Current Input or Voltage Input

I have a question on current inputs and voltage inputs. I have read that current inputs are less sensitive to electrical noise than voltage inputs.
I believe that current inputs are safer than voltage inputs at low voltage because of electrical noise.
I believe a voltage input can make false contact. Can you provide any insight.

Yep you are right, current inputs are less prone to noise, as it relies on a constant current converted into a voltage any small spikes will have very little effect, it's ohms law.
if you pass 0.5A through a resistor of say 100 ohms the voltage drop will be constant regardless of the supply voltage.

Ahhhhh, modern technology!


Some of the current sensitive equipment in the 50's and 60's had very high resistive loops, and sometimes voltages approaching 200vdc.

Chuck said:

I have a question on current inputs and voltage inputs. I have read that current inputs are less sensitive to electrical noise than voltage inputs.
I believe that current inputs are safer than voltage inputs at low voltage because of electrical noise.
I believe a voltage input can make false contact. Can you provide any insight.

Click to expand...

Electrical 'noise' can be considered as a high impedance voltage source.
An instrument current loop is a comparatively low impedance circuit, wheras a voltage loop is a high impedance circuit.
Apply Thevenin's theorem to assess the difference.