Choose the most correct answer

• (() False

LVDT is a normal type of transducer. The main function of thisis to convert the rectangular movement of an object to theequivalent electrical signal. LVDT is used to calculatedisplacement and works on the transformer principle.

An LVDT measures displacement by associating a specific signalvalue for any given position of the core. This association of asignal value to a position occurs through electromagnetic couplingof an AC excitation signal on the primary winding to the core andback to the secondary windings. The position of the core determineshow tightly the signal of the primary coil is coupled to each ofthe secondary coils. The two secondary coils are series-opposed,which means wound in series but in opposite directions. Thisresults in the two signals on each secondary being 180 deg out ofphase. Therefore phase of the output signal determines directionand its amplitude, distance.

An LVDT is incorporated into a pressure measurement device byconnecting the core of the LVDT to the centre of a pressure sensingdiaphragm, so that any flexing of the diaphragm due to changes inpressure will be detected as a position change by the LVDT.

• (a) True,

In reality, accelerometers have long been used to measuredisplacement. The acceleration signal coming from the sensingcrystal is first conditioned, that is, made readable by subsequentmeasurement amplifiers. Once amplified to an acceptable level, thesignal is passed through a doubleintegrator, which is similar in design to a lowpass filter. This AC signal, representative of the machinedisplacement, is fed into the averaging circuit, converted to therequired DC value, and passed out of the sensor as a 4-20 mAsignal. Now, data screens for process control machinery can becalibrated in mils displacement in the same manner that vibrationvelocity signals have been recorded with previous generationsensors.

• (a) True,

Since the time of ultrasonic wave propagation varies inproportion to the frequency generated by the vortexes, it followsthat the flowrate can be measured by detecting changes in the timeof ultrasonic wave propagation.The ultrasonic sensors, being installed outside the conduit of theflowmeter body, allow users to performmeasurement tasks without having to touch the fluid under test. Thesensing flowmeter offers greatervibration immunity, offering a host of features, including highsensitivity.

• Option (c) =0.29 %

An estimate of the overall instrument error is made by combiningthe estimates of all known errors into a term called the instrumentuncertainty. The estimate is computed from the square root of thesum ofthe squares of all known uncertainty values,