This piece is the first in a series designed to assist perishable logistics and quality assurance professional, with information about current Cold Chain Monitoring technology. This first installment discusses the features, benefits, and limitations of traditional “strip chart” temperature recorders.
Anyone involved in the production and distribution of perishable goods has, at some point, interacted with a temperature recorder. How do these devices work, and which ones are best? This piece is designed to provide you, the perishable logistics and quality assurance professional, with the technological and historical information you need to determine what kind of temperature recording technology is best for your application.
Back in the Bad Old Days, receiving personnel had no idea what conditions perishable products experienced in transit. A thorough visual inspection could allow for a best guess, but only that, a guess. The invention of mechanical “strip chart” temperature recorders was an important breakthrough. These allowed receivers to view a long strip of time-indexed paper which recorded temperatures.
“Strip chart” recorders use bi-metallic coil technology—the same technology used in many home climate control thermostats, toasters, hair dryers, and other household appliances. A pointer, or stylus, is attached to the end of a bi-metallic coil, and that moving pointer can record temperatures on a strip of moving chart paper beneath the stylus. Properly calibrated, such a device, crude as it is, can be used to monitor and record temperatures on carefully indexed graph paper.
While the bi-metallic coil is a proven, time-honored technology, it has many limitations. Take accuracy, for example. Strip chart recorders on the market today are typically calibrated to “plus or minus 2 degrees” Fahrenheit. This wide margin of error means a shipment requiring 33° optimum storage conditions could have been 31° or 35°. Either extreme would be within strip chart recorder specifications, yet either extreme could damage the product. When there is temperature damage to product, but the strip chart indicates proper temperatures, an unpleasant and costly dispute will likely follow.
Strip Chart temperature recorders are also subject to a number of mechanical limitations:
- The paper rolls often jam or tear, especially in damp conditions
- The data on the paper charts is difficult to share—the strips are too long to easily fax or scan
- Longer recording periods dramatically reduce data accuracy
- The strip charts do not allow for positive date/time documentation—they only capture an elapsed time reference from when the unit was started
- Data accuracy can only be verified if the bulky bi-metallic coil unit is retained for calibration review
- Archiving strip chart data requires hard copy filing, but many firms are relying on digital file storage
- There are no means to automatically produce summary data reports
While strip chart temperature recorders have met temperature monitoring needs in many industries for decades, product safety and traceability programs have become more sophisticated and more important. As such, perishables logistics and quality assurance professionals will be increasingly responsible for accurately monitoring cold chain integrity. Most such professionals are phasing out obsolete bi-metallic coil technology and embracing superior digital technology for its improved accuracy, archiving, adaptability, and data sharing attributes. You should too.
Digital Temperature Recorder Source: Cargo Data Corporation (www.cargodatacorp.com) of Ventura, CA, offers the Lightning NFC smart-device enabled monitoring system. It’s designed to simplify cold chain monitoring at every level. The system displays highly accurate, time-stamped temperature records that are vastly superior to obsolete strip charts. Additionally, all temperature data from Cargo Data Corporation monitoring devices is automatically saved to the cloud for easy online review from any internet-connected device.
For more information, contact Cargo Data Corporation: email@example.com or 800-338-8134.