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"Being able to archive data electronically is the main reason we switched from chart recorders. I can still remember the frustrating days of searching for records in a cabinet full of chart paper...and then still not finding them."
Government Cal Lab Manager
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Chart recorders to data loggers: Five reasons labs are making the switch
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Typewriters vanished when the word processor emerged. Vinyl records disappeared as CDs arrived. Now, data loggers threaten the chart recorder and the hygrothermograph with the same extinction.
For over seventy years, chart recorders and hygrothermographs have been the industry standard for monitoring temperature and humidity. Now data loggers, palm-sized electronic devices, are driving these mechanical devices from their niche.
The shift towards data loggers is acknowledged in the most recent chart recorder study, issued by Venture Development Corporation. The report projected a 22.3% growth rate in the data logger industry as compared to an annual 5.1% decline for paper chart recorders.
Veriteq Instruments, a leading provider of data loggers, has exceeded these projections, with average growth rates of 40% for the years 1997 to 2002. In the following article, Veriteq shares its experiences and the comments of experts and consumers to explain the five main reasons that people are replacing chart recorders and hygrothermographs with data loggers.
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Reason #1: Accuracy
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Today, calibration labs are seeing a definite movement towards regulatory compliance, with accuracy being a key requirement. For example, a common fail point for accreditation is having insufficient accuracy for temperature monitoring. The industry accepted rule for monitoring is to be at least four times as accurate as the minimum process accuracy requirement. In other words, a lab operating at +/- 1° C needs a monitoring device with an accuracy of at least +/- 0.25° C. Veriteq data loggers exceed this requirement, having an accuracy of +/- 0.10° C.
In general, data loggers offer greater accuracy and precision than paper chart recorders. Firstly, data loggers do not rely on any moving parts because they are completely based on electronic microprocessors and sensors. In contrast, paper chart recorders and hygrothermographs introduce errors by utilizing electromechanical arms with pen and paper.
Data loggers also avoid the errors associated with chart paper itself. Chart paper limits accuracy because the precision of readings is limited to the chart gradations. Another concern is chart paper shrinkage and expansion. Honeywell, a leading supplier of chart recorders, admits that "chart paper can shrink or expand as much as a penny's width in reaction to ambient heat and humidity." Although Honeywell itself offers a solution to this problem, most chart recorders do not.
A final point about accuracy relates to the actual time that each data point was recorded. Veriteq data loggers use an internal clock that compensates for temperature and is set to the user's specific time zone. In contrast, paper chart recorders do not record actual time, but instead record the elapsed time. Typically, the person who changes the chart paper will mark the time and date right on the chart. This works fine most of the time, but there is always a chance that the operator may mislabel the chart, leading to invalid records.
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Reason #2: Reliability
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Ask yourself: "How valuable is the data I'm recording? What would be the cost of losing my data?" Then consider the risks of using chart recorders.
All chart recorders require regularly scheduled chart replacement. However, in a review of calibration lab procedures, Marine Sergeant William Davis notes the following concern: "Charts frequently run past the seven days (because people forget to change them)," he says, adding, "All information after this seven day period is invalid and can be counted as missing data. We have actually had to fail labs because of this."
Data loggers, on the other hand, have excess storage capacity, meaning that a missed download does not cause the logger to fill up and stop recording. For example, a Veriteq SP-2000 temperature and humidity logger set to sample once per hour would take 1.2 years to fill its memory.
Another downside to most chart recorders is their vulnerability to power outages. Ironically, power outages occur at a time when recording devices are most needed - to determine if storage or test conditions were jeopardized by the power outage. With Veriteq loggers, internal lithium batteries provide 10 years of life, eliminating any reliance on external power.
Back up files have long been regarded as the safest means for storing records; this ability to do so is what makes data logger records so secure. Data logger files can be backed up in exactly the same way your company protects all its electronic files. In contrast, paper chart records only have one copy, which will become faded in time, and may even become lost in the filing system.
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Reason #3: Functionality
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Kevin Bull, Veriteq's CEO comments on the limited functionality of paper chart recorders: "We refer to chart recorder information as "dead-end data" because once on the chart, the data is very difficult to use. Anyone who has ever done an analysis involving multiple charts knows the pain of manually measuring and transferring multiple points before the analysis can begin."
With data loggers the story doesn't end with the data; instead, it just gets started. Software allows the user to go directly to any time period and automatically calculate minimum, maximum, and average values. Printing graphs, reports, or exporting to Excel are also functions that Veriteq users have found very useful.
Connectivity is another benefit made possible by a data system. Veriteq data logger users can connect and view real-time readings on a Palm PDA, a desktop PC, or even from a PC located in another room (via WiFi or POE). The same software also has an alarm feature to indicate out of compliance conditions. The alarm signal can be viewed by any computer on the network in addition to triggering an e-mail message.
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Reason #4: Maintenance
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Maintenance is a major factor in making the switch from chart recorders. There are ongoing requirements such as cleaning, chart changes, calibration and unscheduled repairs, all of which are unecessary with viewLinc.
For instance, the Federal Aviation Administration requires that maintenance for chart recorders used in Surface Weather Observation include chart annotation, weekly cleaning, general inspection, and regular replacement of charts and pens. All this servicing must follow a set routine to avoid damaging equipment.
As for calibration, Beth Lindblom Patkus, a consultant for the Northeast Document Conservation Center writes that hygrothermograph style chart recorders require recalibration two or three times a year - or more often if moved or unmaintained. Otherwise, they can accumulate errors of up to 10-20%.
By contrast, Veriteq data loggers maintain an accuracy of +/- 0.10° C (even when moved), and require only a yearly calibration. The difference? Chart recorders are mechanical devices, made of complex inter-connected parts, while data loggers have solid state electronics with no moving parts. There's simply less that can go wrong with data loggers.
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Reason #5: Cost
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Chuck McFarlane, Veriteq Marketing Analyst, notes that, "Customers don't generally inquire about data loggers in a quest to save money. All the same, they're very pleased when cost savings turns out to be an unforeseen benefit."
Aside from the purchase price, data loggers can result in time savings because they do not require chart changes, chart annotation or filing of charts. And as mentioned earlier, the time savings can be most significant when analysis and calculations are required.
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Conclusion
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Veriteq's viewLinc monitoring solution for temperature and humidity recording offes every advantage: accuracy, record keeping, connectivity, maintenance and price.
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