si

Documentation

Overview

Package si defines International System of Units (SI) base and derived units. These form the canonical system for scientific and engineering work.

Canonical units provided here include:

• Length: Meter (m)
• Mass: Kilogram (kg)
• Time: Second (s) [from std]
• Current: Ampere (A)
• Temperature: Kelvin (K), with Celsius (°C) for absolute and delta forms
• Amount: Mole (mol)
• Luminous intensity: Candela (cd)

Derived units such as Newton, Pascal, Joule, Watt, and derived prefixes (milli-, kilo-, mega-, etc.) are also defined here.

Example usage:

dist := si.Meter.Of(250)
mass := si.Kilogram.Of(80)
force := si.Newton.Of(500)

The si package is the primary target for most scientific and engineering calculations, and interoperates cleanly with std and usc units.

Index

• Variables

Variables

var (
	Meter        = uom.DefineUnit[dim.Length]("m", 1.0)
	Kilogram     = uom.DefineUnit[dim.Mass]("kg", 1.0)
	Ampere       = uom.DefineUnit[dim.Current]("A", 1.0)
	Kelvin       = uom.DefineUnit[dim.Temperature]("K", 1.0)
	Mole         = uom.DefineUnit[dim.Substance]("mol", 1.0)
	Candela      = uom.DefineUnit[dim.Luminosity]("cd", 1.0)
	MeterSquared = uom.DefineUnit[dim.Area]("m^2", 1.0)
)

SI base units (coherent)

var (
	Newton            = uom.DefineUnit[dim.Force]("N", 1)
	NewtonMeter       = uom.DefineUnit[dim.Torque]("N·m", 1)
	Momentum          = uom.DefineUnit[dim.Momentum]("kg·m/s", 1)
	NewtonSecond      = uom.DefineUnit[dim.Impulse]("N·s", 1)
	NewtonMeterSecond = uom.DefineUnit[dim.AngularMomentum]("N·m·s", 1)
)

var (
	Kilometer  = uom.DeriveUnit[dim.Length]("km", uom.U(Kilo), uom.U(Meter))
	Centimeter = uom.DeriveUnit[dim.Length]("cm", uom.U(Centi), uom.U(Meter))
	Millimeter = uom.DeriveUnit[dim.Length]("mm", uom.U(Milli), uom.U(Meter))
	Micrometer = uom.DeriveUnit[dim.Length]("µm", uom.U(Micro), uom.U(Meter))
	Nanometer  = uom.DeriveUnit[dim.Length]("nm", uom.U(Nano), uom.U(Meter))
)

var (
	// 1 g = 1e-3 kg
	Gram      = uom.DeriveUnit[dim.Mass]("g", uom.U(Milli), uom.U(Kilogram))
	Milligram = uom.DeriveUnit[dim.Mass]("mg", uom.U(Milli), uom.U(Gram))
	Microgram = uom.DeriveUnit[dim.Mass]("µg", uom.U(Micro), uom.U(Gram))

	// 1 tonne (t) = 1e3 kg — SI accepted unit
	Tonne = uom.DeriveUnit[dim.Mass]("t", uom.U(Kilo), uom.U(Kilogram))
)

Mass units commonly used alongside kilogram base

var (
	KilogramPerCubicMeter = uom.DefineUnit[dim.Density]("kg/m^3", 1)

	GramPerCubicCentimeter = uom.DeriveUnit[dim.Density]("g/cm^3",
		uom.U(Gram),
		uom.U(CubicCentimeter).Per(),
	)

	GramPerMilliliter = uom.DeriveUnit[dim.Density]("g/mL",
		uom.U(Gram),
		uom.U(Milliliter).Per(),
	)
)

Mass density (ρ): mass per unit volume

var (
	KilogramPerMeter = uom.DefineUnit[dim.LinearMass]("kg/m", 1)

	GramPerMeter = uom.DeriveUnit[dim.LinearMass]("g/m",
		uom.U(Gram),
		uom.U(Meter).Per(),
	)

	GramPerMillimeter = uom.DeriveUnit[dim.LinearMass]("g/mm",
		uom.U(Gram),
		uom.U(Millimeter).Per(),
	)
)

Linear mass density (μ): mass per unit length

var (
	KilogramPerSquareMeter = uom.DefineUnit[dim.ArealMass]("kg/m^2", 1)

	GramPerSquareMeter = uom.DeriveUnit[dim.ArealMass]("g/m^2",
		uom.U(Gram),
		uom.U(Meter).Pow(-2),
	)
)

Areal mass density (σ): mass per unit area

var (
	Yocto = uom.DefineUnit[dim.Dimensionless]("y", 1e-24)
	Zepto = uom.DefineUnit[dim.Dimensionless]("z", 1e-21)
	Atto  = uom.DefineUnit[dim.Dimensionless]("a", 1e-18)
	Femto = uom.DefineUnit[dim.Dimensionless]("f", 1e-15)
	Pico  = uom.DefineUnit[dim.Dimensionless]("p", 1e-12)
	Nano  = uom.DefineUnit[dim.Dimensionless]("n", 1e-9)
	Micro = uom.DefineUnit[dim.Dimensionless]("μ", 1e-6)
	Milli = uom.DefineUnit[dim.Dimensionless]("m", 1e-3)
	Centi = uom.DefineUnit[dim.Dimensionless]("c", 1e-2)
	Deci  = uom.DefineUnit[dim.Dimensionless]("d", 1e-1)
	Deca  = uom.DefineUnit[dim.Dimensionless]("da", 1e1)
	Hecto = uom.DefineUnit[dim.Dimensionless]("h", 1e2)
	Kilo  = uom.DefineUnit[dim.Dimensionless]("k", 1e3)
	Mega  = uom.DefineUnit[dim.Dimensionless]("M", 1e6)
	Giga  = uom.DefineUnit[dim.Dimensionless]("G", 1e9)
	Tera  = uom.DefineUnit[dim.Dimensionless]("T", 1e12)
	Peta  = uom.DefineUnit[dim.Dimensionless]("P", 1e15)
	Exa   = uom.DefineUnit[dim.Dimensionless]("E", 1e18)
	Zetta = uom.DefineUnit[dim.Dimensionless]("Z", 1e21)
	Yotta = uom.DefineUnit[dim.Dimensionless]("Y", 1e24)
)

SI prefixes as dimensionless units

var (
	// Standard SI unit of energy; used for heat, work, and internal energy in thermodynamic systems
	Joule = uom.DefineUnit[dim.Energy]("J", 1)

	// SI unit of power; measures rate of energy transfer (e.g., heating or cooling power)
	Watt = uom.DefineUnit[dim.Power]("W", 1)

	// Pressure is central to state equations and phase-change analysis in thermodynamics
	Pascal = uom.DefineUnit[dim.Pressure]("Pa", 1)

	// Thermal conductivity; quantifies ability of a material to conduct heat
	WattPerMeterK = uom.DefineUnit[dim.ThermalConductivity]("W/(m·K)", 1)

	// Heat capacity; total energy required to change an object's temperature by 1 K
	JoulePerKelvin = uom.DefineUnit[dim.HeatCapacity]("J/K", 1)

	// Specific heat capacity; heat capacity per unit mass, key in calorimetry and energy balance
	JoulePerKilogramK = uom.DefineUnit[dim.SpecificHeatCapacity]("J/(kg·K)", 1)

	// Heat transfer coefficient; overall heat transfer rate across a surface per unit area and temperature difference
	WPerM2K = uom.DefineUnit[dim.HeatTransferCoefficient]("W/(m²·K)", 1)
)

var (
	// Canonical SI volume; baseline for storage tanks, flow integrals, and conversions
	CubicMeter = uom.DefineUnit[dim.Volume]("m^3", 1)

	// SI-accepted unit favored in fluids/lab specs; ubiquitous in data sheets and dosing
	Liter = uom.DefineUnit[dim.Volume]("L", 1e-3)

	// Bench-scale measurements; reagents, small containers, pipetting
	Milliliter = uom.DefineUnit[dim.Volume]("mL", 1e-6)

	// Microlab and analytical work; microfluidics, chromatography, assays
	Microliter = uom.DefineUnit[dim.Volume]("µL", 1e-9)

	// Engineering drawings and engine displacement; also packaging volumes
	CubicCentimeter = uom.DefineUnit[dim.Volume]("cm^3", 1e-6)

	// Small parts and precision manufacturing; solder paste, adhesives, beads
	CubicMillimeter = uom.DefineUnit[dim.Volume]("mm^3", 1e-9)

	// Hydrology and geophysics; reservoir and basin volumes
	CubicKilometer = uom.DefineUnit[dim.Volume]("km^3", 1e9)

	// Often seen in chemistry texts and metrology; numerically equal to 1 L
	CubicDecimeter = uom.DefineUnit[dim.Volume]("dm^3", 1e-3)
)

Volumes commonly used across fluids, lab work, and large-scale geophysics

var (
	MeterPerSecond = uom.DefineUnit[dim.Velocity]("m/s", 1)
)

Velocity

var (
	MeterPerSecondSquared = uom.DefineUnit[dim.Acceleration]("m/s^2", 1)
)

Acceleration

var (
	NewtonWeight = uom.DefineUnit[dim.Weight]("N", 1)
)

var (
	StandardGravity = uom.DeriveUnit[dim.Acceleration]("g", uom.U(MeterPerSecondSquared), uom.Const(9.80665))
)