Caracteristic for PI Detector

[Philippe]

Hello
We can found a lot of information every where but all are not the same.
Does anyone who build the PI 1 detector can give me information about the depth of detection in air for some targets:
A box of soda of 33 cl.
A piece of copper of 25mm diam.
A piece of nickel of 25mm.
A gold ring of 20mm.
Many tahnks for your response.
I think that the carl'project is a good start for DIY PI , but does anyone who had make some improvement of this design can exchange them?
I work on a design with a microcontroller but i want to know if the sensitivity of the digital signal analyser will be egal to analog signal analyser like all the PI design that i had see until today.
I have make some test with different AOP and i have found that the AD8055 or EL 2045 is good choice for the speed: what do you think of this?
On all the design there is only one AOP: does using two amplifier with lower gain will not be better for the speed of the signal?
thanks for you answer
PhilippeM

[Carl]

Re: Caracteristic for PI Detector

The PI project is a very basic design for learning how PI works. There are LOTS of improvements that can be made. Using a microcontroller is one... done right, it will simplify the design while not affecting performance (no better, no worse).

The AD8055 should make a good preamp, but you never know 'til you try it. Using a 2-stage preamp probably won't help... it will be a little noisier, and the opamp speed is usually not a limiting factor.

- Carl

[Philippe]

Re: Caracteristic for PI Detector

Thanks for your reply Carl.
As i have only a pulse generator ( ne 555 like PI1) and just the first stage of the preamp ON my prototype, i 'm trying to found some person who have make some test on there design.
I spoke about microcontroleur but it will not managing only the timing but also an ADC in real time.
This is why i ask for some improvement of the first stage amp of a pi design.
At the moment the gain of 1000 in the first stage give me a recovery time of about 5 to 10µs. The first 10µs are very important in PI design so i want to have a bigger gain with a lower time recovery.
I'm trying to make a design by myself.
About the OPamp speed , i have make some measurement and the rise and fall time is better on the AD8055 and EL2045 than on a LM318 or CA3130.

Does anybody have a idea to reduce the recovery
time of the OPAMP form a output'overload?

Does any body who had make the PI1 project can give me information about the depth of detection?
type of metal , size of metal, depth of detection.
Thanks for your reply
PhilippeM