[dsg-hdice] Status

Tue Feb 7 14:33:32 EST 2017

Dear Dr. Sandorfi,

Section I.1.a: Yes, we will check the CT-Box noise level here in the DSG control room. Then we will check the noise level of the CT-Box in the rack.

Section I.1.b: Correct, switching between "CT-Box Enabled" and "CT-Box Off" requires restarting the VI.

Section II: Sounds good, let me know what you find.

Section III: In the single-trigger scenario you are suggesting, the instruments would use their own individual acquisition clocks and run asynchronously.  To synchronize the CT-Box and lock-in amplifier measurements accurately for the data file, the acquisition clocks of both the instruments has to be the same or an integral multiple of the other’s frequency. 
  The lock-in amplifier has fixed sample rate intervals of 64 Hz, 128 Hz, 256 Hz, and a maximum rate of 512 Hz. The CT-Box’s acquisition frequency is programmable from 1 Hz to 100 KHz in 10 μs steps.  Since the acquisition frequencies of the CT-Box is not programmable to be the same as that of the lock-in amplifier or to be an integral multiple thereof, misalignment between the CT-Box and lock-in amplifier measurements will occur.
At an acquisition rate of 512 Hz of the lock-in amplifier, the closest possible CT-box acquisition rate is ~ 513Hz. Using the lock-in amplifier’s full buffer depth, ~16380 data points, the misalignment between the CT-Box and lock-in amplifier measurements by the end of the sweep would be ~ 32 samples.  Even if we did not have this limitation, any drift in the two asynchronously running acquisition clocks after the initial trigger would cause misalignment of the data. 
  Hence, to preclude data misalignment, it is advisable to implement a triggered acquisition system (up to 512 Hz) for both the instruments.

Regards,
Amanda

----- Original Message -----
From: "Dr. A.M. Sandorfi" <sandorfi at jlab.org>
To: "Amanda Hoebel" <amandah at jlab.org>, dsg-hdice at jlab.org
Cc: "Patrizia Rossi" <rossi at jlab.org>
Sent: Monday, February 6, 2017 7:05:41 PM
Subject: Re: [dsg-hdice] Status

Dear Amanda,

Thanks for the updated status report. Let me summarize how I understand the
situation:

Section I.1.a: you plan to investigate the source of noise seen with the
NMRS.vi when in the "CT-Box Enabled" configuration.

Section I.1.b: switching between "CT-Box Enabled" and "CT-Box Off" requires
restarting the vi.

Section II: you have completed all the requested changes, and we will test
and verify.

Section III: regarding the synchronization problem, from your report I've
learned that the shunt can indeed provide an accurate reading (to 0.005%) on
a short time scale (0.01 ms <=> 100 KHz), and so you have asked CAEN for an
upgrade that provides a signal that can be used to trigger the lock-in.
        However, you point out that the lock-in will only accept triggers at
frequencies up to 512 Hz, and you seem to be pondering this problem. This
suggests that you had planned to trigger every lock-in read with a separate
CT-Box trigger. I do not think that is necessary. It should be sufficient
for the start of the lock-in scan (and field sweep) to be triggered when a
current value (measured by the CT-BOX) crosses a user-specified threshold.
In this scenario, the fast trigger capability of the CT-Box is used to keep
up with the changing field, but only one trigger signal is used for every
IPS sweep. (eg. For a field cycle of 300 s down and 300 s up, one fast
trigger would be used to start the lock-in about every 600 s. But now all
subsequent sweeps would start at the same triggered current.) If you see any
problem implementing this approach, please let us know.

Thanks,...Andy Sandorfi

On 2/3/17, 11:47 AM, "Amanda Hoebel" <amandah at jlab.org> wrote:

> Dear Dr. Sandorfi,
> 
> Attached find DSG's response to the Status document. I have also attached the
> CT-Box users manual which contains the specifications.
> 
> Regards,
> Amanda
> 
> ----- Original Message -----
> From: "Dr. A.M. Sandorfi" <sandorfi at jlab.org>
> To: "Amanda Hoebel" <amandah at jlab.org>, dsg-hdice at jlab.org
> Cc: "Patrizia Rossi" <rossi at jlab.org>
> Sent: Thursday, January 26, 2017 6:17:21 PM
> Subject: Re: [dsg-hdice] Status
> 
> Dear Amanda,
> 
> The attached file contains three sections. (We've highlighted a few specific
> places where we would appreciate feedback.)
>  
> (I) a summary of Xiangdong's main points from Dec 5/16. As we send such
> notes back and forth, it would be helpful to "check off" the points when
> completed, and note the extent of the testing.
> 
> (II) the required range of the user-defined parameters that are loaded into
> the setup table for the NMRS program.
> 
> (III) a discussion of our synchronization requirements, with questions as to
> what options you are pursuing.
> 
> Thank you,
> Andy Sandorfi and Xiangdong Wei
> 
> 
>  
> 
> 
> On 1/20/17, 11:33 AM, "Amanda Hoebel" <amandah at jlab.org> wrote:
> 
>> Dear Dr. Sandorfi,
> 
> Thank you for your email. With regards to the 3 items
>> discussed in the meeting (functionality of Rack 2, pump cart diagram, and
>> synchronization of the lock-in amplifier data), we are awaiting the detailed
>> list for the work to be done.
> 
> The following have been completed for Rack 2
>> functionality:
>    1. Updated FRS and NMR programs to LabVIEW 2015.
>    2. Added
>> CT-box to NMR program.
>    3. Replaced old cables with new low-noise cables.
> 
>> 4. Incorporated LCD screen on RF Attenuation box.
>    5. Modified NMR program
>> to run scans with positive and negative current.
>    6. Added Tbottom and Twait
>> times to NMR program.
>    7. Made Tup and Tdown independent of each other (for
>> 10 s  300 s).
> We need to know what else needs to be focused on in order to
>> make Rack 2 completely functional.
> 
> The power-portion of the pump-cart wiring
>> diagram has been completed. The signal-portion of the diagram has not been
>> completed. We believe that the diagram you provided us is more of a block
>> diagram than a wiring diagram; however, we have removed the locks, replaced
>> the UPS batteries, and reconnected the power cords to the pump cart. We¹ve
>> requested Mike Lowry to check the connections.
> 
> For the synchronization of
>> the lock-in amplifier, details are needed for the trigger and acquisition
>> rate. We need the limits for all parameters (maximum and minimum times needed
>> for Tdown, Tbottom, Tup, and Twait), as the program can only acquire data at
>> a
>> fixed rate calculated by the total time requested and buffer depth of the
>> lock-in amplifier.
> 
> Further, we believe the NMR program should be thoroughly
>> tested before the synchronization program can begin, to establish a baseline
>> for how the program should function. At present, we estimate that the
>> synchronization program should take us about 4 months, if we are provided
>> with
>> the necessary tools.
> 
> Please provide us with this information and we will
>> work to have these items
>> completed.
> 
> Regards,
> Amanda
> 
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