L and LN series RTD sensors

Choose the variant according to nominal resistance, package geometry, lead orientation and acceptable thermal response. L220 is the only listed variant offering both Pt100 and Pt1000, with a 2.4 mm nominal body length and 0.4 K/mW self-heating. L416 uses Pt100 in a 3.9 × 1.5 mm body, while L420 uses Pt1000 in a 3.9 × 1.9 mm body; their water t₀.₉ values are both 0.25 seconds. L1020 is the 9.5 mm Pt1000 format with 0.2 K/mW self-heating, whereas L220 P uses Pt100 and places its leads perpendicular to the substrate. Begin with the electrical interface, then confirm the available installation volume and required lead direction.

Select Pt100 or Pt1000 according to the measurement circuit, cable arrangement and acceptable influence of lead resistance. Both use a temperature coefficient of 3850 ppm/K, but Pt1000 has ten times the nominal resistance of Pt100 at 0 °C, reducing the percentage contribution of external lead and contact resistance in a two-wire circuit. The recommended current is 0.3 to 1 mA for Pt100 and 0.1 to 0.3 mA for Pt1000. L220 supports either value, while L416 and L220 P are Pt100 and L420 and L1020 are Pt1000. The final choice should match the analogue front end, excitation source and compensation method planned for the system.

The selected tolerance class determines both the permitted resistance deviation and the continuous temperature interval over which that class applies. Class F 0.3 (B) is available across all five variants and covers −50 °C to +400 °C. Class F 0.15 (A) covers −50 °C to +300 °C on L220, L416, L420 and L1020. Class F 0.1 (1/3 B) is limited to 0 °C to +150 °C on L220 and L420, while the L1020 version extends from −50 °C to +150 °C. Engineers should therefore specify the class and temperature interval together rather than selecting an order number from the class designation alone.

Element-level response depends strongly on the surrounding medium, flow speed and mechanical construction around the sensor. In water flowing at 0.4 m/s, t₀.₅ values range from 0.06 seconds for L220 to 0.20 seconds for L220 P, while t₀.₉ remains between 0.20 and 0.30 seconds. In air flowing at 2 m/s, t₀.₅ ranges from 3 to 6 seconds and t₀.₉ from 9 to 20 seconds. These figures apply to the sensor element under defined test conditions rather than to a completed probe. Encapsulation, sleeve wall thickness, thermal compound, air gaps and mounting pressure should therefore be included when validating the response of the final assembly.

Keep the excitation current within the stated range and calculate I²R power at the highest resistance expected in the application. At 0 °C, a Pt100 element driven at 1 mA dissipates approximately 0.1 mW; with 0.4 K/mW self-heating, this indicates an element-level temperature rise of roughly 0.04 K under the reference condition. A Pt1000 element at 0.3 mA dissipates approximately 0.09 mW, corresponding to about 0.036 K for L220, 0.027 K for L420 or 0.018 K for L1020. Actual temperature rise varies with medium, airflow, mounting and operating temperature. Lower continuous current or controlled pulsed excitation can be considered where measurement uncertainty is sensitive to self-heating.

The elements have defined vibration, shock and lead-strength figures, but their installed capability depends on the surrounding assembly. Each variant is specified for at least 40 g acceleration from 10 to 2,000 Hz and at least 100 g acceleration with an 8 ms half-sine shock pulse. The AgPd connection leads have a tensile strength of at least 8 N. These figures should not be treated as complete probe ratings because unsupported leads, rigid encapsulation and resonant structures can alter the stress applied to the ceramic element. Appropriate strain relief, controlled lead forming and application-level vibration and shock testing are therefore required before production release.

Use a soft-soldering process compatible with the AgPd leads and the operating temperature of the selected solder alloy. A universal soldering profile is not defined for the range, so dwell time, heat transfer and lead forming should be qualified within the intended assembly process. The nominal-resistance measuring point is located 8 mm from the end of the sensor body, which should be considered during incoming inspection and resistance verification. Storage life is at least 12 months after manufacture under the recommended conditions, with a nitrogen atmosphere recommended. Batch-dependent V-shaped bending of the connection wires can occur after sample measurement, but it does not affect the function of the platinum measuring element.