need to build circit to measure energy (kwh) using 6008

[labviewlost]

Hello

I need to build a vi to measure the energy (kwh) consumed by a 500watt load over a 24 hour period. I only have access to NI usb 6008. (Have 10:1 ct, and 230V:6V vt and a few resistors.)

Under considerable pressure to get this working asap.

Thanks in advance for all suggestions

[JÞB]

A 500W load consumes 500W.  you don't need more than a calculator.  0.5KW*24 Hrs = 12 KWH

[rolfk]

I would assume that the power consumption is not constant and that the OP wants a graph of the current power consumptoin which would be then not so much in kWh but in kW instead. What he would need to do is measuring the voltage and the current and do some calculations. If it is a DC current then everything is done. Otherwise one would need to measure the actual phase too and do some extra calculations on that.

Rolf Kalbermatter

[johnsold]

The OP mentioned CT (current transformer) and VT (voltage or potential transformer) so it is reasonable to assume that the load is supplied from the AC power mains.

The USB-6008 has +/-20 volt range so the output of the VT could be connected directly (a MOV or other overvoltage protection might be a good idea).  The CT will require a suitable burden resistor.  Even though the mains current will not be large, the CT should be used to provide isolation.

Set up a continuous Analog In data acquisition with 500 to 1000 samples per second on each channel (voltage and current).  Multiply and integrate.

Save the data to a file periodically, perhaps every few minutes.  That way if the power to the computer fails, not all data will be lost.

If you have more specific questions, please ask.  The members of the Forum cannot do your job for you, but we are willing to help.  The more specific your questions, the better chance of getting good help.

Lynn 

[Alain_S]

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rolfk wrote:

... ...If it is a DC current then everything is done. Otherwise one would need to measure the actual phase too and do some extra calculations on that.

Rolf Kalbermatter

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Unless it's a resistive load

[rolfk]

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Alain S wrote:

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rolfk wrote:

... ...If it is a DC current then everything is done. Otherwise one would need to measure the actual phase too and do some extra calculations on that.

Rolf Kalbermatter

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Unless it's a resistive load

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Of course!  But it's all guess work with the little information we have so far.

Rolf Kalbermatter

[JÞB]

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rolfk wrote:

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Alain S wrote:

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rolfk wrote:

... ...If it is a DC current then everything is done. Otherwise one would need to measure the actual phase too and do some extra calculations on that.

Rolf Kalbermatter

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Unless it's a resistive load

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Of course!  But it's all guess work with the little information we have so far.

Rolf Kalbermatter

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Its why my first post suggested a calulation-  without a defined requirement we can guess all day at what the OP really wants.