| 摘要 |
Temperature of the water in the bathtub is measured as a function of voltage difference using a resistor bridge that includes two NTC temperature sensors, which is also used to register when the water has reached a pre-selected level in the bathtub. A resistor bridge including two NTC temperature sensors is used to record water level as a function of the voltage difference across the bridge when the first sensor`s resistance falls as the temperature of the environment around it increases, due to the bath being filled, whilst the second sensor`s resistance remains constant. Water temperature is measured by the bridge as a function of the voltage difference caused by the difference in resistance between the first sensor and a constant reference potential. An Independent claim is also included for the device used, which registers when a pre-selected water level in the bath has been reached, and also records the water temperature. The sensors are both connected to the in-side of a differential amplifier. The two resistors in the bridge are coupled in series with the first and second sensors respectively. Devices are used to process signals from the amplifier. An operation amplifier has its in-side connected to the first sensor, located at a lower level in the bathtub than the second sensor, whilst its out-side is connected to the in-side of an AC/DC converter, the out-side of which is connected to an LCD display (28). |
