Am I on glue or is this correct......

[CxTurbo]

Here goes the stupid question. Just want to be sure before I contact the seller. I bought 120 5% .47R 3W resistors from Mouser and the markings on them are correct from what I can tell (Yellow,Violet,Silver,Gold). The problem is they Ohm out at 3R when I tested them. Is this correct? Am I missing something here because all of the 1/4W resistors I ordered match the stated values.

Be gentle

James

[udailey]

James,
I am mostly color blind so I never gave in to trying to figure out the color coding. I would inevitably get it wrong anyway.
Test another resistor with your DMM. One you are sure of the value. Then test your .47R resistors and see what happens. If the first reads correct and you still get 3R on the new ones then I guess you have 3R Guess you could put 6 of them in parallel and you would have your .5R for each side of a Pass power supply
Uriah

[CxTurbo]

Thanks for the reply. I was afraid that they where wrong..........


James

[udailey]

Just went and checked my Pass supply and the series resistors are actually all .47R so if that IS what your 3W were for they wont be low enough.
Uriah

[AndrewT]

join them all together in series and measure the resistance of the series combination. Expect 55r to 60r.
Divide by 120 to get an approximate average value for resistance.
You could compare a 56r 1% resistor to allow you to correct for your DMM inaccuracy.

Have you checked what your meter reads when you short your test leads together?

I have found that using a 0.1% tolerance resistor to accurately monitor a CCS and use that CCS to drive a current through low value resistors to be a far better method to check individual resistances (voltage drop / current = resistance). I can match low value resistors 0r1 to 1r0 to better than 0.2% with a little bit of care.

[CxTurbo]

Originally Posted by udailey

Just went and checked my Pass supply and the series resistors are actually all .47R so if that IS what your 3W were for they wont be low enough.
Uriah

Yep that is what they are for. I am building 5 Aleph-J X's. I have to call Mouser for an RMA and order a different brand I gather since all 120 look wrong 8(.


James

[CxTurbo]

Originally Posted by AndrewT

Have you checked what your meter reads when you short your test leads together?

Meter reads at 2.50R with the leads shorted. Is that normal?


James

[udailey]

AHA! Andrew saves the day again!
So you have .47R resistors. Its okay
Your meter just has a 2.5R resistance internally or in the leads. Thats kinda high. Both of mine are .2R
You add the 2.5R to all your readings.
Uriah

[AndrewT]

Originally Posted by udailey

Your meter just has a 2.5R resistance internally or in the leads. Thats kinda high.

buy new test leads.
If that does not reduce the zero ohm reading to below 0r2, then buy a new meter.

[janneman]

Originally Posted by AndrewT

buy new test leads.
If that does not reduce the zero ohm reading to below 0r2, then buy a new meter.

Doesn't the meter have some kind of adjustment to adjust the R-reading to zero with shorted leads?

jd