CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness

The National Metrology Laboratory of South Africa Stopwatch calibration in South Africa Stopwatch calibration in South Africa Louis Marais 2004 NCSL International Workshop and Symposium, July 11-15, 2004

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Contents Introduction Calibration systems –Semiautomatic –Acoustic pickup –Fully automatic Calibration procedure Validation Measurement uncertainty

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Introduction CSIR-NML is the national metrology institute in South Africa Consists of 17 laboratories covering all aspects of metrology Time and Frequency laboratory is responsible for –Maintenance of national time scale –Phase angle –Fast electrical pulse characterization –Phase noise –Fiber optics

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Introduction (continued) Time and Frequency services provided –Internet Time Service –Telephone Time Service –Time and Frequency bulletin –Calibration services Laboratory holds ISO accreditation for a number of calibration services –Accredited by SANAS –Accreditation received July 2003 –Parameters: Frequency, Time Interval, Phase Angle, Rise and Fall time, Waveform aberration, Optical Length

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Introduction (continued) Stopwatches and Timers are used increasingly in industry Quality standards require these instruments to be calibrated Requests received has increased dramatically in the last three years Mostly from manufacturing and chemical industries This prompted development of stopwatch calibration service

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Calibration systems A number of calibration systems were developed depending on functionality of device under test Checking only the clock frequency of the stopwatch was not an option Systems mimic a human user Systems developed: –Semiautomatic calibration system –Acoustic pick-up calibration system –Fully automatic calibration system

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Semiautomatic calibration system First system developed in TF laboratory

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Semiautomatic calibration system (cont.) Start and stop signals generated by user or computer Activates solenoid to trigger stopwatch Simultaneous electronic trigger sent to Time Interval counter (TIC) Metrologist records readings of device under test and TIC Calibration task is very time intensive

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Acoustic pickup calibration system Developed in response to requests for timer calibrations Timers run in count-down mode Calibration system uses microphone to pick up start and end “beeps”

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Acoustic pickup calibration system (cont.) Can also be used to calibrate conventional stopwatches

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Acoustic pickup calibration system (cont.) The timers calibrated generally have a 1 s resolution This relaxes the accuracy requirement of the system System was checked using a calibrated stopwatch with 0,01 s resolution The metrologist is required to take down the device under test and TIC readings The task is very time intensive

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Fully automated calibration system Developed due to time intensive nature of the previously shown calibration systems Utilizes a camera and frame grabber to capture the device under test reading Uses a second solenoid to reset the stopwatch after a measurement Custom software developed for recording of results Metrologist is freed to perform other tasks Results in a saving for the client as less time is required for the calibration

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Fully automatic calibration system (cont.)

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Fully automatic calibration system (cont.)

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Fully automatic calibration system (cont.) Sample result file with captured images

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Calibration procedure The calibration procedure is the same for all the systems Standard calibration is performed at (5, 10, 100 and 300) s All relevant information is captured on a result sheet A verification is performed Data is analyzed and reported on a certificate

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Validation ISO requires validation of measurement procedures This is done by either –Using a calibrated reference standard; –Comparison to another method; –Interlaboratory comparisons; –Systematic assessment of influencing factors; or –Theoretical assessment of method uncertainty The calibration procedure for stopwatches was validated using a calibrated reference standard

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Validation (continued) The reference standard consisted of –A triggering device was built; and –A second Time Interval Counter

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Validation (continued) The validation results indicate that the system accuracy exceeds requirements by a wide margin

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Measurement uncertainty Measurement model Contributing factors: –Counter time base –Counter resolution –Differential channel error –Device under test resolution –Type A component

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Measurement uncertainty (continued) As an example consider the following typical measurement result

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Measurement uncertainty (continued) Assign values to uncertainty contributors: –Counter time base: 2,3· –Counter resolution: 0,75 ns (Calculated from specification) –UUT resolution: 0,01 s –Differential channel error: 1,5 ns (Obtained from specification) –Type A contribution: 0, s (Statistical calculation)

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Measurement uncertainty (continued) Analysis of uncertainty

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Historical data example To verify that the uncertainties calculated are justified historical data is used Below is an example of a yearly calibration of a customer stopwatch (only one point shown)

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Historical data example (continued) Graphical representation

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Conclusion Several stopwatch calibration systems have been developed The systems produce accurate results Calibrations are offered that can satisfy the needs of the South African industry

CSIR National Metrology Laboratory Your measurement technology partner for global competitiveness Questions?