National ESZ force standard 500 N

Name of the standard: National ESZ force standard 500 N

Code designation: ECM 150-8/15-059

Year of publication: 2015

Department: section 8011 CMI LPM Prague

Guarantor: Ing. Petr Kašpar

Number of CMC lines provided​: 1

The National Standard of Force ESZ 500 N is a compact direct load device consisting of a single load cell system and a hanger that transmits the force to the force gauge to be measured. The load cells implement a unit force in the range from 8 N to 500 N. The ESZ 500 N includes electrical power and control circuits to control the electric motors of the load cell systems and to balance the load cell linkage.

The critical parts of the standard that define the unit of force are the load cells and the load cell linkage. The unit of force is defined as the force effect of the earth's gravitational field on the load bodies of a given mass. When the load bodies are just weighed, a correction is made for the buoyancy of the surrounding air. The force exerted by the earth's gravitational field on the load bodies is transmitted to the force gauge to be measured by means of the suspension.

The national standard of force consists of the following parts:

• load cell system,
• hanger of the load cells,
• machine frame,
• drive motors,
• electrical switchboard,
• control panel,
• computers for evaluation of measurements.

Basic metrological characteristics:

The force standard is designed for calibration of force standards in the force range from 8 N to 500 N under tensile or compressive loading. The best measuring capability of the standard is Wfsm=0,004 % of the measured force value.  The best measurement capability of the standard is determined according to EA-10/04 as the expanded uncertainty of the standard calibration with an expansion factor of k=2, corresponding to a probability of coverage for a normal distribution of P=95%.

The force generated by the standard is given by the equation:

Where stands for: