Why I have to use 4channels at the same time ? Can you give me an example please ?
Very useful when you have it. After getting used with 4 channels, you'll never want to go back to 2 again. Two is not enough, especially when working with digital signals.
Examples:
- Repeatedly switching one probe between different measuring points can become a tedious task (while tuning a parameter then checking the tuning results in more than 2 points), the more probes you have, the better.
- Automated testing/measuring, this shows up only if you have a production line (plug all the probes, then start a program to check the functionality in 4 points at once)
- Proper SPI decoding is not even possible without 4 channels
- Measuring a signal at input and output simultaneously, for both current and voltage (to improvise a two ports VNA - Vector Network Analyzer)
- Measure phase between more than 2 signals (e.g. for an SDR, see the incoming signal and the I and Q outputs, and a 4'th probe to synchronize with the signal generator)
- Simply having more probes and channels is better than missing them (as a redundancy in case of failure, more probes mean less wearing for each probe, or simply because being too lazy to keep switching the probes between different measuring points
)
- Data logging from more than 2 points (the oscilloscope can be connected to a computer, and measure/log signals for a very long time, e.g. I spied for over a week on the fridge's signals for compressor, defrost, fan and door switch, in order to see why sometimes the compressor was not working: found out that only during some very hot days the door switch contacts become wiggly, so the fridge thought somebody is keeping the door open and refused to start the compressor)
- As a general rule, as soon as you'll have something extra, you'll find a usage for it