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Measuring Power Factor With a Micro

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I told the "poor guy" that it only works with sine waves, what more do you want?
Should i never talk about this method again because many modern devices are non linear?

my fault, i missed that. i do however think that many do not realize that just because they are supplying sine waves does not mean that they are drawing sine waves. I have to explain that to degreed engineers on occasion.
 
I am shocked no one in this thread mentioned hall sensing:
**broken link removed**

Also, since you like microchip parts, they make an inexpensive analog front end for exactly this purpose:

MCP3901

You could use the ADC on the dsPic but unfortunately only the 10-bit models sample simultaneously.
 
I am shocked no one in this thread mentioned hall sensing:
**broken link removed**

Also, since you like microchip parts, they make an inexpensive analog front end for exactly this purpose:

MCP3901

You could use the ADC on the dsPic but unfortunately only the 10-bit models sample simultaneously.
As I mentioned earlier, the method of using a shunt resistor (or something I have to pass current through in a similar method), while ridiculously simple and solves all my problems, would require me having the 200A service disconnected by an electrician and having him hook up the shunt device ($$$). Im trying to avoid having to disconnect the mains feed as much as possible.
 
I am shocked no one in this thread mentioned hall sensing:
**broken link removed**

Also, since you like microchip parts, they make an inexpensive analog front end for exactly this purpose:

MCP3901

You could use the ADC on the dsPic but unfortunately only the 10-bit models sample simultaneously.


i was under the impression that he wanted higher accuracy
 
Then you need an open loop model. That will cost you some accuracy.

**broken link removed**
Hey hey, that looks like it would work great! However, Im having trouble sourcing one. Do you have any local leads? Even their distributor inventory is empty. Im going to send them an email regardless and see what they say.

i was under the impression that he wanted higher accuracy
What's the accuracy difference, relatively speaking?
 
Keeping your gear isolated from mains is really a plus. So, the shunt resistor idea was pretty dangerous to begin with...

So you have 2 solutions for the current : a current transformer, or Hall sensing.

For the current transformer, if you cannot interrupt the circuit, you'd need a model with a core that can be opened and closed (EI-style) which is probably going to be a bit hard to find.

Hall sensing seems the best. You could get a special-purpose Hall sensor (like the ones posted above), or simply buy a clamp-on ammeter with a scope output, and use the scope output. DigiKey has a "current sensor" category, good hunting.

For sensing voltage, you can simply use a small low voltage transformer. If you isolate from the mains, you can use a scope, a PC programmer, etc... Toroids seem to have higher bandwidth.
 
Hey hey, that looks like it would work great! However, Im having trouble sourcing one. Do you have any local leads? Even their distributor inventory is empty. Im going to send them an email regardless and see what they say.


What's the accuracy difference, relatively speaking?

hard to tell.. off hand i did not see the actual accuracy on the thing ..

the other detail is that the micro does not care if it is connected to the rail. you can do put your A/D on the hot side and opto isolate it from the rest of the electronics if you need really good numbers that you can touch yourself.
 
Hey hey, that looks like it would work great! However, Im having trouble sourcing one. Do you have any local leads? Even their distributor inventory is empty. Im going to send them an email regardless and see what they say.


What's the accuracy difference, relatively speaking?

Most distributors have them. I cant seem to find the clip-on type, I know I have seen it before. Here is one of the honeywell models:

Digi-Key - 480-3252-ND (Manufacturer - CSLT6B100)

The biggest challenge to accuracy is probably going to be magnetic interference. If you can get the sensor inside a metal box and connect the box to earth ground, that would be good. This one claims 1%

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=398-1077-ND
 
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As I mentioned earlier, the method of using a shunt resistor (or something I have to pass current through in a similar method), while ridiculously simple and solves all my problems, would require me having the 200A service disconnected by an electrician and having him hook up the shunt device ($$$). Im trying to avoid having to disconnect the mains feed as much as possible.

what are you trying to measure the power factor on?
 
what are you trying to measure the power factor on?

From my first post in the thread:
SpikedCola said:
My final goal with this project is as follows: Id like to measure (in real-time) frequency, voltage, apparent power, and power factor (among others that may be added later) of the feed for my house. It is a 200A service, in Canada, so 60Hz.
 
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