In Doc Fry’s electronics class, I learned my first engineering standard: resistor color coding. Each color represented a number. Each color also represented a multiplier–power of ten. Some colors also represented a tolerance. The position of the color band indicated how to interpret the color as a number, multiplier or tolerance. A simple standard for reading a resistor. The Table below summarizes the color coding:
To remember the table, Doc Fry taught us a mnemonic. One of many is: Bat Brained Resistor Order You Gotta Be Very Good With. (The boys in the class tried to tease me with a raunchier version, which I chose to ignore!)
All resistor manufacturers follow the same resistor color code standard. Why? Simple–it enables customers to purchase from multiple vendors. All savvy manufacturers source components from at least two suppliers. Why waste time in using a unique coder per resistor supplier? Having a standard applies one of the E’s of Engineering–Efficiency. Other reasons exist for standards, as I learned during my first technical job.
At a National Bureau of Standards lecture the speaker told a story about the Great Baltimore Fire and fire engines. Fire crews came with their fire engines from as far away as Philadelphia and Washington, D.C. The visiting crews’ fire hoses could not connect to Baltimore’s fire hydrants; so they watched in frustration as the fire continued. The fire hydrant connectivity issues contributed to the fire’s duration of 30 hours, and the destruction of an estimated 70 city blocks. Soon after, the National Fire Protection Association adopted a national standard for fire hydrant hose connections. The story illustrated the importance of standards, which was part of the agency’s mission.
Though standards can be viewed as boring, they save cost, time–and sometimes, lives. Standards differ from engineering specifications and requirements, in that they are agreed to by multiple parties. They can be solely internal to a company or they can be subscribed to by multiple companies and engineering associations. Typically, an engineering association or government agency drives standards development and adoption.
Have a productive day,
Anne Meixner
Dear Reader, What memory or question does this piece spark in you? Have you worked with a standard or worked to develop one? Please share your comments or stories below. You, too, can write for the Engineers’ Daughter–See Contribute for more information.
Additional Reading
More about the Great Baltimore Fire.
The Resistor Color Code had a number of Mnemonics
The United States NIST has a long history of standards. This timeline shares some its history.
Interested in learning more about standards, then check out this list of standard organizations.