I read with interest your article, "Long-Distance Calibration" in the March issue of Control. However, they [the users in Ceuta] are not considering the latest technology presented at an ISA International Instrumentation Seminar ("Calibration of Differential Pressure Transmitters On-Line at Process Conditions," Proceedings of the 54th International Instrumentation Symposium, May 5-8, 2008. IIS08 P004).
Understanding the difficulty, costs and production upsets caused by calibration deficiencies, I conceived and presented a method for assuring calibration of a differential pressure transmitter on a flow or liquid level application from a remote control room while on-line, without process interruption, compensating for all steady-state and equilibrated-state, combined, simultaneous process and ambient influences within the entire limits of operation to 0.005% of reading, traceable to NIST with no technician involved. Thus, I could assure calibration from a remote site on demand or as scheduled—a significant advantage compared to shipping three flight cases and a specialist traveling to site. Furthermore, the specialists could not assure calibration to 0.005% of reading under combined simultaneous process and ambient conditions!
President, Avgi Engineering