1. Chelmsford Amateur Radio Society Advanced Course (10) Measurements Part-3 - Oscilloscopes

2. 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

3. Oscilloscope Controls
Y-axis
X-axis
Horizontal timebase (ms/div)
Y input
Vertical gain (V/div)
Focus
Brightness

4. 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

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

6. 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.
Trimmer