Yes.Can I use LCR meter to sense the total capacitance in board ?
I can not understand what you want to mean at all.! how about check it when crystal is connected to 2pins of MCU ?
Yes, you can.I want to know if i still can use LCR meter to measure capacitance
after soldering those two components ?
I don't think so.In the shown layout, capacitance of each crystal pin against ground will be probably larger than differential capacitance,
and fortunately can be better measured with most LCR meters.
In the shown layout, capacitance of each crystal pin against ground will be probably larger than differential capacitance, and fortunately can be better measured with most LCR meters. Measuring differential capacitance requires special considerations.
Generally I presume that the capacitance can be estimated with sufficient accuracy by PCB trace impedance calculation tools. The pin-to ground capacitance will be hardly larger than 1 (or maximal 2) pF and is unlikely to cause trouble, pin-to-pin much smaller. You should know however, if the oscillator circuit is expecting external load capacitors (like e.g. PIC18 secondary oscillator) or none at all like many RTC chips.
What means "too sensitive", by the way? I experienced some cases that a 32 kHz oscillator circuit didn't work due to too large load capacitors.
Show me layers profile of your PCB.
Layers of metal
Thickness of dielectrics
Do you remove pattern underneath of crystal electrode ?
From https://www.edaboard.com/attachment.php?attachmentid=138558&d=1494082194,
Red is L1 plane.
Blue is L2 plane.
What value of thickness do you have between L1 and L2 ?
You should remove L2 plane underneath of crystal electrodes.
For example, assume five metals(L1~L5) PCB.
Crystal electrodes are L1 Plane.
Remove L2~L5 underneath of crystal electrodes.
Wrong.I don't think it should be removed,
the Blue plane is GND not other signals.
Wrong.
If recommended load capacitamce value is small and thickness between red and blue plane is thin, you have to remove blue plane underneath crystal.
This is very common sense regarding crystal, filter, etc.
Return to start of this thread,
was your origin of this thread "you doubts capacitaces seeing from crystal are too large compared to recommended load capacitor" ?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?