Search found 62 matches

by John Myers
Tue Feb 05, 2019 5:45 am
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Spectrum Recorder PCI-E Card?
Replies: 39
Views: 2376

Re: Spectrum Recorder PCI-E Card?

To avoid aliasing sampling needs to be greater then 2 times the signal frequency. ... Sampling too fast can also cause aliasing issues, so faster isn't necessarily better. The roll off rate of a filter isn't about the sample rate it has to do with how fast a frequency can be cutoff completely. Deco...
by John Myers
Fri Feb 01, 2019 8:09 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Spectrum Recorder PCI-E Card?
Replies: 39
Views: 2376

Re: Spectrum Recorder PCI-E Card?

When the time-domain function of each type of pulse, F(x), is known you then use FFT math to convert it to its frequency-domain representation, G(x). Then when you measure a signal with multiple peaks squashed together you can use deconvolution on the G(x)'s to separate the peaks. The number of samp...
by John Myers
Fri Feb 01, 2019 6:56 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Spectrum Recorder PCI-E Card?
Replies: 39
Views: 2376

Re: Spectrum Recorder PCI-E Card?

One way to separate peaks is with deconvolution . Harald, do you just want to precisely measure the number of particles or do you also want to measure the energy of the particle? If you only want to count the particles it seems to me that you wouldn't need such a high sample rate. You would only nee...
by John Myers
Wed Jan 30, 2019 10:29 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Spectrum Recorder PCI-E Card?
Replies: 39
Views: 2376

Re: Spectrum Recorder PCI-E Card?

A rule of thumb is to sample at a rate of 2.5 times the frequency of the signal. In order to avoid aliasing you need to sample above the Nyquist rate (2x the freq). So to accurately reproduce a 20ns pulse you would sample at 125Msps. It may be possible to use a slower rate (undersampling) if there w...
by John Myers
Sun Jan 20, 2019 8:21 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Integrated Lab Measuring and Controlling (Labview, Labjack, ...)
Replies: 38
Views: 2470

Re: Integrated Lab Measuring and Controlling (Labview, Labjack, ...)

industrial Ethernet has been gaining popularity. It offers fast real-time/deterministic communication. POWERLINK and EtherCat are two protocol examples.
by John Myers
Fri Jan 18, 2019 6:53 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Integrated Lab Measuring and Controlling (Labview, Labjack, ...)
Replies: 38
Views: 2470

Re: Integrated Lab Measuring and Controlling (Labview, Labjack, ...)

Harald, Although there are generic USB drivers for things like keyboards and mice even these have special buttons that require a specific driver in order to utilize all the features on the device. There are many standard compliant ways a manufacture can TX/RX the data so even something like the scro...
by John Myers
Fri Jan 18, 2019 6:23 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Integrated Lab Measuring and Controlling (Labview, Labjack, ...)
Replies: 38
Views: 2470

Re: Integrated Lab Measuring and Controlling (Labview, Labjack, ...)

Rex, It's being able to consistently sync multiple discrete IO and interrupt signals that older micro-controllers like AVR can't do well. More modern MCU's like Xmega's do have special modules built in to address these issues. Most ADC's in MCU aren't designed for high speed, their just meant for ba...
by John Myers
Fri Jan 18, 2019 5:20 am
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Integrated Lab Measuring and Controlling (Labview, Labjack, ...)
Replies: 38
Views: 2470

Re: Integrated Lab Measuring and Controlling (Labview, Labjack, ...)

The Arduino code base is meant to be user friendly not necessarily quick and efficient. So even though an Atmel AVR chip can handle 'sensing' frequency's above 3Mhz the Arduino library and the skill of the programmer will limit the actually max frequency that can be counted accurately. Micro-control...
by John Myers
Sun Jan 13, 2019 9:45 pm
Forum: Neutrons, Radiation, and Detection (& FAQs)
Topic: Neutron Test Sources Po210+Be or U238+Be?
Replies: 15
Views: 1193

Re: Neutron Test Sources Po210+Be or U238+Be?

Sealed sources and/or exempt amounts don't require a license for the person receiving it. I just spent a little time on the NRC site and I don't see anything specific to neutron sources that prevents a licensee from distributing a sealed neutron source to the public.
by John Myers
Thu Sep 13, 2018 4:37 am
Forum: New User Chat Area
Topic: Questions on refilling Hydrogen tank
Replies: 4
Views: 998

Re: Questions on refilling Hydrogen tank

At work, for our GC instrument we only pump down the internal CYL before filling if the pressure is too low. Otherwise we just purge the fill manifold and instruments regulator/plumbing before filling.