List of top Sensors and Industrial Instrumentation Questions asked in GATE Instrumentation Engineering

The resistance of a thermistor is measured to be 2.25 k$\Omega$ at 30 Â°C and 1.17 k$\Omega$ at 60 Â°C. Its material constant $ \beta $ is ________ K (rounded off to two decimal places).

An air filled parallel plate electrostatic actuator is shown in the figure. The area of each capacitor plate is $100 \mu m \times 100 \mu m$. The distance between the plates $d_0 = 1 \mu m$ when both the capacitor charge and spring restoring force are zero as shown in Figure (a). A linear spring of constant $k = 0.01 N/m$ is connected to the movable plate. When charge is supplied to the capacitor using a current source, the top plate moves as shown in Figure (b). The magnitude of minimum charge (Q) required to momentarily close the gap between the plates is ________ $\times 10^{-14}$ C (rounded off to two decimal places).
Note: Assume a full range of motion is possible for the top plate and there is no fringe capacitance. The permittivity of free space is $\epsilon_0 = 8.85 \times 10^{-12}$ F/m and relative permittivity of air ($\epsilon_r$) is 1.

A metallic strain-gauge (SG) with resistance $ R_{SG} $ is connected as shown in the figure, where $ R_{L1} $, $ R_{L2} $, $ R_{L3} $ represent the lead wire resistances. The SG has a gauge factor of 2 and nominal resistance $ R_N $ of $ 125 \, \Omega $. When the SG is subjected to a tensile strain of $ 2 \times 10^{-3} $, the resulting change in $ R_{SG} $ is $ \Delta R $. The $ \Delta R $ value is measured as $ \Delta R_{MEAS} = R_{EQ2} - R_{EQ1} $. The $ R_{EQ1} $ and $ R_{EQ2} $ are the equivalent resistances measured between the terminals 1 and 2, and terminals 2 and 3, respectively.
If $ R_{L1} = R_{L2} = 5 \, \Omega $, and $ R_{L3} = 4.95 \, \Omega $, the measured value of tensile strain is ________ $ \times 10^{-3} $ (rounded off to two decimal places).

Power consumed by a three-phase balanced load is measured using two-wattmeter method. The per-phase average power drawn by the load is 30 kW at $ \frac{\sqrt{3}}{2} $ lagging power factor. The readings of the wattmeters will be

A 60 V DC source with an internal resistance $R_{int} = 0.5 \, \Omega$ is connected through a switch to a pair of infinitely long rails separated by $l = 1$ m as shown in the figure. The rails are placed in a constant, uniform magnetic field of flux density $B = 0.5$ T, directed into the page. A conducting bar placed on these rails is free to move. At the instant of closing the switch, the force induced on the bar is

An oscilloscope has an input resistance of $ 1\, {M}\Omega $. A 10X passive attenuating probe is connected to it to increase the input voltage range as well as the effective input resistance. The effective input resistance, in $ {M}\Omega $, seen into the probe tip is:

Match the following sensors with their most suitable applications.

In a single-phase AC circuit, the power consumed by load resistance $R_L$ for an excitation $V_S$ is measured by a wattmeter. The same wattmeter is connected in two different topologies, Topology-A and Topology-B, as shown in the figure. Different branch currents and voltage drops are also marked in the figure. Among the following options, the condition that ensures low error in the wattmeter reading for both the topologies is

In the force transducer shown in Figure (a), four identical strain gauges S1, S2, S3, and S4 are mounted on a cantilever at equal distance from its base. S1 and S2 are mounted on the top surface and S3 and S4 are mounted on the bottom surface, as shown in the Figure (a). These strain gauges are to be connected to form a Wheatstone bridge consisting of four arms A, B, C, and D, as shown in the Figure (b). From the following options, the correct order to maximize the measurement sensitivity is

The primary coil of a linear variable differential transformer (LVDT) is supplied with AC voltage as shown in the figure. The secondary coils are connected in series opposition and the output is measured using a true RMS voltmeter. The displacement $x$ of the core is indicated in mm on a linear scale. At the null position $x = 0$, the voltmeter reads 0 V. If the voltmeter reads 0.2 V for a displacement of $x = +2$ mm, then for a displacement of $x = -3$ mm, the voltmeter reading, in V, is:

The working of the hand-held metal detector most widely used by security personnel for human frisking is based on the principle of: