the probe and
gently wave it back and forth (or place it in a location where there is a
sufficient quantity of moving air), while checking the display for an upward
or downward trend in the readings. When no particular trend is apparent,
the reading has stabilized.
Situations that may require time to stabilize the sensor would be when
moving the instrument from a cold vehicle or storage place into a heated
building. Also, if the end of the probe has been warmed by being handled, it
will need to cool to ambient temperature. Another example would be when
moving from a location with low humidity to high humidity, or vice versa.
Dew Point Function (Model 8360 and 8388 Only)
Press the
DEW POINT
key to display the dew point temperature. The dew
point is calculated using the temperature and relative humidity
measurements. Because dew point is not measured directly, accuracy of this
calculation depends on both ambient temperature and relative humidity. The
dew point reading will be most accurate when the relative humidity is 50%
and above (and dew point temperature is closer to the actual temperature). It