DIY MCA Multichannel Analyzer Module for Hobby Gamma Spectroscopy 10bit ADC

Description

Gamma Viewer 1.00 - DIY MCA 1024 channels 10bit with SD logs and LCD for Hobby Gamma Spectrometry
if you previously purchased this kit you are welcome to contact me to get 1.06 hex file update
The module is assembled hobby project Multi-Channel Analyzer (MCA) board based on PIC18 microcontroller. It allows to view and collect gamma spectrum from detectors instantly without a computer and safe spectra on micro SD card (SD card is not included). The MCA uses internal 10bit ADC of the microcontroller.
The board has analog circuit that translate PMT pulses into signal that 10bit ADC can sample in better way. The spectrum is displayed on 128x64 LCD and stored on micro SD card for further analyzing with freeware BecqMonitor2011 software.
Technical specifications:
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Application: Amateur Gamma Ray Spectroscopy Project
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ADC: 10bit 1024 channels PIC18
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Energy Range: 10keV - 3000keV
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Linear / Logarithmic Scale Display
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CPS (counts per seconds) Counter for optimal measurement control
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Calibration Engineering Menu
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micro SD card socket
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Power Supply Voltage: 5V-12V DC
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Display: 128x64 LCD 2.8" with Backlight
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Require Input Signal Amplitude: 40mV-3000mV
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Require Input Pulse Duration with exponential fall: 50uS-75uS
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Require Input Pulse Raise time: 2uS-10uS
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Recommended count rate for spectra < 1000 CPS
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Module size: 71mm x 55mm x 20mm
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Shipping Weight: 150gr
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UPC Number: 634154871195
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SKU: RH-M-MCA-18
Calibration is REQUIRED -
that's why I recommend this item only for experienced buyer who know how to deal with Photo-Multiplier tubes in Gamma Spectroscopy subject and have oscilloscope available.
Input signal for MCA has it's requirements: amplitude 40mV-3300mV, total pulse duration with exponential fall 50uS-100uS, rising edge time 2uS-10uS. Be sure your pre-amplifier timings is compatible before you buy.
I also can make eBay offer for: compatible pulse amplifier with divider PCB and miniature HV modules with negative polarity for bundle purchase. Here is eBay link for recommend bundle set:
http://www.ebay.com/itm/222673887032
If you use Positive Polarity High Voltage please check compatible pulse amplifier here:
https://www.ebay.com/itm/222968272456
Need more technical details? Ask me.
Because final performance of FWHM% for your setup depend on many factors besides MCA the purchase is recommended only for experienced in subject buyers. With a good NaI(Tl) crystal and correct setup you can get FWHM resolution 7%-9% on 662keV
What is required hardware calibration for the module?
Connect the amplifier to MCA module and test TP1 has 5mV~30mV DC bias coming from pulse amplifier output or from two 0805 installed resistors.
Test TP4 and set voltage on it with small blue potentiometer. The TP4 DC need to be 10mV-40mV above the TP1 DC value. For example TP4 = TP1 + 20mV = 50mV The correct value for your setup depend on tube type, high voltage noise and lowest energy pulse amplitude.
TP2 is voltage reference point for PIC18 ADC. The circuit uses default filtered 3.3V, but the PCB allows to solder VREF IC LM4040 sot-23 or one with same pinout. If you add VREF IC then you will need to change one 0603 resistor on the module. The modification is on your own soldering skills. If you change VREF from 3.3V to any other value between 1.2V-3.0V then be sure your pulse amplifier dynamic range is limited up to your new VREF value. Supplying 3300mV pulses into ADC with VREF of 2500mV is prohibited! Not sure if you need new VREF? Just use default setup.
On TP3 you can view pulses that are coming to ADC. Connect second channel of the scope to TP1 and check that rising edges of simultaneous pulses are synchronized. If it get bumps or slopes on ADC input reading then your pulse amplifier need timings adjustment. I uploaded youtube video with correct pulses shape. Because eBay no longer allows to embed links/videos you can search on youtube for identifier
"
DIY Multi Channel Analyzer MCA test with oscilloscope TP1 and TP3
" to see calibrated pulses shape.
All further setup is only to find correct and best high voltage value on tube for better resolution. Probably TP4 re-adjustment may require for lowest energy range. It trial and error process, no one can say what is exact values you need here with PMT you connect. You can spend all day collecting spectra, comparing it and re-adjusting the settings again. Be preparing for spending hours on it.
Along with finding best HV settings you need to set up the software.
Long press on left button will open the menu. It has following items:
DUMP to SD
– will write spectrum to SD on demand. Require only if you want to safe the data before waiting spectrum collection is ended.
RESTART
– restart new spectrum, all previous data of current collected spectrum will be erased.
RETURN
– exit from menu without making and changes.
SET MAX CNT
– set maximum counts in one channel. You can set from 1000 up to 30000 counts in one channel. The value will stop spectrum measurement when number is reached in particular channel and will trigger auto-dumping to SD.
SET MAX TIME
– set maximum time of spectrum measurement in seconds. You can set from 100 up to 7200. The value will stop spectrum measurement when number is reached and will trigger auto-dumping to SD.
The first reached value between MAX CNT or MAX TIME will trigger auto-dumping spectrum to SD.
SET MIN CH
– this is minimal channel number you want to view on spectrum. It works to filter out PMT noise on energy below 20keV. Trial and error method. Default is 10.
SET MAX CH
– same as previous function, but form the top side of spectrum.
Be careful not to overlap minimum and maximum channels, otherwise the MCA will not capture any spectra.
REMOVE NOISE CPS
- when enabled, allows to show on LCD only relevant CPS counts in range of minimum / maximum channels. When disabled, all CPS events are counted for LCD. This function can be useful when you debug the noise level of your system or want to estimate full spectra CPS vs. activity for selected region. Available in firmware 1.03.
LCD ZOOM RANGE
- added LCD zoom. You can set number of channels to display on LCD from 128 to 1024.
LCD FIRST CH
- Related to LCD zoom, you can set the first channel for LCD zoom range. LCD zoom settings has no influence on SD data file. As before, the log. file will contain all 1024 channels.
SAVE&RESET
– you need to make software reset if any of functions above where changed to get it works.
During spectra measurement you can switch between linear or logarithmic scale by pressing right button shortly.
After dumping to SD make long press on right button to restart new measurement.
MODE -
toggle between MCA mode / Scintillation counter mode / UART logger more
SD FILE TYPE
- toggle between old and new SD file format (Use Spectrum Utility to convert HEX to readable CSV)
What you get on SD?
Use SD card formatted with FAT or FAT16. FAT32 is not supported.
The data is saved in CSV format file.
After spectrum measurement ended the program starts automatically to dump data into SD card. That file can be opened later with BecqMonitor2011 software on computer. You need to wait about 3 minutes in average to allow complete data transfer from microcontroller ram memory into SD log file.
Perform 3-point energy calibration of BecqMonitor2011 before you check resolution at 662keV. Use Cs-137 with K-40 to find channels number for 32keV, 662keV and 1461keV.
The software of MCA  module can automatically create up to 256 CSV files on SD card. The time stamp of files is not updated in current version. Beware, the software currently uses HEX format for file name order! It mean the first file has name SPECTR00.CSV, the tenth file has name SPECTR0A.CSV, the last file has name SPECTRFF.CSV
PIC18 ADC has small known bug on 16, 32, 64, 128, 256, 512 bin. You may see it on histogram in BecqMonitor2011 as small fall in counts with following micro peak on the next bin. Probably it's the way how internal ADC is working in PIC18 microcontrollers.
SCINTILLATION mode for searching with NaI(Tl) / CsI probe.
The mode allows you to use your NaI(Tl) probe for searching of low contaminated areas. First time you activate the scintillation mode the software will run 5 minutes calibration to calculate average and standard deviation for your probe. Calibration need to be performed on natural background without introducing any sources around.
During calibration you’ll see screen with following data accumulated/calculated:
Σ=x…x00 (summing of CPS)
ẋ = xxx (result for mean)
Ϭ = xxx (result for standard deviation)
To avoid floating point calculation the result is presented in result*100 form. That mean standard deviation of 123 should be read as 1.23 CPS. After calibration done, the MCA will show mean and standard deviation result during 10 seconds
and will automatically restart. It will use calculated values for triggering alert during searching. Mean and standard deviation are saved to memory, but cannot be seen later through menu.
Menu Functions related to Scintillation mode:
Mode SCI (SCINT MODE) – activate scintillation mode, restart applied by auto.
BEEP FREQ.HZ – set for sounder clicker frequency.
DEALAY N-pulses – the module will click on every N particle detected.
CONFIDENCE SIGMA – set 2 for fast searching or 3 for more accurate search but slower response of alert.
CALIBRATE SD – will trigger 5 minute scintillation re-calibration on the next restart.
AVERAGING SEC – 2 or 3 seconds to average CPS results. Use 2 for faster search.
Take note, some MCA menu settings for acquisition spectrum is not active in scintillation mode!
To our valued customers, please read purchase terms before you bid or buy!
We'll use the best shipping method availiable to your destination, however some areas and some countries now will take much longer to receive international mail. Please allow longer delivery time than usually and conact me prior buying if you want to change delivery method to DHL Express (recommended).
Packaging:
The product dispatched carefully packed into
antistatic bag and
sturdy carton box. We use only high quality and new packaging materials.
Technical issues and support:
If you purchase this item you are agree that you have skills and tools to perform required DIY soldering (or de-soldering) and you know how to connect additional external components or modules. All project components should be installed and soldered in proper polarity with proper connectors. Any hardware/software modifications
are not covered with warranty. You are welcome to contact us for technical support if you have any questions.
Please read carefully product title, description and include list. Any questions are welcome.
If you received broken or defective parts please contact us first, because we can resolve this problem in best way.
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Shipping:
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