When is a part-per-billion (ppb) NOT a part-per-billion (ppb)?

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…

Understanding Danger

The dictionary defines “danger” as “the state of being exposed to harm : liability to injury, pain, or loss.” Typically, gas detection is deployed in areas that contain potential danger. This danger may result from some sort of upset condition, as in a leak—representing an immediate toxic or explosive risk—or it could be more insidious,…

Surrogate Calibration

The term “surrogate calibration” refers to a practice in instrument calibration whereby a standard different from the entity to be measured is utilized. For example, thermal flowmeters are based on convective heat transfer effects, and can be calibrated at ambient conditions on a specific gas, and then be used at process conditions to make accurate…

Can the detector be calibrated at one concentration to cover the entire range? Since the response is linear, I think the answer is yes. Please confirm. Thanks.

The answer to your question is YES. You are correct in noting that the response of our instruments is linear. More than that, electrochemical voltametric sensors (such as we use) are inherently linear, with no electronic compensation required. However, for optimum accuracy in most applications, it is best to calibrate the instruments at a concentration…

Minimum Detectability

“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,…