Unit of digital numbers?

Question

what is the unit of digital numbers https://en.wikipedia.org/wiki/Numerical_digit. For example what is the unit of the difference of two ADC values:

10 - 2 = 8 digits
10 - 2 = 8 units
10 - 2 = 8 symbols
10 - 2 = 8 ???

Or for example I want to describe a slope:

Temperature example: 2 °C per second = 2 °C/sec
ADC example: 2 ??? per second = 2 ???/sec

What is correct?

Best regards Zlatan

score 1 · Answer 1 · answered Jul 27 '17 at 08:51

1

Numbers don't have units by default. Units are simply a multiplied symbol that represents the "nature" of the quantity.

answered Jul 27 '17 at 08:51

The Quantum Physicist

24,987
19
103
189

Okay. Than what would you suppose to add as "symbol"? – ge45mue Jul 28 '17 at 05:12
@Zlatan Nothing! – The Quantum Physicist Jul 28 '17 at 05:26
Than how would you describe a slope (see example in my question)? – ge45mue Jul 31 '17 at 14:37
@Zlatan It would be `1/sec` or `sec^(-1)`. Like Hz (hertz), which is `1/sec`. There are tons of quantities in physics that have such units, such as the [wavenumber](https://en.wikipedia.org/wiki/Wavenumber#Definition), which has units of `1/meter`, because it's defined as `1/wavelength`. – The Quantum Physicist Jul 31 '17 at 14:50

score 0 · Answer 2 · answered Jul 12 '19 at 10:38

First of all figure out the LSB (least significant bit) of the ADC.

Example: The ADC uses a vref of 1.2V and has 8bit => LSB=1.2V/(2^8-1)=4.7mV

A typical temperature sensor using a bipolar junction has about -2mV/K. The example ADC with LSB=4.7mV will respond with a change of 1LSB per 2.35K temperature decrease. A change of 1LSB/second means you have a change of -2.35K/per second. If this isn't accurate enough for your application you can use an ADC with more bits or stack several diodes acting as temperature sensors.

If you use something else than a bipolar junction the sensitivity of the temperature sensor can be different. Just check the spec of the sensor and the ADC (and it's reference to calculate the LSB)

Parameters you need:

Reference voltage of the ADC
Number of bits of the ADC (to calculate LSB)
Temperature coefficient of the sensor

Unit of digital numbers?

2 Answers2