integratingdualslope

Integrating dual-slope refers to a method used in analog-to-digital conversion that relies on integrating an input signal for a fixed period and then using a reference ramp to discharge the integrator back to zero. The time required during the discharge phase is measured, and this measurement is transformed into a digital value representing the input voltage. The approach is also called dual-slope integration because it employs two stages: an input integration stage followed by a reference-based de-integration stage.

In operation, an integrator, typically built from an operational amplifier and a capacitor, is connected to the input signal Vin. The input is integrated for a known time interval Ti. After Ti, the input is removed and a reference voltage of opposite polarity, Vref, is applied to drive the integrator output back toward zero. The time t2 taken for the integrator output to return to zero is counted with a clock. The resulting digital code is proportional to Vin, often with Vin ≈ (Vref × t2) / Ti, making the conversion largely independent of several analog imperfections.

The method offers several advantages. Its averaging effect provides high DC accuracy and excellent rejection of noise and drift from the integrator components, such as capacitor and op-amp offsets. It is relatively insensitive to component tolerances and certain types of low-frequency noise, making it well suited for precise DC voltage measurements.

Limitations include slower conversion speeds compared with other ADC architectures, as the total conversion time equals the fixed integration time plus the de-integration time. Complexity lies in designing a stable integrator and precise timing circuitry. Integrating dual-slope has historically been used in digital multimeters and instrumentation-grade ADCs where accuracy and noise rejection are prioritized.