How to calculate realtime kwh from a kwh meter with puls output

[hapetter]

Hi.

I have a Kwh meter with puls output.

it give 1000 pulses for each Kwh.

If I have the meter measuring 1 kw load, then it takes 1Hour to get 1000pulses. This is fine, but I like to calculate the real kwh in a fraction of time. So I thought it might be possible to measure the time between 2 pulses and calculate the realtime load (kwh). However I cant fine a formula for this.

Does anyone know how to do this? Formula?

Thanks

 

[Gil47]

60 mins in an hour X 60 seconds in a min =3600
then run a timer at a 1 second time base and every time it gets reset by a pulse from the meter
move the accumulated value and use it to divide the 3600

3600 / No of sec ACC =
Kw that would be used in an hour at the current rate of consumption.

If the time base used is done in msec then the number would be 36 000 000

The number will be a little bouncy but still achieves a very close average.

 

[daba]

Whatever method is used, the resultant values will fluctuate dramatically between successive pulse durations.

I would suggest some sort of averaging or filtering software would be required to make the kWh value usable...

 

[JesperMP]

"realtime load" in kWh does not make sense since kWh is energy, the sum of the power P over the time.
But you could calculate how much energy will result if the power stays constant for one hour or one day.

1000 pulses = 1kWh; then 1 pulse = 1Wh = 3600 Ws

Measure the time between two pulses, "t" in seconds.
Then the approximate power at a given time is:
P = 3600 Ws / t

Example: t=10 s
P = 3600 Ws / 10 s = 360 W.

So the estimated power consumption Qh for one hour becomes:
Qh = P x 1h = 360 W x 1h = 360 Wh = 0.36 kWh

And the estimated power consumption Qd for one day becomes:
Qd = P x 24h = 360 W x 24h = 8640 Wh = 8.64 kWh

edit: A comment - hard to find a formula ? As soon as you get your SI units right, watt, seconds, meters, degrees, then you dont need to look up any formula. You just have to get the SI units to arrive at the "right places".

 

[Honga]

Whatever method is used, the resultant values will fluctuate dramatically between successive pulse durations.

I agree. In this case you would be better off sampling for say 10s counting pulses and divide by 10 for pps. This will give you power.

With this power you should then multiply it by 3600 to get Energy use.

 

[Tom Jenkins]

I agree. In this case you would be better off sampling for say 10s counting pulses and divide by 10 for pps. This will give you power.

With this power you should then multiply it by 3600 to get Energy use.

Actually, you want to make sure that you are getting whole pulses. I'd use an up counter that counts a few pulses in conjunction with a timer that measures the elapsed time for that number of pulses.

 

[OkiePC]

Wait.

Your KwH Meter is sending pulses.

"It gives 1000 Pulses/KWH"

1KWH=1000 counts

All you need to do is sum and scale. It's giving you Kilowatt hours, just count them, and divide by 1000?

You can then store the total at any point in the day, and easily calculate real time, or historical

Am I messing up?

You want real time? Simply monitor the velocity of the pulses. Your HSC card may be able to do it for you.

 

[shooter]

high speed is to have the time difference between two pulses, it will fluctuate but thats with high speed
realtime minus timelastpulse gives a time in milliseconds.
as 1 hour is 3600 seconds so formula is Power is 3600/yourtime
i would also make 1 every second count the pulses and every minute
so pulses*60 will be watts/hour
1 puls is 1 watthouris 1 watt/second= 1 joule.