HKIE Professional Assessment - Electronics Discipline flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

IPC-A-610 Class 3

The highest-reliability acceptance class for electronic assemblies. It permits the least solder-joint voiding and demands full plated-through-hole barrel fill, and is used where continued performance is critical.

MTBF from failure rate

For a constant failure rate lambda, MTBF equals one over lambda, and reliability at time t is exp(-t/MTBF). Doubling MTBF halves the failure probability over a fixed interval.

IP rating digits

The first digit rates protection against solid objects from 0 to 6, where 6 is dust-tight. The second rates water from 0 to 9K, where 7 is temporary immersion and 8 is continuous immersion.

E96 preferred values

A preferred-number series with 96 values per decade, giving roughly one percent spacing. A resistor marked 103 in E96-style three-digit code reads as 10 kilohm.

Junction temperature equation

Junction temperature equals ambient temperature plus dissipated power times junction-to-ambient thermal resistance. Reducing thermal resistance by heatsinking or airflow lowers the junction temperature for the same dissipation.

Creepage versus clearance

Clearance is the shortest distance through air between conductors; creepage is the distance along an insulating surface. Creepage is always at least clearance and grows with pollution degree.

Inverting amplifier gain

With an ideal op-amp under negative feedback, the inverting configuration gives gain of minus feedback resistance over input resistance. The virtual-earth node sits at the non-inverting input potential.

Barkhausen oscillation criterion

Sustained oscillation needs loop gain magnitude of one and total loop phase of zero or 360 degrees at the oscillation frequency. A nonlinear element must limit amplitude growth.

RC time constant settling

For a first-order RC circuit, the time constant is the product of resistance and capacitance. Output reaches 63.2 percent of the step in one time constant and is treated as settled after five.

MOSFET saturation condition

An enhancement MOSFET is in saturation when drain-source voltage exceeds gate-source voltage minus threshold. There, drain current depends mainly on gate overdrive and only weakly on drain voltage.

Parallel RLC quality factor

For a parallel RLC network, resonant frequency is one over two pi root LC, and quality factor is one over resistance times root L over C. Bandwidth equals resonant frequency divided by Q.

Nyquist sampling theorem

Sampling must exceed twice the highest signal frequency to allow reconstruction. An analogue anti-alias filter before the converter is essential because aliasing cannot be removed afterwards.

Common-emitter bias rule

A silicon bipolar transistor drops about 0.7 volts base-to-emitter when conducting. With a large current gain and an emitter resistor, collector current is set by base voltage minus 0.7 over emitter resistance.

Shannon channel capacity

Capacity in bits per second equals bandwidth times log base two of one plus signal-to-noise ratio. Capacity grows linearly with bandwidth but only logarithmically with signal power.

Friis cascade noise figure

Total noise factor equals the first stage factor plus each later stage factor minus one, divided by the product of preceding gains. Low-noise, high-gain first stages therefore dominate receiver performance.

Free-space path loss

Free-space loss in decibels is 32.45 plus 20 log frequency in megahertz plus 20 log distance in kilometres. Loss rises 6 dB per doubling of distance or frequency.

OFDM cyclic prefix role

A cyclic prefix copies the tail of each OFDM symbol to its front. Provided it exceeds the channel delay spread, inter-symbol interference is absorbed and subcarriers stay orthogonal.

Rate-monotonic scheduling

A fixed-priority real-time policy assigning shorter periods higher priority. A set of n periodic tasks is guaranteed schedulable if utilisation stays below n times the nth root of two minus one.

UART frame structure

Serial asynchronous framing begins with a start bit, carries five to nine data bits, optional parity, then one or two stop bits. Baud-rate mismatch above about two percent causes framing errors.

Earned value cost index

Cost performance index equals earned value divided by actual cost. A value below one indicates cost overrun, while schedule performance index compares earned value to planned value.

Critical path total float

Total float equals late start minus early start, or late finish minus early finish. Activities on the critical path have zero float and any delay there delays the project completion.

PERT expected duration

The three-point estimate weights optimistic, most likely and pessimistic durations as one, four and one parts, divided by six. Standard deviation is pessimistic minus optimistic, divided by six.

Risk exposure formula

Risk exposure is the product of probability and impact. Mitigation lowers probability, contingency planning lowers impact, and simple acceptance suits only low-exposure risks.

Brooks's law

Adding staff to a late software project tends to delay it further. Communication paths grow roughly with the square of team size, and new members need ramp-up time.

Lump-sum quantity risk

In a lump-sum contract the contractor prices the works and bears the risk of quantity error. In a remeasurement contract the employer pays measured quantities at tendered rates.

Retention money cap

Hong Kong works contracts commonly withhold five to ten percent of each payment, capped near five percent of the contract sum. Half is released at practical completion and half after the defects period.

Conflict of interest duty

The HKIE code requires members to avoid conflicts and to declare any that arise. Disclosure alone is insufficient; the engineer must remove themselves from decisions where impartiality is compromised.

Variation instruction authority

Only the person empowered by the contract may order a variation. Verbal instructions should be confirmed in writing within the period the contract allows, or the right to payment may be lost.

Electricity Ordinance Cap 406

This Hong Kong ordinance and its regulations govern electrical installation, supply and use. It establishes registered electrical worker grades and periodic inspection and testing requirements.

Registered electrical worker grades

Grades A, B and C license work on installations of increasing maximum demand, while grade H covers higher-voltage work and grade R covers specialised categories. Supervision rules follow the grade held.

Cap 509 occupational safety

The Occupational Safety and Health Ordinance imposes general duties on employers and persons in control of premises. It covers non-industrial workplaces such as offices, shops and schools.

WEEE producer responsibility

Hong Kong's producer responsibility scheme regulates disposal of regulated waste electrical and electronic equipment. It controls import, supply and recycling of items such as air conditioners and refrigerators.

Lockout and prove dead

Before work on or near conductors, isolate the supply, lock and tag the isolator, prove the tester, test for dead at the point of work, and earth where required.