QT designed instrumentation -measure-interference from equipment


Interference shown here is generated by the specific instruments themself. It is a result of the implementation of digital switching circuits.

spikes (rise time 100nS) from the INPUT of a battery-powered handheld multimeter measuring at 100uV resolution on a 10Mohm sample 2mS/div

spikes from the INPUT of a high-end voltmeter measuring at 100nV resolution on a 10Mohm sample, 1mS/div

spikes at the output of a commercial analog lowpass-filter set at 1kHz (possible origin: it has a clocked LED-display at the front) 0.5mS/div, 5mV/div
Interference on the INPUT of a (commercial)currentmeter measuring at pA resolution, 1Mohm sample 200uS/div 200MHz

(lack of)Interference on the INPUT of a QT-design currentmeter measuring at pA resolution, 1Mohm sample 200uS/div 200MHz

Reference trace of the used scope, now with grounded input 200uS/div 200MHz


Although a TFT-monitor has no magnetic fields like a CRT-monitor it still emits some electric fields from the screen. This is measured before the screen of a digital scope:

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