They listed the meter I was looking as coming with Cat 3 leads.
It seems like there should be a way (instrument) that you could short the test
leads and zero like a scale.
So, if I short the leads and it reads 0.5 ohms, I can subtract this from the
test read?
Or, perhaps I could obtain a resistor of known value, check this and apply a
correction?
Thanks for the help on this btw.
I’m presently kind of bummed my ground test didn’t work, but I guess it’s
better than finding out later.
Richard
From: David Erbas-White<mailto:derbas@xxxxxxxxxxxxxxxx>
Sent: Tuesday, January 24, 2017 12:39 PM
To: roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Subject: [roc-chat] Re: Resistance for Electric Matches
On 1/24/2017 11:40 AM, R Dierking wrote:
I think you mean Cat III (roman numerals typically used for measurement
categories).
Cat III allows up to 2 ohms in the test leads, which can throw your measurement
WAY off. That's the whole point of doing your best to measure the test lead
resistance so you can subtract it out, but it's sometimes difficult to minimize
the connection resistance just when holding the leads against each other.
As Allen mentioned, you really need to do a four-wire measurement, and meters
that do that are not cheap (nor are they typically available in your handheld
meter from Frys). I have a benchtop unit that does very well for these low-ohm
measurements, but it is definitely A) not cheap, and B) not all that portable.
There are other ways you can 'get around' this, by using additional meters and
other resistors in part of the measurement. For example, you can improve your
measurement by using a larger value resistance that you ARE able to get an
accurate measurement on, then putting it in series with your circuit under
test, then measure the voltage across each resistor with a second meter while
using the first meter to 'measure resistance'.
I'd also point out that the cheaper the meter, the less precise they will be,
particularly at the lower end of the scale. There's just no way around the
adage, "You get what you pay for..."
David Erbas-White
Looks like the San Marcos store for me.
Are Cat 3 test leads OK for our purposes? Perhaps I just need better test
leads with clips?
