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Chelmsford Amateur Radio Society Advanced Course (10) Measurements Part-3 - Oscilloscopes. Oscilloscopes. Oscilloscopes can be used for Measuring DC voltages Measuring amplitude Measuring waveform period and frequency Checking waveforms Oscilloscopes contain A CRT or LCD display screen
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Chelmsford Amateur Radio Society Advanced Course(10) MeasurementsPart-3 - Oscilloscopes
Oscilloscopes • Oscilloscopes can be used for • Measuring DC voltages • Measuring amplitude • Measuring waveform period and frequency • Checking waveforms • Oscilloscopes contain • A CRT or LCD display screen • A horizontal timebase • A vertical deflection input (or two) • A timebase trigger
Oscilloscope Controls Y-axis X-axis Focus Vertical gain (V/div) Y input Horizontal timebase (ms/div) Brightness
Measuring Amplitude • Check variable controls are as “cal” • Obtain a large trace • Read the pk-pk amplitude in divisions. • Read the vertical gain (volts/division) • Calculate the pk-pk voltage • The amplitude is half the pk-pk value • The RMS voltage is amplitude x 0.707
1 2 3 4 5 Measuring Frequency • Check variable controls are as “cal” • Display a suitable number of cycles (say 5) • Read the total divisions for the cycles • Calculate divisions for 1 cycle • Read timebase setting (ms/division) • Calculate period in seconds • Calculate: Frequency = 1 / Period
Trimmer Oscilloscope Probes • Scope probes reduce input capacitance and divide voltage, usually by 10. • This means you must remember to multiply voltage readings by 10. • All probes must be adjusted to match the ’scope by connecting to ‘probe cal’ point and tweaking for a level-topped square wave.