tr 45-01 criteria for laboratories accredited to calibrate tachometer and measure rotational speeed

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TR 45-01

CRITERIA FOR LABORATORIES ACCREDITEDTO CALIBRATE TACHOMETERS AND

MEASURE ROTATIONAL SPEED.

Approved By: Chief Executive Office: Mike PeetSenior Manager: Mpho Phaloane

Date of Approval: 2008-02-15

Date of Implementation: 2008-02-15



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CONTENTS:

1. Purpose and Scope

2. References, Definitions and Abbreviations

3. Abbreviations

4. Environmental Requirements

5. General Requirements

6. Technical Requirements

6.1 Calibration procedures

6.2 Calibration of Tachometers - Requirements

6.3 Calibration of Tachometers Uncertainty of Measurement

APPENDIX 1: Schedule of Accreditation

ADDENDUM 1: Amendment Record



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1. Purpose and Scope

The purpose of this document is to define the specific environmental, general and technicalrequirements to be met by laboratories accredited by SANAS to calibrate tachometers, stroboscopes,surface speed, and centrifuges with integral tachometers.

2. References, Definitions and Abbreviations

2.1 References

[1] OHS Act, 1993 Environmental Regulations 1987 - Lighting[2] ISO 17025:2005 General requirements for the competence of testing and calibration

laboratories.

2.2 Definitions

2.2.1 Contact Tachometer

A contact tachometer is a tachometer that makes physical contact with the shaft orsurface speed being measured. These tachometers comprise a metal shaft with arubber contact tip, and or rubber surface contact wheel, optical or mechanical

conversion section and readout display. The indication is typically in rpm, m/min, ormm/sec.

2.2.2 Non-Contact tachometers

This type of tachometer makes no physical contact with the object being tested. Non-contact tachometers include Optical, Inductive and Acoustic tachometers.

The optical tachometer comprises a transmitter, receiver and a readout display. Thesetachometers are typically used for measurements on rotating electrical motors ormachines.

An inductive tachometer is used to measure the rotational speed of an internalcombustion engine. This tachometer comprises an inductive pick-up (coil), cylinder

selection and readout display. The magnetic field emitted from the coil of the engine isdetected by the inductive pick-up of the tachometer and converted to an rpm readout.

The acoustic tachometer is used on internal combustion engines. It is comprised of anacoustic transducer, cylinder selection and readout display. The sound emitted by thespark plugs of the engine when fired is detected by the tachometer, and displayed onan rpm readout display.

2.2.3 Stroboscope/Tachometer

A stroboscope is an instrument used for the inspection and/or the measurement ofthe speed of moving or rotating machine parts. The strobe is synchronized to themoving machinery; the rotational speed is then read from the integral tachometer.

2.2.4 Centrifuge with rotational speed indicator

Many medical, laboratory and industrial centrifuges are fitted with instrumentation tomeasure and display the rotational speed of the centrifuge.

3. Abbreviations

AU&V - Acoustics, Ultrasound and VibrationDC LF - Direct Current Low FrequencyRPM - Revolutions per MinuteT&F - Time and FrequencyUUT - Unit under Test



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4. Environmental Requirements

4.1 The ambient temperature and temperature gradients in a laboratory where tachometers arecalibrated shall comply with the relevant requirements for the field of calibration (DC LF,AU&V, T&F) under which this parameter has been included.

4.2 Lighting within the laboratory shall be adequate to facilitate the correct performance of thecalibration work undertaken. Cognisance shall be taken of the minimum levels of lighting asspecified in the environmental regulations of the OHS Act.[1] [2]

4.3 Vibration levels in the laboratory shall be such that they do not have an adverse effect on themeasurement results.

5. General Requirements

5.1 Raw data shall not be recorded in pencil, or erasable ink.

5.2 The laboratory shall have and apply procedures that address the requirements for each typeof tachometer and/or centrifuge that the laboratory wishes to calibrate.

5.3 The schedule of accreditation shall list the types of tachometer that the laboratory is

competent to calibrate under the parameter tachometers. This list may include:

optical non-contact tachometers,

inductive non-contact tachometers,

acoustic tachometers,

contact tachometers,

surface speed tachometers, and

stroboscopes,

rotational speed.

6. Technical Requirements

6.1 Calibration Procedures

Calibration procedures shall be available for all the types of tachometers and centrifuges thatthe laboratory wishes to calibrate.

6.2 Calibration of Tachometers - Requirements

6.2.1 The calibration of a non-contact optical tachometer shall include a verification thatboth the transmitter and receiver are functional over the range of specified distances.

6.2.2 The calibration of a non-contact optical tachometer using a stroboscope is notacceptable due to the high light output of a stroboscope.

6.2.3 Any test rig shall be of adequate design, and any mechanical loading caused by theUUT should not influence the measurement result.

6.2.4 Calibration of contact tachometers shall include either direct coupling ormeasurement using the supplied rubber cone tip and/or surface measuring wheel.The procedure shall also address the contact angle of the probe tip with the rotatingobject, the applied pressure, the condition of the rubber tip or wheel, and slippageunder working conditions.

6.2.5 The procedure for the calibration of a stroboscope shall address the method ofdetection, and detection distance.

6.2.6 Procedures for the calibration of inductive and acoustical tachometers shall addressthe stroke and cylinder selection.



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6.2.7 The tachometer should be calibrated in accordance with the manufacturersspecification; in the absence of such procedures the laboratory shall perform at least5 measurements through the range of the tachometer. Dual or multi-rangetachometers shall be calibrated at least 3 points per range.

6.2.8 Multi function tachometers shall be calibrated for contact and non-contact functions.In instances where only one of the functions has been calibrated the calibration labeland certificate shall clearly indicate limitation imposed partial calibration.

6.3 Calibration of Tachometers Uncertainty of Measurement

6.3.1 The estimation of the uncertainty measurement for tachometers calibrated by thelaboratory shall consider at least the following contributors:

the calibration of the frequency standard,

the resolution of the standard,

or scale interval (analogue) or resolution of the UUT,

alignment of the tachometer probe,

slippage,

stability of reading,

the repeatability.

6.3.2 The calculated uncertainty of measurement shall always be rounded up, and neverdown, so as ensure that the uncertainty value remains within the 95% confidencelimits.



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APPENDIX 1.

S C H E D U L E O F A C C R E D I T A T I O N

METROLOGY

Laboratory Accreditation Number : 0123

Permanent Address of Laboratory:The Tachometer Shop (Pty) Ltd63 West StreetOver the HillJohannesburg

Postal Address:P O BOX 32222Johannesburg2000

Tel: (011) 499-8778Fax: (011) 499-8879

TechnicalSignatory

NominatedRepresentative

Issue No.Date of IssueExpiry Date

: Mr IR Faster

: Ms C Tacho

: 2: August 2005: July 2005

ITEMMEASURED QUANTITY OR TYPE OF

GAUGE OR INSTRUMENTRANGE OFMEASUREDQUANTITY

BMC EXPRESSED AS ANUNCERTAINTY ()

1 Rotational Speed

1.1 Medical, Laboratory and IndustrialCentrifuges

60 to 90 000 RPM 0,06% + 1 LSD

1.2 Tachometers Contact 10 to 3 500 RPM 0,2% + 5 RPM

1.3 Tachometer non-contactOptical

0 to 3 500 RPM3 500 to 12 000 RPM

0,1% + 5 RPM0,1% + 25 RPM

1.4 Tachometer non-contactInductive

50 to 20 000 RPM 1 LSD

1.5 Tachometer noncontactSound

100 to 12 000 RPM 2,0%

1.6 Surface Speed 0,1 to 500 m/min 1% + 1 LSD

2 On-site calibration of item 1.1

Original date of accreditation:1994 Page 1 of 1

The BMC, expressed as an expanded uncertainty of measurement, is stated as the standard uncertainty ofmeasurement multiplied by a coverage factor k= 2, corresponding to a confidence level of approximately95%

ISSUED BY THE SOUTH AFRICAN NATIONAL ACCREDITATION SYSTEM



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ADDENDUM 1.

AMENDMENT RECORD

Proposed By: Section Change

CEO Page 1 Changed to new logo & Front pageFM Changed from R 45 (Requirement) to TR 45 (Technical Requirement)

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tr 45-01 criteria for laboratories accredited to calibrate tachometer and measure rotational speeed

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