Understanding digital device configuration

How to use the intelligence we have intelligently.

By Ian Verhappen

Digital devices—commonly called “intelligent devices”—are easier to calibrate because it can be done semi-autonomously or at least without the interaction between zero and span of older analog devices. However, they compensate for easier calibration by making configuration more complex.

Many end users believe digital devices can't be calibrated in the field, or at least not as well as their factory default settings. So instead of calibrating a device, they run a reference check to verify that when a known input is presented to the sensor input, the device responds within acceptable limits. They note that the definition of acceptable limits is often not specified, and left to the technician's discretion. Other facilities have full quality programs requiring traceability to a certifiable standard. The correct answer when it comes to calibration, reference check and level of repeatability, as with most things, is that it depends on the application. Custody transfer is much more rigorous than a monitor-only signal.

The good news is that digitally transmitted signals, either as wired fieldbus transmissions or as wireless sensor communications, will be more accurate than an analog output because there are fewer analog/digital converters. Plus, the signal itself is digital and normally in engineering units, so the reading won't deteriorate during transmission.

To learn more, read "Digital device configuration" from Control.

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