[Dsg-hallb_magnets] More information for cernox dropout on cryocon

[Renuka Rajput-Ghoshal]

Hello Tyler,
About the grounding issue, please contact Scot Spiegel. He should be able to help/suggest you.
Thanks
Renuka



----- Original Message -----
From: "Tyler Lemon" <tlemon at jlab.org>
To: "dsg-hallb magnets" <dsg-hallb_magnets at jlab.org>
Sent: Monday, November 28, 2016 9:55:09 AM
Subject: Re: [Dsg-hallb_magnets] More information for cernox dropout on	cryocon

Hello Nick, 

Thank you for sharing this information. The Cryocon was submitted for survey so it could be taken out of Hall B for the debugging but it can be put back into the rack. 

Regarding the lack of reference ground, I do not have the training to be able to wire the ground to the Cryocon. Would you or anyone else be able to help wire the reference ground? 

Also, would you have the Quick Start guide that Guy mentioned in his email? I am not able to get to it from Cryocon's website. 

Best regards, 
Tyler 


From: "Nicholas Sandoval" <sandoval at jlab.org> 
To: "Tyler Lemon" <tlemon at jlab.org> 
Cc: "Renuka Rajput-Ghoshal" <renuka at jlab.org>, "Scot Spiegel" <spiegel at jlab.org>, "Christiana Wilson" <grenoble at jlab.org> 
Sent: Wednesday, November 23, 2016 8:32:26 AM 
Subject: More information for cernox dropout on cryocon 

Hi Tyler, 

I compiled a bit more information for you to help with your investigation: 

1)Attached plot of four cernox sensors showing the dropout 
- This behavior started during the transition from ~80K to ~4K 
- The logger(MYA archive) reports 0 the same time the local display reads ...clipping.. 

2)Cernox Cabling diagram and Calibration curves for the sensors in question is B00000-09-0178 Rev A 
-From this drawing you can obtain the serial numbers 
Directory: 
M:\hallb_eng\CLAS12\Magnets\Torus\JLab Torus\C&I_Torus\Controls_&_Wiring\Drawings and Diagrams\In Work Drawings\Torus PDF Files 08-18-2016 
-Using the serial numbers you can look up the calibration curve for a starting point on the dummy loads 
Directory: 
M:\hallb_eng\CLAS12\Magnets\Torus\JLab Torus\C&I_Torus\Controls_&_Wiring\Calibration Information\Cernox Background Info 


3) Looking at Guy's response to Robert and also from his correspondence with me I would start with the lack of reference ground. This probably means any dummy load testing may be better simulated as installed in the Hall. Try to make the controller display clipping first then add a reference ground and see if it goes away, etc. 

CryoconTech Support (Guy): 
"You are correct that the message ..Clip. should not be on steadily. The 
message will sometimes flash with ACR sensors when the unit is first 
searching for the resistance. If it stays on, there is a problem, 
usually from shielding or grounding. The message indicates that there is 
an over-voltage condition on the input. It has nothing to do with the 
calibration curves you uploaded." 


"Please be sure that there is a connection between the rear panel of the 
instrument and a ground point. This can be done by connection of the 
input cable shield to a ground. Since the two-wire external power supply 
does not provide a ground reference, an external one needs to be made. 
Otherwise, AC pickup can cause erratic readings." 

Best Regards, 
Nick 


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