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Topic: acs 714 erratic readings (Read 3 times) previous topic - next topic

MarkT

Quote
Hi. i know that Ac have pulses, but the DC part should
be  continous ?


No, energy is conserved so those AC pulses have to come from / go to the battery or other energy storage device like a capacitor.  Inverters do have capacitors but the bulk of the power is routed to/from the battery (especially when running at full power).  So the DC current will be pulses.

To measure the average DC current you will have to sample at many times the mains frequency and average the readings, or use an analog low-pass filter before the ADC conversion.  Multimeters use integrating ADCs that average over time anyway.
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fca

HI there i'm back to this project...
I'm measuring the acs714 right (i believe ) but i don't know how to do the watt/meter part...

i get watts doing Amps x Volts   for instant read i gues is ok ...
now how do i know how many times should i read and sum ?
like
whatthour=wahtthour+readwatts /3600 seconds

if i do this i must read it once each second ? but i will loose measuring between... i bit lost...

Summary:
how do i get a watthour measure reading amps&volts from a dc source... ??


cyclegadget


  To help make things as simple as possible. DC current and voltage simply means that the "polarity" +side and the -side do not change back and forth. The voltage "level" however can very from almost 0 to infinity up and down as long as the polarity stays the same.


AC current and voltage "alternates" +to- and -to+ on the terminals. In the USA the alternation is 60HZ or 3600times per minute. It makes it handy for clocks because of the relation of 60 seconds in a minute.


Mark

MarkT


HI there i'm back to this project...
I'm measuring the acs714 right (i believe ) but i don't know how to do the watt/meter part...

i get watts doing Amps x Volts   for instant read i gues is ok ...
now how do i know how many times should i read and sum ?
like
whatthour=wahtthour+readwatts /3600 seconds

if i do this i must read it once each second ? but i will loose measuring between... i bit lost...

Summary:
how do i get a watthour measure reading amps&volts from a dc source... ??



Read the current and voltage many times per mains cycle (lets say 1000 times a second), computing the instantaneous power from each set of samples.  Sum these samples and scale the result according to the time between samples and you have a value that is the total energy over time.  Sample and reset this value every second and you have measured the average power every second...

If you are only interested in watt-hours, then this is simply the energy (in Joules) divided by 3,600.  For kilowatt-hours divide by 3,600,000
[ I won't respond to messages, use the forum please ]

fca

#19
Jul 24, 2011, 12:59 am Last Edit: Jul 24, 2011, 06:09 am by fca Reason: 1
Thanks for the info....
My arduino is doing other thinks beside measuring the amps from the acs714, like sensing batt voltage, controlling some relays and outputing to serial the information...
because of this i have some "delays" how can i keep in main loop doing all other stuff and at the same time read "1000/sec" that value ?

ARduino multitasking ;) .. i will have look  on how to accomplish this ... any tip will be useful regards.

Can you please explain better "Sum these samples and scale the result according to the time between samples and you have a value that is the total energy over time" ?

regards.




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