DIDACTICALLY CORRECT SENSORS FOR DIGITAL LABS Denis Zhilin, Moscow Institute for Open Education, School #192, Oleg Povalyaev, Scientific Entertainment Co, Moscow

THE DIGITAL LABS A system allowing to measure different analogous parameters, put them into digital form, store, visualize and process THE BENEFITS Computer takes routine procedures  reducing cognitive overload Fast measurements  can follow quick processes Visualizing parameters that humans do not feel (pH)

THE PROBLEM The choice of sensors: rather available than didactically necessary temperature pH conductivity redox-potential p(I) optical density gas pressure dissolved O 2 

REPLACE SENSOR OR CHANGE CURRICULUM? Gas pressure sensor is used to develop the concept of stoichiometry, but n = p  V/(R  T)  the change of pressure depends on volume that can be very different  connection between gas amount and gas pressure causes cognitive overload

Volume is proportional to gas amount (always p  1 atm, T  290K)  No cognitive overload SOLUTION: GAS VOLUME SENSOR

HOW TO SEE WHAT IS HAPPENING? Colorimeters with 3 mL cuvettes: The cuvettes are concealed No links betweenIt’s impossible to observations andadd something to figuresthe cuvette No sense of Limitations for parameters formsexperimental design

SOLUTION: GATE SENSOR + one can see everything + one can add reactants Problems with adjusting? No! The side light is taking into account Another possible solution: immerse probe with optical fiber and mirror

HOW TO OPERATE? Drop counters for titration: -Requires adjustment -Requires calibration for each titrant -Can’t add large volumes of titrant  Too much time for struggling with the sensor  cognitive overload No waiting time between adding a drop and fixing parameter value  Inaccurate results

SOLUTION: SYRIGNE SENSOR Titrant could be added at any rate Requires calibration only when the syringe type is changed One can wait after adding drops to let the drop distribute in the system

COMPLICATED APPARATUS pH-metric + colorimetric titration (Ex: checking the applicability of indicators)

THANK YOU FOR YOUR ATTENTION Denis Zhilin, Moscow Institute for Open Education, School #192,