a simple question about phase  - Page 1
Forum section: electronics / projects

author: navidrct
author_rank: Regular Contributor
timestamp: June 11, 2015, 05:30:50 am
content: i wanna measure phase for calculate active power & reactive power.any idea?

author: Jeroen3
author_rank: Super Contributor
timestamp: June 11, 2015, 05:46:58 am
content: In what context do you want to measure it?On your oscilloscope, with a fluke power analyzer or with proprietary measurement equipment?

author: coppice
author_rank: Super Contributor
timestamp: June 11, 2015, 05:49:58 am
content: It sounds like you are doing things backwards. Measure the active power, and you can easily derive the phase shift from that.

author: navidrct
author_rank: Regular Contributor
timestamp: June 11, 2015, 05:54:51 am
content: Quote from: Jeroen3 on June 11, 2015, 05:46:58 amin microcontroller

author: navidrct
author_rank: Regular Contributor
timestamp: June 11, 2015, 05:55:30 am
content: Quote from: coppice on June 11, 2015, 05:49:58 amplz tell me how to do that . thanks

author: calexanian
author_rank: Super Contributor
timestamp: June 11, 2015, 06:00:20 am
content: My favorite phase is still plasma. O0

author: coppice
author_rank: Super Contributor
timestamp: June 11, 2015, 06:02:31 am
content: Quote from: navidrct on June 11, 2015, 05:55:30 amI assume you are trying to measure mains power. There are lots of power meter solutions on the web, and most of them show the principals they use. You can work in either the time or the frequency domain. Most solutions use a time domain approach. Sample the voltage and current fast enough to capture sufficient harmonics, For mains power a few k samples per second is usually used. Ensure the voltage and current samples are exactly coincident. Even a 0.01 degree phase error between sample will give a noticeable shift in the active power accuracy at poor power factors. Multiply each voltage sample by the related current sample, and accumulate. This will give you energy accumulating over time. Divide by the number of samples and you have active power.

author: navidrct
author_rank: Regular Contributor
timestamp: June 11, 2015, 06:07:14 am
content: Quote from: coppice on June 11, 2015, 06:02:31 amthanks alot

author: jancumps
author_rank: Unknown
timestamp: June 11, 2015, 07:46:11 am
content: My friend Martin Valencia has created a power quality meter on a microcontroller, with graphic display and calculations.You can find a number of videos on that subject on his youtube channel.Here's an example:https://youtu.be/CAWkpHGFFw4

author: Ian.M
author_rank: Super Contributor
timestamp: June 11, 2015, 08:26:59 am
content: Be *EXTREMELY* careful about mains isolation. Instrumentation quality transformers for voltage measurement and accurate current transformers are expensive so many power measurement chip manufacturers have non-isolated reference designs. If you want to breadboad or use a bare development board for the MCU side of your design, you either need fully isolated sensing, or optoisolation between the measurement chip and the rest of your design, with the non-isolated circuit built up properly in a plastic box. Get it wrong and there is a high risk to you, your PC and any grounded test equipment.

author: navidrct
author_rank: Regular Contributor
timestamp: June 11, 2015, 08:50:04 am
content: Quote from: jancumps on June 11, 2015, 07:46:11 amthanks alot.I'll see it

author: navidrct
author_rank: Regular Contributor
timestamp: June 11, 2015, 09:00:41 am
content: Quote from: Ian.M on June 11, 2015, 08:26:59 amthanks . i will consider that

author: dom0
author_rank: Super Contributor
timestamp: June 11, 2015, 03:49:03 pm
content: Quote from: Ian.M on June 11, 2015, 08:26:59 amWell, actually their app notes are usually non-isolated because electronic power meters don't need isolation. (Neither do these energy meter thingies you can use to check the power consumption of a fridge or something like that, although those are usually of piss-poor quality and have often severely lacking accuracy).The data interface is optical and provides the isolation towards the outside world, no other interconnects there, so...