Products > Test Equipment
Capacitance substitution boxes
watchmaker:
I am at the point where I want to vary capacitance in ckts so I am looking at substitution boxes.
I want one using 5% caps and decadal. What are the "practical" choices for an amateur? I see everything from 50 year old rotary dial boxes to $600 lab grade boxes.
Given I have the ST42, I can always measure the capacitance I think I selected. Since it is used by an amateur, it does not need high life cycle switching (lab grade?).
THANKS
Dewey
tggzzz:
--- Quote from: watchmaker on September 13, 2024, 10:37:55 am ---I am at the point where I want to vary capacitance in ckts so I am looking at substitution boxes.
I want one using 5% caps and decadal. What are the "practical" choices for an amateur? I see everything from 50 year old rotary dial boxes to $600 lab grade boxes.
Given I have the ST42, I can always measure the capacitance I think I selected. Since it is used by an amateur, it does not need high life cycle switching (lab grade?).
--- End quote ---
What is the required capacitance range and voltage and stability?
What is the allowable inductance? (Wires are ~1nH/mm)
watchmaker:
Thanks. As you may know, I am an "innocent" when it comes to this.
I cannot see needing more than 30/50 volts. I am thinking a range of 100pF to 1 uF should suffice. At this point in my studies, I am playing with bypass and coupling in transistor circuits, basic filters and ICs like the 385 and timers like the 555/556.
I am following Boylestad/Malvino/Real analog and so basically trying to replicate a college curriculum. If I outgrow the box, not a big loss; but that is unlikely.
Ease of use and a small footprint would be helpful. I have come to appreciate the importance of capacitance in just about any circuit.
For L, I do not have enough experience to know how to respond to your request. I am not doing much over a few 100 kHz and 30 VDC. Inductance is my next sequence.
I am jumping around a little with some active circuits, but nothing yet has had much to do with inductance other than transformers which I "understand" on a middle school level. And I do understand EMF and electromagnetism, rt hand rule, etc. But that is about it. Nothing with real analysis.
Regards,
Dewey
Phil1977:
Just to mention the cheapest solution that seems possible:
https://de.aliexpress.com/item/1005006235932003.html
Kean:
Models with rotary switches tend to be quite expensive, or they are old and require contact cleaning/repair.
I bought one with slide switches from Element14 (available from Newark in the USA), but it does require you to do a little math. I also have the resistance version. Fine for low frequency applications.
https://www.newark.com/tenma/72-7265/capacitor-decade-box-100pf-11/dp/22H6398
It can also possibly be found on Amazon or elsewhere by searching for TENMA 72-7265
Specs are 100pF to 11.111uF in 100pF steps, 50V max, 5% tolerance (+50pF max internal)
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