Published on: Mar 4, 2016
Transcripts - Pressure meters
Indicating elements for pressure gages:
• Various forms of industrial pressure gages differ mainly in the
method by which the displacement of the measuring element is
arranged to operate an indicating point.
• Mechanical and Electrical means can be used for transmitting
motion of the float, bell or bellows of differential pressure
Torque –Tube Shaft:
(Differential pressure meter)
Torque tube shaft:
• It operates by mechanical means.
• A torque tube system is a driveshaft technology, often used in
automobiles with a front engine and rear drive.
• Driveshaft's are sometimes also used for other vehicles and
• The "torque tube" transmits traction force by directly coupling the
axle differential to the transmission.
• The outer tube is made from relatively thin-metal tubing and is
clamped rigidly to the meter housing.
• The inner shaft is rigid and the force of the bellows causes the
free end of the torque tube to twist.
• The inner shaft then rotates in the same direction.
• The torque tube also serves as a spring.
• This torque tube shaft is often employed in bellows meter.
• Electrical means are also used for transmitting motion of the float, bell,
or bellows of the differential-pressure-meter.
• Electronic pressure transmitters convert input pressure into a digital or
• Electrical type includes:
• An induction coil or "spark coil" is a type of electrical transformer used to
produce high-voltage pulses from a low-voltage
direct current (DC) supply.
• The term 'induction coil' is also used
for a coil carrying high-frequency alternating
current (AC), producing eddy currents to
heat objects placed in the interior of the coil.
• An armature generally refers to one of the two principal electrical components of an
electromechanical machine — generally in a motor or generator.
• In the armature, an electromotive force is created by the relative motion of the armature
and the field.
• Inductance-coil-system and armature are used in Differential pressure meter like
Inductance Bridge pressure differential meter.
Inductance-bridge pressure differential meter:
• The float in leg of the manometer supports an armature on the inside of a non-
• This tube seals the float side of the manometer.
• A divided inductance coil fixed in position on the outside of the tube.
• The instrument contains an identical divided inductance coil, in which a counter
balanced armature is suspended.
• At balance, the armatures are similarly placed in each coil and current flow
through each coil is same.
• When the armature at the transmitter moves to a new position, the reactance at the
side of the transmitter coil differs.
• This difference causes a different current flow in each arm of the circuit.
• The magnetic field at the receiver coil is redistributed and the net force acts on the
armature, tending to bring the system to balance.
• Therefore, for every position of armature in the transmitter there is a corresponding
position in the receiver armature.
• The motion of the float is transmitted to the receiver point.
• Variations of voltage have no effect on the calibration of the system.
• The meter is completely sealed.
• The variation of the inductance-coil is employed in which the balance of the bridge
is detected by a galvanometer.
• A reversible electric motor is used to position the receiver armature in the coil.
• A second variation of the inductance-coil system employs an electronic amplifier for
detecting balance and a reversible electric motor for positioning the receiver