Thermocouples for Dummies

Termocouple diagram

Yes, we make a lot of fun of eHow here: why shouldn't we? Consider the business model of the now-defunct Demand Media Studios (now called Leaf Group) and their flagship site: pay people to scrape internet searches and call them "titles," which those same people categorize. Pay self-appointed freelancers to "research" and write to those titles, and pay "content editors" to ensure that the copy meets the site's standards (mostly format, as opposed to accuracy). That's how you end up with a topic like "How to Calculate Thermocouple Sensitivity" slotted into – are you kidding us? – BUSINESS! (it's now, BTW, at Sciencing.com!) and a serial dumbass like Jennifer Fleming covering it, with help from an unnamed editor. Small wonder it's rife with ignorance.

From the get-go it's clear that Fleming, despite her multiple business degrees, has no friggin' idea what a thermocouple is, what they do, or how they work. Instead, she simply copied, reworded, and pasted information she scraped from a white paper published by knowledgeable people at Analog Devices (which, to be fair, she frequently cites by author names).

The result is a mishmash of instructions for a couple of specific devices sold by Analog Devices, such as

"...input an AC signal to pins 1 and 14 of 10mV p-p, 100 HZ... Adjust the Rgain for a p-p output of 3.481V (device AS594) or 4.451V (device AD595). Reconnect a thermocouple which is in an ice bath or ice point cell at 0 degree Celsius to pins 1 and 14, then adjust R offset until the output reads 320mV..."

...which is little more than a slightly reworded chunk of the instructions for calibrating output in °Fahrenheit. Fleming follows up this essentially useless bullshit by telling her readers to do something she says is "[calculating] the termocouple sensitivity," "...decide on a temperature range T1 to T2 and calculate the average thermocouple sensitivity over that range. For example, this is calculated as (VT1 – VT2)/ (T1 – T2), dividing the desired sensitivity by the average thermocouple sensitivity."

We couldn't figure out how Fleming decided on this step, since eHow's version no longer includes her references. We are pretty certain that, since Fleming already defined T1 and T2 as "temperature range," the denominator of the formula she blithely threw on the page is not "average thermocouple sensitivity": it's the temperature range. When you finish reading this tripe, however, you're struck by this fact: Fleming's assignment is to explain how to calculate value X, and in the last step she tells us to divide Y by X. Is that just plain stupid, or what?

Rubbish like this is what happens when someone who has no idea what she's talking about pretends to have it figured out. Fleming, unfortunately, did this quite frequently: six times already, across a wide variety of disciplines. With a track record like that, it's no wonder Jennifer — notwithstanding the PhD she claims to have — is, once again, our Dumbass of the Day.

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