Transcript Thermometer Calibration

Ice Point and Boiling Point Methods
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Why calibrate a thermometer?
Directives or standards such as ISO 9000 or ISO 17025 require organizations to provide
accurate temperature measurements traceable to national or international standards. It
is an important part of quality assurance in industry - for example in manufacturing to
guarantee the quality of a product- and also to ensure effective testing or calibration by
laboratories.
Temperature is a critical measurement for ensuring the safety and quality of many food
products. Whether monitoring temperatures at receiving, throughout production or final
product storage and distribution, thermometer calibration is essential. The validation,
verification reassessment section of the Hazard Analysis and Critical Control
Point system stated in the Code of Federal Regulations (9CFR 3:417.4) specifies that
instruments used for monitoring critical control points must be calibrated.
Choosing a thermometer:
If your thermometer is not accurate within +/- 2°F of 32°F., adjust the thermometer
accordingly. The ice point method permits calibration to within 0.1°F.
If your thermometer is not accurate within +/- 2°F of 212°F., adjust thermometer
accordingly. The boiling point method permits calibration to within 1.0°F.
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Use an insulated Cup for
thermal stability
◦ We recommend a thermos
over Styrofoam cups
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Measure the cup height
against your thermometer
probe
◦ Probe should be at least one
inch shorter than the cup
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Place hole in center of
thermos lid.
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Add ½ crushed ice and ½ tap
water (distilled preferred)
Allow to set for couple
minutes
Place Thermometer probe in
center hole
Slosh Ice-water to verify
stability.
Readings 32oF +/- 2oF =Ok
◦ 32oF = 0oC
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Prefer 32oF +/- 0.1oF
If the temperature is not at 32oF (0oC), then hold the calibration nut
securely with a wrench and rotate the head of the thermometer until it
reads 32ºF (0oC). Follow manufacture’s instructions.
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Use a Pyrex cup or flask.
◦ Metal pot not preferred
Fill cup 1.5inch below top.
 Bring water to a slow boil.
 Then place Probe in center of
cup for 1-2minutes or until
stable.
◦ Keep probe off bottom of cup
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◦ Use a non-metal support (safety)
with vents/slots (keeps steam off
dial) for visibility. And prevents
loss of probe in hot liquid.
◦ Example: pasta scoop.
•Water boils at 212oF (100oC) at elevations of sea
level to 1,000ft.
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Bimetallic Dial thermometers are sensitive
only to about 2inches from the tip.
 Most have a ‘dimple’ indicator.
Cut away view
The full bimetallic part of this sensor must be immersed in
the liquid (soup) or solid (meat) for accurate readings.
Test ‘slim’ cuts or portions from the side for best results.
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Dial: If the temperature is not at 32oF (0oC), Ice
Point or 212oF (100oC) Boiling Point, then hold
the calibration nut securely with a wrench and
rotate the head of the thermometer.
Digital: Follow manufacture’s instructions.
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Laboratory
Calibration
Boiling Flask, glass
thermometer
supported by
clamp and stand
Correct.
Note:
Thermometer
centered and does
not touch bottom
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Boiling Point
Calibration
Boiling Metal Pot,
with clipped
thermometers.
•Metal Pot and
water not
necessarily same
temperatures
•Does tip contact
the pot or extend
away?
Not Preferred.
Do not ‘cook’
thermometers
during
calibration.
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Boiling Point
Calibration
Salad tongs not
made to hold
thin rods.
Thermometer
can slip out.
Boiling Metal Pot,
With metal tongs.
Not Preferred.
Note:
Cooking
method not
good for
calibration.
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Ice Point
Calibration
Covered insulated
cup, glass
thermometer with
clamp and stand.
Never use glass
thermometers with
food.
Acceptable
Technique
Avoid Styrofoam
when possible
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Ice Point
Calibration
Cubed Ice in water
glass
Not Preferred.
Use crushed ice
and insulated
cup
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Ice Point
Calibration
Glass thermometer
in ice
NEVER USE GLASS
THERMOMETERS
IN FOOD !!!
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CALIBRATION
SUMMARY
Avoid Styrofoam
cups. Save
environment
Pyrex cups work
well for both Ice
Point and Boiling
Point
Insulated Cups
with plastic lids
best for Ice Point
Calibration
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