DC Power Measurement

[Travis E Wethington]

I am working on a project where I need to measure the DC power
efficiency. I am using a microcontroller, and I am looking for the
best way to measure the power and not have to input current and
voltage and then do the digital to analog conversion and the power
calculation. I have been looking for a DC wattmeter but have not had
much luck. I have also considered searched for an individual or
combination of sensors or ICs to make the desired measurement.
Another thought and perhaps ideal situation would be to find a
sensor/IC which would provide digital output (TTL,etc.) I expect to
measure somewhere between 2-5W.

I am open to any suggestions on more methods or circuits that would
give me what I need.
Thanks for all your help!!

 

[John Fields]

On 26 May 2004 17:24:30 -0700, traviswethington@hotmail.com (Travis E
Wethington) wrote:

I am working on a project where I need to measure the DC power
efficiency. I am using a microcontroller, and I am looking for the
best way to measure the power and not have to input current and
voltage and then do the digital to analog conversion and the power
calculation. I have been looking for a DC wattmeter but have not had
much luck. I have also considered searched for an individual or
combination of sensors or ICs to make the desired measurement.
Another thought and perhaps ideal situation would be to find a
sensor/IC which would provide digital output (TTL,etc.) I expect to
measure somewhere between 2-5W.

I am open to any suggestions on more methods or circuits that would
give me what I need.

---
Check Analog Devices.

They have lots of analog multipliers, and maybe one with an internal
ADC which will give you what you need.

--
John Fields

 

[Joerg]

Hi Travis,

Analog Devices was a great hint from John. They've got almost everything
for such tasks. But be careful when wiring up some of their multipliers.
Many of them are made to operate up to hundreds of MHz and without proper
layout, bypassing and so on they can go haywire on you.

Another option is to select a uC that has 8 AD channels. Or since it's DC
you can do dual slope conversion which doesn't require more than a few
discrete parts.

Regards, Joerg

http://www.analogconsultants.com

 

[The other John Smith]

"Travis E Wethington" <traviswethington@hotmail.com> wrote in message
news:ab4c81a7.0405261624.54a8b12e@posting.google.com...

I am working on a project where I need to measure the DC power
efficiency. I am using a microcontroller, and I am looking for the
best way to measure the power and not have to input current and
voltage and then do the digital to analog conversion and the power
calculation. I have been looking for a DC wattmeter but have not had
much luck. I have also considered searched for an individual or
combination of sensors or ICs to make the desired measurement.
Another thought and perhaps ideal situation would be to find a
sensor/IC which would provide digital output (TTL,etc.) I expect to
measure somewhere between 2-5W.

I am open to any suggestions on more methods or circuits that would
give me what I need.
Thanks for all your help!!

Hi, Travis -

As I recall, there is a way to use a linear hall-effect device to do what
you want to do. I don't remember much about it, but this first Google hit
may help get you started:

http://www.allaboutcircuits.com/vol_2/chpt_12/3.html

Good luck.

John

 

[Roland]

"Travis E Wethington" <traviswethington@hotmail.com> wrote in message
news:ab4c81a7.0405261624.54a8b12e@posting.google.com...

I am working on a project where I need to measure the DC power
efficiency. I am using a microcontroller, and I am looking for the
best way to measure the power and not have to input current and
voltage and then do the digital to analog conversion and the power
calculation. I have been looking for a DC wattmeter but have not had
much luck. I have also considered searched for an individual or
combination of sensors or ICs to make the desired measurement.
Another thought and perhaps ideal situation would be to find a
sensor/IC which would provide digital output (TTL,etc.) I expect to
measure somewhere between 2-5W.

I am open to any suggestions on more methods or circuits that would
give me what I need.
Thanks for all your help!!

I use the Cirrus logic CS5460A. Its designed mainly for AC power but will do
DC also.

rd