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Home > Archive > Home Repair forum > October 2006 > How to measure resistance?
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| Author |
How to measure resistance?
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| Mike E. Fullerton 2006-10-30, 8:25 pm |
| I am trying to install a SunTouch spot warming mat. To check for
damage you need to test the resistance of the wires using a digital
ohm meter. Trouble is I have no idea what to set the meter at. If the
Reistance Range of the mat is 70-86 what setting would I use on the
meter? The meter is a Sperry DM-350A if that matters.
Thanks in advance.
_______
Free Windows Clipboard Utility
http://www.clipboardmagic.com/
| |
| Big Al 2006-10-30, 8:25 pm |
|
"Mike E. Fullerton" <inforequest@spam-killer-remove-techie.com> wrote in
message news:sc4dk2l2ts100003pbcn955r6amu0drc7l@4ax.com...
> I am trying to install a SunTouch spot warming mat. To check for
> damage you need to test the resistance of the wires using a digital
> ohm meter. Trouble is I have no idea what to set the meter at. If the
> Reistance Range of the mat is 70-86 what setting would I use on the
> meter? The meter is a Sperry DM-350A if that matters.
>
> Thanks in advance.
200 OHM scale.
Al
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| Mike E. Fullerton 2006-10-30, 8:25 pm |
| On Mon, 30 Oct 2006 17:17:47 -0700, "Big Al" <sal1@qwest.net> wrote:
>
>"Mike E. Fullerton" <inforequest@spam-killer-remove-techie.com> wrote in
>message news:sc4dk2l2ts100003pbcn955r6amu0drc7l@4ax.com...
>
>200 OHM scale.
Setting it to 200 on the OHM section always says 1__. no matter which
wire combination I touch the leads with.
Here's a pic of the meter.
http://www.awsperry.com/sperry/catalog?item=dm-300
I inserted the red lead into the V terminal on the right. Not sure if
that's right or not, the manual is not very clear.
_______
Free Windows Clipboard Utility
http://www.clipboardmagic.com/
| |
| Doug Miller 2006-10-30, 8:25 pm |
| In article <2n7dk2to1d66c7quek81at54coek3aoeo7@4ax.com>, Mike E. Fullerton <inforequest@spam-killer-remove-techie.com> wrote:
>Setting it to 200 on the OHM section always says 1__. no matter which
>wire combination I touch the leads with.
>
>Here's a pic of the meter.
>http://www.awsperry.com/sperry/catalog?item=dm-300
>
>I inserted the red lead into the V terminal on the right. Not sure if
>that's right or not,
It's not.
>the manual is not very clear.
I agree that the manual could be better... but the markings on the front of
the meter are VERY clear. To measure resistance, you plug one lead into the
jack marked with the ohm symbol (Greek letter omega, the second jack from the
left), and the other lead into the jack marked COM (common).
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
| |
| Jeff Wisnia 2006-10-30, 8:25 pm |
| Mike E. Fullerton wrote:
> On Mon, 30 Oct 2006 17:17:47 -0700, "Big Al" <sal1@qwest.net> wrote:
>
>
>
>
> Setting it to 200 on the OHM section always says 1__. no matter which
> wire combination I touch the leads with.
The leads plug into the "common" and "ohms (omega symbol) meter jack holes.
Sounds like you've got a wide open mat.
Tell us, if you touch the two meter leads to each other, do you get a
reading of (or near) zero? If you do, the meter and leads are OK and you
need a new mat.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.
>
> Here's a pic of the meter.
> http://www.awsperry.com/sperry/catalog?item=dm-300
>
> I inserted the red lead into the V terminal on the right. Not sure if
> that's right or not, the manual is not very clear.
>
> _______
> Free Windows Clipboard Utility
> http://www.clipboardmagic.com/
| |
| Robert Barr 2006-10-30, 8:25 pm |
|
>
> Here's a pic of the meter.
> http://www.awsperry.com/sperry/catalog?item=dm-300
>
> I inserted the red lead into the V terminal on the right. Not sure if
> that's right or not, the manual is not very clear.
That's correct. Use the center terminal for the other lead (the COM).
Then connect the two probes together, switch the dial to resistance and
the 200 setting, and the meter should read something near zero. (If it
doesn't read something like zero, perhaps there's a problem -- perhaps
with one of the test leads).
From there, you're all set to measure your mat, or whatever it is.
>
> _______
> Free Windows Clipboard Utility
> http://www.clipboardmagic.com/
| |
| Robert Barr 2006-10-30, 8:25 pm |
| Oops, my mistake. I was looking at the wrong meter.
Use the two center terminals.
Mike E. Fullerton wrote:
> On Mon, 30 Oct 2006 17:17:47 -0700, "Big Al" <sal1@qwest.net> wrote:
>
>
>
>
> Setting it to 200 on the OHM section always says 1__. no matter which
> wire combination I touch the leads with.
>
> Here's a pic of the meter.
> http://www.awsperry.com/sperry/catalog?item=dm-300
>
> I inserted the red lead into the V terminal on the right. Not sure if
> that's right or not, the manual is not very clear.
>
> _______
> Free Windows Clipboard Utility
> http://www.clipboardmagic.com/
| |
| Doug Miller 2006-10-30, 8:25 pm |
| In article <QVx1h.23659$e66.6333@newssvr13.news.prodigy.com>, Robert Barr <not@for.harvest> wrote:
>
>
>That's correct.
I doubt it very much -- what do you suppose the jack labelled with the ohm
symbol is for?
--
Regards,
Doug Miller (alphageek at milmac dot com)
It's time to throw all their damned tea in the harbor again.
| |
| badgolferman 2006-10-30, 9:25 pm |
| Doug Miller, 10/30/2006,8:26:35 PM, wrote:
> In article <2n7dk2to1d66c7quek81at54coek3aoeo7@4ax.com>, Mike E.
> Fullerton <inforequest@spam-killer-remove-techie.com> wrote:
>
>
> It's not.
>
>
> I agree that the manual could be better... but the markings on the
> front of the meter are VERY clear. To measure resistance, you plug
> one lead into the jack marked with the ohm symbol (Greek letter
> omega, the second jack from the left), and the other lead into the
> jack marked COM (common).
And after you get the leads straight and make your readings ensure
there is not a diode in line. Reverse the two terminals where you are
connecting to and check your resistance again.
| |
| RicodJour 2006-10-31, 3:25 am |
| Mike E. Fullerton wrote:
> I am trying to install a SunTouch spot warming mat. To check for
> damage you need to test the resistance of the wires using a digital
> ohm meter. Trouble is I have no idea what to set the meter at. If the
> Reistance Range of the mat is 70-86 what setting would I use on the
> meter? The meter is a Sperry DM-350A if that matters.
If you're just doing the typical installation, don't suspect damage and
are performing the recommended periodic test during the installation
the multimeter is fine. When I install radiant heating cable and
suspect damage, I use a megohmmeter to test the insulation. The
regular multimeter checks for breaks, but the megohmmeter is more
sensitive and checks for leaks through the insulation.
Others have already addressed your original question. I answered one
you didn't ask. ;)
R
| |
| Jim Yanik 2006-10-31, 3:25 am |
| Mike E. Fullerton <inforequest@spam-killer-remove-techie.com> wrote in
news:2n7dk2to1d66c7quek81at54coek3aoeo7@4ax.com:
> On Mon, 30 Oct 2006 17:17:47 -0700, "Big Al" <sal1@qwest.net> wrote:
>
>
> Setting it to 200 on the OHM section always says 1__. no matter which
> wire combination I touch the leads with.
>
> Here's a pic of the meter.
> http://www.awsperry.com/sperry/catalog?item=dm-300
>
> I inserted the red lead into the V terminal on the right. Not sure if
> that's right or not, the manual is not very clear.
>
> _______
> Free Windows Clipboard Utility
> http://www.clipboardmagic.com/
>
Yu need to have the red lead in the "ohms" jack,the one with the Omega
symbol,between "A" jack and COM jack. Then use the 200 ohm range.
--
Jim Yanik
jyanik
at
kua.net
| |
| Jim Yanik 2006-10-31, 3:25 am |
| spambait@milmac.com (Doug Miller) wrote in
news:hZx1h.17609$GR.11906@newssvr29.news.prodigy.net:
> In article <QVx1h.23659$e66.6333@newssvr13.news.prodigy.com>, Robert
> Barr <not@for.harvest> wrote:
>
> I doubt it very much -- what do you suppose the jack labelled with the
> ohm symbol is for?
>
>
he didn't look at the pix... the enlarged .jpg.
some DMMs use the V jack for ohms,this model is not one of those.
--
Jim Yanik
jyanik
at
kua.net
| |
|
| On Tue, 31 Oct 2006 00:03:29 GMT, Mike E. Fullerton
<inforequest@spam-killer-remove-techie.com> wrote:
>I am trying to install a SunTouch spot warming mat. To check for
>damage you need to test the resistance of the wires using a digital
>ohm meter.
You don't need a digital meter. You can use almost any meter that
measures resistance.
> Trouble is I have no idea what to set the meter at. If the
Al is right about 200 ohms for this, but in general, you can just try
ranges at random, or in ascending or descending order until you find
the right one. If you pick a range that is too low, the resistance
will show probably as non-numeric on a digital meter, and the needle
won't move on an analog meter.
If you pick a range that is too high, like 2 MegOhms, the digital
meter will show Zero, and the needle will move all the way to the
right on an analog meter.
Either way it will be unintelligible until you check what it says on
other ranges.
>Reistance Range of the mat is 70-86 what setting would I use on the
>meter? The meter is a Sperry DM-350A if that matters.
>
>Thanks in advance.
>
>_______
>Free Windows Clipboard Utility
>http://www.clipboardmagic.com/
| |
|
| On 31 Oct 2006 03:59:04 GMT, Jim Yanik <jyanik@abuse.gov> wrote:
>Mike E. Fullerton <inforequest@spam-killer-remove-techie.com> wrote in
>news:2n7dk2to1d66c7quek81at54coek3aoeo7@4ax.com:
>
>
>
>Yu need to have the red lead in the "ohms" jack,the one with the Omega
>symbol,between "A" jack and COM jack. Then use the 200 ohm range.
uNLESS I"m looking at the wrong picture, the A jack is for the 10 amp
scale only. Everything else in this meter uses the middle jack for
the black wire**, and the right jack for the red.
**This meter probably has autopolarity, that is, if you connect the
wires backwards it gives the same reading***, but preceded by a
negative sign.
***Unless there is a diode or other semiconductor between the two
probes.
| |
| Mike E. Fullerton 2006-10-31, 1:26 pm |
| On Mon, 30 Oct 2006 20:27:38 -0500, Jeff Wisnia
<jwisnia@conversent.net> wrote:
>Mike E. Fullerton wrote:
>
>The leads plug into the "common" and "ohms (omega symbol) meter jack holes.
>
>Sounds like you've got a wide open mat.
>
>Tell us, if you touch the two meter leads to each other, do you get a
>reading of (or near) zero? If you do, the meter and leads are OK and you
>need a new mat.
Touching the two leads together I get a reading of 00.2 sometimes
00.1. Not sure if this is considered near zero. When I touch the leads
to the White/Black wires I get oscillating values between 78 and 80
which is withing the range of 70-86. White/Green and Black/Green wires
give 1__. Hopefully that means "infinite" ohms (no continuity) and
that would mean my mat is fine. Switching the leads in the terminals
gives the same readings.
_______
Free Windows Clipboard Utility
http://www.clipboardmagic.com/
| |
| Greg Guarino 2006-10-31, 5:25 pm |
| On Tue, 31 Oct 2006 18:37:44 GMT, Mike E. Fullerton
<inforequest@spam-killer-remove-techie.com> wrote:
White/Green and Black/Green wires
>give 1__. Hopefully that means "infinite" ohms (no continuity)
That sort of reading generally means "Over Range". If you're using the
200 Ohm range it could mean anything from just over 200 to no
continuity. You could try the higher ranges to be sure.
Greg Guarino
| |
| Jim Yanik 2006-10-31, 8:25 pm |
| mm <NOPSAMmm2005@bigfoot.com> wrote in
news:hm3fk21olc1vac95igvvd2c1tjlac12eo1@4ax.com:
> On 31 Oct 2006 03:59:04 GMT, Jim Yanik <jyanik@abuse.gov> wrote:
>
>
> uNLESS I"m looking at the wrong picture, the A jack is for the 10 amp
> scale only. Everything else in this meter uses the middle jack for
> the black wire**, and the right jack for the red.
you must be looking at the wrong pic,the DM-350A I looked at had 4 jacks;
A for amps
"omega" for ohms
COM
V for volts.
The TOP pix was a different model (DM-370)than what the OP cited.(DM-350A)
--
Jim Yanik
jyanik
at
kua.net
| |
|
| On 1 Nov 2006 00:19:40 GMT, Jim Yanik <jyanik@abuse.gov> wrote:
>mm <NOPSAMmm2005@bigfoot.com> wrote in
>news:hm3fk21olc1vac95igvvd2c1tjlac12eo1@4ax.com:
>
>
>you must be looking at the wrong pic,the DM-350A I looked at had 4 jacks;
>A for amps
>"omega" for ohms
>COM
>V for volts.
>
>The TOP pix was a different model (DM-370)than what the OP cited.(DM-350A)
This is hard. If homework keeps getting harder, I'm going to have to
drop out of school.
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