Help With EMF Probe with Meter

Something you might look at, instead of the LF351, some single supply low power amplifiers. something similar to a LM386. It's a low power audio amplifier, single supply instead of the +/- that the 351 uses.

I'll have to try it this weekend to see how it works out.

My problem is that I'm a student with the hobby of electronics. I don't know the pratical tips to improve the circuit? I trust you, but because a single supply should be better?

the original circuit shows a 9V source. The 351 is an amplifier designed to work with a +15 and -15V source together. When working with a single source supply. Dual source amplifiers don't function as well as those designed to operate on a single supply.

Here is a good article to help clear up the difference.
http://www.unc.edu/~finley/Device Design/Are single- and dual-supply op amps interchangable.pdf

Here is the pdf, because the link didn't display properly.

Hi, Mike!
If you have tested the circuit let me know how it works, thanks!

I have a new question: in practical, how I connect the meter? Is it necessary some transduction o some transittion?

Luca,

Here is a second version of the probe. I found the original shown on emanorama.net and found that a second version that was a little more stable was made. It has a little better gain control and isolates the meter and audio outputs.

http://www.epanorama.net/zen_schematics/Circuits/Testgear/emfprobe2.html

I'm building it this weekend, and will probably build the other if I can find enough amplifiers. I will most likely use my fluke to measure the current instead of using the FSD 250uA indicator.

Ok I see the second circuit but first i want try to build the first schematic.

A little question: I see in my simulation a current of amplitude about 500-600 uA. If the meter has FSD of 250uA it will be saturate from the current!Isn't it?
The current is too high respect the FSD of tne meter!

If you are seeing the 500-600 uA at the meter points, it could cause it to deflect very hard. In physical operation it will be more difficult to be able to generate the 10mV with the coil. More likely you will be able to pick up uV instead of mV. It will be a process of trial and error to find the best fit for the coil.

Last question: I see in the meter an alternate current. Is it correct? Could the meter work with this current?
Souldn't it be a direct current?

It should be coming through as a DC level, however with the diodes, it should prevent it from going negative. there will be an effective DC voltage component to the waveform and shouldn't cause the meter to wobble too much.

Hi, Mike! How do you do? Do you build and test the circuit?

It's currently half built. I ended up having to put it aside as system builds got in the way. I have the circuit laid out and wired, just adding in the resistors and caps to power.

I'm hoping I have some time this week to work with it, instead of troubleshooting systems.

Hi!
I'm going to built the circuit. Onq question: what I need to connect the 9V to the circuit? Can you link me the components? Sholud I find 9V batteries?

It looks like the transistor amp is not needed. The op amp can drive the meter.