3
Pressure Modules for Dynamic Pressure
Zero Point Correction of the Pressure Sensors
The zero point of the pressure sensors can shift due to positional changes and
temperature variations. Therefore, it is useful to perform a zero point correction
before each measurement. For the zero point correction, the pressure hoses or
the Pitot tube must be removed from the flow conduit. When the measured
value has stabilised, the zero point correction can be performed. This is de-
scribed in the operating instructions supplied with each device under “zero-
point / sensor adjustment” For the necessary interface command please refer
to Section 6.4.2.
The zero point correction must be performed separately for each
active channel (m/s, Pa).
The zero point correction data is lost on switch off. Therefore, a new
correction must be performed for the next measurement.
Temperature Compensation
If the measuring temperature largely deviates from the reference temperature
of 25°C the temperature influence (range -50.0 to +700.0°C) should be com-
pensated by performing a measurement preferably with a NiCr-Ni temperature
sensor. With ALMEMO
®
V5 and V6 devices every suitable temperature sensor
(resolution 0.1°C) can be used for compensation (see 6.3.4). By means of the
reference channel, the air temperature can, at the measuring instrument AL-
MEMO
®
2295-6, for compensation purposes, be entered for one flow measure-
ment channel if the switch position COMPENSATION is selected. If the operat-
ing conditions are relatively constant it is sufficient to enter a correction factor
according to the above table.
Handling the Pressure Modules
Ensure that the Pitot tube is properly connected. A confusion of the
pressure connectors will cause incorrect measurements.
Attention:
The pressure sensors contain very sensitive pressure cells.
Note the permissible maximum pressures - these must not be ex-
ceeded!
Caution when removing the hoses! Do not squeeze the hoses.
Harmful negative pressures can then be avoided. Avoid strong vi-
brations! Do not let aggressive gases penetrate the membrane or
pressure cells, as they could be destroyed!
ALMEMO
®
Manual 3-5-17
(60 páginas)
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