How D.P. transmitter can be applied to close tank?
In closed tank, bottom of the tank is connected to the high pressure side of the
transmitter. Top of tank is connected to the lower pressure side of the
transmitter. In this way vessel pressure can be measured.
How D.P. transmitter can be applied to open tank?
In open tank the lower pressure side is vented to the atmosphere. All pressure
is applied to the high pressure side. This vessel pressure is measured through
high pressure side.
Explain the working of an electronic level troll.
The variation in level of buoyancy resulting from a change in liquid level
varies the net weight of the displacer increasing or decreasing the load on the
torque arm. This change is directly proportional to change in level and
specific gravity of the liquid. The resulting torque tube movement varies the
angular motion of the rotor in RVDT providing a rotor change proportional to
the rotor displacement, which is converted and amplified to a D.C. current.
Explain the working of an enraf level gauge.
Enraf level gauge is based on the ser powered null balance technique. A
displacer serves as continuous level sensing element. A two phase ser motor
controlled by a capacitive balance system winds unwinds the the measuring wire
until the tension in the weight springs is in balance with the weight of the
displaced part immersed in the liquid. The sensing system in balance measures
the two capacitance formed by the moving central sensing rod provided by the
two capacitor plates and the si plates.
What is the constant voltage unit?
The constant voltage circuit consists of a rectifier, CR and a filter capacitor.
It is followed by two stages of zener regulation. Abridge configuration is
provided to lamp line voltage zener regulation. Regulation 1 and regulation 2
provides relatively provide constant current. Resistors form a bridge that may
remoment line voltage effects.
Explain the burnout feature.
Burnout provides the warnsug feature of driving indicator at the end of scale,
if the input circuit is open. A burnout resistor is provided which develops a
voltage drop between the measuring circuit and amplifier. The polarity of the
signal determines the direction of the servo drive upon an open circuit in the
Upscale burnout: R value 10 M
Downscale burnout: R value 22 M
Why thermo wells are used? What materials are used in thermo wells?
In numerous applications, it is neither desirable nor practical to expose a
temperature sensor directly to a material. Wells are therefore used to protect
against damage corresion, arosion, aborsion and high pressure processes. A
thermo well is also useful in protecting a sensor from physical damage during
handling and normal operations.
Materials used in thermo wells: Stainless steel, Inconel, Monel, Alloy Steel,