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SMD Trimmer Potentiometers — Why They Are “Fixed” After a Single Factory Adjustment IEC 60393-6-1:2003 specifies SMD trimmer potentiometer requirements. SMD trimmers are used for one-time factory calibration — amplifier offset nulling, sensor sensitivity calibration — then typically never adjusted…
Your Electricity Meter From “Spinning Disc” to “Digital Screen” — 50 Years of Meter Evolution IEC 60387:1992 specifies AC electricity meter requirements. Traditional induction meters (spinning disc) use the alternating magnetic field from current and voltage coils to drive an…
PTC and NTC — Opposite R-T Curves Covering Everything From Temperature Sensing to Circuit Protection IEC 60388-1:1972 specifies thermistor requirements. NTC (Negative Temperature Coefficient) — resistance decreases as temperature rises, used for precision temperature measurement (Steinhart-Hart equation). PTC (Positive Temperature…
Why Telephone Equipment Survives Lightning Strikes — PTC Thermistor Protection IEC 60389-1:1972 specifies telecom equipment thermistor requirements. Telephone lines (48VDC feed) may suffer lightning-induced overvoltage and power-line cross (>220VAC). A PTC thermistor in series with the SLIC has very low…
Why Any Knob Fits Any Potentiometer — Shaft End and Bushing Standardization IEC 60390:1972 specifies shaft ends and bushings for manual electronic components (potentiometers, encoders, rotary switches). The 6 mm (¼”) shaft diameter with D-cut or slotted design is the…
The “Dictionary” of the PCB Industry — Standardized Definitions for Pads, Vias, and Solder Mask IEC 60356:1971 is an early printed circuit board terminology standard. Though later supplemented by the more comprehensive IEC 60194 series, its fundamental term system (Land/Pad,…
Waveguide Flanges — How Mechanical Precision Determines Electrical Performance IEC 60374:1971 specifies waveguide and waveguide component flange standardized dimensions. Flange flatness (typically ≤0.01 mm) and alignment pin precision directly determine the connection VSWR — every 0.1 mm increase in flange…
Storage vs. Instantaneous Water Heaters — Why Efficiency Numbers Cannot Be Directly Compared IEC 60379:1987 specifies household electric water heater performance measurement. Storage heater efficiency is dominated by standby heat loss — an 80L tank loses 1.5–2.5 kWh Instantaneous heaters…
“Wow and Flutter” — The Most Annoying Sound Distortion of the Analogue Era and Its Measurement IEC 60386:1972 specifies magnetic tape recorder speed stability measurement. Flutter (>10 Hz) and Wow (
The “Safety Bible” Behind Every Appliance — IEC 60335-1 Seven Safety Dimensions IEC 60335-1 is the household and similar appliance safety general requirements standard — the benchmark for safety certification of hundreds of billions of appliances globally. It covers electric…
