Construction and characterization of inexpensive PRT differential thermometer in temperature interval 20–100 °C.

The article focuses on the design, construction, and evaluation of mercury-free differential platinum resistance thermometers based on Wheatstone bridge circuits using four (4 × Pt1000) and two (2 × Pt1000) platinum resistors for precise temperature difference measurements. Experimental and theoretical analyses conducted between 20 and 100 °C demonstrate that the 4 × Pt1000 thermometer offers superior stability and accuracy, achieving a maximal relative error below 0.9% and an absolute accuracy of about 0.20 °C, comparable to some high-quality thermocouples. Both thermometers exhibit an expanded uncertainty of ±0.09 °C, with the 4 × Pt1000 design providing better sensitivity and lower error than the 2 × Pt1000 alternative, despite self-heating effects that were experimentally assessed and corrected. These low-cost, eco-friendly devices are suitable for educational and scientific applications requiring reliable, narrow-margin temperature difference measurements.