Portable direct reading medical thermometer - has battery driven Wheatstone bridge with probe in one arm and galvanometer

摘要

An electronic thermometer comprises a Wheatstone bridge, one arm of which is formed by a thermal probe (2) supported at the extremity of a cable (1) by a sleeve (3). The other arms are resistive (R1, R2, R3) and imbalance is indicated on a moving scale galvanometer (4), with temperature graduations. The resistor (R3) in the arm opposite the probe permits adjustment for the probe used. A resistor (R4) in series with the galvenometer permits scaling corrections. The bridge is powered from a battery (P) which may be rechargeable, the condition being indicated by an indicator (5). Voltage regulation is provided by a zener diode (D) and resistor (R5).