c***@hotmail.com
2005-01-11 04:36:23 UTC
Just as Jack Mormons are untempleworthy and aircraft can be
unairworthy, a PC is unbenchworthy when used as a source or a
demodulator of audio for test and measurement purposes.
For one thing, the drives and power and reset buttons are on the front
whereas the sound card, usually the I/O in this application, is either
a PCI card in the back or on the motherboard.
The input and output are by a couple of sub-mini phono jacks.
This alone makes it unbenchworthy. But these problems can be addressed
by DIY measures. The fact is that others, however, cannot.
The PC has a low-priced, noisy switchmode supply and a usually total
lack of RF shielding internally. While not audible, the noise level can
and will be induced in cabling to the DUT, the DUT itself, and
everywhere else.
The PC soundcard is an entertainment grade, AC-coupled, single ended
affair. PCI cards with more sophisticated, instrument grade design do
exist-however they are often quite expensive. Serious cards designed
for legit T&M work, usually CompactPCI, PXI, or VME/VXI, are
astonishingly expensive. As are their host backplanes, enclosures, and
CPU cards (although old VMEbus stuff can usually be found and the
appropriate software compiled for the OS you wind up running.)
There are PC PCI oscilloscopes, spectrum analyzers, and arbs which
provide their own shielded and filtered micro-environment, but not only
they no cheaper than a standalone piece of test equipment, the host PC
still has all of the above disadvantages.
In short, PC-based test sucks for hobbyists, technicians, and
educators. It's probably OK for ATE installations, usually they go with
the aforementioned PXI or VXI for good measure and inflate the budget
anyway.
unairworthy, a PC is unbenchworthy when used as a source or a
demodulator of audio for test and measurement purposes.
For one thing, the drives and power and reset buttons are on the front
whereas the sound card, usually the I/O in this application, is either
a PCI card in the back or on the motherboard.
The input and output are by a couple of sub-mini phono jacks.
This alone makes it unbenchworthy. But these problems can be addressed
by DIY measures. The fact is that others, however, cannot.
The PC has a low-priced, noisy switchmode supply and a usually total
lack of RF shielding internally. While not audible, the noise level can
and will be induced in cabling to the DUT, the DUT itself, and
everywhere else.
The PC soundcard is an entertainment grade, AC-coupled, single ended
affair. PCI cards with more sophisticated, instrument grade design do
exist-however they are often quite expensive. Serious cards designed
for legit T&M work, usually CompactPCI, PXI, or VME/VXI, are
astonishingly expensive. As are their host backplanes, enclosures, and
CPU cards (although old VMEbus stuff can usually be found and the
appropriate software compiled for the OS you wind up running.)
There are PC PCI oscilloscopes, spectrum analyzers, and arbs which
provide their own shielded and filtered micro-environment, but not only
they no cheaper than a standalone piece of test equipment, the host PC
still has all of the above disadvantages.
In short, PC-based test sucks for hobbyists, technicians, and
educators. It's probably OK for ATE installations, usually they go with
the aforementioned PXI or VXI for good measure and inflate the budget
anyway.