Electronic Measuring Instruments and Testing
This domain tests practical measurement and workshop technique: multimeter use, CRO/oscilloscope reading, signal generators, soldering, and PCB practice.
Core facts
- A multimeter selects voltage, current, resistance, continuity, or diode test. Current ranges are connected in series; voltage ranges in parallel.
- A CRO displays voltage on the vertical axis and time on the horizontal axis. Read peak-to-peak voltage from volts/div and period from time/div.
- A signal generator supplies test waveforms such as sine, square, and triangle at adjustable frequency and amplitude.
- Good soldering uses a clean, tinned iron, rosin flux, and a short contact time. A cold joint looks dull and granular.
Worked example
A CRO trace is 5 vertical divisions peak-to-peak with 2 V/div, and one cycle is 4 horizontal divisions with 1 ms/div. Peak-to-peak voltage is 5 × 2 = 10 V. Period is 4 × 1 ms = 4 ms, so frequency is 1/0.004 = 250 Hz. If the probe is a ×10 type and the display is not corrected, the actual voltage is 10 × 10 = 100 V peak-to-peak. Always check probe attenuation before recording a value.
Traps
- Measuring resistance in a live circuit; this gives wrong readings and may damage the meter.
- Connecting an ammeter in parallel, which can blow its fuse.
- Ignoring CRO probe attenuation and trigger settings.
- Overheating a PCB pad or making a solder bridge between adjacent tracks.