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Hello to All

Postby Eric38 » Mon Feb 05, 2018 3:44 pm

I am engaged in the development of pulse induction metal detectors for various applications and recently purchased a 2206B. I am still on a learning curve with this Picoscope but very impressed by its performance so far. Basically, I am looking at the eddy current decay curve from a metal target at the termination of a succession of magnetic pulses from a search coil. The single coil also acts as a receive coil between each transmit pulse, which can be of a few hundred to a few thousand pulses/sec, depending on the application. For non-ferrous objects the decay is exponential while for ferrous objects the decay is a mixture of exponential and power law decay. I also need to measure the properties of magnetically mineralised soil which has a t^-1 decay.
My one question so far is that when I go from normal mode to persistance mode and then to print, (or save and print) the waveform shifts its vertical postion relative to the grid in the printout. The induced signal in the searchcoil decays to 0V but in the persistance printout the graph has shifted upwards to 1.5 full grid divisions off 0V. This shift also shows in the print preview. Normal mode printing everything is OK.
Observation of the eddy current decay is by means of a wideband amplifier connected to the search coil and using a +5 and -5 volts supply. gain is x500 and Picoscope trigger is the falling edge of the TX pulse.
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Re: Hello to All

Postby Eric38 » Tue Feb 06, 2018 7:16 pm

I found the solution to the level shifting when printing out a persistence plot. Simply convert the data file to a Bitmap or .jpg file and everything is fine.
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Re: Hello to All

Postby Martyn » Wed Feb 07, 2018 9:38 am

Good the hear that you have found a workable solution.

It would be interesting to see a psdata file to understand what is happening. It is possibly linked to retrieving data from the scope prior to printing, where bitmap just grabs a screen image.
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