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View Full Version : HowTo: Read a Liquid Crystal Thermometer



SwordTaleLair
10-29-2010, 05:09 PM
They are not the best in the world, and do a good general job at reporting temperature in a tank. I do recommend a digital thermometer for sensitive tanks and those with a fine need for detail. However, for the general aquarist, most choose to use a plastic liquid crystal strip adhered to the side of their tank to read temperature.

I use them myself, but I have always forgotten and had to research just how to read those little things when I am moving the temp in my tank.

So, I did a search here, and didn't come up with a quick result, so I decided to put a thread here for quick reference.

These strips are made from strips of plastic sectioned off in to squares each with a corresponding temperature number. Each section is filled with a temperature sensitive crystals called chiral nematic liquid crystals. These crystals are mixed specially for a specific temperature range and added to each corresponding square. The crystals are oriented like a coil spring and the rate of the coil determines the reflection of light which in turn indicates the temperature.

The sensitivity of the crystals is about 0.1 degrees celsius. The color scheme is typically tan to blue, with the brightest shade [typically green I have observed] being the indicated temperature. When reading between the temperatures, I have noticed that the tan numbers indicate a rising temperature into the range of the crystal section and the blue indicates a lowering temperature out of the range.

So if the temp is rising and is 75 degrees, the 74 would be blue and the 76 would be tan. Conversely, if the temp was lowering, the 74 would be blue and the 76 would be tan. If the temp was exactly or very close to 76, then the section would be green.

Hope this helps, and as always with a forum, if someone has better knowledge of these things, please post it - I love learning!!

STL. :22:

Maisy
10-29-2010, 11:27 PM
Thanks so much for writing this! I've always wondered what the tan and blue numbers meant, haha. :shappy:




So if the temp is rising and is 75 degrees, the 74 would be blue and the 76 would be tan. Conversely, if the temp was lowering, the 74 would be blue and the 76 would be tan...


I do have a question, though: If the temperature is lowering from 75, wouldn't the 74 be tan and the 76 blue? Or did I read that wrong... =s

SwordTaleLair
11-01-2010, 01:37 AM
In principal, the approaching number will be tan, and the past number will be blue. This is ONLY when the temperature is RISING. Therefore when the temp is falling, the approaching number will be blue and the past number will be tan.

So, yes, I had the temps switched. To reiterate: if the temp is rising and is 75 degrees, the 74 would be blue and the 76 would be tan [if your thermometer has a 75, it would be green]. If the temp is lowering, the colors would be the same.

I verified my info from this site: http://www.telatemp.com/tagsLabels2/tl_liquidCrystalThermometers.asp

Thanks Maisey!!