QT designed instrumentation -measure-interference scope signatures


capacitive coupling with electric field
from mains line 50Hz (poor shielding) 5mS/div

 Magnetic coupling with stray field from
mains transformer 50+150Hz (pick-up loop) 5mS/div

Induced voltage by mainsground-current
via signal wire 50+150Hz (ground loop) 5mS/div

 IDENTICAL ground loop, 10seconds later
mainsground-current fluctuates with loads, 5mS/div

mains powered supply ripple on amp/source
100Hz (poor supply) 5mS/div

 High frequency spikes on amp/source supply
from mains switching (poor supplyfilter) 5mS/div

PC-monitor(16.25kHz or 32.5KHz) or a
switchedmode powersupply (25-100kHz) 50us/div

 Lights in room generating current
in a semiconductor sample (100Hz) 5mS/div

mechanical vibration of a Gohm resistor
in an IV-converter (knock on box) 10ms/div

 movement of an input cable from a
1GV/A current measurement 100ms/div