It's a Recorder! No, It's a Data Acquisition System! Actually, it's Both
DAQ in disguise
Today, the line between chart recorders-paper or paperless-and what's become known as data acquisition systems (DAQs) is very blurry-that's if the line exists at all.
A look in the 2002 Control Engineering Buyer's Guide reveals 29 companies that offer paper chart recorders. However, many of those 29 companies also appear under the headings of paperless chart recorder, data acquisition, and datalogger.
Bottom-line, call it whatever you want, it's really about creating historical records of data.
Early versions of paperless recorders suffered wide acceptance because of missing or very limited security to protect against data tampering. Thus stored data records were not accepted by regulatory agencies, such as U.S. Food and Drug Administration.
Manufacturers have created DAQ systems that masquerade as paperless recorders because of secure software data encryption algorithms, cost-effective microprocessors and data storage media, and the FDA's 21CFR Part 11 regulation covering electronic records.
Several paperless recorder device manufacturers have chosen to focus their efforts on developing the collection and storage devices, and leveraging a popular graphical development application, as the user interface.
Many single- and multi-pen paper recorders use analog electronics-thus inputs are continuously recorded. To improve data readability during periods of high-volume-data, many paper recorders include a selector switch for different chart speeds.
Because paperless recorders apply digital technology, continuous data collection isn't possible. However, digital technology advances allow paperless recorders to sample eight to ten samples per second. While that's as good as ''continuous'' for many applications, sampling at those speeds requires careful consideration of storage requirements.
For example, recording a single channel at 8 samples per second would fill a 1.44MB floppy disk in about a day. However, the same conditions would take over 72 days to fill a 100MB ZIP disk. When purchasing or upgrading a paperless recorder, remember that storage is cheap; install lots, you won't regret it.