3B Scientific U-Tube Manometer S User Manual
A
3B SCIENTIFIC® PHYSICS
U-Tube Manometer U8410450
Instruction Sheet
08/08 ALF
1 Overflow reservoir
2 Supporting plate
3 Glass tube
4 Tubing connection
5 Rubber bung
1. Safety instructions
There is a risk of injury if the U-tube manometer gets
broken.
• Do not put any mechanical stress on glass body.
2. Description
The U-tube manometer is a simple form of pressuremeasuring instrument, and is used for measuring
small pressures or pressure-differences in the region
of 0 to 10 hPa (0 to 10 cm water column).
It consists of a U-tube open at both ends with an
overflow reservoir at one end, mounted on an aluminium supporting plate marked with a scale. On the
back of the supporting plate there is a fixing rod for
clamping the instrument to a stand.
To connect up the manometer in an experiment setup it is recommended that 6 mm silicone tubing be
used (U10146). The Indigo solution (U8410620) makes
a suitable dye for colouring the water.
3. Technical Data
Length of arms: 200 mm
Stand rod: 33 mm x 10 mm dia.
Base plate: 210x70 mm
Hose nipple: 9 mm dia. approx.
Weight: 80 g approx.
4. Operating principle
Pressure p is defined as the quotient of the force F
acting at right angles to a plane and the area A of
that plane.
F
p =
1
The units for this are N/m², also named pascals (Pa).
Pressure is also measured in bars (bar), torrs (Torr),
physical atmospheres (atm), technical atmospheres
(at) and millimetres of mercury (mmHg).
2
approx.
1
The absolute pressure p
is the pressure measured
abs
with respect to the zero pressure in a vacuum. Atmospheric pressure p
is the pressure of air over
amb
and above the absolute pressure. The difference
between the atmospheric pressure and absolute
pressure is called pressure over atmospheric p
.
e
Pressure over atmospheric is positive when the air
pressure is less than the absolute pressure and negative otherwise. If it is negative then it can be called
underpressure or partial vacuum.
This manometer is a U-tube open at both ends and
partially filled with a liquid impervious to air. It is
mainly used for measure small pressures and pressure differences. The pressure in a closed container
to be measured acts on the fluid in one arm of the
tube. The other open arm is subject only to atmospheric pressure. The fluid then rises on one side so
that there is a difference in height Δh between the
two sides. From Δh and the density ρ of the fluid in
the tube, it is possible to calculate pressure over
atmospheric p
p
(mbar) = g·ρ (g/cm³)·Δh (mm) 2
e
in the closed container:
e
6. Conversion table
5. Operation
For the liquid in the manometer it is possible to use
distilled water with coloured dye, ethanol and special
oils, or even mixtures of silicone and anti-freeze
fluid.
• Remove the rubber bung.
• Slowly pour the liquid into the overflow reservoir
until the columns of liquid in both limbs of the
manometer are on the zero mark.
• Attach the tubing and connect it to the vessel for
which the pressure is to be measured.
• Read the height difference Δh, estimating tenths
of the scale divisions.
• Calculate the pressure using equation 2.
Pa bar mbar Torr atm at
1 Pa 1 10-5 10-2 7.5*10-3 9.87*10-6 1.02*10-5
1 bar 105 1 103 750 0.987 1.02
1 mbar 102 10-3 1 0.75 0.987*10-3 1.02*10-3
1 Torr 133 1.33*10-3 1.33 1 1.32*10-3 1.36*10-3
1 atm 101325 1.01325 1013.25 760 1 1.033
1 at 98100 0.981 981 736 0.968 1
Elwe Didactic GmbH • Steinfelsstr. 6 • 08248 Klingenthal • Germany • www.elwedidactic.com
3B Scientific GmbH • Rudorffweg 8 • 21031 Hamburg • Germany • www.3bscientific.com
Rights to amend technical specifications reserved
© Copyright 2008 3B Scientific GmbH
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