Units

A unit in Release 3 is a Pint name. Dendra stores the canonical form, such as degree_Celsius. Shorter spellings such as degC resolve to that name when you save.

Conversion runs when data is queried. Stored datapoints keep the recorded numbers. The datastream unit is what values are converted to on the way out, and each field mapping’s input unit is what those numbers were recorded in. Change either one and later queries use the new conversion, including older datapoints. You do not re-import the data or create a derived datastream to show existing values in another unit. If the input unit is blank, Dendra treats the field as already in the datastream unit and does not scale the numbers.

The converter is pint-go, a Go port of Pint’s English definition files and conversion rules.

Pint’s defaults cover the usual scientific units. Dendra also loads extra definitions for environmental measurements, including photosynthetic photon flux, turbidity (NTU, FNU, and FAU), and TEOS-10 salinity. If a unit you need does not come up, contact us.

Where you Set a Unit

• Datastream. unit_name is the unit of the series you query and chart. Set it when you create or edit the datastream.
• Input field. input_unit_name on a field mapping is the unit that source column was recorded in. Set it under Field Mappings in the datapoints config.

An attribute can carry a unit too, such as a sensor height in meter. That unit describes the attribute, not the series.

When entering a unit name, start by typing the first few letters. Matches appear as you type.

Conversion

On query, Dendra converts each numeric value from the input unit to the datastream unit. That conversion is recomputed from the current names, so editing them changes what the next query returns for the whole series. The stored datapoints stay as recorded.

Conversion Domains

You only need a conversion domain when a query fails to convert the recorded values into the datastream unit. Pairs that already share a dimension, such as degC and degF, convert without needing one defined.

Pint calls these contexts. Dendra calls them conversion domains so the label matches a domain of study, such as chemistry or salinity. With a domain turned on, a query can convert across dimensions: moles to mass, or practical salinity (PSU) to absolute salinity (g/kg).

Set the domain on the datastream, in Conversion domains beside the unit. Every query of that series uses it.

Some domains ask for parameters once you turn them on. Chemistry needs a molecular weight, a solution volume, and a solvent mass. Spectroscopy needs a refractive index. Salinity needs an absolute salinity anomaly (0 is the TEOS-10 reference mix). The editor marks each value required. Conversion ignores that domain until the values are filled in.

Try a name, a domain, or a conversion before you set it by visiting the Unit Conversion playground.

Unit Conversion playground