How to test Crystal?

Crystal are use to keep the frequency of the clock from drifting. If
the signal from this clock stops, or is weak, or the pulses begin to
vary, the electronic equipments might show intermittent faults or
might stop altogether. The microprocessor pins that hold the crystal
are usually called OSC IN and OSC OUT as shown in Figure 1 and the
frequency is marked on the crystal. Typical examples of crystal
oscillator frequency are 3.58MHZ, 4MHZ, 8MHZ, 24MHZ etc.

Testing Crystal

Crystals are quite fragile components because of their construction.
Unlike a resistor or capacitor, if you drop one on the ground from a
decent height, its 50-50 bet whether it will work again. Testing the
crystal is not a breeze either. You cannot just take out your trusty
multimeter and plug the crystal in it. In fact, there are three right
ways to test a crystal.

Using Oscilloscope: A crystal produces a sine wave when excited. It
is appropriate then, to see a waveform representative of a sine wave
on the clock pins. If the clock is not functioning properly, replace
the crystal. In most cases this should solve the problem since
microprocessors are usually very reliable. Check the crystal with
power on.


Frequency Counter Frequency Counter can be use to check the frequency
of the crystal. The reading must be taken when the equipment power is
switch "on". Place the probe of frequency counter to the crystal pin
and read the measurement. Be sure that your frequency counter meter
has the range that is higher than the crystal frequency you are
measuring.


Crystal CheckerWith this method, usually the crystal is placed in the
feedback network of a transistor oscillator. If it oscillates and the
LED is lighten up, this mean that the crystal is working. If the
crystal doesn't work, the LED stays off. Instead of using LED, some
other crystal checker uses a panel meter to indicate if the crystal is
working or not.

more tips visit http://nunesinstruments.blogspot.com/

 

hi, try this..

http://www.diy-electronic-projects.com/p218-Crystal-Tester


mark k