| 摘要 |
<p>In the resistance measuring circuit a measuring capacitor (Cm), as controlled by a microcomputer (10), is charged in a first cycle to a predefined charging voltage (Vcc) and discharged via a reference resistor (Rref) to a predefined discharge voltage before then being recharged in a second cycle to the charging voltage and discharged via the resistance to be measured (Rs1) to the discharge voltage. The microcomputer (10) measures in each cycle the time duration between the start of the discharge procedure and the point in time of attaining a predefined fixed value of the voltage between the charging voltage and the discharge voltage across the measuring capacitor (Cm). From the product of the reference resistance and the ratio of the time duration measured in the second and first cycle the resistance value to be measured is determined. There is provided a closed loop (10, 14, 16) for controlling the discharge voltage to a fixed predefined constant value. <IMAGE></p> |
