Perhaps the most well-known example of two point calibration involves liquid-in-glass thermometers, the most popular of which used to be mercury thermometers. That device was invented by physicist Daniel Gabriel Fahrenheit in Amsterdam (1714). Brilliant in its simplicity and accuracy, it took advantage of important physical constants: The predictable expansion of mercury as a function…
The subject of bump testing was introduced in this Knowledge Base article. While bump testing is primarily a coarse functional test, rather than a true calibration, it is a common practice—especially for confined entry instruments. If many units need to be screened, the time savings of bumping over calibration can be significant. However, we are…
One of our older sales reps faced this issue many years ago, on a source monitoring job. His instruments were set up in a trailer, ready to demo to a prospective customer. The customer had provided a nice new cylinder labeled “sulfur dioxide in air, 500 ppm.” However, when this gas was applied to an…
Especially when doing low range work, it is important to make sure that your instrument is properly zeroed. Ideally, zeroing should be performed with a certified zero gas. However, mostly since it adds another step to the calibration process, this practice has somewhat fallen out of favor. The alternative to a zero gas requires that…
For a good introduction, first read this Knowledge Base article. Then, if you really want to get techie, we present an article (3.7 MB) entitled “Generating Calibration Gas Standards with OVG-4 and Permeation Tubes,” from our friends at Owlstone.
ASTM promulgates numerous publications covering analytical methods. One of the most widely cited is ASTM D3249, entitled “Standard Practice for General Ambient Air Analyzer Procedures.” Section 8 of this document covers calibration. You can tell that the standard was written by knowledgeable instrument people, for several reasons—not the least which is the first sentence of…
The closest thing to an official definition of “bump test” appears in an OSHA Safety and Health Information Bulletin (SHIB 09-30-2013) entitled “Calibrating and Testing Direct-Reading Portable Gas Monitors.” We have posted a Knowledge Base article providing some commentary on that Bulletin. Here is what the Bulletin says about Bump Testing (DRPGM = Direct Reading…
This material is presented on OSHA’s website as a Safety and Health Information Bulletin [SHIB 09-30-2013]. The content was written by the International Safety Equipment Association (ISEA). We post the article here, and offer commentary in maroon type… The information in this Safety and Health Information Bulletin (SHIB) provides workers and employers guidance on calibrating…
Time to get seriously techie on perm tube calibration fundamentals… This is a detailed analysis of the so-called “K” constant used with permeation devices, to enable the calculation of the emitted gas concentration. Over the years, many of our customers—and Interscan’s own technical personnel—have been frustrated by the confusing and inconsistent documentation on this matter…
How To Use Permeation Devices (courtesy of VICI Metronics, Inc.) Permeation devices provide an excellent method of producing known gas concentrations in the PPM and PPB level for calibration of analytical instrumentation. The basic requirement of any calibration system used with these devices is to maintain the permeation device at a constant temperature in a…