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Does SCC-A10 module provide isolation similar to SCC-AIxx module?

Does SCC-A10 module provide isolation similar to SCC-AIxx module?

I have a NRSE signal with range of 0 to 13 volts.  I am using an SC-2345 and a DAQ-6035E.

 

I have both SCC-AI04 modules and SCC-A10 modules.  I currently have it set up with the SCC-AI04 module and a resistor voltage divider on the input to scale the input from 0-13 volts to 0-5 volts.

 

I wish I could use an SCC-A10 module as a first stage and a SCC-AI04 module as a second stage, but this appears to be forbidden.

 

If I use only the SCC-A10 module, will I lose the benefit of the isolation?

 

Thanks if advance.

 

Regards, Ed Pirog

 

 

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Re: Does SCC-A10 module provide isolation similar to SCC-AIxx module?

Hi Ed,

 

Yes, the SCC-AC10 is not an isolated module. Is there something in particular you need isolation for? What’s your application?

Matt
Applications Engineer
National Instruments
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Re: Does SCC-A10 module provide isolation similar to SCC-AIxx module?

We have a number of existing systems which use a photomultiplier tube to monitor an optical process.  Mostly we use Hamamatsu R928 PMTs with C6271 sockets.  The systems have been around for years and I only recently got involved with them.  The NI hardware is 10 or more years old and it makes more sense to move forward to the current generation of hardware.

 

The operators of the existing systems do not well understand the electrical and/or electronic aspect of the system and there is lots of shop talk about 'noise' and 'ground loops'.  I am working to simplify the rats nest of wiring and to separate the myths from the facts.  There is a general sense that isolated everything is required.  I am not convinced, but I don't want to go backwards.

 

The interesting bit is that I got involved because one of the operators took a screwdriver to a home-built low pass filter and when he shorted it out, it fried up the $1500 DAQ card and the PC as well.  If it hadn't been for the screwdriver, I would not have seen it.

 

Thanks in advance for your help.

 

Regards, Ed Pirog

 

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Re: Does SCC-A10 module provide isolation similar to SCC-AIxx module?

Hi Ed,

 

I took a look at the photomultiplier tube and socket data sheets. It appears the output is on a coaxial cable, is this a BNC? These photomultipliers are grounded, correct (They are plugged in at the wall)? You can avoid ground loops by measuring your signal in a differential configuration. Take a look at this document that has a lot of information about noise and ground loops.

 

http://zone.ni.com/devzone/cda/tut/p/id/3344

 

 

I particular there is a picture about halfway down that has all the different input and terminal configurations. With a ground input signal differential or NRSE connections to your DAQ card will avoid potential ground loops. You should be able to directly connect your signal to the SCC-A10 module since it is a differential module without fear of a ground loop. Let me know if need more assistance.

Matt
Applications Engineer
National Instruments
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