Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What sensor to choose to find the shape of current

  1. Mar 28, 2016 #1
    I want to choose a sensor which can sense the current flowing from the electricity meter of the residential houses, the sensor should be able to sense the shape of electrical signal each second that how it looks like. can some one help me with that ?
     
  2. jcsd
  3. Mar 28, 2016 #2

    anorlunda

    User Avatar
    Science Advisor
    Gold Member

    The sensor is a shunt resistance. Only a licensed electrician can install one. Do not attempt to do it yourself.
     
  4. Mar 28, 2016 #3
    thanks for your reply, so what is the name of the sensor and what do you mean by shunt resistance sensor ?
     
    Last edited by a moderator: Mar 28, 2016
  5. Mar 28, 2016 #4

    anorlunda

    User Avatar
    Science Advisor
    Gold Member

    If you don't know that answer, then you are not qualified to go forward with that project.
     
  6. Mar 28, 2016 #5

    berkeman

    User Avatar

    Staff: Mentor

    Can you say more about why you want to do this? As anorlunda points out, you may need a licensed electrician to help you with this, depending on what you are trying to do. Are you the homeowner?
     
  7. Mar 28, 2016 #6
    There are two main sensor types for current, Shunt Resistor - is installed in series, that is inline with the current path, the other is a Current Transformer ( or a related Hall Effect) - there are others. Since both of these require you to access the individual cables (conductors) of the Mains ( residential feed) - it is a job for a proerly qualified individual. Also note - to combat theft of electricity the actual electrical meters ( external ) are pretty hardened, making it nearly impossible to measure these values "at the meter", you can not walk up to the meter and get this data..
    These are JUST the sensor - you then need an instrument to interpret the signal and provide you with the data as you have asked for it. For example a sensor does not tell you "how it looks"... that is the instrument's job.

    Based on your language - it seems you are suspecting the utility, or the meter itself to be at fault.
     
    Last edited by a moderator: Mar 29, 2016
  8. Mar 29, 2016 #7
    thanks
     
    Last edited by a moderator: Mar 29, 2016
  9. Mar 29, 2016 #8

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    In the UK you can buy devices to monitor domestic electricity use. They come in two parts connected by a wireless link. One part is a small display, the other is a clip on sensor. The clip on sensor must be attached to a single core wire so it's usually installed in the meter cabinet. No special skills are required to fit the sensor - just follow the instructions supplied with the kit. The down side is they aren't particularly accurate.
     
  10. Mar 29, 2016 #9

    anorlunda

    User Avatar
    Science Advisor
    Gold Member

    But the OP didn't ask about power, he asked about current. He also wanted the shape of the waveform. We can only guess at his intent.

    If they sell inaccurate power sensors in the UK to monitor the service entrance, I foresee lots of unjustified disputes with the power company.
     
  11. Mar 29, 2016 #10

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Those sensors are actually measuring current only, they infer power from the voltage and some assumption about phase shift - with a single wire they have no proper access to it.
     
  12. Mar 29, 2016 #11
    From the meter the power feed will go to the main breaker box. There the wires are more accessible. (By the electrician. I'm an EE and I don't mess with the breaker box. Leave it to professionals. One obscure mistake and your house burns down in the middle of the night with your family in it.)

    The simplest way would be to measure the voltage across an inserted shunt resistance with a logging digital scope, then transmit the images to your computer. (Bluetooth, perhaps.) This should give you a clear picture of the current.

    Or I could tell you what it looks like. It's a sin wave.

    I assume you are looking for something odd. But whatever it is, it is likely small in comparison to the main power wave. Unless it's a significant power draw, its effects will likely be under the noise floor.

    This will include some noise from every source in your house, and your neighbors' houses. (These will slightly affect the voltage, which in turn affects the current in your house.)

    They do make power quality monitors which look for odd sorts of problems. Perhaps one of these will work for you.
     
  13. Mar 29, 2016 #12

    NascentOxygen

    User Avatar

    Staff: Mentor

    By "shape of the electrical signal each second" I would proceed on the basis that OP intends for the current's amplitude to be sampled every second, and ask clarifying questions accordingly.
     
  14. Mar 29, 2016 #13

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Sampling the current current (...) once per second won't give anything interesting with 50 or 60 oscillations in between. You would need a much higher sampling rate to see anything. Averaging I2 over a second to produce one reading per second would be a bit more interesting. But then the phase issue is still there.
     
  15. Mar 29, 2016 #14

    NascentOxygen

    User Avatar

    Staff: Mentor

    Phase angle need not always be a crucial factor, e.g., if wishing to determine how close to tripping the breakers is a household's pattern of electricity usage, to see whether they need an additional circuit.
     
  16. Mar 29, 2016 #15

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    They measure the current but assume the voltage is some nominal value which is why they aren't very accurate.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: What sensor to choose to find the shape of current
  1. Eddy current sensor (Replies: 3)

  2. Current sensor (Replies: 1)

  3. What is this sensor? (Replies: 1)

Loading...