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Measure Capacitance — Parallax Forums

Measure Capacitance

mynet43mynet43 Posts: 644
edited 2011-10-06 22:11 in Propeller 1
I'm sure this has been covered before.

Is there code/circuit available to measure the capacitance of an unknown capacitor?

I assume it would measure the charge time, and convert it. I can probably figure it out, but I'd rather not re-invent the wheel.

Thank you for your help.

Jim

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2011-10-06 10:17
    Read the section of the BASIC Stamp Syntax and Reference Manual on the RCTIME statement. This measures the charge or discharge time of an RC circuit and there's a description of the theory and sample programs. There are a variety of techniques using the Propeller to do the same thing. The simplest is to use the RCTIME routine in the BS2_Functions object from the Propeller Object Exchange.
  • mynet43mynet43 Posts: 644
    edited 2011-10-06 10:26
    Hi Mike,

    Thank you for the quick response.

    This is exactly what I was looking for.

    Jim
  • GerryKeelyGerryKeely Posts: 12
    edited 2011-10-06 11:16
    Hi have a look at this thread

    http://forums.parallax.com/showthread.php?133712-Capacitance-Meter-demo-on-VGA&highlight=measure+capacitance



    Gerry
  • frank freedmanfrank freedman Posts: 1,983
    edited 2011-10-06 12:09
    mynet43 wrote: »
    I'm sure this has been covered before.

    Is there code/circuit available to measure the capacitance of an unknown capacitor?

    I assume it would measure the charge time, and convert it. I can probably figure it out, but I'd rather not re-invent the wheel.

    Thank you for your help.

    Jim

    Download or find the Prop ed. kit lab manual V-1.1. Check out the section on counters page 122 on measuring the rc delay of a network on one pin of the prop chip. (I have NOT tried this because I tend to find/learn/use what I need in a JIT manner. Like everyone else or my own ADD eh, who knows?) But the example uses finding the unknown value of R on a potentiometer and a known cap value. Seems that once the delta t is known it is just math from there on. Use a fixed known value of R and go from there.

    Frank
  • mynet43mynet43 Posts: 644
    edited 2011-10-06 12:32
    Thanks all!

    I think you filled in all the holes. I'm off and running.

    Jim
  • frank freedmanfrank freedman Posts: 1,983
    edited 2011-10-06 22:11
    mynet43 wrote: »
    Thanks all!

    I think you filled in all the holes. I'm off and running.

    Jim

    Hey Jim,

    I just noticed a goof in the prop Ed kit (v1.1 and v1.2) that could potentially mislead you and others on the RC ckt as shown. I am going to put it in the main part of the forum. P123 (v1.1),p127 (v1.2) manuals

    Frank
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