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3．Pressure of measurement and connection of piping
a) Measurement of positive pressure
Connect the tube to the high pressure side piping connector (indicated by red color or letter H).
The lower pressure port (blue or L) should opened to atmosphere, but do not remove the piping
connector.
b) Measurement of negative pressure
Connect the tube to the low pressure side piping connector (blue or L). The high pressure port (red or
H) should be opened to atmosphere, but do not remove the piping connector.
c) Measurement of differential pressure
Connect the tube from the high pressure piping connector to the high pressure port (red or H) and from
the low pressure piping connector to the low pressure port (blue or L).
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Caution
Measurement of single pressure using an instrument with zero point center range.
Connect the tube to the high pressure side piping connector (red or H). In this case again,
leave the piping connector attached to the low pressure side, which is opened to atmosphere.
The single pressure is as displayed on a zero point center scale (+-).
4．Caution of piping
・Prohibition of common piping
Piping each of pressure detectors and pressure receiving
instruments tube exclusively dedicated for it, and do not
connect the piping commonly with the adjacent system as
shown in the right figure.
Common piping causes measurement error because the
pressure of each system interferes.
・Prevention of clogged piping due to drain
If drain remains within the line, it causes measurement error.
Be sure to install the pressure receiving instrument above the
pressure outlet port of the pressure detector and arrange the
line so that the drain water should not remain in the slack
piping.
If the arrangement mentioned above in not possible, install a
drain tank within the line as shown in the right figure and clean
it once in a while.
After the cleaning of the tank, check that the air tightness is
fully kept.
・Measurement of high temperature gases
In the pressure measurement of high temperature gas, use the
pressure detector (pitot tube) made of the heat-proof metal
(such as stainless steel), and connect it with the pressure
receiving instrument through a metal tube which is long
enough to cool down the high temperature gas.
・Errors caused by long distance piping
The speed of response is delayed when the product is used for
remote monitoring.
In such application, the I.D. of the connection tube should be
as large as possible.
If the piping conditions of the high and low pressure side are
significantly different, the difference in the piping resistance
between high and low pressure side causes the difference in
pressure transmission time, and the measurement becomes
inaccurate.
Independent piping○
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Room B
Room A
Room B
Room A
EMT1
EMT1
EMT1
EMT1
Common piping×
Drain
Drain
tank
