TR 45-01
CRITERIA FOR LABORATORIES ACCREDITED
TO CALIBRATE TACHOMETERS AND
MEASURE ROTATIONAL SPEED.
Approved By:
Date of Approval:
Date of Implementation:
Chief Executive Office:
Senior Manager:
2008-02-15
2008-02-15
SANAS
Mike Peet
Mpho Phaloane
Page 1 of 7
TR 45-01
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
SANAS
Page 2 of 7
TR 45-01
1.
Purpose and Scope
The purpose of this document is to define the specific environmental, general and technical
requirements 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]
[2]
OHS Act, 1993
ISO 17025:2005
2.2
Definitions
2.2.1
Environmental Regulations 1987 - Lighting
General requirements for the competence of testing and calibration
laboratories.
Contact Tachometer
A contact tachometer is a tachometer that makes physical contact with the shaft or
surface speed being measured. These tachometers comprise a metal shaft with a
rubber contact tip, and or rubber surface contact wheel, optical or mechanical
conversion section and readout display. The indication is typically in rpm, m/min, or
mm/sec.
2.2.2
Non-Contact tachometers
This type of tachometer makes no physical contact with the object being tested. Noncontact tachometers include Optical, Inductive and Acoustic tachometers.
The optical tachometer comprises a transmitter, receiver and a readout display. These
tachometers are typically used for measurements on rotating electrical motors or
machines.
An inductive tachometer is used to measure the rotational speed of an internal
combustion engine. This tachometer comprises an inductive pick-up (coil), cylinder
selection and readout display. The magnetic field emitted from the coil of the engine is
detected 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 an
acoustic transducer, cylinder selection and readout display. The sound emitted by the
spark plugs of the engine when fired is detected by the tachometer, and displayed on
an rpm readout display.
2.2.3
Stroboscope/Tachometer
A stroboscope is an instrument used for the inspection and/or the measurement of
the speed of moving or rotating machine parts. The strobe is synchronized to the
moving 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 to
measure and display the rotational speed of the centrifuge.
3.
Abbreviations
AU&V
DC LF
RPM
T&F
UUT
-
Acoustics, Ultrasound and Vibration
Direct Current Low Frequency
Revolutions per Minute
Time and Frequency
Unit under Test
SANAS
Page 3 of 7
TR 45-01
4.
5.
Environmental Requirements
4.1
The ambient temperature and temperature gradients in a laboratory where tachometers are
calibrated 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 the
calibration work undertaken. Cognisance shall be taken of the minimum levels of lighting as
specified 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 the
measurement results.
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 type
of 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:
•
•
•
•
•
•
•
6.
optical non-contact tachometers,
inductive non-contact tachometers,
acoustic tachometers,
contact tachometers,
surface speed tachometers, and
stroboscopes,
rotational speed.
Technical Requirements
6.1
Calibration Procedures
Calibration procedures shall be available for all the types of tachometers and centrifuges that
the 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 that
both 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 not
acceptable 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 the
UUT should not influence the measurement result.
6.2.4
Calibration of contact tachometers shall include either direct coupling or
measurement 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 rotating
object, the applied pressure, the condition of the rubber tip or wheel, and slippage
under working conditions.
6.2.5
The procedure for the calibration of a stroboscope shall address the method of
detection, and detection distance.
6.2.6
Procedures for the calibration of inductive and acoustical tachometers shall address
the stroke and cylinder selection.
SANAS
Page 4 of 7
TR 45-01
6.3
6.2.7
The tachometer should be calibrated in accordance with the manufacturer’s
specification; in the absence of such procedures the laboratory shall perform at least
5 measurements through the range of the tachometer. Dual or multi-range
tachometers 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 label
and certificate shall clearly indicate ‘limitation imposed – partial calibration’.
Calibration of Tachometers – Uncertainty of Measurement
6.3.1
The estimation of the uncertainty measurement for tachometers calibrated by the
laboratory shall consider at least the following contributors:
•
•
•
•
•
•
•
6.3.2
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.
The calculated uncertainty of measurement shall always be rounded up, and never
down, so as ensure that the uncertainty value remains within the 95% confidence
limits.
SANAS
Page 5 of 7
TR 45-01
APPENDIX 1.
SCHEDULE OF ACCREDITATION
METROLOGY
Laboratory Accreditation Number : 0123
Permanent Address of Laboratory:
The Tachometer Shop (Pty) Ltd
63 West Street
Over the Hill
Johannesburg
Postal Address:
P O BOX 32222
Johannesburg
2000
Tel: (011) 499-8778
Fax: (011) 499-8879
ITEM
1
Technical
Signatory
: Mr IR Faster
Nominated
Representative
: Ms C Tacho
Issue No.
Date of Issue
Expiry Date
: 2
: August 2005
: July 2005
MEASURED QUANTITY OR TYPE OF
GAUGE OR INSTRUMENT
RANGE OF
MEASURED
QUANTITY
BMC EXPRESSED AS AN
UNCERTAINTY (±)
Rotational Speed
1.1
Medical, Laboratory and Industrial
Centrifuges
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-contact
Optical
0 to 3 500 RPM
3 500 to 12 000 RPM
0,1% + 5 RPM
0,1% + 25 RPM
1.4
Tachometer non-contact
Inductive
50 to 20 000 RPM
1 LSD
1.5
Tachometer non–contact
Sound
100 to 12 000 RPM
2,0%
1.6
Surface Speed
2
0,1 to 500 m/min
1% + 1 LSD
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 of
measurement multiplied by a coverage factor k = 2, corresponding to a confidence level of approximately
95%
ISSUED BY THE SOUTH AFRICAN NATIONAL ACCREDITATION SYSTEM
SANAS
Page 6 of 7
TR 45-01
ADDENDUM 1.
AMENDMENT RECORD
Proposed By:
Section
Change
CEO
FM
Page 1
Changed to new logo & Front page
Changed from R 45 (Requirement) to TR 45 (Technical Requirement)
document.
SANAS
Page 7 of 7