PC based measurements

Hello Everybody,
I am trying to use my PC to measure resistance, capacitance and inductance
of the
respective components.
I would like to use the parallel or serial port to do it.
Do I need to have a ADC circuit to do it ?
I would appreciate any advice on this.

Thank you,
Indroneel

 

Yes, and a lot more hardware and software, including parallel port
driver and a software packet to display/store thr results.

I think you will be better off with a DVM with serial output and the
related software.

 

Yes, and a lot more hardware and software, including parallel port
driver and a software packet to display/store thr results.

I think you will be better off with a DVM with serial output and the
related software.

http://www.linuxtoys.org/dvm/dvm.html
might get you started

 

I'm not usually happy when I say how I want to do something
and people immediately respond by telling me to throw away
everything I have and do it all differently, I'm really sorry,
but ANY chance you might have a sound card you could use instead?

If you put together a tiny oscillator with the frequency
controlled in part by the component you want to measure,
adjust the amplitude to be something the sound card likes.

And then you could use available software to show the
waveform, or software to measure the frequency, and from
that calculate the value of your component.

This might be easier than building an ADC or trying to get
control of the pins on the printer port so you can measure
pulse widths and/or frequencies.

And if you really need to use one of the other ports then
just ignore everything I said.

 

If the OP had to ask this question then obviously he's got no chance
of building his own serial/parallel port LCR meter!
An off the shelf RS232 connected LCR meter (or similarly equiped
multimeter) is the way to go.

Dave

 

Yes, you need an ADC circuit, but it doesn't need to
be a "conventional" one using a commercial ADC chip.
If you are handy with programming low-level real-mode
DOS, you can do all sorts of tricks based upon timing
of printer port interrupt requests. You would need to
convert your input variables to an appropriate period or
frequency.

You can make a simple 8-bit R-2R ladder DAC that
the proper software can use to make a successive
approximation ADC. The LPTX driver for my Daqarta
software <www.daqarta.com/download> includes
complete tutorial information on how to build this,
which you can read on-line before you download.
In many cases the whole works can be completely
passive; nothing but resistors, while the PC does
all the active stuff. If you use this circuit with the
LPTX driver, Daqarta can read it as a waveform
for a scope display, spectrum, or spectrogram in real-time.

Finally, the simplest way to do many measurement
tasks is to use the joystick port on a sound card.
There have been many articles written on how to
do this. The PC essentially measures resistance
based upon how long it takes to charge up a
capacitance as the resistance varies. You can
thus measure capacitance by the reverse approach.

Hope this helps!


Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com

 

Thank you all for your replies.
Using the sound card is something, I didnt know could be done.
It looks most promising as an LCR is out of my budget and
building a ADC is a more work.
Time to read about what my sound card can do for me.
Indroneel

 

Try and google for the "parallel port faq" for how to interface circuits
with the printer port. An interesting alternative on a PC is the game
port, as it can measure resistance directly.

Note however that direct access to the pp is possible only with DOS
based operating systems, modern (?) Windozze versions require kernel
modules. So it is probably easiest to recycle an old 386 or 486 for that
type of experiments.

 

Easier and less expensive if you happen to do something wrong! Unless
you're already familiar with Windows development I'd go for Linux or
one of the BSDs - plenty of good, free development tools for more
languages than you can shake a stick at.


Tim

 

Look for "io.dll" in google, it is a free 'dll' file from which you can call routines
to access the Parallel Port. With some tricky programming it works in all versions
of Windows.
I have just purchased PureBasic (59 Euros) which works in windows, creates full 32 bit
applications, has a wysiwyg interface generator so you can create nice standard
'Windows' in minutes, and this connects to the Parallel Port via "io.dll" easily.
I am a novice programmer, only learning enough to get done what I need, and I
created a simple application that drove my P.Port interface in the first couple of days.
Regards, KT

 

Of course, when you install Linux, you can do anything you want to do
to anything in/on the machine.