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Olin Student Projects 2008. Keith Gendreau Code 662 NASA/GSFC 301-286-6188. A PIC Microcontroller Based Pulse Detection and Measurement System .

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Olin student projects 2008 l.jpg

Olin Student Projects 2008

Keith Gendreau

Code 662 NASA/GSFC

301-286-6188


A pic microcontroller based pulse detection and measurement system l.jpg
A PIC Microcontroller Based Pulse Detection and Measurement System

Take an input analog signal, look for pulses above a threshold, detect the peak voltage of each pulse, digitize the peak voltage, write to a file the pulse time and peak pulse height, continue….

Build on last year’s “Flux Meter”, if possible.


X ray detection and pulses l.jpg
X-ray Detection and Pulses System

X-ray photons

Vsignal

X-ray Detector

Amplifier

X-rays pack a lot of energy. X-ray detectors see individual X-ray photons. If the detectors and electronics are good enough, they can determine the energy of the photon.

Science is to be gained by the energy of the photons.


Pulses on an analog signal from an x ray detector l.jpg
Pulses on an analog signal (from an X-ray detector) System

V

vpulse

Vpulse is proportional

to Energy of photon

Pulse widths: ~25 ns- 2µsec

t

tpulse

V

Noise pulses?

vthresh

t

Pulse#1

Pulse#2

Pulse#3


Desired layout top view l.jpg
Desired Layout: Top view System

Computer

With Olin

Software

To display/save

Events

Olin Pulse

Height Box

Analog signal

From X-ray

Detector

On a BNC

Connector

USB Output

Any type of computer, PC or Mac

(I prefer Mac, but whatever is doable)

Knob for

Lower Voltage

Threshold

Knob for

Additional

gain


Requirements l.jpg
Requirements System

  • Must handle pulses ranging from ~< 100 nsec to ~ 100 microsec wide

  • Goal of achieving ~106 counts per second (typically, it is much less than this, I’d be happy with ~104 cps)

  • Should be able to handle pulseheights ranging from ~0 to 10 volts (positive).


Output desires l.jpg
Output Desires System

  • ASCII file with time and pulseheight for each event above threshold

  • Plot with histogram of pulseheights

  • Flux vs time (like on the flux meter)

  • Be creative.

  • TCP/IP port?

    • eg, The computer reading the instrument can make the data available as a server to others as client computers via a TCP/IP Sockets protocol

    • Would be an extremely useful feature for beamline work.


From http www edn com article ca216167 html l.jpg
From http://www.edn.com/article/CA216167.html System

This is a circuit design I found that can detect a pulse peak

And hold the pulse long enough for a slow ADC to measure the peak voltage. It can then be reset to detect the next pulse after the measurement has been made.

** just a suggestion, maybe other things exist…

This one should be fast, though…


Other parts l.jpg
Other parts System

  • A threshold comparator

  • A gain circuit to provide additional signal amplification if necessary

  • A PIC microcontroller to digitize the voltage, control the peak detector circuit, and communicate the results to computer via USB. (Maybe build on last year’s “Flux meter” Project?)


How to proceed l.jpg
How to proceed? System

  • Use a signal generator to produce simulated X-ray pulses that would come out of a detector…

    • Easy to control pulse width, rate, and pulse height

  • Easier than using a detector..

  • Toward last weeks of project, I will send you a detector to try instead of the signal generator


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