Fiber Optic Probe Calibration

Osensa Fiber-Optic Probe Calibration

Accurate, repeatable and traceable temperature measurement for medical, research and industrial applications

Osensa phosphor-based fiber-optic probes provide high-resolution temperature measurement in environments where conventional electronic sensors may be unsafe, unreliable or affected by electromagnetic fields.

Why Calibration Matters

Fiber-optic temperature probes are used in MRI systems, thermal therapies, medical and veterinary research, RF and microwave heating, wireless charging evaluation, and industrial process monitoring. Calibration characterizes the complete measurement system so that the transmitter can convert the probe’s optical response into an accurate temperature reading.

Depending on the application, the measurement objective may be absolute temperature accuracy, relative temperature change, or both. Osensa systems can provide resolution as fine as 0.01°C and calibration accuracy of ±0.1°C, depending on the transmitter, probe, calibration range and operating conditions.

Absolute and Relative Temperature Measurement

Absolute measurement determines the true temperature of an object. It is important when small errors could change a clinical or engineering decision, such as monitoring an infant during an MRI examination.
Relative or differential measurement determines temperature rise or change. Examples include MRI implant safety testing, wireless charging coil evaluation, RF heating and reliability testing.

The Two Parts of Osensa Calibration

High-accuracy operation requires both a calibration table and an individual probe offset. These corrections serve different purposes and must match the probe and transmitter configuration.

Calibration Table

The calibration table describes the optical response of a specific probe model used with a particular transmitter family over a defined temperature range. It contains temperature and decay-time data, together with the correction coefficients required by the transmitter. A table generally applies to probes of the same model, but Osensa can create a custom table for a specialized probe, range or application.

Individual Probe Offset

Normal manufacturing tolerances give each probe slightly different optical characteristics. The offset is a small positive or negative temperature correction that compensates for this probe-to-probe variation. It is recorded on the probe or calibration report and identifies the transmitter family for which it applies.

Both corrections are required for best accuracy. Using the wrong calibration table or omitting the probe offset can produce a significant measurement error; depending on the probe, the error may approach ±1°C.

Using Calibration Data

When Osensa supplies a new system, the appropriate calibration table is normally loaded into the transmitter for the specified probe type. The probe offset is entered in OsensaView and uploaded to the assigned transmitter channel. During operation, the transmitter automatically applies the stored table and offset to calculate the corrected temperature.

If a probe is replaced, a probe model changes, or the probe is used with a different transmitter family, confirm that the correct calibration table and offset are available. If the probe serial number is known, contact info@osensa.com to request the applicable calibration information.

How Accurate Calibration Is Performed

Osensa and accredited calibration laboratories use a precision metrology well together with a traceable platinum reference thermometer, precision readout, stable environmental conditions and specialized calibration software. The metrology well alone is not sufficient: the reference thermometer establishes the traceable temperature against which the Osensa system is compared.

Typical Equipment

Precision deep metrology well or dry-well calibrator
Traceable platinum reference thermometer and precision readout
Osensa temperature transmitter and OsensaView or factory calibration software
Probe fixtures or inserts that maintain consistent depth and close thermal coupling

Calibration Workflow

Confirm the probe model, serial number, transmitter family, channel assignment and required temperature range.
Insert the Osensa probe and reference thermometer to the same controlled depth and position them as close together as practical.
Seal unused openings to limit ambient-air circulation and allow the metrology well to stabilize.
At each calibration point, wait until both the reference and Osensa readings have reached thermal equilibrium before recording data.
Use the measured response to generate or verify the calibration table and determine the individual probe offset.
Load the approved calibration data into the transmitter and verify system performance at multiple temperatures.

Insertion Depth and Settling Time

Repeatability depends on placing the probe and reference thermometer in a uniform section of the well at a consistent insertion depth. Unused holes should be sealed where practical to reduce heat loss and outside-air circulation.

Settling time depends mainly on probe construction, tip mass, diameter, insertion depth and temperature step. Smaller probes generally stabilize more quickly. Record measurements only after both instruments are stable; inadequate settling time can introduce errors even when the calibration equipment itself is accurate.

Applications and Materials for Heating and Drying

Osensa can support:

Standard or custom temperature ranges
New and customer-specific probe designs
Custom calibration tables and individual probe offsets
System-level verification using the final cable lengths, interconnects and transmitter channels
Calibration reports and traceability documentation

Independent ISO/IEC 17025 Verification

When independent verification is required, Osensa can arrange testing through an ISO/IEC 17025-accredited calibration laboratory. Each probe is typically assigned to a specific transmitter channel and the complete system is verified against traceable standards. The laboratory then issues independent calibration documentation, which may support regulated applications or government submissions.

Frequently Asked Questions

Why are both a calibration table and an offset required?

The table corrects the response of the probe model and transmitter family over the calibrated range. The offset corrects the remaining variation of the individual probe. Together, they provide the best system accuracy.

How often should a probe be recalibrated?

For applications requiring approximately ±0.1°C accuracy, annual recalibration is generally recommended. For applications requiring approximately ±1°C accuracy, a two-year interval may be acceptable. The final interval should follow the user's quality system, operating conditions, regulatory requirements and calibration history.

Can Osensa create a custom calibration table?

Yes. Osensa can develop tables for specialized probe designs, transmitter families, temperature ranges and application-specific requirements.

Does changing the cable length affect calibration?

Normally it does not, provided the LED drive current remains within the specified operating range. For demanding applications, Osensa can verify the complete system using the final cable length and interconnections.

Where can I obtain the correct calibration data?

Check the probe label and calibration report first. If the information is unavailable, contact info@osensa.com with the probe serial number, probe model and transmitter model.

Why Choose Osensa Calibration?

Probe-level traceability and individual offsets
Calibration tables matched to probe and transmitter families
Traceable calibration methods and reports
Medical, research and industrial application experience
Custom probe, temperature-range and system-level verification support

Need a custom calibration? Contact the Osensa technical team at info@osensa.com to discuss your probe, transmitter, temperature range, accuracy and documentation requirements.