Hello,
I would like to design a magnetic induction loop and to integrate it in my project. In fact, I have few information about this stuff and I want some help from the members of this forum. Just for information, the space covered by this loop must be 50 cm² (I will use it into an intercom system) that's why I decided to use an amplifier with a power of 3W which is "LM4871M", also I have to follow a specific standard (It's not obligatory to follow this standard now, for this moment, I hope to succeed to hear a bit clear my voice by using a hearing aid for hard of hearing persons). As I understand from the documents that I have read, for the magnetic induction loop, I have to use a current amplifier. I think that "LM4871M" which I have used is a voltage amplifier, right? Can any one help me how to design a current amplifier for my own magnetic induction loop?
Thanks,
I would like to design a magnetic induction loop and to integrate it in my project. In fact, I have few information about this stuff and I want some help from the members of this forum. Just for information, the space covered by this loop must be 50 cm² (I will use it into an intercom system) that's why I decided to use an amplifier with a power of 3W which is "LM4871M", also I have to follow a specific standard (It's not obligatory to follow this standard now, for this moment, I hope to succeed to hear a bit clear my voice by using a hearing aid for hard of hearing persons). As I understand from the documents that I have read, for the magnetic induction loop, I have to use a current amplifier. I think that "LM4871M" which I have used is a voltage amplifier, right? Can any one help me how to design a current amplifier for my own magnetic induction loop?
Thanks,
You must make your loop, measure the inductance and then build an amplifier with the correct output impedance.
If you use a loop of 1.0mm twin and earth, (red and black in series), that will increase the impedance to say 60Mtrs in length, (twice wound) it will be approximately a 4R load. Double it again and that wll give you about 8R so any amplifier will do. Place your loop at ear height along your wall, up over doors etc.
If you use a loop of 1.0mm twin and earth, (red and black in series), that will increase the impedance to say 60Mtrs in length, (twice wound) it will be approximately a 4R load. Double it again and that wll give you about 8R so any amplifier will do. Place your loop at ear height along your wall, up over doors etc.
Duplicate thread deleted in chip amps. One thread only per topic on the forum. Thank you.Thank you for your answer, my loop is just a simple perimeter one (it will border my intercom system) with the length of max 1 meter and the section of cable will be 1.0mm2 copper or may be more depending on the tests. Well, I found some difficulties to understand the recommendations of the standard which are:
Recommended magnetic field strength is 1000 Hertz : 20 dB (± 3 dB) re 1 A/m -approx 100 mA/m
Maximum magnetic field strength is : 8 dB re 1 A/m - approx 400 mA/m
Recommended frequency response: from 100 to 5000 Hertz at +/- 3 dB at 1000 Hertz.
Signal to noise ratio greater than 47 dB
As I understand the output current of the amplifier must be between 100mA and 400mA, is it right? Also from the documents that I have read, they say that the amplifier of the induction loop must be a current amplifier not a voltage one, but you said that any amplifier can make this stuff if I make the impedance of the loop equal to 8R? could you more explain because I'm a little blocked.
Recommended magnetic field strength is 1000 Hertz : 20 dB (± 3 dB) re 1 A/m -approx 100 mA/m
Maximum magnetic field strength is : 8 dB re 1 A/m - approx 400 mA/m
Recommended frequency response: from 100 to 5000 Hertz at +/- 3 dB at 1000 Hertz.
Signal to noise ratio greater than 47 dB
As I understand the output current of the amplifier must be between 100mA and 400mA, is it right? Also from the documents that I have read, they say that the amplifier of the induction loop must be a current amplifier not a voltage one, but you said that any amplifier can make this stuff if I make the impedance of the loop equal to 8R? could you more explain because I'm a little blocked.
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