Ensayo De Aptitud En El Área De Masa En El Alcance De Calibración De Instrumentos Para

Force Comparison Protocol,

50 kN to 200 kN

Force testing machines calibration,

Compression mode

SIM

Cárdenas Moctezuma, Alejandro

Torres Guzmán, Jorge C.

Force and Pressure, CENAM

June 2013

Content

1.INTRODUCTION

To support the NMIs CMCs comparisons in force, at SIM area was proposed by the Centro Nacional de Metrología (CENAM). A comparison in calibration of force testing machines, in compression mode, within the interval of (50.0 to 200.0) kN was organized, where CENAM is the reference laboratory.

1. OBJECTIVE

This comparison has the objective to determine the compatibility of results for the calibration of force testing machines. The reference values will be the results of the reference laboratory (CENAM). The values to be determined in this comparisonare the average error and the uncertainty, for each point of force calibrated.

1. SCOPE

The force testing machine will be calibrated in the interval from 50 kN to 200 kN in compression mode, using direct comparison method, according to the procedure described in this protocol.

1. REQUIREMENTS

The laboratory must have technical competition to do calibrations of force testing machines, using a force transducer calibrated, to cover the points of force indicated in this protocol

1. ORGANIZATION

5.1Contacts

Logistics Coordination: CENAM

Fax. 442-2110568

Reference Laboratory: CENAM, Force Laboratory.

5.2Participants

5.3Description of equipment

The arrangement of force testing machine, including force transducer, used as Transference Standard (TS) is showed in table 1.

Table 1. Transfer Standard data (TS).

5.4Comparison procedure

To realize the comparison, the TS will be calibrated by the reference laboratory and the participants. At the end of the measurements, each laboratory willdeliver the readings and results. The reference laboratory will produce a reportwith the results obtained. The reference laboratory will calibrate the TS before and after the participation of the other laboratories.

5.4.1 Installation

To install the participating laboratory calibration standardon the TS:Connect the participating laboratory standard and turn on the TS at least 1 hour before beginning the calibration.

5.4.2 Measurement Process

Initiate the measurements applying three pre-loads, up to 200 kN.

To perform the first round of measurements by increasing force, with the participant standard in initial position (0°).To domeasurements in zero force and then the 5 target force points (50 kN, 75 kN, 100 kN, 150 kN, and 200 kN).

The second round consists in rotating the participant standard 120° with respect to the initial position, to apply one preload and measure the zero force and then the 5 target force points (50 kN, 75 kN, 100 kN, 150 kN, and 200 kN).

For the third round, rotate the participant standard 240° respect to the initial position, apply one preload and measure the zero force and then the 5 target force points.

The next diagram describes the measurements process:

5.4.3Calculations

Each participant laboratory will carry out the necessary corrections to its measurements as it find suitable.

5.4.4Uncertainty

To estimate the combined uncertainty of the TS, the minimum components to consider are:

The standard uncertainty due tothe calibration system.

The standard uncertainty due to reproducibility.

The standard uncertainty due to resolution.

The standard uncertainty due to zero error.

The expanded uncertainty (U) of the measurements will be reported using a coverage factor of k = 2. The laboratory should report the uncertainty according to its CMCs declared (or the ones to be declared).

1. CRITERIA FOR EVALUATION OF RESULTS

The criteria to evaluate the compatibility of results for the comparison are:

Normalized Error (En), as shown in the next model.

Where:

xlab is the error of the TS, determined by each participant laboratory.

xref is the error of the TS, determined by the reference laboratory.

Ulab is the expanded uncertainty, estimated by each participant laboratory.

Uref is the expanded uncertainty, estimated by the reference laboratory.

And according to the normalized error model:

if |En| ≤ 1 the results are satisfactory,

if |En| > 1 the results are not satisfactory.

7.PRESENTATION OF RESULTS

The report of the results will be edited by CENAM and distributed among the participants firstly as report B and ones an agreement have been reached among all participants the final report (report A) will be edited. The final report will be sent to SIM and to BIPM for inclusion in their data bases.

8.TEST DATES

The measurements are to be performed by each participating laboratory according to the scheduled presented in the following table.

Table 2. Measurements dates.

Force ComparisonProtocol

SIMJune2013

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