SI unit: Force and torque

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This article is part of a series detailing the SI units and our calibration services. This article centers around force and torque.

Unit of force: newton (N)

The SI unit of force is the newton (symbol N), which is the force required to accelerate a one kilogram mass at a rate of one meter per second squared, or kg·m·s−2​. Force is a derived unit in the SI with a special name and symbol.

Unit of torque: newton metre (N m)

The quantity torque (or moment of force) may be thought of as the cross product of force and distance and the SI unit for torque is Newton metre, N m (m2 kg s-2). Even though N m is the same as Joule, torque is not work or energy and hence torque should only be expressed in newton metres and not in Joules (J).

Calibration services for force and torque

Calibration of force

VTT MIKES-Kajaani performs force calibrations from 1 N to 1.1 MN. Calibrated measurement devices are usually force transducers, force measurement devices, balances (eg. hook, wheel weight and airplane) and pull force testers. The smallest measurement uncertainty is 2×10-5.

The calibration of force is based on the ISO 376 standard. The force calibration from 1 N to 110 kN is carried out in dead weight force standard machines. A dead weight machine is a mechanical structure that generates force by subjecting dead weights to the local gravitational field. Hydraulic force standard can be used in the calibrations from 20 kN to 1.1 MN.

Calibration of torque

VTT MIKES Kajaani performs calibrations of torque in the range 0.1 Nm ... 20 kNm, the smallest uncertainty being 5×10–4. The calibration of torque is carried out using reference standards for torque or standards based on reference sensors.