Design, fabrication, and validation of a low-cost open-source multi-sensor automatic titrator with gravimetric titrant delivery for real-time endpoint and enthalpy determination

Acid–base titration underpins analytical measurement across the chemical and process industries, yet in teaching laboratories it is still performed with a manual buret that yields sparse data points and subjective visual endpoints, while commercial automatic titrators remain too costly and closed for widespread hands-on use. We report the design, fabrication, and validation of a Multi-Sensor Automatic Titrator (MSAT): a low-cost, open-hardware instrument developed as a hands-on platform for chemical engineering education. An ESP32 microcontroller with 3D-printed probe mounts integrates four endpoint-detection channels (potentiometric pH, conductometric, colorimetric, and thermometric), titrant is metered gravimetrically by a load cell, and all channels are logged at 2 Hz against a common time-and-mass axis. A web-based controller runs the titration and a companion Python analyzer extracts equivalence points, pK a values, and reaction enthalpies. Synchronous four-channel logging lets students watch the probes jointly locate and cross-validate every equivalence point, with the thermometric channel resolving final endpoints in overlapping- pK a polyprotic systems. Across nine acid–base systems (potassium hydrogen phthalate (KHP), HCl, H 2 SO 4 , H 3 PO 4 , oxalic, malic, succinic, citric, benzoic), the colorimetric, conductometric, and thermometric channels showed no significant difference from the potentiometric reference and were equivalent to it within ± 1 % of titrant (paired t -tests, p > 0.05; two one-sided equivalence tests (TOST), p < 0.001; Pearson r > 0.999; N = 21-86); mole ratios matched theory within ± 5 %, and calorimetric enthalpies agreed with reference values to within 11 %. The complete hardware, firmware, and analysis pipeline are released open-source as a reproducible, extensible teaching resource.