Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Laser Pointer Store

Choosing resistor for indirect current test. Help!

Joined
Jan 20, 2009
Messages
3,635
Likes
91
Points
0
I was planning to buy some stuff for laser building and testing, and I found www.parts-express.com, wich seems to have good offers.

What power do a resistor for laser testing need to have and what tolerancy is acceptated. I found 1ohm at 5% toelrance with 1/2 watt, 1 watt, etc, I actually have no idea of what to choose.

Also
 

Joined
Feb 5, 2009
Messages
199
Likes
10
Points
0
Re: Choosing resistor for indirect current test. H

well, your right with the 1 ohm, the wattage would have to be set where it can handle the maximum current draw of the laser....
Usually a shunt resistor is used to measure current too large for you to directly connect your ammeter/multimeter to, before going about looking/researching for resistors... do tell what sort of current are you trying to measure? 10ma? 100ma? 1A? 10A? 100A?

Common shunt resistor's usually have a common Accuracy of +/- 0.1%, 0.25% in North America and 0.5% in the rest of the World.
 

Cyparagon

Well-known member
Joined
Sep 12, 2007
Messages
9,520
Likes
1,045
Points
113
Re: Choosing resistor for indirect current test. H

What are you running that exceeds 20A?
 

691175002

New member
Joined
Jan 6, 2009
Messages
202
Likes
0
Points
0
Re: Choosing resistor for indirect current test. H

I would recommend a tolerance closer to 1% or better. With 5% error in the resistor and perhaps a few percent in a cheap/uncalibrated multimeter you could conceivably be looking at 5-10% error. 117-143mA is a pretty wide range of uncertainty for powering a PHR diode.
 
Joined
Jan 20, 2009
Messages
3,635
Likes
91
Points
0
Re: Choosing resistor for indirect current test. H

my multimeter is good enough, but where to get a resistor with less than 5% tolerance? Remember I live in spain, parts-expres.com won't ship to me :(

Yours,
hallucynogenyc
 

lasersbee

Well-known member
Joined
Sep 20, 2008
Messages
17,455
Likes
1,558
Points
113
Re: Choosing resistor for indirect current test. H

--Hallucynogenyc-- said:
I was planning to buy some stuff for laser building and testing, and I found www.parts-express.com, wich seems to have good offers.

What power do a resistor for laser testing need to have and what tolerancy is acceptated. I found 1ohm at 5% toelrance with 1/2 watt, 1 watt, etc, I actually have no idea of what to choose.

Also
A resistor that has a tolerance of 5% is not necessarily 5% off... it is just a tolerance
percentage that the manufacturer guarantees will not be exceeded..

You can take a batch of 1 ohm 5% resistors and test them individually with your DMM...
Note the values and choose one from the middle range of values and you will have
a good chance to get one that is a lot better than 5% error ...
The bigger the sample lot... the closer to 1% or less you will get... ;)

Jerry
 




Top