Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Need Urgent assistance: Testing a crystal oscillator circuit

Status
Not open for further replies.

d_enthusiast

New Member
Hi guys, hope you could help me....

How could I check if I got a good frequency response of my crystal oscillator circuit, i.e. 24MHZ mounted in my motherboard. I got the board powered up, only thing is that the oscillation I measured does not respond to the value of my crystal oscillator (100kHz rather than 24MHZ) whenever I check the pin 1 with respect to DGND of my crystal oscr. I used Lecroy and Fluke 45 multimeter (frequency measurement). I already tried replace the crystal but didn't work out.

How could I measure the correct response of the crystal oscillator since I am expecting good sinusoidal waveform corresponding to the crystal value?

Is this affected by the program of my PIC but I already tried to reflash the with MPLAB using the good firmware?

Please advise. Thanks...
 
When measuring signals at that high of a frequency you need to make sure to use a x10 probe, otherwise you load the circuit down and your measurement will be incorrect if it oscillates at all. A quick and easy way is to toggle a pin high and low with a set delay between states then measure the output with a scope or frequency counter. Say you have the pin high for 20 milliseconds and then low for 20 milliseconds. look at the waveform with a scope and see if the periods match up. It is very rare that a crystal oscillates at a frequency other than what it is marked.
 
The frequency measurement facility of a Fluke 45 is only rated to 1Mhz.
Attempting to read 24Mhz will result in a fairly random display.
You need a proper frequency counter or an oscilloscope.

JimB
 
You can check if the oscillator is running by holding a short wave receiver nearby that can tune to 24 MHz. If the oscillator is running, you should be able to hear a carrier with no modulation, perhaps a small buzz sound at that frequency.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top