I search some good 0.33R 3W resistor to build an AX.
I found this:
http://www.caddock.com/Online_catalog/Mrktg_Lit/MP9000_Series.pdf
www.distrelec.ch ref: 721705 or 720703
What do you think about these parts?
With 1% tolerance must I match them?
Tanks in advance.
Alex
I found this:
http://www.caddock.com/Online_catalog/Mrktg_Lit/MP9000_Series.pdf
www.distrelec.ch ref: 721705 or 720703
What do you think about these parts?
With 1% tolerance must I match them?
Tanks in advance.
Alex
Seems like a very nice resistor. I wouldn't bother matching them at 1% quoted tolerance.
Personally, I just used four 1.3Ω 1W BC Components metal film resistors in parallel to get 0.33Ω. Only costs US$0.34.
Personally, I just used four 1.3Ω 1W BC Components metal film resistors in parallel to get 0.33Ω. Only costs US$0.34.
Parrallel Resistors
In my AX, I needed .4ohms. In order to do that I found .82 ohm 2watt MOX resistors. Used two per device. Since they were 5% tol, I measured them.
What was interesting was looking at the actual tolerence. Out of 200 resistors, only 4 were over 1% deviation. Infact the general population of the the groups was better than 0.5%. This supports not needing to measure 1% tol resistors. Of course we are DIY, why not measure them.
I used a method I saw on the forum of attaching 10 in series and passing 1 amp of current through them. The voltage drop across each device is equiv to the resistance in ohms. I was able to measure all of them in about 4 hours.
By selecting the resistors to use, the effective tolerence for the resistors is theoretically 0.01%. In reality, I think my meter has more error than that.
I did a similar thing for the current sense resistors and the ground resistors as seen in the photo
Scott
In my AX, I needed .4ohms. In order to do that I found .82 ohm 2watt MOX resistors. Used two per device. Since they were 5% tol, I measured them.
What was interesting was looking at the actual tolerence. Out of 200 resistors, only 4 were over 1% deviation. Infact the general population of the the groups was better than 0.5%. This supports not needing to measure 1% tol resistors. Of course we are DIY, why not measure them.
I used a method I saw on the forum of attaching 10 in series and passing 1 amp of current through them. The voltage drop across each device is equiv to the resistance in ohms. I was able to measure all of them in about 4 hours.
By selecting the resistors to use, the effective tolerence for the resistors is theoretically 0.01%. In reality, I think my meter has more error than that.
I did a similar thing for the current sense resistors and the ground resistors as seen in the photo
Scott
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