How are Digital Thermometers Calibrated?
Over time, results and accuracy provided by temperature measurement devices, such as digital thermometers, tend to "drift." To be confident that your thermometer is providing accurate readings, regular calibration is essential.
The Calibration Process
Digital thermometer calibration involves comparing the readings of the thermometer being tested (the unit under test) against a reference standard with known accuracy. This is typically done at multiple temperature points across the instrument's operating range.
Step 1: Preparation
The thermometer is visually inspected for physical damage and the sensor is cleaned. The calibration laboratory prepares a stable temperature source — either a dry-well calibrator, a liquid bath, or an ice point reference — depending on the temperature range being tested.
Step 2: Comparison at Reference Points
The thermometer and a calibrated reference probe are both placed in the temperature source. Once the temperature stabilizes, the readings from both instruments are recorded. This process is repeated at multiple temperature points (such as 0°C, 25°C, 50°C, and 100°C) to assess accuracy across the full range.
Step 3: Calculating Error and Uncertainty
The difference between the thermometer's reading and the reference standard at each point is calculated. This "error" or "correction" value is documented along with the measurement uncertainty — a quantified statement of the confidence level of the calibration results.
Step 4: Documentation
A calibration certificate is issued that includes the as-found readings, as-left readings (if adjustments were made), reference standards used, environmental conditions during calibration, and measurement uncertainty. For ISO/IEC 17025 accredited calibrations, this certificate provides metrological traceability to national standards.
When Should You Calibrate?
Most organizations calibrate their digital thermometers on an annual basis, though the appropriate interval depends on how frequently the instrument is used, the environment it operates in, and the criticality of the measurements being taken.
For more information about digital thermometer calibration, contact Custom Calibration at (203) 484-3707 or email info@customcalibration.com.
Custom Calibration provides ISO/IEC 17025 accredited calibration services in North Haven, CT. We offer pickup and delivery, onsite calibration, and fast turnaround times with our Bullseye Guarantee.