How it works
Reading an analogue clock is two questions: where is the short hand, and where is the long one.
- The short hand gives the hour — read the number it has passed, not the one it is nearest.
- The long hand gives the minutes: each number is five minutes, each small mark one minute.
- Write it as hours:minutes, then add am or pm — or add 12 to the hour for the 24-hour clock in the afternoon.
The usual mistake is at, say, 2:55: the short hand is almost on 3, but the hour is still 2 until the long hand passes 12.
Examples
Reading the dial:
| Hands | Digital | Spoken |
|---|---|---|
| Short past 3, long on 12 | 3:00 | three o'clock |
| Short between 3 and 4, long on 3 | 3:15 | quarter past three |
| Short between 7 and 8, long on 6 | 7:30 | half past seven |
| Short between 9 and 10, long on 9 | 9:45 | quarter to ten |
| Short between 11 and 12, long on 11 | 11:55 | five to twelve |
For the 24-hour clock, add 12 to any afternoon hour: 3:15 pm is 15:15.
Related: Energy Converter, Power Converter, Frequency Converter.
Analog-to-Digital Converter: frequently asked questions
- What is ADC resolution?
- The number of bits n, which sets 2ⁿ output levels. A 12-bit ADC has 4,096 levels; with a 3.3 V reference each step is about 0.8 mV.
- What is an LSB?
- The least significant bit: the smallest voltage change the ADC can resolve, equal to Vref ÷ 2ⁿ.
- What is quantization error?
- The difference between the actual input and the voltage its digital code represents; for an ideal ADC it is at most 1 LSB (±½ LSB with rounding).