SOR recently published a white paper about selecting the right instrumentation for the job. The article presents three questions to help the engineers determine the best instrumentation for the application. The technical paper is titled, Weigh Your Instrumentation Options, Switch, Transmitter or Hybrid?
The white paper outlines three application specific questions that will help the designers identify the preferred instrumentation for the application in question. It discusses process variables, the need for display or remote communication and alarming as well as potential consequences if the process variable moves outside of its intended range.
For decades, process instrumentation specifiers have faced the decision whether to use a mechanical switch or a continuous transmitter for a given application. Either type of instrument can be used to effectively control industrial processes and protect equipment and personnel — and each has associated pros and cons. Application specifics typically drive decision-making, dictating which approach is most effective from performance, cost and lifecycle support perspectives.
While a separate transmitter and switch provides more secure operation than either instrument by itself, this approach does entail the purchase of two instruments, two process penetrations, and all the attendant effort and expense they represent. For this type of application, the hybrid transmitter/switch represents a more cost-effective yet secure solution: a continuous transmitter and solid-state switch installed together in a single device. Indeed, the hybrid switch-transmitter addresses all three key application considerations raised above. Like a standalone transmitter, it can provide continuous setpoint control over a range of values as well as drive a local display or remote communications. Further, because the integrated switch and its output are functionally independent of the transmitter and its output, this single instrument configuration provides a more cost-effective alternative for applications where a continuous measurement is needed together with a functionally independent layer of switched protection.
More info: Weigh Your Instrumentation Options: Switch, Transmitter or Hybrid? (pdf)