Craig, what a great video, thanks. Suggestion: I usually screw two abrasive disks to my Dremel mandrill to give me the ~.060" gap in the core with one cut. Also, it might be more advantageous to use a CMOS rail-to-rail opamp for the boost. Thanks again, wonderful video.
I built this configuration with an unknown core. I found the core I used had significant magnetic hysteresis which skewed the resulting analog value say 5% in the direction last traveled. I set up a 49E on a breadboard hooked to a meter without a core and took a voltage reading. I then placed my sample core near the sensor to establish a reference output. I then exposed the sample core to a strong magnet then back to the sensor. If the core retained a magnetic charge I rejected it. Rather crude but it worked for me to find a core which gave me repeatable readings. I ended up with a 50T 26ga outputting 1 to 4V directly to a Arduino. No preamp was needed. Scale was +- 1A. Zero location was 512+-2 counts in all my current testing.
That seems to be a lot more useful for high currents than low currents. For low currents, a shunt is usually a good choice, dropping 100mV max is usually not a big problem and 100mV can still be measured reasonably well. However, for higher currents, you need to either lower the voltage drop dramatically (range of 1mV or lower) and have difficulty measuring such low voltages accurately, or you have large amount of heat generated + energy wasted on the shunt. Making magnetic measurements is far easier, just lower the amount of turns (or even have just one turn) and select the sensor to fit the measurement range in a way that most of the GND-VCC swing is observed, being easily measured by standard 5v or 3.3V microcontrollers.
Easy to calculate the magnetic field between the airgap is "1.25(current x airgap(mm)) this will give you values in milliTesla. So for your setup it could be 1.25(1x1.91)= .6544 now multiply that by 20 that is number of turns so you will get 13.08mt which is equal to 130.8gauss spot on in your case.
one of the best video ever found on internet, hatsoff! I am making a project to measure DC current using Hall sensor and a CT(split core) how can i measure by using your provided circuit with a split core CT?
Thank you for this video, it is very informative and easy to follow. Can you suggest a way to measure AC current (in the mA scale)? Can this setup be used for that?
This circuit will measure AC as well. The signal will oscillate around the 2.5V bias. To increase sensitivity, add more turns to the coil. Good luck with your experiments and thanks for watching!
exist an error in your equation in the minute 5:30, because you ecuation should be B=(0.4*pi*Ur*N*I)/MPL+Uº*Lg; the term Uº indicate that is the permeability of air and Ur permeability of material.
Assumptions and simplifications were made to get to that formula. The term MPL + UoLg just calculates the increase in the MPL (mean-path-length) of the core by the air gap scaled by the core's relative permeability. With the air gap, the core appears to be much longer. The formula in the video is correct. Thanks for watching.
Thanks for this. I was wondering how DC current sensors work bu of course the wire carrying the current is a síngle wire passíng through the móddle óf thecore...
I'm not sure what you are asking, so I'll assume you are planning to measure the magnetic field near a wire carrying a high current with a Hall sensor. As we know, a current passing through a wire (line) creates a magnetic field around the wire. As we also know, the strength of a magnetic field decreases as the distance from the source of that field increases. The strength of the magnetic field at a given distance from a current carrying wire would therefore depend on two things: 1) the magnitude of the current in the wire, and 2) the distance the sensor is from the wire. The Hall sensor detects the strength of the magnetic field passing through it, but only in a certain direction, through the plane of the large flat surfaces of the sensor. If the magnetic field passes through the Hall sensor in any other direction, the response won't be as good or even zero. In order for a Hall sensor to work well, it needs a strong magnetic field passing through it. Placing one next to a current carrying wire probably would not intercept enough magnetic field to work well. This is the reason I went through the effort of winding a wire around a toroid core with a slot cut in it and the Hall sensor positioned in the slot. I needed a way to concentrate the magnetic field through the sensor. I hope this long-winded explanation answered you question.
You might be able to use the Hall sensor I used to detect the magnetic field at 1 meter produced by 400A in the wire. The output of the sensor would be pretty small though, and maybe not very useful without some amplification. You can calculate the magnetic field strength 1 meter from the wire by: B = u * I / (2 * PI * r) = (4 * PI * 10^-7 Tm/A) * 400A / (2 * PI * 1m) = 2 * 10^-7 * 400 = 800 * 10^-7 T = 80uT (Look up the formula with a Google search) To convert Tesla to Gauss just multiply by 10^4 (again, Google). B = 80uT * 10^4G/T = 800mG or 0.8G The hall sensor I used had a sensitivity of 1.4mV/G. So with this magnetic field strength, the output of the Hall sensor would change by 0.8 * 1.4mv or 1.12mV. Not a lot. There may be equipment out there that can do this for you. Good luck.
Very good and clear explanation! I am building a Voltage-Current Tracer circuit to use as a cheap but accurate component tester. It will function much like a standard Octopus Circuit and use the X-Y inputs of an oscilloscope to display the resultant Lissajous pattern. To do this I plan to build a Hall Effect Current Probe to make the current measurement part as non-invasive as possible. To protect sensitive components, however, I need to use low current values of around 1 ma and voltages of about 1 VAC, and to keep from adding unnecessary inductance to the circuit only one pass through the toroid will be used. Can this circuit work under these circumstances, perhaps with a higher gain op amp stage? Thanks!
I did this a while ago, so my memory is a little weak. In theory you could. But if I remember correctly, I had a fair bit of noise in the signal. Mind you, I built everything on a bread board, so not a low noise situation. If you increase the gain, you will increase noise. A better circuit layout on a well built PCB using low noise components would help. Keep the amplifier impedance as low as you can and use low noise opamps and metal film resistors. There are ICs available that can do this kind of measurement. I'm not very familiar with them so I can't make any recommendations, but if you spent some time searching on the Internet, I'm sure you'll come up with something. Good luck with whatever route you take.
The circuit will work on both AC and DC without modification. Not sure what the maximum AC frequency the circuit can handle but normal line frequencies 50/60Hz won't be a problem. Thanks for watching!
The output of the Hall sensor sits at 1/2 of it's supply voltage when there is no magnetic field. In this case, the supply voltage was 5V so the output would be at 1/2 of 5V which is 2.5V. The direction the output moves from 2.5V depends on the polarity of the magnetic field. With one polarity the voltage would increase, with the other polarity the voltage would decrease. This is the way the sensor works. I hope this explanation clears up any confusion you may have. Thanks for watching!
at 1:10.. I think it was Oersted that discovered this and not Ampére... Ampére then added to this with his two wire experiment where current in one wire generates a current in the other parallel running wire..
You are correct. Oersted noticed the affect a current carrying wire had on a compass needle, Ampere went on from there. They both lived at the same time (different parts of the world though) and were aware of each others work. Thanks for clarifying this.
I am using ACS 750 Hall effect sensor by Allegro....and want to observe the current values from my system (Electric Discharge Machining)....will this system be helpful? And what changes do i need to do? And if I use Arduino to get the values of current, what should I do? Plzz Help...
I imagine the ACS750 would work. A quick Google search turned up the data sheet: www.google.ca/search?q=ACS+750&ie=utf-8&oe=utf-8&gws_rd=cr&ei=3TmSWdapFcnYjwOgzbWYCg . The first result gives you the .pdf. The chip does essentially the same as my simple circuit with the OpAmp. Read the data sheet and figure out how to interface it to an analog input of the Arduino. I don't think it would be too hard to do. You may not be aware, but this is now an obsolete part. Could be hard to get. Good luck with your project. Craig.
Reversing the direction of the current would cause the output of the OpAmp to go negative. In the case of the circuit I presented in the video, the output of the OpAmp would stay at 0V since it's minus power supply is at 0V. If the OpAmp minus supply was connected to a negative voltage, say -5V, the output would then be able to go negative. In either case, the OpAmp would be OK.
Just passing a wire straight through the toroid is counted as one turn. In my example in the video, I used 20 turns. With a single turn coil, a current of 20A would be required give the same voltage readings as I was getting with 1A.
The toroid concentrates the magnetic flux so that most of it passes through the Hall sensor. Without the toroid, there would be a lot less magnetic flux for the Hall sensor to sense, thus the current measurements would be less sensitive.
I haven't done this with an Arduino. It wouldn't be very difficult though, just connect the output of the OpAmp to one of the analog inputs of the Arduino. Write some code to read the input, apply a scaling factor to convert the voltage reading of the OpAmp to current, then output that value to the Serial Monitor.
The pot was a leftover from my experimentation to set the opamp offset level. The output of the Hall sensor is biased to half of it's power supply. It's output will go above the offset with one orientation of the magnetic field, below with the other orientation. The opamp is powered from a single positive supply so you have to offset the it's input to the same level as the Hall sensor in order for the whole range of the sensor signal to appear at the output. The opamp has some gain, therefor the offset is affected by the gain. I used the pot to vary this offset to match that of the Hall sensor. I could have eventually replaced the pot with a resistor divider, but never got around to it. I hope this long explanation answers your question. Thanks for watching.
You really stripped it down for easy understanding and anyone can easily pick it up and use it in an application. Thank you for doing the video
Very effective instruction. Would have learned more with teachers like this in the college electronics engineering courses I studied.
Thanks for your comment and thanks for watching.
Craig, what a great video, thanks. Suggestion: I usually screw two abrasive disks to my Dremel mandrill to give me the ~.060" gap in the core with one cut. Also, it might be more advantageous to use a CMOS rail-to-rail opamp for the boost. Thanks again, wonderful video.
Thanks. The opAmp I used is what I had lying around. The circuit was strictly for demonstration purposes.
I built this configuration with an unknown core. I found the core I used had significant magnetic hysteresis which skewed the resulting analog value say 5% in the direction last traveled. I set up a 49E on a breadboard hooked to a meter without a core and took a voltage reading. I then placed my sample core near the sensor to establish a reference output. I then exposed the sample core to a strong magnet then back to the sensor. If the core retained a magnetic charge I rejected it. Rather crude but it worked for me to find a core which gave me repeatable readings. I ended up with a 50T 26ga outputting 1 to 4V directly to a Arduino. No preamp was needed. Scale was +- 1A. Zero location was 512+-2 counts in all my current testing.
Very clear explanation! Especially where the deviations/errors come from. Thank you for your effort.
That seems to be a lot more useful for high currents than low currents. For low currents, a shunt is usually a good choice, dropping 100mV max is usually not a big problem and 100mV can still be measured reasonably well. However, for higher currents, you need to either lower the voltage drop dramatically (range of 1mV or lower) and have difficulty measuring such low voltages accurately, or you have large amount of heat generated + energy wasted on the shunt. Making magnetic measurements is far easier, just lower the amount of turns (or even have just one turn) and select the sensor to fit the measurement range in a way that most of the GND-VCC swing is observed, being easily measured by standard 5v or 3.3V microcontrollers.
Easy to calculate the magnetic field between the airgap is "1.25(current x airgap(mm)) this will give you values in milliTesla. So for your setup it could be 1.25(1x1.91)= .6544 now multiply that by 20 that is number of turns so you will get 13.08mt which is equal to 130.8gauss spot on in your case.
Very nicely explained...Please over other sensors and example of them with microcontroller
one of the best video ever found on internet, hatsoff!
I am making a project to measure DC current using Hall sensor and a CT(split core) how can i measure by using your provided circuit with a split core CT?
@craig
I'm not sure what you mean by CT? My circuit will measure DC.
Thank you for this video, it is very informative and easy to follow. Can you suggest a way to measure AC current (in the mA scale)? Can this setup be used for that?
This circuit will measure AC as well. The signal will oscillate around the 2.5V bias. To increase sensitivity, add more turns to the coil. Good luck with your experiments and thanks for watching!
@@craighollinger9972 Thank you!
exist an error in your equation in the minute 5:30, because you ecuation should be B=(0.4*pi*Ur*N*I)/MPL+Uº*Lg; the term Uº indicate that is the permeability of air and Ur permeability of material.
Assumptions and simplifications were made to get to that formula. The term MPL + UoLg just calculates the increase in the MPL (mean-path-length) of the core by the air gap scaled by the core's relative permeability. With the air gap, the core appears to be much longer. The formula in the video is correct.
Thanks for watching.
Very cool topic. THANX
Thanks for this. I was wondering how DC current sensors work bu of course the wire carrying the current is a síngle wire passíng through the móddle óf thecore...
Amazing video .Thank you for this great video
The video was so helpful. I have a project on high current lines. What is the relation between current and distance from the line.. ?
I'm not sure what you are asking, so I'll assume you are planning to measure the magnetic field near a wire carrying a high current with a Hall sensor.
As we know, a current passing through a wire (line) creates a magnetic field around the wire. As we also know, the strength of a magnetic field decreases as the distance from the source of that field increases. The strength of the magnetic field at a given distance from a current carrying wire would therefore depend on two things: 1) the magnitude of the current in the wire, and 2) the distance the sensor is from the wire.
The Hall sensor detects the strength of the magnetic field passing through it, but only in a certain direction, through the plane of the large flat surfaces of the sensor. If the magnetic field passes through the Hall sensor in any other direction, the response won't be as good or even zero. In order for a Hall sensor to work well, it needs a strong magnetic field passing through it. Placing one next to a current carrying wire probably would not intercept enough magnetic field to work well.
This is the reason I went through the effort of winding a wire around a toroid core with a slot cut in it and the Hall sensor positioned in the slot. I needed a way to concentrate the magnetic field through the sensor.
I hope this long-winded explanation answered you question.
Thanks manh.. thats what i wanted..
Glad I could help.
Hey.. One more doubt.. Is there any method to detect(Not measuring) a 400A or above Current carrying conductor Within 1 Meter ?
You might be able to use the Hall sensor I used to detect the magnetic field at 1 meter produced by 400A in the wire. The output of the sensor would be pretty small though, and maybe not very useful without some amplification.
You can calculate the magnetic field strength 1 meter from the wire by:
B = u * I / (2 * PI * r) = (4 * PI * 10^-7 Tm/A) * 400A / (2 * PI * 1m) = 2 * 10^-7 * 400 = 800 * 10^-7 T = 80uT
(Look up the formula with a Google search)
To convert Tesla to Gauss just multiply by 10^4 (again, Google).
B = 80uT * 10^4G/T = 800mG or 0.8G
The hall sensor I used had a sensitivity of 1.4mV/G. So with this magnetic field strength, the output of the Hall sensor would change by 0.8 * 1.4mv or 1.12mV. Not a lot.
There may be equipment out there that can do this for you.
Good luck.
Very good and clear explanation! I am building a Voltage-Current Tracer circuit to use as a cheap but accurate component tester. It will function much like a standard Octopus Circuit and use the X-Y inputs of an oscilloscope to display the resultant Lissajous pattern. To do this I plan to build a Hall Effect Current Probe to make the current measurement part as non-invasive as possible. To protect sensitive components, however, I need to use low current values of around 1 ma and voltages of about 1 VAC, and to keep from adding unnecessary inductance to the circuit only one pass through the toroid will be used. Can this circuit work under these circumstances, perhaps with a higher gain op amp stage? Thanks!
I did this a while ago, so my memory is a little weak. In theory you could. But if I remember correctly, I had a fair bit of noise in the signal. Mind you, I built everything on a bread board, so not a low noise situation. If you increase the gain, you will increase noise. A better circuit layout on a well built PCB using low noise components would help. Keep the amplifier impedance as low as you can and use low noise opamps and metal film resistors.
There are ICs available that can do this kind of measurement. I'm not very familiar with them so I can't make any recommendations, but if you spent some time searching on the Internet, I'm sure you'll come up with something.
Good luck with whatever route you take.
Very good explanation. Thank you very much
Thanks for watching!
Very nice video. Does it work for measuring DC current? Or does it works only for AC current? Thanks.
The circuit will work on both AC and DC without modification. Not sure what the maximum AC frequency the circuit can handle but normal line frequencies 50/60Hz won't be a problem. Thanks for watching!
why 2,558V in output if the hall sensor not have any flux? in this case the output voltage is not 5V?
The output of the Hall sensor sits at 1/2 of it's supply voltage when there is no magnetic field. In this case, the supply voltage was 5V so the output would be at 1/2 of 5V which is 2.5V. The direction the output moves from 2.5V depends on the polarity of the magnetic field. With one polarity the voltage would increase, with the other polarity the voltage would decrease. This is the way the sensor works.
I hope this explanation clears up any confusion you may have. Thanks for watching!
at 1:10.. I think it was Oersted that discovered this and not Ampére... Ampére then added to this with his two wire experiment where current in one wire generates a current in the other parallel running wire..
You are correct. Oersted noticed the affect a current carrying wire had on a compass needle, Ampere went on from there. They both lived at the same time (different parts of the world though) and were aware of each others work.
Thanks for clarifying this.
What model of Hall sensor did you used in video?
I believe it was a Honeywell SS49E.
@@craighollinger9972 Thank you very much
I'm wondering what the model number/type of hall sensor it is that you are using?
Sorry for taking so long to answer, this is the first time I've looked here in quite a while.
The sensor I was using was a Honeywell SS49E.
I am using ACS 750 Hall effect sensor by Allegro....and want to observe the current values from my system (Electric Discharge Machining)....will this system be helpful? And what changes do i need to do?
And if I use Arduino to get the values of current, what should I do?
Plzz Help...
I imagine the ACS750 would work. A quick Google search turned up the data sheet: www.google.ca/search?q=ACS+750&ie=utf-8&oe=utf-8&gws_rd=cr&ei=3TmSWdapFcnYjwOgzbWYCg . The first result gives you the .pdf. The chip does essentially the same as my simple circuit with the OpAmp. Read the data sheet and figure out how to interface it to an analog input of the Arduino. I don't think it would be too hard to do.
You may not be aware, but this is now an obsolete part. Could be hard to get.
Good luck with your project.
Craig.
what would happen if current reversed direction? Would op-amp than get into a trouble?
Reversing the direction of the current would cause the output of the OpAmp to go negative. In the case of the circuit I presented in the video, the output of the OpAmp would stay at 0V since it's minus power supply is at 0V. If the OpAmp minus supply was connected to a negative voltage, say -5V, the output would then be able to go negative. In either case, the OpAmp would be OK.
You did not take into account the drop over the 9 ohms, probably part of your error.
Very interesting.
Thanks for sharing!
Frej Kling Thanks!
great application! very cool
Thanks!
What if I didn't turn the wire around the toroid. The current is around 200A.
Just passing a wire straight through the toroid is counted as one turn. In my example in the video, I used 20 turns. With a single turn coil, a current of 20A would be required give the same voltage readings as I was getting with 1A.
Craig Hollinger For the flux strength fomula the current I should always be "1"?
In the formula, the current 'I' is the current flowing in the wire. It would be whatever you set it to.
Does this also work with AC current?
Yes, see my reply to SHELKE above.
how we can measure voltage with Hall effect sensor
Hall effect sensors only respond to magnetic fields. There are better ways to measure voltage. Look it up on Google, you'll find many examples.
Can this be done without the toroid?
The toroid concentrates the magnetic flux so that most of it passes through the Hall sensor. Without the toroid, there would be a lot less magnetic flux for the Hall sensor to sense, thus the current measurements would be less sensitive.
Ok, thanks ... have you used this with an Arduino yet?
I haven't done this with an Arduino. It wouldn't be very difficult though, just connect the output of the OpAmp to one of the analog inputs of the Arduino. Write some code to read the input, apply a scaling factor to convert the voltage reading of the OpAmp to current, then output that value to the Serial Monitor.
nice video, thank you...
Thanks for watching!
Why did you use 1k pot... Instead of simple voltage division
The pot was a leftover from my experimentation to set the opamp offset level. The output of the Hall sensor is biased to half of it's power supply. It's output will go above the offset with one orientation of the magnetic field, below with the other orientation.
The opamp is powered from a single positive supply so you have to offset the it's input to the same level as the Hall sensor in order for the whole range of the sensor signal to appear at the output. The opamp has some gain, therefor the offset is affected by the gain. I used the pot to vary this offset to match that of the Hall sensor. I could have eventually replaced the pot with a resistor divider, but never got around to it.
I hope this long explanation answers your question. Thanks for watching.
Very good explanation. Thank you very much
Thanks for watching!