SOT223 housed sensor

The recommended measuring current is 0.1 to 0.3 mA, with the lower end preferable where thermal error must be minimised. At 0 °C and 1,000 Ω, this range dissipates approximately 0.01 to 0.09 mW. Using the mounted self-heating coefficient of 0.049 K/mW, the idealised temperature rise is about 0.0005 to 0.0044 K; the package-only coefficient of 0.2 K/mW gives about 0.002 to 0.018 K. Actual error changes with resistance, PCB construction, airflow, duty cycle and thermal coupling. Engineers should validate the excitation under worst-case conditions and consider pulsed measurement where the analogue front end permits it.

Thermal response depends strongly on the surrounding medium and installation, so the stated times should be treated as defined reference conditions. In water flowing at 0.4 m/s, t₀.₅ is 0.45 seconds and t₀.₉ is 1.2 seconds; in air at 2 m/s, the corresponding values are 8 and 26 seconds. The wide connection lug transfers heat between the PCB and sensor, meaning copper area, solder coverage and distance from the heat source will affect the reading. For board compensation, the sensor should be placed where local temperature follows the component or copper region of interest. Prototype testing should reproduce the expected airflow, power cycling and enclosure conditions.

The sensor should be selected where Class F 0.6 (2B) provides an appropriate element tolerance across -50 °C to +150 °C. It has a nominal resistance of 1,000 Ω at 0 °C and a temperature coefficient of 3850 ppm/K, following the DIN EN IEC 60751 characteristic. The class applies to continuous operation throughout the stated temperature range, supporting established RTD conversion methods and predictable replacement between sensors using the same characteristic. However, the class does not include excitation-current error, PCB track resistance, ADC error, reference drift or thermal gradients. These terms must be included in the complete system error budget, with calibration added where tighter installed accuracy is required.

The component uses an SOT housing with overall dimensions of 6.5 ±0.2 mm long, 7 ±0.3 mm wide and 1.7 mm high. The layout should allow clearance for the body while treating the wide connection lug as a deliberate thermal-coupling feature rather than only an electrical terminal. Increasing the connected copper area can change response time and move the reading towards the average board temperature. A complete recommended land pattern is not defined, so the footprint should be derived from the mechanical outline and qualified with the intended soldering process. Thermal simulation or prototype measurements are advisable when the sensor is monitoring a concentrated heat source.

The sensor uses soft-solder connections formed from tin-coated copper alloy, and the assembly process should be qualified to preserve its measurement characteristics. It is supplied on a blister reel, with alternative packaging available on request. Storage life is 9 months in the original packaging, and a nitrogen atmosphere is recommended. As no numerical solder temperature profile is defined, a generic SOT223 power-device profile should not be assumed to be suitable without verification. Peak temperature, dwell time, solder wetting, cleaning chemistry and open-reel storage should therefore be covered by the production work instructions and trial-build assessment.

Typical R₀ drift is 0.06% after 1,000 hours at +150 °C. For a Pt1000 sensor, this represents approximately 0.6 Ω at 0 °C, equivalent to about 0.16 °C near 0 °C when 3850 ppm/K is used as a first-order conversion. The stated upper bound after 1,000 hours at the maximum operating temperature is the tolerance value of the declared class, while the 0.06% figure is typical rather than a guaranteed worst case. Long-term designs should combine this drift with initial tolerance and electronic measurement drift. Qualification should reproduce the intended duty cycle, board stress and operating atmosphere where calibration retention is important.

The duroplastic housing has a UL94-V0 flammability classification, thermal conductivity of 1.04 W/mK and moisture absorption below 1.0% after 48 hours in boiling water. These figures support material and thermal assessment, but UL94-V0 is a flammability classification rather than an ingress or functional-safety approval. No IP rating is defined, so exposure to condensation, wash fluids and contaminants must be managed at PCB or enclosure level. The operating range remains -50 °C to +150 °C, with local self-heating and neighbouring heat sources included in the design review. Harsh-environment applications should validate coating, cleaning chemistry, thermal cycling and mechanical mounting in the finished assembly.