Elenco Electronics M-1006K, Сборка и инструкция по эксплуатации, Страница: 13 / 20

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The integrate period begins at the end of the autozero period. As the period begins, the AZ switch opens and
the INTEG switch closes. This applies the unknown input voltage to the input of the A/D converter. The voltage
is buffered and passed on to the integrator to determine the charge rate (slope) on the INTEG capacitor At the
end of the fixed integrate period, the capacitor is charged to a level proportional to the unknown input voltage.
During the read period, this voltage is translated to a digital indication by discharging the capacitor at a fixed
rate and counting the number of clock pulses that occur before it returns to the original autozero level.
As the read period begins, the INTEG switch opens and the read switch closes. This applies a known reference
voltage to the input to the A/D converter. The polarity of this voltage is automatically selected to be opposite
that of the unknown input voltage, thus causing the INTEG capacitor to discharge at a fixed rate (slope). This
rate is determined by the known reference voltage. When the charge is equal to the initial starting point
(autozero level), the read period is ended. Since the discharge slope is fixed during the read period, the time
required for discharge is proportional to the unknown input voltage. Specifically, the digital reading displayed is
1000 (V
IN
/ V
REF
).
The autozero period and thus a new measurement cycle begins at the end of the read period. At the same time
the counter is released for operation by transferring its contents (the previous measurement value) to a series of
latches. This stored data is then decoded and buffered before being used to drive the LCD display.