Capiciance measurement device

[yash gupta]

Does anyone have any idea about making a simple device using a multimeter(without capacitance meter) and some other components to make a circuit which can measure capacitance up to say 1uF.

 

[ericgibbs]

Does anyone have any idea about making a simple device using a ammeter and some other components to make a circuit which can measure capacitance up to say 1uF.

hi,
Look at this link:
Simple Capacitance Meter - RED - Page144

I Googled simple capacitance meter lots of hits.

 

[Ubergeek63]

hi,
Look at this link:
Simple Capacitance Meter - RED - Page144

I Googled simple capacitance meter lots of hits.

that particular one seems flawed... I have to wonder if it would be as sensitive to supply voltage if he was not relying on the drain source resistance which is highly dependent on supply voltage. It seems to me he could replace the regulator with a resistor on the DUT IC driver pin.

My experience with schmidt triggers is that they are reasonably well matched within a single IC.

 

[yash gupta]

It seems to me he could replace the regulator with a resistor on the DUT IC driver pin..

Would you please explain me what it means, as I am very new to electronics and I don't have much knowledge about it.

 

[yash gupta]

Thanks for the circuit.

 

[MikeMl]

How about a 555 as an astable oscillator. If you have an oscilloscope, or frequency counter, the frequency of oscillation is a direct function of the unknown capacitance.

I have**broken link removed**

 

[Ubergeek63]

Would you please explain me what it means, as I am very new to electronics and I don't have much knowledge about it.

sorry DUT=Device Under Test ... Cx in the schematic. A small resistor on IC1 pin 10 will keep swamp out the varying output resistance of IC1 over supply voltage.

the IC called out (CD4093) has a 560 ohm output resistance at 5V and a 170 ohm output resistance at 15V...

a 74HC132 has 75 ohm at 4.5 and 58 ohm at 6V supply.

a 74LVC132 has 33 ohms at 3V and 110 ohms at 1.65V

as the supply voltage changes so does the PWM since the IC output resistance is changing. using a better IC and a resistor in series with pin 10 is less costly than adding a regulator

 

[yash gupta]

using a better IC and a resistor in series with pin 10 is less costly than adding a regulator

Please suggest me a 'better IC' and the value of the resistor to be used.
Thanks for your interest and I want to know that should I make the circuit or not(Do you think it is good and will work?).

 

[yash gupta]

Sorry, but I don't have an oscilloscope or a frequency counter.

 

[Ubergeek63]

i think would use a 74HC132 as it is readily available, as opposed to the LVC part, with a 1K resistor on pin 10.

I would further move the scale switch to pin 10 eliminating C1,3-5 as well as SW1B and calibrating the 10uF position with R6 still between pins 1 & 3.

simpler to build, simpler to get parts for and more accurate. 0.01uF caps are easy to get NPO if you want more stability.

 

[MikeMl]

Does your computer have a sound card? There is free frequency counter software that will count the freq applied to the LINE input as long as that frequency is between ~20Hz and 20,000Hz. The 555 oscillator circuit I mentioned can be calibrated to produce an frequency in that range.

 

[yash gupta]

Please, please, post the circuit diagram of the circuit you are suggesting.
I would be very thankful to you for that. and thanks for the help you have given till now.

 

[yash gupta]

Yep, I have a sound card, but I would not like to carry my computer or my caps everywhere to measure them, and is it safe to put external currents into a computer(it may get damaged)?

 

[Ubergeek63]

schematic

not all the values worked out...

should not need to adjust zero when switching ranges

 

[MikeMl]

Here is the 555 oscillator. If substituting for R1, keep it between 10K and 1Meg. Try to keep the oscillator frequency between 20Hz and 20Khz. Use a shielded RCA jack audio cable to go the Line-IN (either channel) on the computer. It will not damage the sound card. Herei s some sample software.

 

[yash gupta]

Thank you for the schematic.
I'm sorry to eat your brain, but till me what does "not all the values worked out..." mean.
Which values are you talking about?

 

[yash gupta]

Thanks guys for the help!