Units

Introduction to Units

HIM keeps a list of the units of measurements that can be used as the value of the unit metadata, see the example below.

Vehicle.Speed:
  datatype: float
  type: sensor
  unit: km/h
  description: Vehicle speed.

Data that has an associated unit from the list shall declare it using the unit metadata. It is allowed for a domain to specify an additional list with domain specific units that complement the common units list. Units shall if possible be based on SI-units, but exceptions like the speed example above are acceptable. The list contains entries of a unit with a prefix, e. g. mm for millimeter, which are the only prefixes that are valid. The unit must be written exactly as shown in the list.

In some cases it is natural to omit the data unit type. This concerns typically signals where data type string is used, but also signals where the value just represents a number, like in the example below:

Vehicle.Cabin.DoorCount:
  datatype: uint8
  type: attribute
  default: 4
  description: Number of doors in vehicle.

HIM also supports percent and ratio as data units.

List of supported Units

This list is mainly derived from the International System of Units (SI).

Unit Domain Description
mm Distance Distance measured in millimeters
cm Distance Distance measured in centimeters
m Distance Distance measured in meters
km Distance Distance measured in kilometers
inch Distance Distance measured in inches
km/h Speed Speed measured in kilometers per hours
m/s Speed Speed measured in meters per second
m/s^2 Acceleration Acceleration measured in meters per second squared
cm/s^2 Acceleration Acceleration measured in centimeters per second squared
ml Volume Volume measured in milliliters
l Volume Volume measured in liters
cm^3 Volume Volume measured in cubic centimeters
celsius Temperature Temperature measured in degree celsius
degrees Angle Angle measured in degrees
degrees/s Angular Speed Angular speed measured in degrees per second
W Power Power measured in watts
kW Power Power measured in kilowatts
PS Power Power measured in horsepower
kWh Energy Consumption Energy consumption measured in kilowatt hours
g Weight Mass measured in grams
kg Weight Mass measured in kilograms
lbs Weight Mass measured in pounds
V Electric Potential Electric potential measured in volts
A Electric Current Electric current measured in amperes
Ah Electric Charge Electric charge measured in ampere hours
ms Time Time measured in milliseconds
s Time Time measured in seconds
min Time Time measured in minutes
h Time Time measured in hours
day Time Time measured in days
weeks Time Time measured in weeks
months Time Time measured in months
years Time Time measured in years
UNIX Timestamp Time Unix time is a system for describing a point in time. It is the number of seconds that have elapsed since the Unix epoch, excluding leap seconds.
mbar Pressure Pressure measured in millibars
Pa Pressure Pressure measured in pascal
kPa Pressure Pressure measured in kilopascal
stars Rating Rating measured in stars
g/s Mass per time Mass per time measured in grams per second
g/km Mass per distance Mass per distance measured in grams per kilometers
kWh/100km Energy Consumption per distance Energy consumption per distance measured in kilowatt hours per 100 kilometers
ml/100km Volume per distance Volume per distance measured in milliliters per 100 kilometers
l/100km Volume per distance Volume per distance measured in liters per 100 kilometers
l/h Flow Flow measured in liters per hour
mpg Distance per Volume Distance per volume measured in miles per gallon
N Force Force measured in newton
Nm Torque Torque measured in newton meters
rpm Rotational Speed Rotational speed measured in revolutions per minute
Hz Frequency Frequency measured in hertz
ratio Relation Relation measured as ratio
percent Relation Relation measured in percent
… … …