| 摘要 |
A digital representation of an analogue physical quantity, e.g. temperature value, is obtained by measuring a first impedance (RM) the value of which depends on the quantity. The measurement is obtained by applying a voltage to the series combination of this impedance and a second impedance (C) of a different kind and counting, in a counter (PCT), the pulses produced by a source (CL) between the instant the voltage is applied and the instant a threshold detector (DT) detects that the voltage across the second impedance (C) reaches its threshold (Vo). The result is stored in a register (RP1). In order that variations in certain parameters should not affect the result the operation is immediately repeated replacing the first impedance (RM) by a reference impedance (RR), the new result also being stored in a register (RP2). The contents of the two registers are then divide one by the other in a processing unit (PM) to yield a digital representation of the relative values of the first (RM) and reference (RR) impedances. The various operations may alternatively be performed by a programmed digital processing system. <IMAGE> |
