1. Is Your Food Safety
Thermometer Even Accurate??
ThermoWorks “Winning at Food Safety” Webinar Series
Special Guest Thomas Wiandt, Chief Metrologist ThermoWorks
Sept 30, 2021

2. Tom Wiandt
• graduated 1982 from US Air Force Precision Measurement
Equipment Lab
• has worked in DoD, nuclear power, instrument manufacturing,
laboratory accreditation, and independent consulting
• positions at Fluke, Hart Scientific, Southern California Edison,
Northrop, USAF before joining ThermoWorks
• trainer, consultant, and laboratory assessor for NVLAP, A2LA, and LAB
• member of ASTM since 1995—Chairman of ASTM E20 on
Temperature Measurement from 2012 to 2017
• awarded the Award of Merit and granted the title of ASTM Fellow
in2011, the highest award presented by ASTM
• Chief Metrologist at ThermoWorks since 2018

3. What is accuracy?
Official definition:
n ― of a temperature measurement, closeness
of agreement between the result of a
temperature measurement and a true value of
the temperature.
Source:
ASTM E344 Terminology Relating to
Thermometry and Hydrometry
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4. What can impact a thermometer’s accuracy?
Thermal Stress Rugged Handling Sensor type/quality
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5. How can an inaccurate thermometer
adversely affect my business?
Examples:
• Pharm – not properly sterilized, (above 121°C)
• Foodservice – too long in the danger zone (above 41°F) causing
pathogen growth
• Food processing – Cooking SOP affected by higher than expected
temp (losing a batch of noodles)
• Plastics – poor injection molding yields
• Genetics – improper gene amplification and results, low PCR yield
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6. What does calibration mean?
Official definition:
n ― of a thermometer or thermometric system, the set of
operations that establish, under specified conditions, the
relationship between the values of a thermometric quantity
indicated by a thermometer or thermometric system and
the corresponding values of temperature realized by
standards.
Source:
ASTM E344 Terminology Relating to Thermometry and
Hydrometry
ThermoWorks ASTM-Accredited
Calibration Lab
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7. How can a thermometer’s accuracy be
verified?
Calibration Certificate Calibration Equipment
(certified standard)
Known Stable Test Point
(ice bath or boiling water)
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8. Historical “calibration” method: Bi-Metallic
• Bi-metallic nut adjustment (historical)
• Why did that require daily calibration?
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9. How to verify the accuracy of a digital
thermometer? (Do I even need to?)
• Best Method: Compare to a certified reference thermometer
• Next Best Method: Properly prepared ice bath
• Boiling point? Many variables to keep track of
• Sous vide bath? Only if you have a reference thermometer
• Food? Never
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10. How to verify the accuracy of a digital
thermometer? (Do I even need to?)
• Best Method: Compare to a certified reference thermometer
• Next Best Method: Properly prepared ice bath
• Boiling point? Many variables to keep track of
• Sous vide bath? Only if you have a reference thermometer
• Food? Never
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11. But how do I know that a thermometer that is
accurate at 32°F is accurate at food temperatures?
• Instrument calibration certificates typically come with more than
one certification point
• A calibrated instrument that is still accurate at the ice point is
generally still accurate across its range
• A thermometer that is experiencing drift at food temperatures will
manifest that drift at the ice point, as well
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12. How frequently should you verify?
• Depends upon the use of the thermometer
1. Thermometer risk analysis
• Thermometers regularly used near the limit of their ranges should be verified
more frequently
2. Process risk analysis
• Some processes require daily verification (i.e. large food processors)
• With others, verification every month or so is fine
3. Regulatory requirements
• Consult your state, county, or city regulatory authorities
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13. Video Clips 1 & 2: Testing Against a Traceable Standard
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14. Ice Bath tips and facts
• Ice cube size: the smaller the radius the better—crush big cubes
• Purity of water: the purer the water the better—i.e. drinkable water purity
Better
Better
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15. Benefits of ice bath calibration
• Results to 32.0 ±0.05°F
• Made with common items: ice, tap water, insulated mug
• Quick and easy to make
• As long as you follow the recommended precautions
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16. Ice Bath Precautions
1. Make sure the container is clean (clear sides preferable)
2. Use ice with small radius (crush big ice cubes)
3. Fill the container with the ice
4. Add water to ½ inch below the ice level
5. Make sure the ice isn’t floating
• If it is, pour off water OR put more ice in and push it down
6. Plunge the probe tip into the center of the ice container (not top or
bottom)
7. Stir the probe while testing
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17. Download and Print Our Ice Bath Poster Now:
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Laminate it and put it in
your kitchen with your
verification schedule…
FREE for our webinar
attendees

18. Helpful products
Super high accuracy to ±0.1°F (±0.05°C)
with 5-pt UKAS Accredited Calibration
20% Off Reference Thermapen®
$219.00 $174.20
Step-by-step instructions on making a
proper ice bath
FREE Ice Bath Mug
$7.50 FREE w/ purchase
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19. Next Session:
Thursday, October 14th, 10:00-10:30am MDT
• Top 5 Common Food Safety Mistakes and How to Avoid Them
• Learn to avoid mistakes you're probably making in your operations that could put your
patrons at risk…
This Session:
• Replay of this session going out by email
• Go to www.thermoworks.com/webinar-series
• Share with colleagues and friends
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