technical guide

Working Thermometers
Calibration
Procedures

Published by:
International Accreditation New Zealand
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Telephone 64 9 525 6655
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AS TG3, March 2002

ISBN: 0908611 58 7

© Copyright International Accreditation New Zealand 2002

 Working Thermometers – Calibration requirements

Contents Page

1 Introduction ............................................................... 3

2 Thermometer Calibration Schedule ........................ 3

3 Construction of Thermometers ............................... 3

4 Inspection and Repair of Thermometers ................ 3

5 Selection of a Reference Thermometer ................... 4

6 Ice Point Checks ........................................................ 5

7 Uncertainty of Measurement..................................... 6

8 Comparison of Working Thermometers with

Reference Thermometers .......................................... 6
8.1 General Procedure.......................................... 6
8.2 Uncertainty of Calibration greater then ± 0.5°C 6
8.3 Uncertainty of Calibration between ± 0.5°C
and ± 0.1°C ..................................................... 10
8.4 Correction of Total Immersion Thermometers
used at Partial Immersion ............................... 13

9 Packing for Safe Transport ....................................... 13

Appendix 1 Traceability to National Standards of

Measurement (SI Units) ................................ 14

Tables
1 Thermometers complying with BS 593:1989 ............... 4
2 Calibration at 36.5oC .................................................... 8
3 Calibration at 37.5oC .................................................... 9
4 Calibration at 36.9oC .................................................... 11
5 Calibration at 37.1oC .................................................... 12

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Working Thermometers – Calibration Requirements

1 Introduction 3 Construction of Thermometers

It is fundamental to good laboratory practice that the A liquid-in-glass thermometer comprises a bulb, a
calibrations of both working and reference fine capillary and one or more expansion chambers
thermometers be traceable to the New Zealand at the top of the column. There may also be an
national standards of temperature and thus to SI expansion chamber between the ice point and the
units. beginning of the scale. To give the required
sensitivity the bulb of a reference thermometer is
Laboratories achieve this by sending their reference extremely thin (less than 0.5mm) so careful handling
thermometer(s) to an appropriate calibration agency. is imperative.
They then use the reference thermometer(s) to
check their own working thermometers. When a thermometer is first made the glass is in a
highly stressed state. This stress slowly relaxes in
This IANZ Technical Guide describes a procedure time causing the bulb to contract. This pushes the
that may be used for the comparison of working mercury higher up the capillary and causes the ice
grade thermometers with calibrated reference point to rise. There is a consequent change to all
thermometers. In addition, procedures for ice-point other scale points. Such “ageing” of the bulb is fairly
checks on reference thermometers and single-point rapid immediately after manufacture but gradually
checks on working thermometers are also described. slows down with time. An ice-point check every six
months, which is required by most thermometer
2 Thermometer Calibration Schedule calibration schedules, is a good monitor of the bulb
contraction. In general, any rise detected can be
Good laboratory practice with regard to the subtracted linearly along the entire scale of the
calibration of liquid-in-glass thermometers is as thermometer.
follows:-
Heating a thermometer to its maximum temperature
Type Calibration Schedule and then reducing it to ambient temperature causes
Reference Initial complete calibration, traceable a temporary depression of the ice point through bulb
to national standard of temperature. expansion. This may take several days to relax.

Further complete calibrations at five- A total immersion thermometer is one that is

yearly intervals thereafter. designed to be immersed in the medium being
monitored to the level of the current reading. A
Ice-point check six months after partial immersion thermometer is designed to be
initial calibration and at six-monthly immersed to the depth of a specific mark on the stem
intervals thereafter. (usually at 76mm or 100mm).

Working Initial check against a calibrated 4 Inspection and Repair of

reference thermometer followed by Thermometers
further single-point checks at six-
monthly intervals. (Note that the The first step in the calibration procedure is to
single point may be the ice-point.) visually check the thermometer for gross defects.
Points to look for are non-uniform or missing
Working thermometers need only be graduations, missing numbers and improper etching.
checked over their whole range if Next the thermometric liquid should be checked for
they are routinely used over a wide defects such as inclusions, a broken column or
temperature range. In general, separated liquid in the expansion or contraction
biological testing and chemical chamber. More stringent and extensive
testing laboratories use particular specifications are given in appropriate standards
thermometers over only a narrow such as BS 593:1989 “Specifications for Laboratory
range or at a single temperature. As Thermometers” and BS 1900:1976 “Specification for
long as the thermometers are not Secondary Reference Thermometers”.
interchanged a scale check at the
particular temperature at which each Gas inclusions and broken columns are best
is used can be made instead of the removed by carefully cooling the bulb of the
six-monthly ice-point check. Any thermometer in a thermos flask of either ice and
thermometer used over a range methanol, dry ice and methanol or liquid nitrogen,
greater than 5 deg should be depending on the temperature range of the
subjected to checks at several points thermometer. This will draw all the liquid into the
within the range of use. bulb and enable the gas inclusion to be expelled or
the broken thread rejoined. Avoid rapid cooling
which may freeze the liquid in the thermometer and
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 Working Thermometers – Calibration requirements

break the bulb. If the broken thread sticks, tap the 5 Selection of a Reference
thermometer gently. Separation of the column of a Thermometer
reference thermometer can occur in transit and
requires the same treatment for repair. Spirit left in
the expansion chamber or near the top of the The selection of an appropriate reference
thermometer can be gently heated to distil it off. thermometer will be influenced by the range of
temperature measurements that are to be made and
the uncertainty of measurement that it is required to
achieve.

Table 1 lists a number of thermometers complying

with the requirements of BS 593:1989. Those for
which the designation includes / TOTAL are total
immersion thermometers. Those for which the
designation includes / 100 are partial immersion
thermometers (immersion to 100mm).

Table 1 Thermometers complying with BS 593:1989

Designation Range (°C) Graduated Max Error Least Uncertainty

to (°C) Allowed (°C) of Test (°C)

A40C/TOTAL 0 TO +40 0.1 0.2 ± 0.02

A70C/TOTAL -0.5 to +0.5 and

40 to 70 0.1 0.2 ± 0.02

A100C/TOTAL -0.5 to +0.5 and

70 to 100 0.1 0.2 ± 0.02

A130C/TOTAL +0.5 to +0.5 and

100 to 130 0.1 0.2 ± 0.05

A40C/100 0 to +40 0.1 0.4 ± 0.05

A70C/100 -0.5 to +0.5 and

40 to 70 0.1 0.4 ± 0.05

A100C/100 -0.5 to+0.5 and

70 to 100 0.1 0.4 ± 0.05

A130C/100 -0.5 to +0.5 and

100 to 130 0.1 0.4 ± 0.1

Note: This table is not complete and BS 593 should be consulted for the full range of thermometers
specified.

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Working Thermometers – Calibration Requirements

BS 1900:1976 provides similar information about in a clean cloth with a mallet or a hammer and put
secondary reference thermometers whilst ASTM E1 into a thermos flask deep enough to immerse the
provides details of ASTM and IP thermometers. If an thermometer to the correct level. Distilled water is
uncertainty of calibration of less than 0.02°C is then added until the whitish ice colour disappears
required then a BS 1900 thermometer must be used. and clear ice remains. Excess water should then be
drained off but the whitish colour should not return
Let us suppose that a laboratory intends to purchase The ice point reading can now be taken providing
a reference thermometer with which to calibrate a test thermometers are inserted to the 0°C mark or
group of its own working thermometers. The partial immersion mark, whichever is appropriate.
reference thermometers must first be submitted to an Read the thermometer with a magnifying eyepiece
appropriate calibration agency to be calibrated. and record the reading. Repeat that measurement at
least twice (preferably with another observer). An ice
The working thermometers in question will be used point used for extended periods should have the
to measure the temperature of a water bath set at excess water drained off occasionally.
44.5°C. They must be calibrated with an uncertainty
of ± 0.2°C. Any change in the temperature correction at the ice
point, which has occurred between the current
In general, the uncertainty of calibration of the calibration and the initial calibration of the
reference thermometer should be a factor of five thermometer made by the external calibration
smaller than the uncertainty of calibration that is agency, should be applied at all other calibrated
required for the working thermometer. In this case, points.
as an uncertainty of calibration of ± 0.2°C is required
for the working thermometer, the uncertainty of the For example, a laboratory may perform an ice point
reference thermometer’s calibration must be ± check on a reference thermometer which was
0.04°C (0.2x1/5). subjected to a complete calibration at the time it was
purchased.
A good quality reference thermometer can generally
be calibrated with an uncertainty of one fifth of a The initial calibration report may have indicated the
following results:
scale division so if an uncertainty of ± 0.04°C is
required this implies that the reference thermometer
must have scale divisions of 0.2°C (0.04x5).
Thermometer Reading (°C) Correction (°C)
For the application under consideration, therefore, a
reference thermometer covering the region of
44.5°C, with graduations of at least 0.2°C is required. -0.04 +0.04
The BS 593 thermometer A70C/TOTAL listed above 5.00 +0.04
meets this specification. 10.00 +0.06
15.00 +0.02
In summary, a reference thermometer must have 20.00 +0.06
scale divisions equal to, or less than, the uncertainty 25.00 +0.08
of measurement required in the calibration of the 30.00 +0.06
working thermometer with which it is to be compared. 35.00 +0.04
40.00 +0.04
6 Ice Point Checks
Checks on the relaxation changes in both a To obtain the correct temperature the correction
reference and working thermometer should be made must be added to (or subtracted from if negative) the
every six months on the ice point (0°C mark) of the thermometer reading.
thermometer. The ice point check need not,
however, be made on a working thermometer used The laboratory might obtain three ice point readings
continually at one temperature (say 37°C). Such a as follows:
thermometer would be more appropriately checked -0.02°C; -0.02°C; -0.02°C
at this temperature every six months against a single
reference thermometer (which itself would still The new ice point reading is the average of the
require the ice point check). above, i.e. –0.02°C. The thermometer is, therefore,
reading low by 0.02°C and so the correction to be
An ice point is made with distilled water frozen in applied is +0.02°C. This compares with the earlier
clean trays in a freezer. It is preferable for the ice to calibration which gave a correction at 0°C of
be shaved in a food processor or purpose built +0.04°C. Corrections at all other temperature
shaver (low cost ice shavers are available from some reported by the calibration agency must now be
department stores). Alternatively the ice is crushed altered by (0.02 – 0.04) i.e. –0.02°C, thus:

5
 Working Thermometers – Calibration requirements

working thermometer’s reading at the required

Thermometer Reading (°C) Correction (°C) temperature.

If the working thermometer is only being checked at

-0.02 +0.02 one point for its regular six-monthly check then only
5.00 +0.02 one set of readings is required. If the thermometer is
10.00 +0.04 being subjected to an initial check before being put
15.00 +0.00 into use then readings should be taken at
20.00 +0.04 approximately ten degree intervals along its scale.
25.00 +0.06
30.00 +0.04 The procedures outlined below presume that up to
35.00 +0.02 four working thermometers are being checked at one
40.00 +0.02 time. They are equally valid, however, for checks on
fewer than four. The calibration of more than four
Ice points made with reasonable care should thermometers at one time is not recommended.
reproduce 0°C ± 0.05°C or better.
8.2 Uncertainty of Calibration Greater than
7 Uncertainty of Measurement ±0.5°C
8.2.1 Equipment
With the introduction of ISO/IEC 17025 there is now (i) A well-stirred, temperature–controlled water
a requirement for all laboratories, testing laboratories bath which is stable to at least half the
as well as calibration laboratories, to determine the required uncertainty in the calibration of the
uncertainty of each of their measurements. working thermometer. A very slowly rising
Obviously for equipment being used to make temperature is desirable but in no case should
measurements in testing the starting point for this the temperature be falling during calibration as
determination will be an awareness of the uncertainty sticking of the liquid in the thermometer
contribution provided from each measuring capillary will lead to errors. Spatial
instrument. Accredited metrology laboratories are temperature gradients (both vertical and
required to report the uncertainty for their calibrations horizontal) within the area of the bath being
and all IANZ endorsed calibration certificates will used for comparison should be checked
provide this information. As appropriate, this data before calibration begins. These must be less
can be directly used in the testing laboratory’s own than one quarter of the uncertainty of
determination of uncertainty of measurement in calibration required.
testing. (ii) At least one reference thermometer, the
uncertainty of calibration of which is at most
When a testing laboratory chooses to carry out its one-fifth of the uncertainty of calibration
own in-house calibration, the uncertainty of that required for the thermometer under test. The
calibration will need to be determined using reference thermometer(s) must be calibrated
appropriate methods. Depending on the degree of by an appropriate agency. (See Appendix 1).
rigor required, there are a number of different The reference(s) should be of the partial
approaches to this. Various guidance documents immersion type if the working thermometers
are available and testing laboratories should adopt are partial immersion and/or if the depth of
methods appropriated for their purposes. immersion in the comparison bath is limited.
Note that in Table 1 the calibration uncertainty
of partial immersion thermometers is generally
8 Comparison of Working greater than that for total immersion
Thermometers with Reference thermometers covering the same range.
Thermometers (iii) A magnifying eyepiece to reduce parallax
errors and improve readability.
8.1 General Procedure (iv) A flat plate, drilled to take both reference and
The working thermometer and the reference working thermometers, which can be clamped
thermometer with which it is to be compared are held over the bath. O-rings or rubber grommets
side-by-side in a temperature controlled water (or oil) can be used to hold the thermometers at the
bath. The bath is allowed to stabilize at the required correct height in the plate.
calibration temperature before the readings of the
thermometers are compared. 8.2.2 Procedure
(Note: In general, no attempt should be made to
If it is required to compare the thermometers at a calibrate a working thermometer (in-house) to an
particular temperature 37°C say, then the two sets of uncertainty of less than half a scale division.)
readings are taken to either side of the required
temperatures (36.5°C and 37.5°C). These two sets Let us presume that a working thermometer is to be
of readings are averaged to find the correction to the compared with a reference thermometer at a

6
Working Thermometers – Calibration Requirements

particular temperature (37°C say). Insert the

reference thermometer into the supporting plate with
no more than four working thermometers in the order
Reference, Test 1, Test 2, Test 3, Test 4. Stabilise
the bath temperature to just below 37°C (36.5°C
say).
Thermometers should be immersed to the reading if
they are of the total immersion type or to the
appropriate mark (e.g. 76mm) if partial immersion.

Thermometers should remain vertical and the water

bath level should be increased if immersion is
insufficient.

If total immersion thermometers are used at partial

immersion their readings will require correction (see
8.4).

When the bath temperature is stable (or increasing

slowly) read the thermometers in the following order
(tapping each thermometer, gently, first):

Ref 1 2 3 4 4 3 2 1 Ref

and record the thermometer readings as they are

made.

Repeat the measurements at a temperature above

37°C (say 37.5°C). Similar checks should be made
at least every 10°C of the scale if the thermometer is
to be used over a wide range of temperatures.

8.2.3 Calculation of Corrections

Average the two sets of readings for each of the five
thermometers as shown below. Correct the
reference thermometer reading from its calibration
certificate allowing for any change in the ice point as
shown previously. It may be necessary to interpolate
the correction to the reference thermometer reading
for the actual bath temperature chosen. (i.e. If the
correction to the reference thermometer at 35°C is +
0.01°C and at 40°C the correction is + 0.03°C then at
37°C the correction will be +0.02°C).

Subtract the corrected reference thermometer

average reading from the average readings of the
working thermometers to obtain the error in each
thermometer. The correction is found by changing
the sign of each error, as shown in Tables 2 and 3.

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 Working Thermometers – Calibration requirements

Table 2 Calibration at 36.5°C

Reference T1 T2 T3 T4

Reading 1 (°C) 36.65 36.5 36.7 36.6 37.0

Reading 2 (°C) 36.70 36.6 36.7 36.6 37.0

Average 36.68 36.55 36.7 36.6 37.0

Correction to reference
from calibration
certificate +0.02°C +0.02

Therefore average
temperature 36.70
in bath at calibration =

Subtract average bath

temperature from average
test thermometer reading (-36.70) (-36.70) (-36.70) (-36.70)
to obtain error in test
thermometers -0.15 0.00 -0.10 +0.30

Correction (1) to test

thermometers (change sign) +0.15 0.00 +0.10 -0.30

Repeat this procedure for the results of the second test carried out at 37.5oC.

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Working Thermometers – Calibration Requirements

Table 3 Calibration at 37.5°C

Reference T1 T2 T3 T4

Reading 1 (°C) 37.45 37.3 37.4 37.3 37.5

Reading 2 (°C) 37.48 37.3 37.4 37.3 37.5

Average 37.46 37.3 37.4 37.3 37.5

Correction to reference
thermometer +0.02

Temperature in bath 37.48

(-37.48) (-37.48) (-37.48) (-37.48)

Error in test thermometers -0.18 -0.08 -0.18 +0.02

Correction (2) to test

thermometers +0.18 +0.08 +0.18 -0.02

Correction (1) to test

thermometers from above +0.15 0.00 +0.10 -0.30

Average of corrections (1)

and (2) to test
thermometers +0.16 +0.04 +0.14 -0.16
at 37°C

Round to nearest 0.1°C +0.2 0.0 +0.1 -0.2

(readability of thermometer)

The procedure outlined above should be carried out at each point on the working thermometer’s scale that is to be
calibrated.

The corrections to a thermometer being used over a wide range of temperatures can be plotted against
temperature to produce a calibration curve. This procedure facilitates interpolation of corrections at intermediate
temperatures.

9
 Working Thermometers – Calibration requirements

8.3 Uncertainty of Calibration between ± 0.5°C When the bath temperature is stable or slowly
and ± 0.1°C increasing begin reading from left to right and back
8.3.1 Equipment recording the readings as you go. Tap each
(i) A well stirred temperature-controlled water thermometer gently before reading. The readings
bath which is stable to at least half the should be made in the following order:
uncertainty of the calibration required. A very
slowly rising temperature is desirable but in no Ref 1, Test 1, 2, 3, 4, Ref 2, Ref 2, Test
case should the temperature be falling during 4, 3, 2, 1, Ref 1
calibration as sticking of the mercury will lead
to calibration errors. Spatial gradients within Repeat the measurements at approximately 37.1°C.
the area of the bath being used for
comparison should be checked before If the working thermometer is to be calibrated over a
calibration begins and must be less than half wide range such as 0°C to 50°C, tests should be
the uncertainty of test required. carried out at the ice point, 9.9°C and 10.1°C,
(ii) Two calibrated reference thermometers, the 19.9°C and 20.1°C etc, up to 50°C.
uncertainty of calibration of which should be at
most ¼ of that of the uncertainty of calibration 8.3.3 Calculation of Corrections
required for the thermometer under test. Average the two sets of readings for each of the six
These should be partial immersion if the thermometers and correct the reference
working thermometers are partial immersion thermometer readings using data from their
and/or if depth of immersion in the comparison calibration certificates. Presume that at 37°C the
bath is limited. Note that in Table 1 the corrections required are +0.02°C for Reference 1
calibration uncertainty of partial immersion and +0.05°C for Reference 2. (These figures will
thermometers is generally greater than that for probably have been interpolated from corrections
total immersion thermometers covering the given by the reference thermometers’ calibration
same range. The reference thermometers certificates at 35°C and 40°C.)
must be calibrated by an appropriate agency
(see Appendix I). The average of the two corrected reference
(iii) A magnifying eyepiece to reduce parallax thermometers’ readings are now subtracted
errors and improve readability. algebraically from the average for each test
(iv) A flat plate, drilled to take both reference and thermometer to give the error as shown in Tables 4
working thermometers, which can be clamped and 5.
over the bath. O-rings or rubber grommets
can be used to hold the thermometers in the
plate at the correct height.

8.3.2 Procedure
Let us assume that a working thermometer is to be
compared with a reference thermometer at a
particular temperature (37°C say). Insert the
reference thermometers into the support plate with
no more than four working thermometers in the
order:

Reference 1, Test 1, Test 2, Test 3,

Test 4, Reference 2

Stabilise the bath reading below 37°C (at 36.9°C for

example).

The thermometers should be immersed to the

reading if total immersion or to the appropriate mark
(e.g. 76mm) if partial immersion. Thermometers
should remain vertical and the water bath level
should be increased if immersion is insufficient;
otherwise the calibration of total immersion
thermometers used at partial immersion will need to
be corrected (see 7.4).

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Working Thermometers – Calibration Requirements

Table 4 Calibration at 36.9°C

Ref 1 T1 T2 T3 T4 Ref 2

Reading 1 (°C) 36.88 36.8 36.8 36.7 37.0 36.85

Reading 2 (°C) 36.92 37.0 36.9 36.8 37.0 36.87

Averages 36.90 36.9 36.85 36.75 37.0 36.86

Reference correction
from calibration
certificate = +0.02 +0.05

Reference
Temperature (1) 36.92 Reference Temperature 36.91
(2)
Average of
references 36.92
(Temperature in bath)

Subtract average bath (-36.92) (-36.92) (-36.92) (-36.92)

temperature from average
test thermometer reading
to obtain error in test
thermometers -0.02 -0.07 -0.17 +0.08

Correction (1) to
test thermometers
(change sign) +0.02 +0.07 +0.17 -0.08

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 Working Thermometers – Calibration requirements

For the second test at 37.1oC the calculations might be as follows:

Table 5 Calibration at 37.1oC

Ref 1 T1 T2 T3 T4 Ref 2

Reading 1 (°C) 37.08 37.1 37.1 37.3 37.2 37.05

Reading 2 (°C) 37.16 37.2 37.1 37.3 37.2 37.05

Averages 37.12 37.15 37.1 37.3 37.2 37.05

Correction to references
from calibration
certificates +0.02 +0.05

Reference
Temperature (1) 37.14 Reference Temperature (2) 37.10

Average of
References 37.12
(Temperature in bath)

(-37.12) (-37.12) (-37.12) (-37.12)

Error in test thermometers

+0.03 -0.02 +0.18 +0.08

Correction (2) to
test thermometers
(Change sign) -0.03 +0.02 -0.18 -0.08

Correction (1) from above +0.02 +0.07 +0.17 -0.08

Average of corrections
(1) and (2) to test
thermometers at 37.0°C 0.00 +0.04 0.00 -0.08

Round to 0.1°C
(readability of
thermometer) 0.0 0.0 0.0 -0.1

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Working Thermometers – Calibration Requirements

The corrections to a thermometer being used over a 2) A total immersion mercury in glass
wide range of temperatures can be plotted against thermometer (0-300°C divided to
temperature to produce a calibration curve. This 0.5°C) in an oil bath at 105°C but
facilitates interpolation of corrections at intermediate immersed at the 30°C mark.
temperatures.
k = 0.00016
8.4 Correction of Total Immersion
Thermometers used at Partial Immersion N = 105°C - 30°C = 75°C
If it is not possible to fill the comparison bath
sufficiently to immerse a total immersion reference Tc = 105°C
thermometer to the reading, then another small
thermometer should be attached to the stem of the Tu = 40°C (measured on the exposed scale)
thermometer about one-third of the way up the
exposed column. This will read (approximately) the Correction = 0.00016 x 75 (105-40)
average temperature of the emergent length of
= +0.78°C
mercury (or spirit). A correction now needs to be
= +0.8°C rounded
applied to the thermometer reading because of the
generally lower temperature of the mercury (or
These corrections are made in addition to any scale
spirit) not immersed. This correction is given by:
corrections required by the calibration certificate.
kN (Tc – Tu)
9 Packing for Safe Transport
Where k = 0.00016 for mercury
Reference thermometers for calibration should be
= 0.001 for spirit
carried by hand if at all possible, but failing that
should be packed in such a way that the whole
N = the number of degrees of the scale
length of the thermometer is supported. This can be
exposed
achieved by cutting slots in a solid slab of
polystyrene foam or by supporting the thermometers
Tc = the temperature of the calibration bath
between long slabs of foam rubber in a wooden box
during the original calibration
with a screw-on lid. Some calibrating agencies have
shipping containers which can be procured for a
Tu = the temperature of the exposed scale
deposit which is refundable on return of the box.
during this calibration (given by the small
thermometer attached to the stem)

e.g. 1) Total immersion mercury in glass

thermometer (0-100°C divided to
0.5°C) in a bath at 55°C but
immersed to the 30°C mark.

k = 0.00016

N = 55° - 30°C = 25°C

Tc = 55°C

Tu = 25°C (say) on the small thermometer

attached to the scale

Correction = 0.00016 x 25 (55-25)

= +0.12°C
= +0.1°C rounded to the
readability of the
thermometer

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 Working Thermometers – Calibration requirements

APPENDIX 1
Traceability to National Standards of Measurement (SI Units)

1. New Zealand

The Measurement Standards Laboratory of Industrial

Research Limited (MSL) maintains the New Zealand
National Standards of Measurement under authority
enacted in the Scientific and Industrial Research Act
1989.

The laboratory can undertake calibration work to

specific uncertainties defined by the laboratory in
addition to the routine calibration services which are
detailed in Appendices B and C of the National
Metrology Institutes’ (NMI) mutual recognition
arrangement. Enquiries should be directed to:

The Chief Metrologist

Measurement Standards Laboratory
Industrial Research Limited
P.O. Box 31 310
Lower Hutt

Traceability to New Zealand’s National Standards of

Measurement for specific measurements can also be
obtained via laboratories accredited by IANZ for such
measurements. Information regarding these
laboratories can be gained from the IANZ website or
by phoning the organisation direct.

2. Overseas

Traceability to SI units via national metrology

institutes (NMI) is acceptable to IANZ. This may be
obtained by calibration by an overseas NMI that is
part of the international mutual recognition
agreement for NMIs. Alternatively calibration by a
laboratory accredited by an overseas laboratory
accreditation body with which IANZ has a mutual
recognition agreement is also acceptable.

For a list of NMIs that are part of the agreement

contact the Chief Metrologist of MSL. For
accreditation bodies belonging to the mutual
recognition arrangements contact IANZ.

14