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I'm working on a project that is using ACS37800 for measuring current and voltage and for detecting zero-crossing.

However, there is some issues with the timing as the zero-crossing detection is off.

The ACS37800 has been setup with the squarewave_en so that it toggles the zero-detection pin signal each time it detect a zero-crossing. However as can be seen on the attached image, the signal is toggled almost a 1 ms before the actual zero-crossing.

I might have missed something, but I do not see anything in the datasheet that can explain this.

I would appreciate if anyone have an idea for what could cause this issue.

image of oscilloscope

Datasheet: https://www.allegromicro.com/-/media/files/datasheets/acs37800-datasheet.ashx

teb
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Page 14. "Voltage zero crossings are detected with time-based hysteresis that removes the possibility of noise causing multiple zero crossings to be reported at each true zero crossing."

The function of the 'zero crossing' system is to count the number of periods for the calculation of the power. It does not make a difference if the delay (due to the system hysteresis for avoiding noise) is always the same.

Antonio51
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  • The datasheet also state that the typical delay for voltage zero-crossing detection is 250 micro seconds. The image shows that the current delay is almost 9 ms, not something I want to go into production without an explanation for. – teb Jul 19 '21 at 08:14
  • Don't depend of mode ? Ok. I will go deep in the data sheet. – Antonio51 Jul 19 '21 at 08:18
  • Seems to be "Figure 13 : zerocrossedgesel = 0, Square Wave Mode". I don't see 9ms delay ? What is your schematic ? – Antonio51 Jul 19 '21 at 08:51
  • Voltage seems also not very sinusoidal. Where does this tension come from? – Antonio51 Jul 19 '21 at 09:01