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Entry  Tue Apr 23 22:28:53 2013, tara, Notes, TempCtrl, temp sensor on heat shields 
    Reply  Fri May 10 01:24:01 2013, tara, Notes, TempCtrl, temp sensor on heat shields 
Message ID: 1173     Entry time: Fri May 10 01:24:01 2013     In reply to: 1158
Author: tara 
Type: Notes 
Category: TempCtrl 
Subject: temp sensor on heat shields 

AD590s on both thermal shields are not working. I was wrong when I checked them at the first time.

The temp sensors in the vacuum tank for monitoring temperature on heat shields are wired as shown in the picture. The resistor,R, is 30k ohms. According the the datasheet, the current from AD590 should be ~ 300uA, (30kx300uA = 9V). But what I read from the voltage across the readout R was 20V which was over the input range of EPICS (+/-10V). This happened on both of them. I compared the readout with a left over AD590, and got ~ 9.3 V readout which was expected at room temp.

At first I thought it might still be working linearly and useable if I just switched to lower R. However, with R=12 k, the readout voltage was 18V (I expected 20x(12/30) =8V). So certainly, this is not working.

I think the reasons they are broken is that they were overheated when I soldered them. I tried to be careful, but, apparently, that was not enough.

I'll check if there are spare AD590s in the lab or not, otherwise I'll order some more.

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