Environmental Sciences Gadgets & Gear

Five ways conductivity data met an untimely demise

Dr. Martini February 23, 2016

I’ve been looking at a lot of data lately. Visions of data are dancing in my head. Why? Because often, an oceanographic sensor will just crap out. And I must find that bad data and banish them from my analysis.

Every sensor has the potential for a problem. Water velocity, temperature, oxygen, nitrate and conductivity have all been known to rebel. THE STRUGGLE IS REAL. Even though they are super useful for computing seawater salinity and density when combined with a with temperature-sensing thermistor, conductivity cells were the worst offenders. Maybe it’s because they are delicate glass tubes that are just trying to measure how well electricity conducts through seawater? Or maybe it’s because they are just jerks. Nonetheless, after looking at literally 1000’s of data records I’ve gone ahead and categorized some of the most common ways I saw conductivity go wild so you don’t have to. YOU’RE WELCOME SCIENCE.

THE DAILY GRIND.

Just ignore that my plots look like unicorn barf, this is what healthy conductivity data looks like. Magical one-horned horse barf.
Just ignore that my plots look like unicorn barf, this is what healthy conductivity data looks like. Wiggles at many depths that show water moving up and down. It truly is magical.

 

THE FLATLINE.

There never was, nor shall there ever be, conductivity.
Sometimes your conductivity cells just choose to never sample at all. There never was, nor shall there ever be, conductivity.

 

GONE BINARY.

Your choices for conductivity are now 1 and 0. You have been assimilated by the BORG.
Your choices for conductivity are now 1 and 0. You have been assimilated by the BORG.

DESCENT INTO MADNESS.

One day something just clicks, and whilst in the deep end, go off the deep end.
Sometimes conductivity goes off the metaphorical deep end.

THAT SINKING FEELING.

PoppedBalloon
And at other times, your conductivity sensor ends up in the physical deep end.

ATTACK OF THE CNIDARIA.

Jellyfish can be small. Jellyfish can be squishy. Jellyfish are conductive. Jellyfish get sucked into the conductivity cell. Jellyfish suck at measuring conductivity.
Jellyfish can be small. Jellyfish are squishy. Jellyfish are conductive. Jellyfish can get sucked into your conductivity cell. Jellyfish suck at measuring conductivity.

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11 Replies to “Five ways conductivity data met an untimely demise”

  1. Thanks for the entertaining classification of conductivity failure modes! I’ve seen these all during my career; now I know what to call them (other than the unprintable things I call them at the time).

  2. What do you do with that data? Do you discard it? Or do you have a way of correcting for it?

  9. Just apply the discipline of Probability and Statistics to your data. Better yet, do it on a device called a Computer so you don’t drive yourself crazy looking through all the data. You will be fine – provided your confidence goals are reasonably set – and met in the end :-)

  10. OMG DAVID! WHAT IS THIS COMPUTER YOU SPEAK OF? PROBABILITY AND STATISTICS! NO ONE HAS EVER THOUGHT OF THIS EVER.

    Thanks for mansplaining.

  11. This could not have come at a better time as I think I had something like “attack of the Cnidaria” in the data I was looking at yesterday and I was going goggle-eyed trying to make sure it wasn’t a real phenomenon before excluding it. And no, @David, statistics were not good enough to remove the bad data points, I had to do it by hand.

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