monitor high and low voltage on the same channel

[asuwish4]

Hi all,

I need to monitor high and low voltage across the same source output.  The source is a welder that uses a high-frequency, high-voltage pulse to initiate an arc.  The pulse is 3600V at 1 MHz.  Once arcing has been established between the two electrodes, the pulse automaticcaly stops and the welder produces 50 or 60 VDC at 50 amps.  In reality, I don't really need to measure the pulse, just the arcing.  However I do need to ensure that I acquire the acquire data from the start (or just before the start) the arcing. 

I'm using a PXI-6229 M-Series DAQ card interfacing with SCC-68.  The sample rate is to be 25 kHz.

Has anyone had any experience with this acquisition?  Is there a low-pass filter that can handle this kind of power?

Any info would be appreciated.

Thanks!
Charlie

[Jeff_T.]

Charlie,

We do have a couple of hurdles to jump before we can measure this arcing voltage.  As you have already stated, we will need to remove the 3600V pulse off the line.  If you are able to find a filter that can handle that large signal and we gain access to a 60V signal, we still cannot measure it directly from the PXI-6229.  The 6229 has a maximum input range of 10 Volts so we will need to attenuate the 60V signal to something in that range.  We offer a signal conditioning solution with the SC-2345 and SCC-A10.  The 2345 is a signal conditioning carrier that you can connect directly to your 6229.  The SCC-A10 is a module that plugs inside the 2345 that will attenuate your 60V signal to a level that your DAQ card can handle.  Best of luck with your application, let us know how it goes.

Regards,

Jeff Tipps
Applications Engineer
National Instruments