oscilloscope how to use it ?

[Hetal]

hey

well i am doing a project on pic16f877 and i coded it . now my problem is when i want to chek the signal from the output i cannot get the right output using the oscilloscop . if i do it using the analog chanel i get a sine wave with a high frequency and even if i dont place the probe i just get a smaller amplitude frequency. i tried using a digital channel , of no avail.

the chip is connected rite...

what i want to know i s how to use the oscilloscope... since my pic is operating at ...78.12 khz .. is tht the cos of me not getting a proper signal ???

 

[Nigel Goodwin]

First off you need to know what you should be getting - as you don't give any indication of what the PIC is doing, or how it's connected, then it's hard to make suggestions.

However, outputs from the PIC will be 5V p-p rectangular waves (assuming it's written to output such waveforms?). If you're getting a high frequency sinewave, you're most probably scoping the external oscillator pins.

 

[ThermalRunaway]

He says that even when he doesn't place the probe at the test point he still gets the same signal, just of a smaller amplitude. I wonder if he's picking up mains hum from surrounding equipment?

When you placed your probe at the point you wanted to test, did you ensure that it was properly grounded?

Brian

 

[giaosucan]

you had better take a pic of your osc ,we will help you ,
we need some more detail about your problem

 

[tkbits]

Well, my first question is a "did you plug it in" type of question.

The actual question is - did you connect the ground lead of the probe?

[edit] Oh, I see ThermalRunaway is also asking that question [/edit]

 

[Hetal]

output

well my pic is basically .. converting analog to digital conversion, so from the ccp1 pin i want to chek if i amgetting any output.. basicaly in the beginning i am just cheking if my pic16f877 works.. i fed the program in but i dont know how to connect to my oscilloscope,instead of a sqare wave , i am geting a sine wave which is the same even if i dont connect it ...

yes i have grounded it proprly..

is it cos i am using a high frequency that i cant see it in the oscilloscope?

 

[ThermalRunaway]

I think we need to see a circuit schematic to see how you're connecting everything and how you're stimulating the ADC. It'd also help to see a snippet of your software (the ADC handling part) to see what's going on there.

Regarding the scope, unless you're using a particularly slow scope I wouldn't have thought you'd have a problem there. Bear in mind that unless you've got a changing analog signal, the digital output will remain the same and so you won't see any change! That's why I think we need to see a circuit schematic and an idea of what you're using to test the ADC.

Brian

 

[raybo]

Your oscilloscope open will give you all kinds of waveforms in the low range. To test it tie the ground of the probe scope to the input of the probe and if you still see the waveform your scope is oscillating. next remove your probe and repeat the test. Here the idea to find out what is going on.