crystal oscillator frequency test

Thread Starter

starir

Joined Nov 11, 2011
9
Hi. I've made a frequency meter with arduino that can measure signals made by signal generator. but when I connect it to a crystal in microcontroller circuit or crystal in crystal driver (transistor driven) circuit, it can't measure the frequency to test the target crystal. I measured the signals and guess the amplitude is low. how I can amplify the amplitude of output signal of crystal oscillator ?
thanks.
 

Alec_t

Joined Sep 17, 2013
10,385
Your Arduino input impedance may be stopping the crystal oscillator, or the oscillator frequency may be too fast for the Arduino + software to cope.
 

ian field

Joined Oct 27, 2012
6,543
Hi. I've made a frequency meter with arduino that can measure signals made by signal generator. but when I connect it to a crystal in microcontroller circuit or crystal in crystal driver (transistor driven) circuit, it can't measure the frequency to test the target crystal. I measured the signals and guess the amplitude is low. how I can amplify the amplitude of output signal of crystal oscillator ?
thanks.
Integrated oscillators are usually a linear biased inverter gate - the in and out pins are usually identified so you can tap a sync signal for other devices. A CMOS buffer should do the trick.

With a transistor oscillator; i'd suggest a JFET source follower buffer, but the cut off VGS will probably be too much for this application.
 

Thread Starter

starir

Joined Nov 11, 2011
9
we are producing some MCU based boards that all have 16MHz SMD 4 pin (2 GND pin) crystal oscillator in high volume. unfortunately the number of failures on crystal oscillators is high and I'm trying to make a equipment to test crystals before production.
your link is helpful and I tested some of this circuits before. I created three circuit for this purpose but the amplitude is low yet.

one of my created circuits (from google search) have 2 section (tests crystal out of microcontroller circuit), the first section drive the under test crystal with a transistor and turn it on and the second section will turn on a LED with a transistor that will be on by the first transistor and show the status of under test crystal. this circuit is around the web with variety of parts values but with similar scenario. the problem of this circuit is, when I insert target under test crystal into this circuit, the LED will turn on even if the crystal output be half of the frequency defined for it, for example if the crystal give 8MHz signal instead of 16MHz, the LED turn on.
you know that output frequency of crystals may be change after damages, instead of completely disconnect or short circuit.
the second circuit I made was with 74HC4060 and the third was with 74LS93. all these three circuits only can show the frequency with oscilloscope or LED, when I connect arduino frequency meter to this circuits, the frequency show zero and the amplitude is low.
 

Alec_t

Joined Sep 17, 2013
10,385
Sounds like you need a buffer stage between the oscillator and the Arduino. What are the input (pulse rise/fall time, voltage and maximum frequency) ratings for the Arduino frequency meter?
 

Thread Starter

starir

Joined Nov 11, 2011
9

Janis59

Joined Aug 21, 2017
767
If to increase up the amplitude on the crystal, You will get a cracked crystal. Just the "activity" of ZQ is killed in this way. Normally one ought be careful at any amplitudes above few Volts. If there is needed more, apply an amplifier AFTER the oscillator.
Secondly, all ZQ has TWO (different) frequencies, F(serial) and F(parallel) what differs not so very much but enough to play out the bad jokes. You ought to know which one You measure, thus the oscillator schematics have a meaning.
 
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