Process Instrumentation Basics interview questions
27 real Process Instrumentation Basics questions from the Chemical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is Orifice plate flow measurement?
Junior
A.ratio of maximum to minimum flow a meter reads within stated accuracy, about 4:1 for orifice plates against 20:1 or more for Coriolis
B.differential pressure across a sharp-edged restriction where flow is proportional to the square root of DP, so the transmitter needs square-root extraction
C.vibrating tube whose phase shift between inlet and outlet sensors is proportional to mass flow, also giving density and needing no straight run
D.platinum resistance element reading 100 Ω at 0 °C and about 0.385 Ω per °C, more accurate and linear than a thermocouple but limited to about 600 °C
2. Which term means: "differential pressure across a sharp-edged restriction where flow is proportional to the square root of DP, so the transmitter needs square-root extraction"?
A.Orifice plate flow measurement — platinum resistance element reading 100 Ω at 0 °C and about 0.385 Ω per °C, more accurate and linear than a thermocouple but limited to about 600 °C
B.Orifice plate flow measurement — hydrostatic head between bottom and top taps gives liquid level; a wet leg on the low side requires zero elevation or suppression
C.Orifice plate flow measurement — two dissimilar-metal junctions generating a Seebeck voltage proportional to temperature difference; K type (chromel-alumel) covers up to about 1200 °C
D.Orifice plate flow measurement — differential pressure across a sharp-edged restriction where flow is proportional to the square root of DP, so the transmitter needs square-root extraction
A.two dissimilar-metal junctions generating a Seebeck voltage proportional to temperature difference; K type (chromel-alumel) covers up to about 1200 °C
B.differential pressure across a sharp-edged restriction where flow is proportional to the square root of DP, so the transmitter needs square-root extraction
C.vibrating tube whose phase shift between inlet and outlet sensors is proportional to mass flow, also giving density and needing no straight run
D.ratio of maximum to minimum flow a meter reads within stated accuracy, about 4:1 for orifice plates against 20:1 or more for Coriolis
5. Which term means: "two dissimilar-metal junctions generating a Seebeck voltage proportional to temperature difference; K type (chromel-alumel) covers up to about 1200 °C"?
A.Thermocouple — differential pressure across a sharp-edged restriction where flow is proportional to the square root of DP, so the transmitter needs square-root extraction
B.Thermocouple — two dissimilar-metal junctions generating a Seebeck voltage proportional to temperature difference; K type (chromel-alumel) covers up to about 1200 °C
C.Thermocouple — platinum resistance element reading 100 Ω at 0 °C and about 0.385 Ω per °C, more accurate and linear than a thermocouple but limited to about 600 °C
D.Thermocouple — digital signal superimposed on the 4–20 mA loop so a handheld or DCS can read diagnostics and re-range the transmitter without rewiring
A.platinum resistance element reading 100 Ω at 0 °C and about 0.385 Ω per °C, more accurate and linear than a thermocouple but limited to about 600 °C
B.two dissimilar-metal junctions generating a Seebeck voltage proportional to temperature difference; K type (chromel-alumel) covers up to about 1200 °C
C.vibrating tube whose phase shift between inlet and outlet sensors is proportional to mass flow, also giving density and needing no straight run
D.digital signal superimposed on the 4–20 mA loop so a handheld or DCS can read diagnostics and re-range the transmitter without rewiring
8. Which term means: "platinum resistance element reading 100 Ω at 0 °C and about 0.385 Ω per °C, more accurate and linear than a thermocouple but limited to about 600 °C"?
A.Pt100 RTD — platinum resistance element reading 100 Ω at 0 °C and about 0.385 Ω per °C, more accurate and linear than a thermocouple but limited to about 600 °C
B.Pt100 RTD — two dissimilar-metal junctions generating a Seebeck voltage proportional to temperature difference; K type (chromel-alumel) covers up to about 1200 °C
C.Pt100 RTD — ratio of maximum to minimum flow a meter reads within stated accuracy, about 4:1 for orifice plates against 20:1 or more for Coriolis
D.Pt100 RTD — bluff body sheds vortices at a frequency proportional to velocity, well suited to steam and gas, but reads zero below a minimum Reynolds number
A.vibrating tube whose phase shift between inlet and outlet sensors is proportional to mass flow, also giving density and needing no straight run
B.standard analogue transmitter output where 4 mA is zero of range; the live zero lets a broken wire (0 mA) be distinguished from a true zero
C.differential pressure across a sharp-edged restriction where flow is proportional to the square root of DP, so the transmitter needs square-root extraction
D.hydrostatic head between bottom and top taps gives liquid level; a wet leg on the low side requires zero elevation or suppression
11. Which term means: "standard analogue transmitter output where 4 mA is zero of range; the live zero lets a broken wire (0 mA) be distinguished from a true zero"?
A.4–20 mA signal — two dissimilar-metal junctions generating a Seebeck voltage proportional to temperature difference; K type (chromel-alumel) covers up to about 1200 °C
B.4–20 mA signal — standard analogue transmitter output where 4 mA is zero of range; the live zero lets a broken wire (0 mA) be distinguished from a true zero
C.4–20 mA signal — ratio of maximum to minimum flow a meter reads within stated accuracy, about 4:1 for orifice plates against 20:1 or more for Coriolis
D.4–20 mA signal — vibrating tube whose phase shift between inlet and outlet sensors is proportional to mass flow, also giving density and needing no straight run
14. Which term means: "hydrostatic head between bottom and top taps gives liquid level; a wet leg on the low side requires zero elevation or suppression"?
A.DP level measurement — platinum resistance element reading 100 Ω at 0 °C and about 0.385 Ω per °C, more accurate and linear than a thermocouple but limited to about 600 °C
B.DP level measurement — differential pressure across a sharp-edged restriction where flow is proportional to the square root of DP, so the transmitter needs square-root extraction
C.DP level measurement — hydrostatic head between bottom and top taps gives liquid level; a wet leg on the low side requires zero elevation or suppression
D.DP level measurement — bluff body sheds vortices at a frequency proportional to velocity, well suited to steam and gas, but reads zero below a minimum Reynolds number
17. Which term means: "vibrating tube whose phase shift between inlet and outlet sensors is proportional to mass flow, also giving density and needing no straight run"?
A.Coriolis mass flow meter — two dissimilar-metal junctions generating a Seebeck voltage proportional to temperature difference; K type (chromel-alumel) covers up to about 1200 °C
B.Coriolis mass flow meter — hydrostatic head between bottom and top taps gives liquid level; a wet leg on the low side requires zero elevation or suppression
C.Coriolis mass flow meter — ratio of maximum to minimum flow a meter reads within stated accuracy, about 4:1 for orifice plates against 20:1 or more for Coriolis
D.Coriolis mass flow meter — vibrating tube whose phase shift between inlet and outlet sensors is proportional to mass flow, also giving density and needing no straight run
20. Which term means: "digital signal superimposed on the 4–20 mA loop so a handheld or DCS can read diagnostics and re-range the transmitter without rewiring"?
A.HART protocol — standard analogue transmitter output where 4 mA is zero of range; the live zero lets a broken wire (0 mA) be distinguished from a true zero
B.HART protocol — differential pressure across a sharp-edged restriction where flow is proportional to the square root of DP, so the transmitter needs square-root extraction
C.HART protocol — platinum resistance element reading 100 Ω at 0 °C and about 0.385 Ω per °C, more accurate and linear than a thermocouple but limited to about 600 °C
D.HART protocol — digital signal superimposed on the 4–20 mA loop so a handheld or DCS can read diagnostics and re-range the transmitter without rewiring
23. Which term means: "ratio of maximum to minimum flow a meter reads within stated accuracy, about 4:1 for orifice plates against 20:1 or more for Coriolis"?
A.Turndown ratio — ratio of maximum to minimum flow a meter reads within stated accuracy, about 4:1 for orifice plates against 20:1 or more for Coriolis
B.Turndown ratio — digital signal superimposed on the 4–20 mA loop so a handheld or DCS can read diagnostics and re-range the transmitter without rewiring
C.Turndown ratio — standard analogue transmitter output where 4 mA is zero of range; the live zero lets a broken wire (0 mA) be distinguished from a true zero
D.Turndown ratio — vibrating tube whose phase shift between inlet and outlet sensors is proportional to mass flow, also giving density and needing no straight run
A.bluff body sheds vortices at a frequency proportional to velocity, well suited to steam and gas, but reads zero below a minimum Reynolds number
B.platinum resistance element reading 100 Ω at 0 °C and about 0.385 Ω per °C, more accurate and linear than a thermocouple but limited to about 600 °C
C.vibrating tube whose phase shift between inlet and outlet sensors is proportional to mass flow, also giving density and needing no straight run
D.differential pressure across a sharp-edged restriction where flow is proportional to the square root of DP, so the transmitter needs square-root extraction
26. Which term means: "bluff body sheds vortices at a frequency proportional to velocity, well suited to steam and gas, but reads zero below a minimum Reynolds number"?
A.Vortex flow meter — hydrostatic head between bottom and top taps gives liquid level; a wet leg on the low side requires zero elevation or suppression
B.Vortex flow meter — bluff body sheds vortices at a frequency proportional to velocity, well suited to steam and gas, but reads zero below a minimum Reynolds number
C.Vortex flow meter — digital signal superimposed on the 4–20 mA loop so a handheld or DCS can read diagnostics and re-range the transmitter without rewiring
D.Vortex flow meter — two dissimilar-metal junctions generating a Seebeck voltage proportional to temperature difference; K type (chromel-alumel) covers up to about 1200 °C
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