As if it weren’t bad enough that clueless environmental authorities try to impose their ignorance on the field by using so-called “metric” units of gas concentration, another trap may be lurking for you. Everyone around the world agrees that a part-per-million (ppm) equals 10-6. Unfortunately, since everyone around the world does not agree with what…
Rise time to 50% of final value, rise time to 90% of final value, and fall time to 10% of original value are typical specifications presented for gas detection instruments. The 50% figure is useful when considering how fast an instrument will respond in a critical (alarm) situation, whereby “full” response is not as important…
“Minimum Detectability” is one of those instrumentation terms that is used frequently, but is seldom defined. Indeed, even though you will encounter this term on many data sheets, its definition does not appear in any of the usual learned references, including Process Instrumentation Terminology, ANSI/ISA—51.1—1979(R1993) and Standard Terminology Relating to Sampling and Analysis of Atmospheres,…
Definitions “Accuracy” as defined in the ANSI/ISA—51.1—1979 (R1993) standard Process Instrumentation Terminology is: [T]he degree of conformity of an indicated value to a recognized accepted standard value, or ideal value. Two common methods of rating or expressing accuracy are: As a percent of scale length (or percent of full scale). This rating method is most…