[Dsg-hallb_magnets] TR817A2 at 325 K, LV cRIO restarted.

[Amrit Yegneswaran]

you see brian, its just like between you and me. 
we argue about so many many things, but never on those you understand! 
amrit 


From: "Probir Ghoshal" <ghoshal at jlab.org> 
To: "Brian Eng" <beng at jlab.org> 
Cc: "Amrit Yegneswaran" <yeg at jlab.org>, "dsg-hallb magnets" <dsg-hallb_magnets at jlab.org>, "Glenn Young" <gyoung at jlab.org>, "Ramakrishna Bachimanchi" <bachiman at jlab.org>, "Ruben Fair" <rfair at jlab.org> 
Sent: Friday, April 21, 2017 2:03:10 PM 
Subject: Re: [Dsg-hallb_magnets] TR817A2 at 325 K, LV cRIO restarted. 

Brian, 
Excellent..! 
Now i get this...this is to target a voltage instead of power..! 
and still is current driven and doing the differential maths for calculating resistance. 
suggest to target 15mV and lower end to a current 400nA...as discussed and agreed with Rama. 

I am happy if you can deploy this at the earliest...as discussed you can do this but please keep Tyler in the loop. 

Regards 

Probir 

----- Original Message ----- 
From: "Brian Eng" <beng at jlab.org> 
To: "Probir Ghoshal" <ghoshal at jlab.org> 
Cc: "Amrit Yegneswaran" <yeg at jlab.org>, "dsg-hallb magnets" <dsg-hallb_magnets at jlab.org>, "Glenn Young" <gyoung at jlab.org>, "Ramakrishna Bachimanchi" <bachiman at jlab.org> 
Sent: Thursday, April 20, 2017 11:17:29 AM 
Subject: Re: [Dsg-hallb_magnets] TR817A2 at 325 K, LV cRIO restarted. 

I'm still not entirely sure why this is the case. 

The Cernox will work with a fixed voltage since that's how they were calibrated from the factory. The chassis also works fine when using a fixed voltage (and usually with a lower power dissipation as well). 

Instead of varying the current to target a wattage, it varies the current to target a voltage (and only uses V1 & I1 for the target, but still uses V1/V2 & I1/I2 for the actual temperature calculation). Just as a side note, that's what the start up algorithm does as well (only using V1 & I1). 

Granted I've only simulated it on a few channels of a few example chassis numbers, but if you have any outlier sensors you'd like me to test I can. This is being tested with the same calibration values as the real system. 

As an example, using chassis 1 cernox 1 @ ~4K (~76000 ohms) the fixed voltage (10 mV for V1) algorithm has a power of ~0.001 uW instead of 0.009 uW that the current algorithm uses. 

> On Apr 20, 2017, at 10:20 AM, Probir Ghoshal <ghoshal at jlab.org> wrote: 
> 
> Dear All, 
> 
> This has been discussed, reviewed and explained that we cannot use fixed voltage solution..! 
> This system is not designed for.. 
> The cernox resistance changes from ~150 Ohms at 300K to ~70,000 Ohms at 4.2 K over the operational range. 
> This is based on the Power and constant current... 
> 
> Rama - Please let Tyler set a fixed current say below 30-25K..Instead of I2-I1..! 
> 
> Regards 
> 
> Probir 
> 
> 
> ----- Original Message ----- 
> From: "Amrit Yegneswaran" <yeg at jlab.org> 
> To: "dsg-hallb magnets" <dsg-hallb_magnets at jlab.org>, "Glenn Young" <gyoung at jlab.org>, "Ramakrishna Bachimanchi" <bachiman at jlab.org> 
> Sent: Wednesday, April 19, 2017 6:04:33 PM 
> Subject: Re: [Dsg-hallb_magnets] TR817A2 at 325 K, LV cRIO restarted. 
> 
> tyler, 
> adding what you didn't mention in your e-mail: 
> as we discussed in the dsg meeting today, are there plans to implement brian's fixed voltage solution? 
> or are we going to continue restarting in the foreseeable future? 
> amrit 
> 
> 
> From: "Tyler Lemon" <tlemon at jlab.org> 
> To: "Glenn Young" <gyoung at jlab.org> 
> Cc: "dsg-hallb magnets" <dsg-hallb_magnets at jlab.org>, "Ramakrishna Bachimanchi" <bachiman at jlab.org> 
> Sent: Wednesday, April 19, 2017 5:15:36 PM 
> Subject: Re: [Dsg-hallb_magnets] TR817A2 at 325 K, LV cRIO restarted. 
> 
> Hello Glenn, 
> 
> The table attached shows since January, 1 2017, which Cerenoxes have had the error, how many times a Cerenox has had the error, and the dates of the error. 
> 
> Best regards, 
> Tyler 
> 
> 
> 
> 
> 
> From: "Glenn Young" <gyoung at jlab.org> 
> To: "Tyler Lemon" <tlemon at jlab.org> 
> Cc: "dsg-hallb magnets" <dsg-hallb_magnets at jlab.org>, "Ramakrishna Bachimanchi" <bachiman at jlab.org> 
> Sent: Wednesday, April 19, 2017 4:47:55 PM 
> Subject: Re: [Dsg-hallb_magnets] TR817A2 at 325 K, LV cRIO restarted. 
> 
> Dear Tyler, 
> Do we have statistics of which Cernox exhibit the 325k error? I.e. is it randomly distributed or are there a few specific ones that are most like to have the problem? 
> Thanks, Glenn 
> 
> ----- Original Message ----- 
> From: "Tyler Lemon" <tlemon at jlab.org> 
> To: "dsg-hallb magnets" <dsg-hallb_magnets at jlab.org>, "Ramakrishna Bachimanchi" <bachiman at jlab.org> 
> Sent: Wednesday, April 19, 2017 4:10:47 PM 
> Subject: [Dsg-hallb_magnets] TR817A2 at 325 K, LV cRIO restarted. 
> 
> Hello, 
> 
> TR817A2 was at 325 K this afternoon. The Torus LV cRIO was reset and the Cerenox now reads 4.75 K. 
> 
> I did not get a screen shot of the raw data from the error. I initially connected to the LV cRIO from a different PC than usual. This PC did not have the required LabVIEW packages installed, causing an error when connecting to the cRIO. This error stopped the program. After moving to the PC normally used for Hall B LabVIEW, the program was successfully restarted following the normal restart procedure. 
> 
> Best regards, 
> Tyler 
> 
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