Wednesday, 29 July 2015

analog - Questions on interfacing circuit for an NPN input


I have to use this sinewave outputting sensor with the NPN input of this converter. My previous question was related to the same issue but the question was about a totally different circuit design i.e. a single CE amplifier. Even the circuit was working in practice, from many expert comments I was suggested to make an interface with a comparator instead and use voltage protection.


Input is a sensor which outputs sine waves from 200mVpp to 12Vpp between 1Hz upto 100Hz. The circuit below I aim to convert these sinusoidal inputs to pulses and via comparator's open collector I want to pull down NPN input (Y1) of the F2V converter. Output impedance of Y1 is not given so I measured it with different resistors as around 2k (R1 in the circuit).


enter image description here


In simulation I get the following voltage output at Y1:


enter image description here


It seems this works in simulation for the desired input ranges.



Is my way of driving this sensor to the converter correct? Can this circuit be optimized or improved? Are the locations of TVS and diodes correct? I'm just wondering if there is fundamental error before I start soldering.


edit:


![enter image description here


Above is how I'm going to configure the setup. The points A, B, C and D are in question for protection. I was only thinking for the moment MOV or TVS for the point A.


EDIT2:


Corrected comparator circuit: enter image description here


Suggested self powered transistor circuit: enter image description here


I apply this noisy signal as an input to both:


enter image description here


With 100mV hysteresis the comparator circuit inputs:



enter image description here


Comparator circuit final output at Y1:


enter image description here


Transistor circuit's final output at Y1:


enter image description here




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