Capacitor tolerance for oscillator

Thread Starter

Jotto

Joined Apr 1, 2011
151
Have a board that I need a 200pf 100v cap. Does the tolerance have to 1% or just go with the standard 5%? There is no tolerance marking.
 

Adjuster

Joined Dec 26, 2010
2,148
All together now, with feeling: post a schematic!

Seriously though, it depends on the role of the capacitor (e.g. a coupling capacitor may not be so critical, a tuning capacitor in an LC oscillator may matter more).

It also depends on what the oscillator is for - is its frequency critical?
 

Thread Starter

Jotto

Joined Apr 1, 2011
151
All together now, with feeling: post a schematic!

Seriously though, it depends on the role of the capacitor (e.g. a coupling capacitor may not be so critical, a tuning capacitor in an LC oscillator may matter more).

It also depends on what the oscillator is for - is its frequency critical?
There is no schematic available. They will not release one, proprietary equipment. No longer manufactured.
 

Thread Starter

Jotto

Joined Apr 1, 2011
151
All together now, with feeling: post a schematic!

Seriously though, it depends on the role of the capacitor (e.g. a coupling capacitor may not be so critical, a tuning capacitor in an LC oscillator may matter more).

It also depends on what the oscillator is for - is its frequency critical?
If I had one I would post it, all together now ....
 

Adjuster

Joined Dec 26, 2010
2,148
A photograph might help, at least to identify the physical type of capacitor used. For instance, compact ceramic types often have wider tolerances, polystyrene film or especially mica tend to be close tolerance.

You did not say anything about the frequency of the oscillator, or how accurate it may need to be. Is this similarly unknown?

A 200pF capacitor could well have a frequency determining function. If you do know the required frequency accuracy, and what class of oscillator this is,this may give you an idea of how accurate the capacitor might need to be. For instance, in an LC oscillator the frequency varies inversely as the square root of the tuning capacitance, of which which this capacitor may represent a greater or lesser fraction.

In the end, in the absence of other data you may be advised to fit the closest tolerance device you can get.
 
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Adjuster

Joined Dec 26, 2010
2,148
@Jotto: I'm sorry that I seem to have upset you by my comments about the difficulty of answering enquiries where very little data is given. I am trying to answer such queries as I can these days, and I find the dearth of of information supplied in many cases frustrating.

If you are subject to a confidentiality agreement, you might have thought to have made it clear at the outset that only limited information could be supplied. Alternatively, in the context of such an agreement, one might wonder if it was correct to make any mention of this issue in a public internet forum.

I have to say however that in my turn I am quite upset by your PM.

Perhaps it is better to say no more on the subject.
 
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