| 摘要 |
<p>A level detector circuit (10) for detecting a level of immersion of an elongated probe (12) within a liquid. The level detection circuit includes a first set of transistors (112, 114). One of these transistors charges an elongated probe and a second charges a capacitor (60). A reference current source (54) provides a reference current based on the charging current provided to the elongated probe by the first transistor and an additional transistor which also charges the probe at a rate such that the voltage on the capacitor and the probe are maintained the same. A monitoring circuit (62) develops an analog level signal based on the current provided by the reference current source. This analog level signal is converted by the combination of an analog to digital circuit (82) and a microprocessor (50) for providing a pulse frequency modulated communications signal corresponding to the analog level signal which in turn is related to the length of the probe immersed within the liquid.</p> |
