A student sets up the apparatus shown below to investigate how the electrical resistance of a thermistor changes over the temperature range of 10∘C10^{\circ}\text{C}10∘C to 90∘C90^{\circ}\text{C}90∘C using a water bath.

State one modification the student could make to this experimental setup to investigate resistance at temperatures below 0∘C0^{\circ}\text{C}0∘C.