"DoN. Nichols" wrote in message
...
On 2013-07-28, Jim Wilkins wrote:
Windows polls them, destroying your setup.

Hmm ... no way to tell Windows to keep its hands off those
ports? Another reason not to like Windows, then. :-)

Windows periodically checks printer status with the control bits, and
has a fit when it sees some combinations of the status bits. AFAIK it
leaves the data bits alone. I wrote a program to display and control
each bit.

Sounds like the team got the payback satisfaction, then. Were
the problems in the code a result of some limits which he put on the
team, thus making it even more appropriate that he get the
o-dark-hundred calls? :-)

A state-of-the-art semiconductor test station is a very complex and
tricky machine that the IC designers may use in ways they wouldn't
reveal to us. Like machine tools some combinations of operations will
misbehave or crash.

For example to measure the resistivity of certain IC structures you
might have to apply 100 Volts and measure the resulting current flow
in picoAmps. 100 V in the wrong place can do a bit of harm.

The current sensing circuit for that was an AD515 op anp integrator
with a 10pF silver-mica feedback cap. Its residual noise level was a
few hundred femtoAmps.

At those levels the error current from dielectric absorption can
appear huge, so we had W.L.Gore make us special Teflon-insulated reed
relays for the switching matrix. Even they weren't immune but the
absorption current dropped below a picoAmp within 5mS, which was
acceptable.
http://en.wikipedia.org/wiki/Dielectric_absorption

Simply not tightening the shelding enough raised the noise
dramatically. Without the shield it was a fine intruder detector.

Surprisingly I needed only a space frame box with wide-open sides to
fully shield it for the test and calibration fixture. The circuit
rejected 60 Hz and above very well and the seemingly gaping access
holes were too small for lower frequencies.

At a previous job I had designed and built a test station that
measured the reverse leakage of TV high voltage rectifier diodes. The
circuit forced 1 microAmp at up to 40,000V. The sample diodes measured
over 25KV at that microAmp. The current regulator was a 1 MegaWatt
(pulse) radar transmitter tube with X-Ray shielding.
jsw