Instrumentation and Measurement Sensors
Questions covering various types of measurement sensors and instrumentation including LVDTs, Hall effect sensors, thermistors, strain gauges, accelerometers, pyrometers, spectrum analyzers, potentiometers, and load cells.
Questions
An LVDT produces an rms output voltage of 2.6 V for displacement of 0.4 micrometer. Calculate the sensitivity of the LVDT.
- 0.15 V/micrometer
- 5.6 V/micrometer
- 6.5 V/micrometer
- 1.54 V/micrometer
A Hall effect element used for measuring magnetic field strength gives an output voltage of 10.5 mV. The element is made of silicon and is 2.5 mm thick and carries a current of a 4 A. The Hall coefficient is 4.1 x 10-6 Vm/A-wb/m2. Calculate the magnetic field strength.
- 1.6 Wb/m2
- 2.6 Wb/m2
- 0.63 Wb/m2
- 4.7 Wb/m2
Which of the following statements is incorrect about thermistors?
- Their name is derived from thermally sensitive resistors
- With high positive temperature coefficient, they behave as thermistors
- They are more sensitive than platinum resistance thermometers
- They have a non-linear resistance temperature relation
A strain gauge has a resistance of 120 ohm and gauge factor of 2. This strain gauge is connected in series with a ballast resistance of 120 ohm across a 6 V supply. Determine the voltage sensitivity of the circuit when the gauge is subjected to pressure of 240 MN/m2. The modulus of elasticity is 200 GN/m2.
- 5 volts per unit strain
- 48 volts per unit strain
- 1.98 volts per unit strain
- 3 volts per unit strain
An acceleration has a seismic mass of 0.06 kg and a spring constant of 4500 N/m. Maximum mass displacement is + - 0.025 m (before mass hits the top). Determine maximum measurable acceleration and natural frequency.
- 1275 m/s; 60 Hz
- 1875 Hz; 44 m/s
- 1875 m/s; 44 Hz
- 4113 m/s; 60 Hz
The temperature of a hot body, when measured by radiation pyrometer, is found to be 2450 deg. celsius assuming a surface emissivity of 0.85. Later on, it was found that the true surface emissivity is 0.78. Determine the actual temperature and error in temperature measurement.
- 2509 deg. celsius; - 59 deg. celsius
- 2509 deg. celsius; - 72 deg. celsius
- 3000 deg. celsius; - 60 deg. celsius
- 3490 deg. celsius; - 60 deg. celsius
What is the minimum detectable signal of a spectrum analyser with a noise figure of 20db using a 1KHz, 3db filter?
- - 124 dbm
- - 120 dbm
- - 144 dbm
- - 94
A linear resistance potentiometer is 50 mm long and is uniformly wound with a wire of total resistance 5000 ohm. Under normal conditions, the slider is at the centre of the potentiometer. Determine linear displacement when the resistance of the pot, as measured by the Wheatstone bridge is 1850 ohm. If it is possible to measure the value of 5 ohm resistance with the above arrangement, determine the resolution of pot in mm.
- 4.5 mm and 0.5 mm
- 6.5 mm and 0.05 mm
- 65 km and 0.05 mm
- 6.5 mm and 0.005 mm
Choose a pot that has the greatest possible sensitivity and meets the non linearity requirements of 2 percent (max) from available pots having a thermal rating of 5 watts and resistance ranging from 200 ohm to 5000 ohm in steps of 50 ohm. The output of the pot is to be measured with a device of 4000 ohm input resistance. Determine maximum excitation voltage that can be employed with this pot?
- 57 V
- 300 V
- 100 V
- 50 V
A load cell consists of a solid cylinder(steel) of 30 mm diameter with four strain gauges bonded to it in Poisson’s arrangement and connected into the four arms of a wheatstone bridge. The gauges are 200 ohm each with a gauge factor of 2.0. Determine the sensitivity of the load cell when load applied to the cell is 2000kg and voltage applied to the bridge is 12 V, the modulus of elasticity of steel is 200 GN/m2 and Poisson’s ratio = 0.295.
- 9.16 x 10-6
- 10
- 9.16 x 106
- 8.23 x 106