[Halld-tracking-hw] noise/cables

[Fernando J. Barbosa]

Hi Naomi,

The signal cable shield is connected to ground at the shaper end, only. 
You need to determine what the source of noise is (UPS, power supply, 
PC, pump, etc) and minimize its impact on the readout (turn it 
off/remove, shield it, move it away). The fact that you see well defined 
frequencies points to some switching noise on supplies or UPS, although 
some of these can also have variable frequencies.

You may also want to try an isolation transformer for the power supplies 
(HV and LV). Also use a thick insulated ground wire/braid connecting the 
end-plate to a common grounding point of the HV and LV supplies 
(chassis). What HV and LV supplies are you using? Make sure the LV 
supply is floating, i.e. the negative terminal is not connected to 
ground. There is additional information on the wiki/portal about HV, LV 
distribution and grounding.

Best regards,
Fernando




Naomi Jarvis wrote:
> Hi Fernando,
>
>
> while tracking down sources of electronic pickup in our lab, I found that the pickup is reduced by a few mV when the preamp ground is connected to its end of the preamp-to-shaper cable shielding.  
>
> I have put some scope traces online here:
>
> http://www.jlab.org/Hall-D/software/wiki/index.php/Noise_studies
>
>
> best regards,
>
> Naomi.
>   
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