MOS-type gas sensors (described below) have been around for almost a half-century. The original TGS-109 (Taguchi Gas Sensor 109) was introduced in about 1969!

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From http://www.figaro.co.jp/en/company/history.html

These days a wide variety of Arduino and Raspberry Pi-friendly hobby sensor outlets sell devices with part numbers in the range MQ-2 through MQ-9 (along with MQ-135 and others), for example:




MQ-2 through MQ-9 and some higher numbers are all variants of MOS technology. MOS stands for Metal Oxide Semiconductor, but not MOS as in CMOS. Instead, it is a semiconductor material which is an oxide of a metal.

In this case they are made from a sintered composite based on the semiconductor material SnO2, which is the metal oxide. The different sensors have different admixtures and operating conditions to achieve different sensitivities to different gasses.

The principle of operation of MOS-type gas sensors is explained here.

There are a variety of more recent data sheets out there from current manufacturers and suppliers of these older model numbers, but I'm interested in the heritage and lineage as well, thus the addiction of on the question.

Where do the "MQ series" initially come from? Which company originally sold this series? Have these pretty much remained the same in terms of specs and operation over the decades, or has there been significant improvement?

Unfortunately there doesn't seem to be an analog of the Transistor Museum for gas sensors.

From the page http://www.figaro.co.jp/en/about-us/

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    \$\begingroup\$ I'm voting to close this question as off-topic because it is not specifically answerable and because it requests aid in finding online resources, two things questions on SE sites must not do. The topic matter is interesting, but leaving this open only invites problematic misuses of the answer form. \$\endgroup\$ – Chris Stratton Nov 26 '18 at 20:54
  • \$\begingroup\$ @ChrisStratton I've rewritten the question to remove any request for resources and adhere to the constraints of the history tag. After 18 months and almost 200 views, I don't see any evidence nor risk of problematic misuse, but it only required a small adjustment to address. I think it now fits nicely within the spirit and constraints of the tag. Have I addressed your concerns? Thanks! \$\endgroup\$ – uhoh Nov 27 '18 at 0:52
  • \$\begingroup\$ The problematic misuse was proven yesterday with a now deleted non-answer response. While the topic is interesting, the problem is that the question is not specifically answerable within the intended purpose of SE sites. Although you've accepted an answer, which allows it to appear resolved, the reality is that it answers only a small part of what you are asking. Because the question itself violates SE rules, it invites responses from well intentioned new users that are also in violation of the rules, something we saw yesterday. Your topic would better fit on a discussion site. \$\endgroup\$ – Chris Stratton Nov 27 '18 at 14:03
  • \$\begingroup\$ @ChrisStratton okay because of my low rep in this site I guess there could be a deleted question I can't see; I'd forgotten about that. I also forgot that there are still some people who use phrases like "your question has violated Stack Exchange rules" for anything that they think is potentially closable. There are almost 200 SE sites and each one has a community and collective best practices. SE does have rules for serious issues like abusive or unethical behavior, but there is no stack exchange "rule" about asking about the history of a technology on a technology site with a history tag. \$\endgroup\$ – uhoh Nov 27 '18 at 16:32
  • \$\begingroup\$ There is very much an actual rule against asking overly broad questions which cannot be concisely answered. And that is exactly what you have done. This is a very worth subject, but it belongs somewhere like eevblog, not on EESE. \$\endgroup\$ – Chris Stratton Nov 27 '18 at 16:35

I believe that the Japanese company Figaro was the original manufacturer. Source: memory.

  • \$\begingroup\$ +1 A well-sourced answer! Happen to have a catalog from the 1980's laying around somewhere? \$\endgroup\$ – uhoh Apr 28 '17 at 3:04
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    \$\begingroup\$ Not handy, maybe in the shudder catacombs. But you can check out their history- they claim to have invented it in 1968 and established the company Figaro in 1969. \$\endgroup\$ – Spehro Pefhany Apr 28 '17 at 3:56
  • \$\begingroup\$ I've hit the library and done some more reading - Taguchi has quite an interesting personal story. Now, to find out who first started selling the "MQ-n" series, and if there was any standardization or better information than the error-prone data sheets available on-line now ;) \$\endgroup\$ – uhoh May 2 '17 at 17:45

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