Re: [core] Proposed new SenML Units

[Jaime Jiménez <[e-mail]>]

Hi Michael, 

thank you very much for your confirmation and insights on the topic. 
I now wonder if we should add ug/l as well as NTU. For IPSO it looks like NTU would be sufficient.

Ciao!
-- Jaime


On 09.11.2020 07:43, Michael Koster wrote:
>
>> On Nov 9, 2020, at 7:12 AM, Carsten Bormann <[e-mail]> wrote:
>>
>>>
>>> +===========+================================+=======+
>>> | Symbol    | Description                    | Type  |
>>> +===========+================================+=======+
>>> | NTU       | Nephelometric Turbidity Unit   | Float |
>>> +-----------+--------------------------------+-------+
>>> | mg/l      | milligrams per liter           | Float |
>>> +-----------+--------------------------------+-------+
>>
>>
>>> NTU is the most common way to measure turbidity.
>>
>> This one is interesting.  There are several Turbidity units, which are not in a simple linear relationship, so I would like to get some input from domain experts which ones we should have (and which are more of a historical interest).
>>
>>
>
>FWIW
>
>While I'm not specifically a domain expert, I do have experience in a water turbidity measurement program.
>
>I was responsible for process control and measurement systems in a large number of oil & gas installations in Alaska in the 1980s (please no "historical interest jokes...)
>
>One of the installations was a water injection facility that needed to be accountable for the purity of the water injected into the ground over a period of decades. We maintained a fleet of "Surface-Scatter Turbidimeters" which measured turbidity in NTU. I was responsible for calibration of the machines and "certification" of the measurement record.
>
>Turbidity is an indirect measure of suspended solids in water or other fluid, measured according of the amout of light blocked from transmission through the fluid. The Surface-Scatter Turbidimeter, or Nephelometer, measures the diffraction of light from surface roughness caused by the suspended solids. Standard solutions or cards (for field calibration) are used to calibrate the measurements.
>
>A quick check on Wikipedia and discussion with an acquaintance who is a (retired) water treatment consultant (chemical salesman) confirms that NTU is still the metric of choice, though some facilities that know what their contaminants are can convert it to a concentration unit like ug/l for "internal" use.
>
>Best regards,
>
>Michael