Why do we need a voltage regulator here?

[Neyolight]

Hi all

Here is the circuit that I will refer to: LINK : Very Accurate LC Meter based on PIC16F628A

Ok my first question, Why do we need a voltage comparator (LM311) there? A voltage comparator compare the + and - voltages and output the difference??

What I want to do is, measure the inductance of the L and then send that value to a computer for further analysis.

Thanks

 

[Prototyp_V1.0]

Ok my first question, Why do we need a voltage comparator (LM311) there? A voltage comparator compare the + and - voltages and output the difference??

Because PIC cannot read L or C directly, so there need to be something between to convert it to either time (pulse length measurement) or voltage that can easilly be read by a pic.

What I want to do is, measure the inductance of the L and then send that value to a computer for further analysis

Then you need a computer interface chip too (if the pic cannot be used to work directly to usb).

I'm not a PIC programmer, so for the last question I cannot provide any more help.

 

[Neyolight]

Because PIC cannot read L or C directly, so there need to be something between to convert it to either time (pulse length measurement) or voltage that can easilly be read by a pic.

Thats my question, why cant we simply measure the voltage drop across the inductor.

The volatge drop across inductor Vl= Xl * Il [ where Xl is the impedance of the inductor and Il is the current across it]

Xl = w * L [ w= frequency, L= inductance]

Now if we keep everything the same, change in inductance will change the voltage drop across it.

Hence, I believe measuring the voltage across the L is sufficient to measure L.

 

[betwixt]

You are assuming the meter works on a different principle. Your calculation is measuring the center voltage of a potential divider with XL as the top element and R as the bottom one. It will work but it relies upon a constant frequency and voltage as the signal source and both would have to be selectable to cater for different L and C values. It can be done but it isn't paractical.

Most LCR meters work by applying a step change in voltage to one end of the component then measuring the time delay before the other end reaches a certain potential. In other words it produces a single time measurement which can then be mathematically converted back to the value. The comparator is there to sense when the measuring side has reached the necessary voltage. It's a much easier way to take measurements.

Brian.