When someone asks us about converting force to mass, Morehouse can now say we have an app for that. Not only will our app convert force to mass, but it will convert mass to force as well as convert units. It will convert force, torque, and pressure units. Anyone interested in downloading the app can visit the Google Play store: https://play.google.com/store/apps/details?id=com.mhforce.localgravity
Let’s look at why this app is needed.
Using force instruments to calibrate in mass has measurement error.
Forces are defined by Newton’s second law of motion expressed by F =kMA. Forces are not the same as or can they be substituted for mass without correction. Phillip Stein once wrote in his paper Gravity of the Situation, “Some measurements and calibrations require knowledge of little g. Errors and uncertainties in little g fall right to the bottom line (a 1% error in g results in a 1% error in the force reported) and therefore exert an important influence on the correctness of measurement results.”
A common example of these measurement errors occurs with scales (a mass measurement device). If 1000 lbs mass is used to calibrate a scale at Morehouse and that scale is shipped to Denver, CO, it would have to be calibrated again or corrected by formula to obtain the proper mass. Just comparing the gravity in York (9.801158 m/s2) and Denver (9.79620 m/s2), we find a difference of about 0.05 %. Without correction, 1000 lbs applied would read as 999.5 lbs. If the accuracy of the scale were 0.01 %, then the device would be at least five times greater than the accuracy specification.
Dynamometers, crane scales, tension links, handheld force gauges, and other similar devices are not always “Legal for Trade Scales.” Mainly, they can be used as force measuring devices because their displayed value can be adjusted based on a known force. If a known mass is used on-site, there is insignificant gravitational measurement error. The device can be used as a low-accuracy mass comparator. Since many of these instruments are used for measuring loads of 1 ton through 300 tons, it’s impractical to have the mass weights necessary to calibrate on-site and calibrating using force may be the only practical method to certify the device.
Therefore, the best solution is to have your load cells, proving rings, crane scales, etc., calibrated in force and convert the force readings at the location the instrument is being used to mass. If this is not done, the end-user can live with the error, or they can have someone with large amounts of masses come on location and calibrate the weighing device on-site. It’s often a logistics matter and calibrating in force and converting to mass is simple enough. It’s been further simplified by downloading the free Morehouse local gravity app.
