List of measurement unit

[Garyhsu1982]

Here is a list of system-defined unit from Chemotion (Eletronic Lab Notebook). Unfortunately, the content seems to be removed from the website, but I can still access it through the notebook I install in my laptop. There is also no description about each unit and we need to define it.

Name	List
Acceleration	mm/s²
Agitation	rpm
Amount enzyme as nmol/min	U, mU
Chem. concentration (Molarity)	mol/L (M), mmol/L (mM), nmol/L (nM), pmol/L (pM)
Chem. distances	Å
Concentration	ng/L, mg/L, g/L
Conductivity	S/m
Current	A, mA, µA, nA
Degree	°
Density	g/cm3, kg/l
Duration	day(s), hour(s), min(s), sec(s), millisec(ms)
Elastic modulus	MPa, Kpa, Pa
Electric field	V/m
Energy	J, kJ
Enzyme activity	U/L, U/mL
Flow rate	µl/min, ml/min, l/min
Frequency	Hz, kHz
Heating rate	K/min
Length	mm, cm, m
Magnetic flux density/inductivity	T
Mass	g, mg, µg, ng, pg
Mass of molecule	D, kD
Molecular weight	g/mol
Percentage	%
Pressure	atm, Pa, Torr
Reaction rate	mol/Lmin, mol/Ls
Specific volume	cm3/g
Speed	cm/s, mm/s, cm/h, mm/h
Subatomic length	µm, nm, pm
Surface	A², mm², cm²
Temperature	°C, °F, K
Turnover number	1/s
Dynamic viscosity	Pas, mPas
Kinematic viscosity	m²/s
Voltage	mV, V
Volumes	I, ml, µl, nl

[kobbejager]

Certainly a good starting point. What you notice in these kind of lists, is that they mainly cater the community that compiled the list. It seems this community is doing chemical synthesis and/or physicochemistry :-). We'll need to add quite a few of them (wavelength, wavenumber for spectroscopies, (atomic) mass unit for mass spectrometry, energy expressed in eV in x-ray spectrometries...).

There are a few oddities in the list, such as

• different lists for length/atomic distances/subatomic length or pressure/elastic modulus. If they are expressed in the same units (or variants thereoff), shouldn't they be the same quantity with alternative names? As for Å, we were taught in uni to understand it, but express chemical distances in SI units (1Å = 0.1nm).
• there seem to be little uniformity in their use of unit prefixes (milli, kilo...), and I can see many examples where the proposed prefixes are not suitable. Difficult to solve, however, because including the full range of possible unit prefixes would grow the lists tremendously, destroying user-friendliness. Possibly multiplied if multiple units exist (e.g. Pa, bar, atm, tor, mmHg). Possible solutions are
  • removing the prefixes and requiring the researchers to express their values as "1e-10" (not user-friendly, and possibly limited by JSON Schema libraries
  • add a separate 'prefix' field, besides 'value' and 'unit' fields. (yet more fields for the researcher to fill in)
  • creating sublists (high pressure vs vacuum pressure, different length sublists to express atomic/molecular vs archaeological site lengths...)

We need to find the right balance between semantically correctness and user-friendliness. Personally, I wonder if forcing all quantity types and units into vocabulary-supported controlled lists, making the forms more complicated and more time-consuming to fill in, isn't pernicious for the user-friendliness. I would therefore consider using fixed enum properties in the JSON Schema, adapting the possible choices to each specific case, and use const were possible (even though Cordra / json-editor do not support this well). If needed, we can make more complete lists in opentheso, not to be used as controlled lists, but rather as units to choose from when populating the enums in the schemas.

[Garyhsu1982]

I would like to point out that these measurement units are used in the electronic lab notebook when users want to define a metadata profile for a technique.