Polystyrene Capacitors

[Agent24]

I'm thinking of making a project (or two) that specify polystyrene for some capacitors.


A quick look shows up Farnell has at least one value out of stock, and the price rather high anyway.


I don't really know much about polystyrene capacitors, what was the reason for their use, and their disuse now?

I assume some new capacitor type came along that was better... but which one?

Is there anything I can use as a substitute or do polystyrene capacitors have some special properties that nothing else can match?

[japlytic]

Re: Polystyrene Capacitors

What project(s) are they?

Polystyrene capacitors are usually chosen for applications requiring tight tolerance coupled with high stability. The temperature coefficient is predictable when used in conjunction with particular ferrite cores to make highly stable tuned circuits or oscillators.

[larrymoencurly]

Re: Polystyrene Capacitors

Be careful about ordering styrene caps in the summer because their max temperature rating is something like just 60-65C, even in storage, and a vehicle parked with the windows rolled up on a hot summer day can ruin them. I don't know if polycarbonate or polypropylene caps are a practical alternative. You may want to search "dielectric absorption", audio websites, and websites about A/D converters.

[Agent24]

Re: Polystyrene Capacitors

First project is the capacitor meter from Silicon Chip. The ones I need for that are in stock, so it's OK. I think I will definitely use them to ensure it works as it was designed.

The other project is an induction balance metal detector from ETI (Project 549)

I am not sure how critical the use of polystyrene capacitors is in that circuit.

Would it help if I scan and upload a PDF of the article?