Industrial Instruments N5 — Memo
April 2020 — N5 — Industrial Instruments
N5
2020
Nated Engineering
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Q1— Section header —
1.1• The large pipe carries a greater volumetric rate of water flow than the small pipe. • Since the vortex-shedding frequency is proportional to the fluid velocity, the flow velocities in both cases must be the same (given identical bluff
1.2• Primary device or measuring unit • Secondary device or recording unit (2)2
1.3• Gravity • Pump (2) [10]10
Q2— Section header —
2.1Q = V 1 A 1 = V 2 A 2 2,21( ) = V 2 2,21( ) = V 2 ( -3 0,0141 = 2,827 × 10 V 2 V 2 = 4,988 m/s (6)6
2.22.2.1 (6) Copyright reserved Please turn over MARKING GUIDELINE -3- INDUSTRIAL INSTRUMENTS N5
2.2.2Advantages : • No moving parts • Low-pressure losses • High accuracy Disadvantages: • Expensive • In-mounting requirement • Not accurate in slurry application (3 + 3) (6)6
2.2.3(6) [24] TOTAL SECTION A: 34 SECTION B: DENSITY, HUMIDITY AND VISCOSITY24
Q3— Section header —
3.1• In the displacement meter liquid flows continuously through the displacer chamber. • An upward force acts on the balance beam because of the volume of liquid displaced by the float. • A pneumatic system balances this upward force and transmits a signal
3.2Newtonian fluids: When fluids are deformed by strain the ratio between shear rate and shear stress will be a constant value. Non-Newtonian fluids: When fluids are deformed by strain the ratio between
3.3• The instrument should not be mounted near doors or other openings where it will be exposed to artificial drafts. Flush mounting on the panel should be avoided because the atmosphere in the back of the panel is
3.43.4.1 Rs “s” Rx Ry Rm R1 R2 CONDUCTIVITY CELL R3 AC VOLTAGE (6)6
3.4.2Reference conductivity-cell sampling which is a solution of typical composition and subject the same temperature as the measuring cell. Bring a thermistor in contact with the process fluid and
Q4— Section header —
4.1A screened glass electrode can be used and the electrode assembly must be located at a point where the residual field is smallest. (3)3
4.2The main purpose is to complete the electrical circuit with the glass-membrane electrode. It must provide a stable potential that is relatively invariable, despite changes in either the chemical composition or
4.3Hydroxyl ions (2)2
4.4For a glass-membrane electrode to function, both surfaces of the membrane must be hydrated. Hydration occurs by absorption of water by the membrane interface in contact with the solution. There is also an exchange of univalent
Q5— Section header —
5.1• All four bellows will have the same pressure. • The motion pin will be on its true centreline. • There will be no control actions generated. (3)3
5.2• The output will increase by 10 kPa if the gain is direct. • Should the gain be indirect the output will decrease by 10 kPa. • This would be due to the pressure increasing in the process bellows while
5.3100% Pb = 100/gain (1)1
5.4By swivelling the gain adjustment dial directly to reverse (1)1
5.5• When the integral action is marke d in repeats per minute it indicate s that the integral will repeat per minute • When marked in minutes per repeat it indicates the time to repeat the proportional band (3)3
5.6• The derivative action time taken for proportional action to repeat the derivative action for a ramp change • Most controllers do not produce the true theoretical output due to interactions between the control actions and are therefore called
5.7Advantages of a live zero-based signal: • Difference between power on and power off • See movement from zero in both directions • Two-wire system (no high voltage in hazardous area) Advantage of a zero-based signal controller:
Mark Allocation
Total100 marks
Sections10 + 24 + 28 + 18 + 20 = 100 marks
Per-question sum100 marks
Paper information
TitleMemo
SubjectIndustrial Instruments
LevelN5
Document typeNated Engineering
Year2020
MonthApril
Pages6
Downloads3
Examination context
Decade2020s
Years ago6y
SeasonAutumn (SH)
Start dayWednesday
Exam periodApril 2020
Days since exam2,385
About Industrial Instruments examination preparation
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For stronger examination practice, complete the paper without unnecessary interruptions and keep track of the questions that take the most time. Afterwards, review the memorandum and separate knowledge gaps from mistakes caused by interpretation, calculation, structure, or examination technique.
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A practical revision approach
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