W. C. Kreiger (waltk@VNET.IBM.COM)
Fri, 9 Aug 96 09:46:26 EDT
Thanks for your response. I'll infer from some of the statements that the
slight amount of "noise" or "ripple" on the relay's dc power source will
not cause an appreciable change in the H field. The application here is
characterization fixturing for A.T.E. connected thru a Johnstech socket
to a relatively high speed DRAM. We do have diodes across the coils, but
usually we only use relays to take the big capacitors out of the circuit
for measuring chip power supply currents. This particular application is to
allow insertion of OCD(off chip driver) load capacitance by picking the N.O.
relay. This occurs with the device off; the insertion-with-device-running is
done via FET switches on another set-up and has a different set of problems.
We decided on a shielded relay because of the low capacitance (0.1-0.3pF
COTO 9402's) when the relay is open.