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Traditional pen-and-dot
chart recorders, such as the Yokogawa hybrid recorder on the right, are
antiquated products. Here are some of their disadvantages:
- Continuous expense: chart recorder paper and ink.
- Paper recorders are prone to mechanical failure because they contain chart drives, paper feeds, moving pens and knobs.
- Paper recorders are large, cumbersome and not easily transportable.
- Analyzing cryptic and /or hard-to-read paper records created with a chart recorder is often difficult.
Modern, paperless recorders offer far greater reliability, with the option to print a hard-copy on demand.
Here are some things to look for in such a product:
The paperless recorder should be a compact unit that can monitor temperature and voltage; and it should also function as a data-logging and control instrument. Convenient safety jack, subminiature plug, and screw-terminal connectors also make signal connection easier than those loggers/recorder which don't have them. The system should offer high speed, high-channel counts, voltage isolation, and user-selectable signal conditioning.
above: Iotech's ChartScan/1400
Paperless Voltage and Temperature Recorder
Most hybrid recorders are also inferior to paperless recorders because they have unfriendly menu systems, low-visibility LCD displays, and non-ergonomic multi-purpose keypads.
Isolated Inputs:
Excellent channel-to-channel isolation is a must in voltage and temperature recorders. The system, e.g., may provide 500V isolation for high-voltage applications using an external module, and 200V isolation when the thermocouple and other voltage modules are used. The systems may achieve this high isolation by using individual relays on each channel, yet continue to maintain a very fast scan rate (e.g., 147 channels/second).
Faster Scanning:
Most paperless data-loggers offer faster scanning than traditional strip-chart recorders, and exceed the typical 2 Hz found on most strip-chart, multi-point, or hybrid recorders. These new designs also offer many additional scanning capabilities beyond even the better hybrid recorders. Since data-logging and chart-recording applications frequently require logging at fixed time intervals, a newer-type data-logger may still use the standard hours-minutes-seconds (hh:mm:ss) format to specify the time interval between channel scans. Users can, hence, configure the unit to begin and end data-logging on a specified event such as a TTL signal, temperature level, alarm condition, absolute time of day, or upon the completion of a specified number of readings.
When shopping for a new data-logger/data-recorder, look for programmable scan rates. These are often necessary for applications requiring acceleration of the measurement rate on a specified event, such as an alarm condition. e.g., you should be able to program the unit to scan once per minute and then, upon the occurrence of a specified alarm condition, switch to scanning once per second. When the alarm condition is gone, the unit resumes scanning at the rate of once per minute.
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