Simple probe for measure

[Userr]

I want create Simple probe for measure AC,DC,scope diagram, and resistance.

please look and tell how I can measure AC voltage, does this correct?

http://c.1asphost.com/Userr/probe.jpg

- DC measure(R1 and R2 - not 10k - devider by 30)
- RX measure - simple (maybe not stable) current source with n-channel
transistor.

PGA use Microchip msp6s22 for choose gain and switch channel
(Can I by software in PIC measure AC without using RTS-to-DC
converter?) Maybe masure peak of signal?


For view scope-signal use nokia3310 lcd.

For high-speed measure different signal and place to lcd - PIC18F2431
with 200kbs 10bit A/D converter

Power from battery nokia - 3.6V
Help with ref voltage - chip with 2.5 vref.

[SherpaDoug]

That is a REALLY crude way to measure resistance. I think a simpler and better way is in Microchip App note 512. It uses a software controlled RC oscillator with two port pins and gives very good performance with minimal parts.
_________________
The search for better is endless. Instead simply find very good and get the job done.

[Userr]

Thanks . maybe else some circuits for measure resistance.



See at analog.com rms-to-dc ad737 ;maybe this device I can use for
AC measure.

[SherpaDoug]

For AC measurement you have to know what the signal is and what you want to measure. If the AC is 60Hz power line the PIC can probably use the DC circuit and use software to find peak to peak and RMS. If the AC is audio you may still be able to do this. You have to look at the sampling speed of the A/D, the processing speed of the PIC, and the speed at which the signal moves.

If the signal is too fast you will need either a RMS to DC chip, or a peak detector circuit, depending on which measurement you want to make.

There are litterally thousands of ways to do this. Tell us more and we can narrow the choices.
_________________
The search for better is endless. Instead simply find very good and get the job done.