A/D Converters: Notes
Analogue/Digital Converters convert analogue sensor values to digital values that the CPU can read (via the Input/Output unit). Converts in 256 steps as this corresponds to one byte or 8 bits.
8 leads go between the A/D converter for a temperature sensor, for example, and the Input/Output unit. If all are 0 (no voltage), it means that voltage over the NTC resistor is 0 V. See below for more information on A/D conversion.
| NTC voltage (V) | Digital (binary) | Decimal |
|---|---|---|
| 0 | 00000000 | 0 |
| 0.02 | 00000001 | 1 |
| 0.04 | 00000010 | 2 |
| 0.06 | 00000011 | 3 |
| 0.08 | 00000100 | 4 |
| 0.1 | 00000101 | 5 |
| 0.12 | 00000110 | 6 |
| 0.14 | 00000111 | 7 |
| 0.16 | 00001000 | 8 |
| ... | ... | ... |
| 5.00 | 11111111 | 255 |
Some control modules have analogue inputs with 10-bit conversion. The advantage is improved accuracy or resolution. Resolution doubles with each extra bit.
10 bits means 1024 steps for an analogue sensor. This is used for pedal position sensors, for example. In most cases, however, 8-bit conversion is sufficient. 256 steps is sufficient for a tank sensor, for example.