HKIE Professional Assessment - Electronics Discipline cheat sheet

IEEE 315/ANSI Y32.2 graphic symbols and IEC 60617 symbols are the two reference symbol sets; Hong Kong submissions commonly accept either but must not mix them within one drawing set.

Preferred number series E6/E12/E24/E48/E96 give component tolerances of roughly ±20/±10/±5/±2/±1 percent; a resistor marked 4R7 is 4.7 Ω and 103 on an SMD body means 10 kΩ.

IPC-A-610 Class 1/2/3 defines solder-joint acceptance: Class 3 (high reliability) limits fillet voids and requires full barrel fill on through-hole unless the part is exempted.

IPC-2221 creepage/clearance: for external uncoated conductors at 31–50 V DC, minimum spacing is about 0.6 mm (B4 column); spacing scales upward with voltage and altitude.

Ingress protection IPXY: first digit is solids (0–6), second is liquids (0–9K); IP67 is dust-tight plus temporary immersion, IPX4 is splash-only.

MTBF is the reciprocal of failure rate λ for a constant-rate model; MTBF = 1/λ, and reliability over time t is R(t) = e^(−λt) = e^(−t/MTBF).

Standard 19-inch rack: 1U = 44.45 mm; usable panel width is 482.6 mm with 465 mm between mounting flanges.

Thermal: T_j = T_a + P·R_θja; forced-air or heatsink design reduces R_θja, and derating typically keeps T_j at least 20 °C below rated maximum.

Ideal op-amp rules: no input current, V+ = V− under negative feedback; inverting gain = −R_f/R_in, non-inverting gain = 1 + R_f/R_g.

First-order RC step response: v(t) = V_final + (V_initial − V_final)e^(−t/τ), τ = RC; 1τ reaches 63.2 %, 5τ is treated as settled.

BJT bias: V_BE ≈ 0.7 V (0.6–0.75 V depending on current); I_C = βI_B, and thermal stability requires an emitter resistor so I_C ≈ (V_B − 0.7)/R_E when β is large.

MOSFET saturation condition: V_DS > V_GS − V_th; in saturation I_D ≈ ½μC_ox(W/L)(V_GS − V_th)²(1 + λV_DS).

Barkhausen criterion for oscillation: loop gain magnitude = 1 and loop phase = 0° (or 360°) at the oscillation frequency; a gain margin above 1 starts oscillation and a nonlinearity limits amplitude.

Second-order resonance: f_0 = 1/(2π√(LC)); Q = (1/R)√(L/C) for a parallel RLC, and bandwidth = f_0/Q.

Nyquist sampling requires f_s > 2·f_max; an anti-alias filter must precede the sampler, since aliasing is irreversible after conversion.

PCB transmission-line rule of thumb: treat a trace as a transmission line when length exceeds about one-sixth of the wavelength of the highest significant frequency; microstrip Z_0 falls as trace width rises.

Shannon capacity C = B·log2(1 + S/N); doubling bandwidth doubles capacity, but each extra 3 dB of SNR gives only a diminishing log increment.

Friis noise figure for cascaded stages: F_total = F_1 + (F_2 − 1)/G_1 + (F_3 − 1)/(G_1G_2) + …; the first stage dominates, so a low-noise amplifier goes first.

Link budget in dB: P_rx = P_tx + G_tx + G_rx − L_path − L_misc; free-space path loss FSPL(dB) = 32.45 + 20log10(f_MHz) + 20log10(d_km).

AWGN bit error rate: coherent BPSK/QPSK is Q(√(2E_b/N_0)); in dB, E_b/N_0 = C/N_0 − 10log10(R_b).

OFDM subcarrier spacing Δf = B/N and symbol length T_u = 1/Δf; the cyclic prefix must exceed the channel delay spread to prevent ISI.

Embedded memory map: vector table at reset address, stack grows downward on ARM Cortex-M, and NVIC priority is lower number = higher urgency.

RTOS scheduling: rate-monotonic assigns higher priority to shorter periods; utilisation bound for n tasks is n(2^(1/n) − 1), about 69 % for large n.

UART framing is start bit, 5–9 data bits, optional parity, 1–2 stop bits; baud rate error must stay under about 2–3 % for reliable reception.

Earned value: CV = EV − AC, SV = EV − PV, CPI = EV/AC, SPI = EV/PV; CPI < 1 means cost overrun.

Critical path is the longest-duration path through the network; total float = LS − ES = LF − EF, and zero float marks the critical path.

PERT expected duration t_E = (O + 4M + P)/6 with standard deviation (P − O)/6.

Risk exposure = probability × impact; mitigation reduces probability, contingency reduces impact, and acceptance is valid only for low exposure.

Configuration management baselines: functional, allocated and product baselines; any change after a baseline requires formal change control.

Quality cost categories: prevention, appraisal, internal failure and external failure; external failure is the most expensive per defect.

Design review gates typically run concept, preliminary (PDR), critical (CDR) and production readiness; PDR freezes the architecture, CDR freezes the detailed design.

Team growth: Brooks's law states adding people to a late software project makes it later because of communication overhead and ramp-up.

HKIE Code of Conduct core duties: competence, honesty, public safety and health, confidentiality, and avoidance of conflicts of interest; a declared conflict must be managed, not merely disclosed.

Under a lump-sum contract the contractor bears quantity risk; under a remeasurement (BQ) contract the employer pays for actual measured quantities at the tendered rates.

Variation orders must be issued by the authorised person under the contract; verbal instructions should be confirmed in writing within the contract's stated period.

Hong Kong construction contracts commonly use the HKIA/HKIS Standard Form; the Airport Core Programme and latter government works use the GCC (General Conditions of Contract for Civil Engineering Works).

Retention money is typically 5–10 % of each payment, capped at 5 % of contract sum, released in two halves at practical completion and at the end of the defects liability period.

Professional indemnity and negligence: a designer owes a duty of care to persons foreseeably affected; contributory negligence and limitation periods (6 years in contract, 6 years in tort in Hong Kong) affect exposure.

Whistleblowing duty: where public safety is at material risk, the engineer must escalate internally first and may report to the regulator (e.g. EMSD, BD) if not resolved.

Electricity Ordinance (Cap. 406) and its Regulations govern electrical installation, supply and use; the Electrical Products (Safety) Regulation (Cap. 406G) covers household electrical product safety.

Only a registered electrical worker of the appropriate grade (A, B, C, H, or R for special classes) may carry out or supervise fixed electrical installation work under Cap. 406.

EMSD requires periodic inspection, testing and certification (WR1/WR2 forms) of fixed installations; the interval depends on the installation's maximum demand.

Buildings Energy Efficiency Ordinance (Cap. 610) mandates energy audits and retro-commissioning for prescribed central building services installations in prescribed buildings.

Factories and Industrial Undertakings Ordinance (Cap. 59) and its subsidiary regulations impose general duties on employers and persons in control of premises; the Occupational Safety and Health Ordinance (Cap. 509) covers non-industrial workplaces.

Waste Disposal Ordinance (Cap. 354) controls chemical and electronic waste; the Producer Responsibility Scheme on Waste Electrical and Electronic Equipment (WPRS) regulates disposal of regulated WEEE.

Radio communications and wireless devices fall under the Telecommunications Ordinance (Cap. 106) and the Radio Communications Ordinance (Cap. 106 subsidiary regulations); type approval and licensing come from OFCA.

Electrical safety signs and lockout/tagout: Hong Kong practice follows the Factories and Industrial Undertakings (Electricity) Regulations, requiring isolation, proving dead, and earthing before work on or near live conductors.