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

This area is for discussions involving any fusion related radiation metrology issues. Neutrons are the key signature of fusion, but other radiations are of interest to the amateur fusioneer as well.
Harald_Consul
Posts: 96
Joined: Sat Oct 20, 2018 10:01 am
Real name: Harald Consul

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

Post by Harald_Consul » Tue Jan 15, 2019 7:32 pm

Yes, but you won't be able to assemble the (high-frequency) data from different instruments correctly by time, then (even if they would allow a data export on USB stick or SD card).

Michael Bretti
Posts: 177
Joined: Tue Aug 01, 2017 4:58 pm
Real name: Michael Bretti

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

Post by Michael Bretti » Tue Jan 15, 2019 7:45 pm

My control and acquisition system is only for infrastructure currently, not integrating different high-precision timed instruments. For my systems (both the accelerator and propulsion chamber), chances are I will be going the very old-school route and be using an older multi-channel decent-bandwidth oscilloscope for certain timed stuff and taking photographs of the screen (I recently acquired a working Tektronics 2465 4-channel 300MHz scope for free that I will be using for my system) for the time being. This will work for what I need to accomplish (due to my own cost restraints and experimental requirements) however your system and requirements will certainly be different. However, I can say that at least for controlling your vacuum system and monitoring the vacuum, MegunoLink can be convenient for quickly building a user interface. If using multiple fast-timed instruments, depending on the instrument, they can be synchronized through various analog input and output triggers as needed (if they include such IO). You do not necessarily need to use a sophisticated control software for this, though there are advantages to this.
Last edited by Michael Bretti on Wed Jan 16, 2019 4:05 am, edited 2 times in total.

Chris Mullins
Posts: 59
Joined: Sun Feb 19, 2017 4:32 pm
Real name: Chris Mullins
Location: Shenandoah Valley, VA
Contact:

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

Post by Chris Mullins » Wed Jan 16, 2019 1:23 am

For high speed data acquisition, I'll use a Siglent scope permanently dedicated to my system. Two channels at up to 1Gsamp/sec, 14Msample storage is pretty good for under $400, and can always be put back in service as a standalone scope. I can't stream high speed data to the PC continuously, but I have all the trigger mechanisms supported by the scope to capture what I need at whatever timebase I want.

I tend avoid Windows instrument drivers whenever possible. I've found it's better to use an instrument's RS-232/Ethernet/GPIB/RS-485/USB virtual comm port, and send SCPI commands directly to it with its own native command set. That avoids any finicky Windows or Labview driver issues, is OS-agnostic, and makes it easier to work with a range of tools like Python, MATLAB, BASIC, or even right on a command line by hand. That's how I'll be interfacing my venerable Keithley 617 electrometer alongside my shiny new Siglent scope with MegunoLink. The MegunoLink interface to each device will be through their standard SCPI command sets, not some high level Labview driver.

Michael Bretti
Posts: 177
Joined: Tue Aug 01, 2017 4:58 pm
Real name: Michael Bretti

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

Post by Michael Bretti » Wed Jan 16, 2019 2:13 am

Chris brings up a very good point. Something like MegunoLink could be used to interface with your high speed acquisition modules and synchronize everything. You wouldn't use the software or arduino by itself for the high speed acquisition part directly. I know that the software can in theory support unlimited serial devices. So it will act as the control system, where all of the peripherals are interfaced to it. Similar with how something like EPICS is used for accelerators.

Eventually I would like to have my software synchronize timing (like firing pulsed thrusters or the accelerator and synchronizing aquisition to it through various scope and instrumentation triggers) and do plan on adding control pages for the two systems, but cost prohibits me for running all of the necessary cabling for now (my system needs to be remote and at a distance since the accelerator would be far too dangerous to be directly near.) So I'm going with less automated, more direct alternatives now to just get stuff running.

Chris, sounds like you are working on a pretty sweet setup, looking forward to seeing more how it progresses! If you do go the MegunoLink route, I'd also definitely be interested in seeing your implementation for it.

User avatar
Richard Hull
Moderator
Posts: 11611
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

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

Post by Richard Hull » Wed Jan 16, 2019 5:34 am

I view the Arduino as strictly a micro-controller. Odd how that is what such items are called and labeled in the real world. When I say controller I am talking more or less industrial level measurement and control. ie. sensing a voltage, pressure, temperature and rather immediately working a mechanical contrivance, pump, valve, moment arm, warning klaxon, relay, solenoid, motor, etc.

I have tested the response time on a 5 line coded interrupt service routine on the stock 16mhz, Arduino Uno, Pro-mini and Nano which are virtually all identical and interchangeable by their control functionality. I found the average response input to the interrupt line to an output signal from the performance of the interrupt service routine to vary between 10-30 usec under most situations. The Arduino is used where milliseconds matter in a process under control.

This is far faster than needed for virtually all "real world" control applications, but totally untenable for tight multi-measurement, time ordered situations. The o'scope is needed... or.... special, ultra-fast, dedicated hardware/software devices specific to the application.

If you don't like riding around on O,scoping efforts in your application where it is far too hands-on, be prepared to pull out a fat, well endowed wallet and see it go on a rapid monetary diet plan. This is when 1 microsecond is considered an eternity. You are obviously not controlling anything in the real world sub-microsecond other than perhaps a laser pulse or pockels cell, you are just taking data for dabbling with later, at your leisure in ponderous human time frames.

Definitely apples and Ferraris

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Jerry Biehler
Posts: 874
Joined: Tue Nov 24, 2009 8:08 am
Real name:
Location: Beaverton, OR

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

Post by Jerry Biehler » Wed Jan 16, 2019 7:52 am

No, I didn't hack the sensors, they come with analog out as standard, in the manual they tell you how to decode the voltage signal to get useful information. I just apply the math in labview and I get my pressure reading out.

I have a 2465 too, good scope. If it is the original 2465 they have an issue with the cooling fan you need to watch out for. If it stops running you can fry the U800 chip which is basically unobtanium at this point. Mine was dead when I got it and I found a rebuilt one from a company on the internet. They are a custom buehler brushless motor and tough to replace without a lot of mods. The B and C versions of the scope went to a traditional muffin fan for cooling.

Kinda meh on the Megunolink. Like I mentioned before you can get the real full version of LabView for $50 for home use and it is way more capable than that and about the same price. There is even a LabView interface for it from NI: http://www.ni.com/gate/gb/GB_EVALTLKTLVARDIO/US Have not tried it so I dont know anything about it thought.

I would say the arduino is more of a devkit than anything else since it has the support circuitry needed to program it and get it to talk to the outside world. Just has a fancy boot loader on it to talk to the arduino IDE. I personally use Teensys instead of arduinos, they are compatible software wise but offer some micro controllers that are much more powerful.

Harald_Consul
Posts: 96
Joined: Sat Oct 20, 2018 10:01 am
Real name: Harald Consul

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

Post by Harald_Consul » Wed Jan 16, 2019 1:24 pm

Thank you all for those good contributions to the topic.

Maybe some overviewing this field could do a short summarizing synopsis with the strengths and weaknesses of each measuring approach to provide guidance for the others?

Harald_Consul
Posts: 96
Joined: Sat Oct 20, 2018 10:01 am
Real name: Harald Consul

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

Post by Harald_Consul » Thu Jan 17, 2019 12:43 pm

Ok, I got you. Once I want a summarizing synopsis, I have to do it.

But these points are stil open (to do this):
  • High frequency sensing with Atmel controller chip (Arduino)
  • Time synchronisation of different (high frequency) meters
Maybe a trigger signal e.g. from a pulse generator can be used for time synchronisation?

User avatar
Richard Hull
Moderator
Posts: 11611
Joined: Fri Jun 15, 2001 1:44 pm
Real name: Richard Hull

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

Post by Richard Hull » Thu Jan 17, 2019 2:44 pm

Regarding HF sensing for synchronization for the Atmel IC. If you go native and don't use the IDE in the Arduino, I have no idea. I use the Int0 on the Arduino and am able to count and record up to about 24,000 pulse per minute with a simple three line interupt service routine one of thus lines demands a 300us delay every time it is run.

I guess we need to know what you might figure is high frequency.

A test might involve the one line code in the service routine ( count++;) and see how close it comes to the frequency on the int pin. I would be stunned if it did an accurate count beyond 20khz

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Harald_Consul
Posts: 96
Joined: Sat Oct 20, 2018 10:01 am
Real name: Harald Consul

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

Post by Harald_Consul » Thu Jan 17, 2019 6:50 pm

Update. Currently these points are still open:
  • High frequency (> 3 MHZ) sensing with Atmel controller chip (Arduino)
  • Time synchronisation of different (high frequency) meters
  • Running (old) USB-drivers on (old) Windows in a virtual machine to reenable old measuring equipment (typically the Windows drivers of the equipment do not work on the second next Windows version any more)

Post Reply