 You
have probably heard the old (erroneous) adage, "Ground is ground the
world around." That might have been true prior to the advent of electronics,
but it certainly isn't so anymore. Even in the vacuum tube days it wasn't
so. Once frequencies get high enough that reactance rivals resistance
for dominance, you can forget about simple grounding concepts for anything
other than providing a measure of safety against electrical shock. This
latest installment of EDN's Sherlock Ohms series is an account by John
Lombard on his experience in, "Looking
for Common Ground." He begins, "The term 'ground' should be used
more carefully. In our equipment, we distinguish between ground and
DC common for good reason. Ground refers to chassis or safety ground
to take errant AC voltage to ground instead of through an operator's
body..."
Posted September
19, 2013 |
