Platinum does two distinct sensing jobs in industrial and automotive equipment: as a Pt100 resistance temperature detector (RTD), it measures temperature through its own resistance change, and as the electrode material in a lambda (oxygen) sensor, it measures the oxygen content of exhaust gas. Both roles trade on the same underlying property, a resistance-temperature and electrochemical behavior that stays reproducible and stable over long service life, which is why platinum, not a cheaper metal, sits inside both device families. This page covers what each sensor type is, why platinum is the reference metal for resistance thermometry, how platinum thermocouples extend measurement beyond an RTD's range, how a platinum oxygen sensor is built, and why oxygen-sensor demand has become a live, quantified line in platinum's industrial demand.
What Is a Pt100 Sensor?#
A Pt100 is a resistance temperature detector built around a pure platinum sensing element rated at 100 ohms nominal resistance at 0°C, with its resistance-temperature relationship standardized in IEC 60751. As the element's temperature rises, its electrical resistance rises with it in a predictable, repeatable curve, and a connected instrument reads that resistance back as a temperature value. This resistance-based principle is what separates a Pt100 from a thermocouple, which instead generates a small voltage from the junction of two dissimilar metals, one reason platinum shows up across two different sensor families rather than one. Pt100s sit within the wider set of uses of platinum group metals, which spans catalysis, electronics, medicine and jewelry alongside this metrology role.
Pt100 vs Pt1000: Two Standard Platinum RTDs#
A Pt1000 is the same platinum element rated at 1,000 ohms nominal resistance at 0°C, ten times more sensitive per degree than a Pt100 but otherwise identical in governing standard and construction. Because both are standardized under IEC 60751, the resistance-versus-temperature curve shape is the same for both types; only the nominal base resistance differs by a factor of ten, and an instrument reading a Pt1000 must be configured for that different base value or it will report the wrong temperature. A basic continuity check on either sensor at room temperature reads close to its rated 0°C nominal value, since room temperature sits only a few tens of degrees above the reference point; an open circuit or a reading of 0 ohms indicates a fault in the element or its wiring rather than a valid low-temperature reading.
Is a Pt100 an RTD or a Thermistor?#
A Pt100 is an RTD, not a thermistor: a thermistor is a non-platinum semiconductor sensor with a much larger, non-linear resistance change per degree, built from metal-oxide ceramics rather than a pure metal element. The two technologies solve the same broad problem, temperature-to-resistance conversion, with different trade-offs: an RTD's platinum element gives a smaller but highly linear and stable resistance change, while a thermistor's semiconductor element gives a larger, more sensitive but less linear response over a narrower range. This distinction matters for sourcing and specification, since thermistors fall outside the platinum group metals this site covers, and confusing the two technologies leads to selecting the wrong instrument calibration.
Why Platinum Is the Reference Metal for Resistance Thermometry#
Platinum is the reference thermometry metal because its resistance-temperature relationship is exceptionally reproducible, near-linear and stable, not because it catalyzes anything in this application. Two identical Pt100 elements manufactured to the same specification give matching readings within a tight tolerance, and a single element's calibration holds over years of service without significant drift, a combination that base metals such as copper or nickel cannot match at the same level of precision. That reproducibility is the entire basis for using platinum here: unlike platinum's catalytic uses in autocatalysts or chemical processing, its value in a resistance thermometer comes from being an inert, stable conductor with a well-characterized response curve, not from any surface chemistry.
Platinum Resistance Thermometers and the International Temperature Scale#
Standard Platinum Resistance Thermometers (SPRTs) are the defining interpolating instruments of the International Temperature Scale of 1990 (ITS-90) across the range from the triple point of hydrogen up to the freezing point of silver. Per the Wikipedia article on thermocouples, platinum resistance thermometers have taken over the standardization role that Type S thermocouples held before ITS-90 was adopted, because an SPRT's resistance-temperature relationship can be interpolated with lower uncertainty than a thermocouple's voltage output over that range. Gold-platinum thermocouples are also noted as competitive alternatives to platinum resistance thermometers for standards-laboratory work, though SPRTs remain the primary interpolating instrument named in ITS-90 itself. National metrology institutes, calibration laboratories and precision industrial processes rely on this platinum-based standard whenever a measurement needs to be traceable to the international scale rather than only to a local reference:
- Primary and secondary temperature calibration laboratories, which maintain SPRTs as transfer standards between fixed points.
- Semiconductor and pharmaceutical manufacturing, where process temperature must be traceable to a documented national standard.
- Industrial process control in petrochemical and power generation plants, where Pt100 and Pt1000 sensors (built to the same IEC 60751 standard, though not to SPRT-grade tolerance) provide day-to-day traceable readings.
Platinum Thermocouples vs Pt100 RTDs#
Platinum thermocouples extend temperature measurement far beyond a Pt100 RTD's practical range, reaching temperatures where a platinum resistance element itself would be unsuitable for continuous service. Three platinum-based thermocouple types cover this high-temperature territory, each pairing a platinum-rhodium alloy leg against a second leg of differing rhodium content or pure platinum, a design distinct from the single pure-platinum element used in a Pt100 or Pt1000. Full detail on how these three types are built and specified lives on DailyPlatinum's dedicated platinum thermocouples page; the comparison below only orients the two platinum sensor families against each other.
| Sensor type | Platinum-based element | Governing standard | Upper range | Note |
|---|---|---|---|---|
| Pt100 / Pt1000 RTD | Pure platinum, 100 or 1,000 ohms nominal at 0°C | IEC 60751 | Within the ITS-90 SPRT interpolation range | Resistance-based; no cold-junction compensation needed |
| Type S thermocouple | Pt-10% Rh (positive leg) / pure Pt (negative leg) | IEC 60584 | 1,600°C | Practical standard thermometer from 630°C to 1,064°C before ITS-90 |
| Type R thermocouple | Pt-13% Rh (positive leg) / pure Pt (negative leg) | IEC 60584 | 1,600°C | Stable with long operating life in clean, favorable conditions |
| Type B thermocouple | Pt-30% Rh / Pt-6% Rh (both legs alloyed) | IEC 60584 | 1,800°C | Same output at 0°C and 42°C, unusable below about 50°C, no cold-junction compensation needed at normal ambient |
Type S and Type R thermocouples both reach 1,600°C, while Type B extends to 1,800°C by alloying rhodium into both legs instead of leaving one leg as pure platinum. That extra range comes with a documented quirk: because Type B's two alloyed legs produce nearly identical voltage output at 0°C and at 42°C, the sensor cannot distinguish temperatures in that low band and is unusable below roughly 50°C, though the same characteristic means it needs no cold-junction compensation circuitry at normal ambient temperatures, unlike Type S and Type R. A Pt100 or Pt1000, by contrast, never approaches these ranges; its resistance element is a metrology instrument for the ITS-90 interpolation range and everyday industrial process temperatures, not a high-temperature furnace or kiln sensor.
Platinum Oxygen (Lambda) Sensors#
A platinum oxygen (lambda) sensor uses a yttria-stabilized zirconia electrolyte with porous platinum electrodes on both faces, an entirely different sensing principle from the Pt100's resistance element. Oxygen ions migrate through the solid zirconia electrolyte between the exhaust-side and reference-side platinum electrodes, and the resulting Nernst voltage across the cell reports the ratio of oxygen partial pressure between exhaust gas and reference air. Platinum plays three roles in this single component at once: it forms the electrode itself, it acts as an electrocatalyst that equilibrates the surrounding gas at the electrode surface, and it serves as the current collector carrying the generated signal out of the cell, a combination of duties that explains why the electrode material cannot simply be substituted with a cheaper conductor.
This electrochemical design is the same broad sensing principle behind the oxygen sensor's role in a catalytic converter, where the signal it produces tells the engine control unit whether the exhaust is running rich or lean so the fuel injection system can correct in real time, closing the loop that keeps a three-way catalyst operating in its narrow effective window.
Narrowband vs Wideband Oxygen Sensors#
Narrowband oxygen sensors report only whether the exhaust is running rich or lean of stoichiometric, switching sharply either side of the ideal air-fuel ratio rather than measuring the exact deviation from it. Wideband, or universal exhaust gas oxygen (UEGO), sensors add a second electrochemical pumping cell to the same zirconia structure and carry higher platinum loadings than a narrowband design, which lets the engine control unit read the precise air-fuel ratio across a much broader operating range instead of a simple rich or lean switch. That higher platinum content per sensor is the mechanical reason wideband adoption feeds directly into platinum demand, a link covered in the next section.
Oxygen Sensor Demand: A Live Driver of Platinum's "Other" Industrial Category#
The World Platinum Investment Council's Platinum Quarterly for Q1 2026 reports that platinum demand from sensors "has continued to strengthen," after WPIC recalibrated its metal-loading assumptions to reflect lower spark plug loadings alongside a higher uptake of wideband oxygen sensors. WPIC attributes that faster-than-expected wideband adoption to the need for enhanced fuel economy and durability in modern engines, a shift its earlier forecasts had underestimated. This is a dated, quantified demand line rather than a general claim about sensor markets: it comes from a single named report and should be read on that basis rather than as an industry-wide consensus figure.
Oxygen sensors sit inside WPIC's "Other" industrial category, which totaled 600,000 ounces of platinum demand in 2025, a classification that groups sensors together with platinum's other minor automotive and industrial uses, such as platinum and iridium in spark plugs, rather than counting them inside platinum's separately reported automotive autocatalyst demand.
That 600 koz figure is a category total, not a sensor-only number, so it should not be read as the size of the oxygen-sensor market by itself; WPIC's own commentary, not the category total, is the source for the sensor-specific strengthening trend.
The mechanical driver behind that strengthening is straightforward: wideband sensors carry higher platinum loadings than the narrowband designs they replace, so wideband adoption raises platinum content per vehicle before it shows up as any change in vehicle production volumes. Readers tracking platinum's demand side more broadly can follow this and the other minor industrial uses on DailyPlatinum's industrial platinum demand page, which covers the chemical, glass, petroleum and medical categories that sit alongside sensors and spark plugs in non-automotive platinum consumption.
Platinum Sensors in Context#
Platinum sensors sit alongside platinum's other automotive and industrial roles, from spark plug electrodes to autocatalysts, within DailyPlatinum's wider applications and market coverage. Readers who want the supply-and-demand picture behind the sensor-demand figures above can follow the platinum group metals market page for the current balance between mine supply, recycling and total demand across all of platinum's end uses.
That market-wide balance is what sensor-grade platinum wire and foil are ultimately priced against, since a sensor manufacturer buys into the same metal market as every other platinum application.
Current pricing for the metal these sensors are made from is tracked separately on DailyPlatinum's platinum price today page, which carries the live spot price rather than a historical figure.
Sensors are only one entry in that wider list, alongside platinum's roles in autocatalysis, jewelry, electronics and fuel cells.
For the fuller list of where else platinum is used, see the site's dedicated platinum uses page.
Platinum Sensors FAQ#
What is a Pt100 RTD sensor? A Pt100 RTD sensor is a temperature probe built around a 100 ohm platinum resistance element, standardized under IEC 60751 so that any compliant Pt100 from any manufacturer follows the same resistance-versus-temperature curve.
What are the disadvantages of a Pt100? A Pt100's main limitation is temperature range: its role in the International Temperature Scale of 1990 stops at the freezing point of silver, while platinum-rhodium thermocouples continue on to 1,600°C to 1,800°C for the highest industrial temperatures a Pt100 cannot reach. A rough continuity check with a multimeter can confirm a Pt100 is functional, since a working element reads close to its rated 100 ohm value at room temperature, but this is a basic pass or fail test, not a calibrated temperature measurement, and it cannot substitute for a proper resistance-to-temperature conversion.
Which is more accurate, an RTD or a thermistor? Accuracy within the platinum RTD family is set by IEC 60751 tolerance classes, not by a single number that settles "RTD versus thermistor" in general. A thermistor is a different, non-platinum semiconductor technology with its own accuracy and range characteristics, so a meaningful comparison depends on the specific tolerance class of RTD and the specific thermistor type being compared, rather than a blanket claim that one technology always outperforms the other.
What are platinum's symbol, atomic number and CAS number? Platinum has the symbol Pt, atomic number 78 and CAS number 7440-06-4. Full detail on platinum's physical and chemical properties is covered on DailyPlatinum's platinum (Pt), element 78 page.