PC Based oscilloscope with at lest 1MHz

[anandpv2009]

PC Based oscilloscope

I need a PC based oscilloscope circuit.It should have a bandwidth at least 1mhz.
My idea is

VOLTAGE TO FREQ.CONVERTER IC ------>PIC18F2550/4550----->PC----->SOFTWARE


I am willing to write software for oscilloscope in PC but I have no enough knowledge to design the circuit.I am planning to use HID communication to interface PIC with PC

Any idea.... Please post your idea because i need a scope but i don't like to spend more money to buy one...



Thanks.....

 

[betwixt]

Re: PC Based oscilloscope

That *might* work but I doubt you would see any advantage over simply measuring the voltage with the on-board ADC.

The problem:
To measure DC up to 1MHz your V to F converter will have to run at a much higher frequency and have a linear conversion factor. The PIC can measure frequencies but not if they are very high, the resolution will not be good. Also consider that trying to accurately and continuously measure frequency may be difficult while also handling USB transfers.

Brian.

 

[anandpv2009]

Re: PC Based oscilloscope

I think it is possible if V to F conversion is possible.
Any one can suggest a circuit that converts Voltage to Freq. (1mhz bandwidth)





Thanks[/code]

 

[nandhu015]

PC Based oscilloscope

hai anand

Have you searched the net?

There are some nice completed projects on the net

this is one of them
**broken link removed**

search the net you will find more

Nandhu

 

[Jack// ani]

Re: PC Based oscilloscope

this is one of them
**broken link removed**

Nice one, very resourceful link.

Thanks for sharing with us.

 

[dian]

PC Based oscilloscope

i agree with betwixt why dont you direct convert the volatge with ADC? Every conversion step will reduce the accuracy, would you explain why you need to convert the V to F first?

 

[anandpv2009]

Re: PC Based oscilloscope

Amplitude of voltage to the PIC A/D input is limited that is why I suggested V to F ICs. I recently saw a EFY magazine (not new) with constructional details + schem. of microcontroller based oscilloscope.

 

[betwixt]

Re: PC Based oscilloscope

Measuring in the voltage domain is quite easy although achieving 1MHz bandwidth without using special hardware could be a problem. The internal ADC in a PIC isn't fast enough to sample at 2MHz (the absolute minimum rate to see 1MHz signals).

If you convert to frequency, the measurement becomes far more difficult. To be able to measure a frequency which is modulated at 1MHz, it has to be at least (Nyquist limit) 2MHz at it's lowest and a PIC will struggle to measure such short cycles accurately. If you increase the frequency to improve resolution, you decrease the ability to measure it accurately. Even if you could measure it, at such high frequency deviation it would be very difficult to keep the frequency increase linear to the voltage.

You might be able to sample fast enough if you use two or more PICs with the ADC triggering alternating between them but keeping them in sync would be difficult.

Brian.

 

[anandpv2009]

Re: PC Based oscilloscope

I think it is not easy to synchronize two or more PICs. But i will try to do....

If any ideas please post it.