Hello, i am doing a project for non-contact current measurement using a Hall Effect Sensor built into an air gaped toroid core such as the Honeywell CSLA1CD( +- 57A) - https://sensing.honeywell.com/index.php?ci_id=49794 ; this is the data sheet. My understanding is that the hall effect sensor is a transducer that outputs mV in relation to the flux density in a linear fashion. An idea i have come up with is too have a current carrying conductor pass through the toroid core, inducing a magnetic field onto the core, which will then concentrate the flux density onto the Hall Effect Sensor, which in return will output a mV value depended on the induced flux density of current passing through. Now i assume that this mV output is going to have to be amplified ( i was thinking an LM358DT amplifier ) before going into the ADC converter of a micro-controller ( Arduino UNO ) but my issue lies in the fact that i am not too sure on what the gains of my amplifier should be, if or how to range the output/arduino so that the displayed reading is accurate, or how to convert the signal going into the micro-controller from mV to mA to be read off of a LCD display. Any insight on my problem would be greatly appreciated, and if you see anything that you see that you think might not work please let me know so we can further discuss the issue. Thank you.

 

Check out the Allegro sheet for the ACS712, it shows examples of a similar sensor ratiometric output.
Max.

 

Welcome to AAC.

An idea i have come up with is too have a current carrying conductor pass through the toroid core, inducing a magnetic field onto the core, which will then concentrate the flux density onto the Hall Effect Sensor

That is the standard way of using these cores.

Now i assume that this mV output is going to have to be amplified

Yes. That is not a trivial task, considering that you don't get many mV per Amp being sensed, and the input offset voltage of many low-end opamps is comparable to what you may be trying to measure. Note that the datasheet quotes 'nominal' values for sensitivity, so you would have to calibrate the sensor. I can't make out from the datasheet whether the value is per sensed Amp or is for the full rated sensed current. The output is ratiometric (dependent on the supply voltage), so that will be a factor in determining the required gain.

 

Hello, thanks for the quick reply. For this particular sensor the output is 49.6 mV/A, that is if 1 ampere of current is being carried through the conductor going through the toroid core, 49.6 mV will the output from the sensor, some confusion lies in the fact that if no current is being passed, the output of the sensor will be 1/2vcc which vcc being 5v would be 2.5v. For this project i want to be able to pass a known current say .5A through the sensor and be able, from the magnetic flux induced into the core, and the mV output of the hall effect transducer, have a LCD display this current. Not worrying too much about temperature compensation or residual magnetism drifts but would like it to be reasonable accurate, i am not going to be pushing a lot of current through this circuit as it is only for a thesis project.

 

As for the voltage in i was thinking on using either +-5v or +-12v, i also wonder if the saturation curve of the core is going to cause inaccuracy. hmm.

 

So you need to subtract the output signal DC offset and then add gain to the residual signal. This is not a difficult circuit, but it depends on the DC offset being known and stable down the the millivolt level. 1 mV of offset cancellation error equals a 2% error in the output signal. If the output is ratiometric, then do you have access to the sensor power? If so, then as this voltage varies and the output DC offset varies, you can use the same voltage to develop the DC cancellation and it all should track once tweaked.

ak

 

Would it be possible to take a more accurate measurement by looping a number of turns through the coil, and dividing the result by the number of turns?

 

Have you taken a look at this thread?

 

Have you taken a look at this thread?

Is it possible to save in older version of Autocad?
Mine is 2006.
Max.

 

Would it be possible to take a more accurate measurement by looping a number of turns through the coil, and dividing the result by the number of turns?

Yes, but only for AC unless you add parts. That is the basis of most closed-loop Hall sensors from people like LEM. However, they do have both gain and offset drift issues with temperature.

ak

 

Yes, if you loop the current carrying conductor around the core it increases the flux as well as the output proportionally. I have been searching up different sensors and came across an interesting one where it has a feedback coil around the core to act as to "null" the flux They place a Hall sensor into a gap, just as my original idea stated, and the differential output from the Hall sensor goes directly into the inverting and non inverting inputs of an op amp. The output of the op amp drives current through a multi turn coil wound on the ferrite toroid.

The idea is that the op amp drives current in such a direction through the coil as to always null out the flux in the toroid. This is an extremely linear process, because the full gain of the op amp seeks the flux null. Doing it the first way the flux in the core must change, and due to non linearities in the BH (saturation) curve of the core, the millivolt output will be highly non linear as well as temperature dependent.

This is a typical example of this type of sensor:
http://www.alldatasheet.com/datashee...LEM/LA55P.html

What do you guys suggest?

 

Is it possible to save in older version of Autocad?
Mine is 2006.
Max.

It was there now its gone?
Max.

 

It was there now its gone?
Max.

Just checked... it's still there.. have you tried reloading the page?