SAC-SINGLAS Accredited · ISO/IEC 17025
PRT Probe Calibration
Unitest provides SAC-SINGLAS accredited PRT probe calibration in Singapore from -80 C to 660 C in the lab (and -95 C to 660 C on-site), with lab measurement uncertainties (CMC) from 0.01 C to 0.39 C under method UNI-T001, and traceable ISO/IEC 17025 certificates.
Reference PRTs and SPRTs: lab-grade platinum thermometers
This page covers reference-grade platinum resistance thermometers: reference PRTs and standard platinum resistance thermometers (SPRTs) used as temperature standards rather than everyday process sensors. An SPRT is the highest-accuracy class, built to interpolate the International Temperature Scale of 1990 (ITS-90), while a reference PRT is a robust, high-stability platinum thermometer used as a working laboratory standard. Industrial Pt100 and Pt1000 process sensors are covered on our separate RTD probe calibration page.
We calibrate the reference thermometer on its own, or together with its readout bridge or indicator, so the certificate reflects how the standard is actually used in your laboratory.
Comparison and fixed-point calibration
Reference PRTs are most often calibrated by comparison against a higher-order reference thermometer in a stable, uniform bath or furnace, with the deviation recorded across the range. For the lowest uncertainty on the highest-grade thermometers, calibration is instead tied to defined fixed points, precisely reproducible phase transitions such as the triple point of water (0.01 C), gallium (29.7647 C) and aluminium (660.3226 C), which underpin the ITS-90 scale.
Fixed-point work is offered under our separate fixed-point temperature service. Comparison calibration under method UNI-T001 covers reference PRTs and SPRTs across our accredited range, and we will advise which approach suits the accuracy your standard needs.
Accredited range and why PRT calibration matters
Unitest's accredited range for PRT and reference sensors with indicator runs from -80 C to 660 C in the lab, with CMC uncertainties from 0.01 C up to 0.39 C at the top of the range, and from -95 C to 660 C on-site, all under method UNI-T001. Standard turnaround is 5 to 7 working days, with a 2 to 3 day express option, and free collection and delivery across Singapore for orders of S$300 and above.
A reference thermometer that has drifted silently corrupts every calibration performed against it, so the case for keeping it in check is stronger than for any working sensor. Reference PRTs and SPRTs are typically recalibrated every 12 months, or every 6 months for the most demanding work, and always after any shock, repair or exposure to out-of-range conditions.
What we calibrate
PRT Probe instruments we calibrate
- Standard platinum resistance thermometers (SPRTs)
- Reference PRTs
- Laboratory temperature standards
- Reference thermometers with readout / bridge
- High-accuracy platinum resistance probes
- Secondary reference PRTs
Accredited under SAC-SINGLAS LA-2023-0845-C. View our accreditation & scope →
Questions
PRT Probe calibration FAQ
What is the difference between a PRT and an SPRT?
A PRT (platinum resistance thermometer) is any resistance thermometer with a platinum element. An SPRT (standard platinum resistance thermometer) is the highest-accuracy class of PRT, built to interpolate the International Temperature Scale of 1990 (ITS-90) and used as a primary reference standard. In short, every SPRT is a PRT, but the SPRT is the reference-grade end of the range, while reference PRTs are the robust working standards used day to day in a calibration lab.
Is Unitest's PRT calibration SAC-SINGLAS accredited?
Yes. PRT sensor calibration is on our SAC-SINGLAS accredited schedule under method UNI-T001, with an accredited lab range of -80 C to 660 C (and -95 C to 660 C on-site). Certificates are issued under our ISO/IEC 17025 accreditation, LA-2023-0845-C, with stated measurement uncertainty at each point.
Do you offer fixed-point calibration for reference thermometers?
Yes. For the lowest uncertainty on the highest-grade thermometers, we offer fixed-point calibration tied to defined phase transitions such as the triple point of water (0.01 C), gallium (29.7647 C) and aluminium (660.3226 C) under our separate fixed-point temperature service. Many reference PRTs are calibrated by comparison under method UNI-T001, and we will advise which approach suits your standard.
What is the difference between this PRT service and your RTD page?
Both calibrate platinum resistance thermometers under the same accredited method, UNI-T001. This PRT page focuses on reference-grade and lab-grade thermometers (reference PRTs and SPRTs) used as temperature standards. Our RTD probe calibration page covers industrial Pt100 and Pt1000 process and lab sensors. Choosing the page that matches how your thermometer is used keeps the scope clear.
How often should a reference PRT be calibrated?
Typically every 12 months, and every 6 months for the most demanding reference work. Because a reference thermometer sets the accuracy of everything calibrated against it, it should also be recalibrated after any mechanical shock, repair, or exposure to out-of-range conditions. Your laboratory's quality management system will usually specify the interval.
Range information
PRT, Reference Sensor with Indicator, method UNI-T001. Lab: -80 C to 660 C, CMC 0.01 C to 0.39 C. Site: -95 C to 660 C, CMC 0.033 C to 0.39 C. Refer to the SINGLAS schedule LA-2023-0845-C for the full accredited range.
Accredited ranges
PRT Probe calibration ranges & measurement uncertainty
The parameters, ranges and calibration & measurement capability (CMC) below are taken from our SAC-SINGLAS Schedule of Accreditation (LA-2023-0845-C, to ISO/IEC 17025). CMC is the smallest measurement uncertainty we can achieve under accredited conditions.
RTD, PRT Sensor with Indicator & Temperature Measuring instruments (Lab)· UNI-T001 Rev:0
| Range / measured quantity | Measurement uncertainty (CMC) |
|---|---|
| -80 °C – -40 °C | 0.011 °C |
| >-40 °C – 0 °C | 0.01 °C |
| >0 °C – 50 °C | 0.01 °C |
| >50 °C – 140 °C | 0.01 °C |
| >140 °C – 210 °C | 0.01 °C |
| >210 °C – 270 °C | 0.011 °C |
| >270 °C – 450 °C | 0.018 °C |
| >450 °C – 500 °C | 0.02 °C |
| >500 °C – 660 °C | 0.39 °C |
RTD, PRT Sensor with Indicator & Temperature Measuring instruments (Site)· UNI-T001 Rev:0
| Range / measured quantity | Measurement uncertainty (CMC) |
|---|---|
| -95 °C – 0 °C | 0.066 °C |
| >0 °C – 60 °C | 0.033 °C |
| >60 °C – 140 °C | 0.047 °C |
| >140 °C – 270 °C | 0.26 °C |
| >270 °C – 450 °C | 0.33 °C |
| >450 °C – 660 ° | 0.39 °C |
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