[Dsg-hallb_magnets] [Dsg-internal] cernox sensors.

[Tyler Lemon]

Regarding a conversion effect or rounding effect, we are converting the excitation currents written to the LV Chassis to hexadecimal. Using a separate hexadecimal conversion test VI, there is a situation where if 1.0 uA < I1 < 1.5 uA and 0.5 uA < I2 < 0.75 uA (since I2 = I1 / 2), it is causing the hexadecimal conversions of I1 and I2 to be the same. 

However, I am not sure if I1 is in that range when the hang-up at 325K occurs. This can be checked next to time the error occurs. 

I am also not sure if this is something that could just be fixed by changing a setting in how LabVIEW converts the decimal value to hexadecimal. 

Tyler 


From: "Brian Eng" <beng at jlab.org> 
To: "Amrit Yegneswaran" <yeg at jlab.org> 
Cc: "dsg-hallb magnets" <dsg-hallb_magnets at jlab.org>, "dsg-internal" <dsg-internal at jlab.org> 
Sent: Thursday, February 9, 2017 1:18:49 PM 
Subject: Re: [Dsg-internal] [Dsg-hallb_magnets] cernox sensors. 

> On Feb 9, 2017, at 12:57 PM, Amrit Yegneswaran <yeg at jlab.org> wrote: 
> 
> thanks for the info brian. 
> glad to know you are back. 
> 
> since it is algorithmic on the spare excitation chassis, one could infer that the spare excitation chassis is in the clear. 
> for the one in use, one can't make this inference, i guess because you haven't tested it. 

It isn't a true spare, more like a prototype. Plus we usually only simulate a few channels at a time with it, not even a fully loaded one like in the Hall. There's also the fact that there's six chassis to read from, which also could be a factor in the bad readings. 

> one other question: since you say the resistance goes down to 0 ohms, V1 must be very very close to V2. 
> so when the difference is taken, could there be any precision/ bit resolution/ rounding effects in play. 
> i'm sure you have looked at this possibility. 

Not just close but both voltage readings are the exact same when it gets stuck at 325. 

So that's what would be used to determine if the initialization should be performed again, if they were merely just close that would be a valid reading. 

_______________________________________________ 
Dsg-internal mailing list 
Dsg-internal at jlab.org 
https://mailman.jlab.org/mailman/listinfo/dsg-internal 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/dsg-hallb_magnets/attachments/20170209/3dd3825a/attachment.html>