# I Weight measurements and gravitational acceleration

1. Jul 18, 2017

### tjosan

Hi all,

Since the gravitational acceleration varies depending on location, then how do you know if your scale is precisely calibrated? If I use a calibration weight (e.g. 100.000000 g) that was manufactured and tested around at equator where g=9.780 m/s^2, in my lab at the north pole where g=9.832 m/s^2, wouldn't I get a systematic error on my measurements?

2. Jul 18, 2017

### Khashishi

Correct. So mass is usually measured using a balance. The balance compares two weights against each other. In your doctors' office, they don't measure your weight, they measure your mass.

3. Jul 18, 2017

### tjosan

Thank you.

Didn't distinguish between scale/balance and mass/weight. But now it makes sense :)

4. Jul 18, 2017

### pixel

5. Jul 18, 2017

### Khashishi

Only in US.

6. Jul 18, 2017

### pixel

And do they use one value of g throughout the U.S.?

7. Jul 18, 2017

### jbriggs444

Scales (both balance and spring/load cell) used for commerce in the U.S. are calibrated to deliver an accurate assessment of the mass of the objects placed thereon in the location where they are to be used.

Just like scales everywhere else in the world.

Edit: g does not figure in. The pound is legally a unit of mass.