Discussion in '8051/8951' started by JeffreyPeter, Feb 3, 2013.

1. JeffreyPeterNew Member

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If I designed an energy meter with 3200 imp/kwhr, should I count 3200 pulses for 1 kWhr ?

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The way I read it is if you read a frequency of 2500 then the power is 2500 imp/kwh.. simple as..

You don't have to count that... you can deduce the frequency in 1 second... They recommend 2 seconds to be accurate..

I may be wrong..

3. JeffreyPeterNew Member

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I actually have 3200 impulse/Kwhr as meter constant. Does it mean - 3200 pulse from CF pin = 1 Kwhr ... ?

4. DaveNew Member

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Like I said... The way I read it is.. If you have 3200 impulse / Kwh, then CF will have a frequency of 3.2Khz...

You just need to measure the frequency... The text also said that the frequency on the CF pin is a tad unstable so sample for a minimum of 2 seconds

If you count 6400 pulses per two second period and divide by 2... 3200 or 3.2Khz.

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6. JeffreyPeterNew Member

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How to measure the frequency in 8051 pls explain a bit more... In some design I found the sampling at 10 sec what does it mean..

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8. JeffreyPeterNew Member

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From datasheet,
Average Freq = Counter/ timer
=> 6400 counts for 2 sec => 6400/2 = 3200
Energy = Counter/timer * timer
=> 3200 * 2 = 6400.
for our meter 3200 imp/kwhr so 2 kwhr...

for example count = 20 for 2 sec.
Then how should I proceed with the calculation to get energy ??
pls correct me if Im wrong..

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It also said...

So Doesn't that mean that the counter represents Watts?

10. JeffreyPeterNew Member

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Yes It should be in watts... As meter constant is 3200 imp/kwhr, can't I count 3200 pulses from cf and account for 1 kwhr ?

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I still reckon that 3200 = 3.2khz = 3.2KWh..... I may be wrong but thats what I'm seeing..

You'll need to experiment with a know source.... Take a 40 watt bulb and measure that... see what the frequency is.... if its 40hz then you'll know..

I was also looking at this..