Platinum resistance thermometers (PRTs) measure temperature by passing current through a platinum wire—but that current generates heat, turning the sensor into a tiny heater. This “self-heating” can add 0.1°C to 1°C to your readings, ruining precision. Here’s how to minimize it.

Lower the excitation current:
Most PRTs use 1mA–5mA, but even 1mA creates heat. Drop to 0.5mA if your data logger can detect the smaller resistance change (look for 24-bit ADCs). This cuts self-heating by ~75%.

Use 4-wire connections:
2-wire setups measure the PRT’s resistance plus the cable resistance, requiring more current to get a signal. 4-wire setups separate measurement and excitation currents, letting you use lower current without losing accuracy.

Match current to probe size:

· Small probes (≤1mm diameter): Use ≤0.5mA—their tiny wires can’t dissipate heat.

· Large probes (≥5mm diameter): 1mA is safe—more surface area cools them.

Test in still vs. moving media:

· Still air or liquids trap heat around the PRT—self-heating errors double here. Use lower current (0.25mA) if flow is slow.

· Fast-moving fluids (≥1m/s) carry heat away—1mA is okay.

Calculate the error:
Most PRT specs list “self-heating coefficient” (e.g., 0.05°C/mW). If your setup uses 1mA at 100Ω, power = I²R = 0.01W = 10mW → error = 10mW × 0.05°C/mW = 0.5°C. Adjust readings accordingly.

Pro tip: For critical tests, alternate between 0.5mA and 1mA. The difference in readings is your self-heating error—subtract it from your final data.