Sensorsoft Thermometer User Manual
Resolution, Accuracy and Calibration
The terms resolution, accuracy and calibration frequently cause misunderstanding for many
individuals who have not been trained in metrology. We endeavor here to explain these terms and
how they might affect your application of Sensorsoft devices.
Resolution or precision is the fineness of the measurement. It is usually specified in terms of the
smallest unit that can be resolved.
Accuracy is the trueness of the measurement or how close it can be to the true value (National
Standard). Accuracy is often specified as a percentage (i.e. +/- 3 % of reading), or a fixed value
(i.e. +/- 0.5 ) that the reading can vary from the true value.
Calibration is a process where accuracy is verified (and often corrected) with respect to a
standard. Calibrations are routinely carried out to certify that a device has not lost its accuracy,
linearity and stability. Calibrations can be carried out at a time interval that is required by your
industry. In many cases this is done at least once every year. When a calibration or verification
takes place, it must always be done with equipment that has significantly better accuracy and
resolution then the device under test. When a calibration is performed on a unit under test with an
instrument that is proven as traceable to the National Standards Laboratory, the unit under test is
also considered to be traceable.
Avoid making invalid judgements or comparisons
Using any of the following measurement devices or situations is unacceptable for comparing to,
or judging the accuracy of a Sensorsoft device:
•Measurement device purchased from a hardware or drug store
•Digital display on HVAC or cooling/heating equipment
•Location of the active sensing element is unknown
•Measurement device has its active sensing element more than one inch (2.5 cm) away from
the Sensorsoft device/probe
•Measurement device has similar specifications to the Sensorsoft device
•Measurement device has unknown specifications
•Measurement device has not been calibrated within one year, has no calibration certificate or
is not traceable to a standard
Use the proper instrument and method to make comparisons
We recommend one of the following instruments (or equivalent) that have a recently dated
traceable calibration certificate, for judging the accuracy or stability of your Sensorsoft device:
•Vaisala HM34 Humidity & Temperature Meter (Hand held, approx. price $500 USD)
•Vaisala HMP233 Humidity & Temperature Transmitter and external probe (Wall mount,
RS232 interface, order with 115/230 VAC power supply, approx. price $1800 USD)
•Vaisala HMI38/HMP35E Humidity & Temperature Data Processor and external probe (Desk
top unit, RS232 interface, approx. price $2580 USD)
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