How is automatic reference junction compensation carried out in temperature
In automatic reference junction compensation, variable nickel resistor is used.
As the temperature changes, so does its resistance. This reference junction
compensator is located, so that it will be at the temperature of the reference
junction. The reference junction is at the poset where the dissimilar wire of
the thermocouple is rejoined. This joint is invariably at the terminal strip of
What are de-saturators?
When, in some processes, e.g. batch processes, long transient responses are
expected during which a sustained deviation is present the controller integral
action continuously drives the output to a minimum or maximum value. This
phenomenon is called ‘integral saturation of the control unit’. When this
condition is met, then this unit is de-saturated.
Explain the working of Rota meter.
Variable area meters are special form of head meters. Where in the area of flow
restrictor is varied. So as to hold the differential pressure constant. The
rota meter consists of a vertical tapered tube through which the metered fluid
flows in upward direction. As the flow varies the ‘float’ rises or falls to
vary the area of the passages that the differential across it balances the
gravitational force on the ‘float’. The differential pressure is maintained
constant. The position of the ‘float’ is the measure of the rate of flow.
What is the working principle of the magnetic meter?
An electric potential is developed when a conductor is moved across the magnetic
field. In most electrical machinery the conductor is a wire. The principle is
equally applicable to a moving, electrically conductive liquid. The primary
device of commercial magnetic meters consist of straight cylindrical
electrically insulated tube with a pair of electrodes nearly flush with the
tube walls and located at opposite end of a tube diameter. This device is
limited to electrically conducting liquids. The magnetic meter is particularly
suited to measurement of slurries and dirty fluids.
Explain the mechanism behind the turbine meter.
Turbine meters consist of straight flow tube within which a turbine or fan is
free to rotate about it s axis which is fixed along g the centre line of the
tube. Mostly, a magnetic pick up system senses the rotation of the rotor
through the tube walls. The turbine meter is a flow rate device
, since the rotor speed is directly proportional to the flow rate. The output
is usually in the form of electric pulses from the magnetic pick up with a
frequency proportional to the flow rate.
How would you choose differential range?
The most common range for differential range for liquid measurement is 0-100.
This range is high enough to minimize the errors caused by unequal heads in the
seal chambers. It is also dependent on the differences in the temperature of
the load lines. The 100 range permits an increased in capacity up to 400. While
decrease down up to 20 by merely changing the range tubes or range adjustments.