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| How do you measure and use a low value power resistor? |
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| Terry01:
--- Quote from: capt bullshot on December 17, 2018, 09:19:27 am --- --- Quote from: technix on December 17, 2018, 04:14:21 am ---That is why I am thinking about using two meters. One meter in amps range measuring the actual output current from the power supply, and the other measuring the voltage developed across the resistor. --- End quote --- Yes, that would be the correct answer considering your equipment. Just take care to connect the voltmeter "Kelvin Style" to the resistors leads. Usually these resistors come in standard values, so "round" your result to the nearest standard value (e.g. 0.1 Ohm, 0.22 Ohm, whatever). --- End quote --- When you say to make sure to connect it "Kelvin style" do you mean like this? |
| beanflying:
--- Quote from: Terry01 on December 17, 2018, 09:02:20 am ---Maybe a decent picture of "said resistor" will help the guys help you to work out the value and power rating of your unknown resistor. :) --- End quote --- Until you have an accurate resistance the size and then likely wattage is a moot point. |
| capt bullshot:
--- Quote from: Terry01 on December 17, 2018, 10:02:29 am ---When you say to make sure to connect it "Kelvin style" do you mean like this? --- End quote --- Yes |
| technix:
Here comes the measurements: Resistance: 250mΩ. Body length: 27mm. Body width: 14.5mm. Body height: 13mm. The body I am talking about includes the aluminum heatsink it comes with Any estimate of its power rating? A similarly sized 33Ω resistor has a rating of 25W. |
| beanflying:
Looking at the dimensions it is about the same size as a few 25W Ohmite resistors I have around here. Some useful data here https://www.ohmite.com/assets/docs/acl_hs10.pdf Heat sinking is really key if you want to push it toward that or if you are considering using it as a current shunt you will want to keep the power way down to minimize any Temp Co issues. |
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