#### metlab123

Joined Dec 13, 2015
1
we need to test the quality of small bearings through motor load test.
For that we made an apparatus with a small DC motor of 24V & 1Amp. capacity.
can i measure milliamps through digital multimeter (with data logging).
Pls. suggest the proper method and measuring instruments.

Joined Jul 18, 2013
23,127
What characteristics of the bearings are you wishing to measure?
Max.

#### hp1729

Joined Nov 23, 2015
2,304
What characteristics of the bearings are you wishing to measure?
Max.
How much the bearing loads down the motor relative to ... ?? some other bearing??? by measuring motor current. Yes, it would give a relative value, but how do you give meaning? You could say one bearing has less drag than another.

Joined Jul 18, 2013
23,127
I would think a simple current meter measurement, using standard off the shelf bearings and you could include sintered bronze sleeve bearings for a comparison to a ball bearing.
No load and maximum load could be included in the test across the full rpm range, in the end it is just a comparative test, unless you have some qualified data to compare it to.
Max.

#### Alec_t

Joined Sep 17, 2013
12,080
can i measure milliamps through digital multimeter (with data logging).
A common way is to use a current-sense resistor (e.g. 10 milliOhms) to convert current to a small voltage, then use an opamp to bring the voltage up to something in the 0-5V range suitable to feed an ADC input of a microcontroller which logs data to an SD card.

#### hp1729

Joined Nov 23, 2015
2,304
I would think a simple current meter measurement, using standard off the shelf bearings and you could include sintered bronze sleeve bearings for a comparison to a ball bearing.
No load and maximum load could be included in the test across the full rpm range, in the end it is just a comparative test, unless you have some qualified data to compare it to.
Max.
I think the problem is making the current value into some "drag" value. Is a relative comparison all we can make?