Multimeters typically supply a small voltage through the probes and measure
the current. That's why in the old days you had to "zero" your ohm meter, to
account for variations in the batteries, etc.
The easiest way to measure resistance with the Stamp is to use the POT
(Stamp I) or RCTime (Stamp II) commands. These are made to measure the time
it takes a capacitor to charge or discharge through a resistance. Therefore
you can use it to determine R or C if you know the other one. The idea is
that you discharge the capacitor and then wait for it to charge up to the
Stamp's input threshold voltage. When the voltage on the capacitor flips
from a logic 0 to a logic 1, the Stamp reports the time. You can do the same
thing if you reverse the words charge and discharge along with 0 and 1 in
the above sentence.
Read the Stamp manual under RCTime. You'll also find a capacitance meter
project in my book Microcontroller Projects with Basic Stamps that could
have been an ohmmeter very easily.
Regards,
Al Williams
AWC
* Measure 8 pulse inputs with the PAK-VII -
www.al-williams.com/awce/pak7.htm
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the current. That's why in the old days you had to "zero" your ohm meter, to
account for variations in the batteries, etc.
The easiest way to measure resistance with the Stamp is to use the POT
(Stamp I) or RCTime (Stamp II) commands. These are made to measure the time
it takes a capacitor to charge or discharge through a resistance. Therefore
you can use it to determine R or C if you know the other one. The idea is
that you discharge the capacitor and then wait for it to charge up to the
Stamp's input threshold voltage. When the voltage on the capacitor flips
from a logic 0 to a logic 1, the Stamp reports the time. You can do the same
thing if you reverse the words charge and discharge along with 0 and 1 in
the above sentence.
Read the Stamp manual under RCTime. You'll also find a capacitance meter
project in my book Microcontroller Projects with Basic Stamps that could
have been an ohmmeter very easily.
Regards,
Al Williams
AWC
* Measure 8 pulse inputs with the PAK-VII -
www.al-williams.com/awce/pak7.htm
>
Original Message
> From: BJTkid3@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=ZBRPNWYU1Luyvb0y0UiyO-B9sLP5hbSWIHIqW_q1exxmHSEoNwAELtLQRQprUWoWfDUS-WIkB3mFtg]BJTkid3@a...[/url
> Sent: Sunday, April 02, 2000 11:36 AM
> To: basicstamps@egroups.com
> Subject: [noparse][[/noparse]basicstamps] Multimeter
>
>
> How do multimeters measure resistance? and is there any way to do
> this with a
> stamp
>
>
>
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