| ??? 09/27/09 13:18 Modified: 09/27/09 13:20 Read: times |
#169195 - Zero-crossing doesn't always work well Responding to: ???'s previous message |
But a zero-crossing detector can get into troubles with some types of loads - remember that the current wave may not be even close to a sine wave - just look with a scope what happens when you use a rectifier (possibly not even full bridge) together with a capacitor.
And if the OP wants to compute the power factor, he will just have to integrate the voltage and current curves anyway, since the phase angle is only meaningful for pure wave forms. You would still present the power factor as "cos phi" but there would not be a true phi. Just a numeric ratio between W and VA. The next thing here is that to measure the voltage, the peak voltage and the rms voltage can differ alot if there is noise. That is one more reason for letting the processor make many samples and compute the voltage and current. |
| Topic | Author | Date |
| Power Factor Meter using 8052 | 01/01/70 00:00 | |
| The clue is in the names? | 01/01/70 00:00 | |
| Phase | 01/01/70 00:00 | |
| Is that true? | 01/01/70 00:00 | |
| Extra device? | 01/01/70 00:00 | |
| Extra device | 01/01/70 00:00 | |
| Zero-crossing doesn't always work well | 01/01/70 00:00 | |
| momentaneous ?! | 01/01/70 00:00 | |
| You sure? | 01/01/70 00:00 | |
| Definitions | 01/01/70 00:00 | |
| But instantly or instantaneously is actually something else. | 01/01/70 00:00 | |
| Common abuse | 01/01/70 00:00 | |
| Like | 01/01/70 00:00 | |
| Be fast | 01/01/70 00:00 | |
| OED | 01/01/70 00:00 | |
| Citation, please? | 01/01/70 00:00 | |
| Ah but | 01/01/70 00:00 | |
I see what you mean, Steve | 01/01/70 00:00 | |
| I wouldn't rely on the www for language and definitions | 01/01/70 00:00 |