Issue link: http://read.dmtmag.com/i/550313
60 tobaccoasia content result. Yet more sophisticated models may use spectrum analysis and can thus reliably determine actual water vapor in relation to other components, making such devices also useful to check for nicotine, total sugars, and additives like menthol, for example. What the eye can't see Many suppliers meanwhile have put their money on NIR technology, which uses light wavelengths that are invisible to humans. "The human eye is only working in the range of 400 to 700nm. That's the visual spectrum. But our machines work fur- ther up the spectrum, from 1,100 up to 2,500nm wavelength. There are absorption bands in that area which the sensor captures. Our software then interprets the readings and through pre-pro- grammed algorithms equates them into total mois- ture," elaborated Moist Tech's Herrington. Always at the forefront, NDCT has ventured an important step further and makes use of a unique dual detector concept, which allows the in- strument to be continuously validated on a micro- second by microsecond basis. "So it is incredibly stable, and against its independent reference check little or no instrument change will be seen over many months. Other techniques suffer from opti- cal imbalance and all show long-term drift prob- lems," Benson claimed. Beware the light! Although air temperature and air humidity have little – if any – impact on moisture meters (or at least they can be calibrated to compensate for these two factors), near-infrared sensors gener- ally appear to be rather susceptible to ambient lighting conditions that may prevail in any given environment. Machines therefore have to be de- signed in a way that they "ignore ambient light", as Herrington likes to put it. Additionally, as NIR technology measures on the product surface, sam- ples must be taken while they're fresh, i.e. right at the feeder or – after conditioning – at the start of the processing line. "You don't want to set up the meter at the end of a 60m conveyor belt, but someplace where the tobacco is just coming out of a conditioner, for example; or it's been freshly turned before we inspect it," said Herrington. High performance, simple calibration System flexibility and high performance are indis- pensable requirements for moisture meters. They must be deployable wherever they are needed and must deliver reliable reading results under any conditions. Easy calibration – or better still, no calibration at all – is also a key factor, as complicat- ed recalibrations may interrupt production flows and thus can be both costly and time-consuming. "Our instruments use diode array based NIR tech- nology, which is more advanced than the previ- ously used filter NIR technology. It can analyze all blends without recalibration and also is capable of measuring additional parameters such as nicotine, sugars, and various others," assured Perten Instru- ment's Tordenmalm. André Tews, Tews Elektronik GmbH & Co. KG Markus Löns, Brabender GmbH & Co. KG Stefan Tordenmalm, Perten Instruments Greg Brown, Process Sensors Corp. Tews Elektronik model MW4420 with display panel User interface of NDCT's TM710e