Integrating or Dual Slope ADC

•There are basically 4 types of Analog to Digital converter (ADC).

1.Integrating or Dual slope ADC

2.Successive approximation ADC

3.Flash ADC

4.Delta sigma converter

•Dual slope ADC is use for converting analog to digital value.

•This is integrator.

•Dual slope ADC is slow but have high accuracy and have high resistance to noise.

•This method is use in digital multimeter or digital voltmeter.

•It is basically have integrator, comparator, control logic, clock, counter and electronically controlled switches.

•Its operation requires two voltage slopes hence it is name as Dual slope.

•The unknown voltage is applied to Vin and Known but with negative polarity voltage is applied to Vref.

•Vin is for fixed amount of time and Vref is applied for variable amount of time.

•One slope (/) is made due to unknown voltage.

•The negative polarity voltage is then applied until it become zero means second slope (\) will form.

•The comparator is use to detect zero crossing.

•Capacitor charges and discharges linearly with a constant slopes.

•T de-int is more than T int because discharging time of capacitor is more than its charging time.

•If T de-int is large means large voltage and if T de-int is less means less voltage.

•When the switch is at Vin position capacitor charges (charging time of capacitor is less).

•And when the switch is at Vref position capacitor discharges (charging time of capacitor is more).

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