I read with interest John Rezabek's article in the October 2012 issue ("One Remarkable Transmitter," www.controlglobal.com/articles/2012/rezabek-remarkable-transmitter.html). In it, he made a number of significant points about the evolution of electronic pressure transmitters.
I do take issue though with the reference to manufacturers' "digital transmitters." While all "smart" transmitters have microprocessers and digital circuitry, there is truly only one digital transmitter manufacturer today. Yokogawa's EJA and EJX series of transmitters are the only ones that have digital sensors using their exclusive dual resonance technology. All other manufacturers start with an analog sensor, like capacitance in the case of the 3051 you mentioned, and have to use an A/D in their circuitry.
The other issue that I had was your reference to the "Rosemount 3051C DP cell." DP cell is a registered name of Foxboro. They registered the term when they introduced the 13A pneumatic DP transmitter. Their products are the only ones that should be associated with the term DP cell. I understand that many people use the term, but I did want to point that out to you.
RM Controls, Inc.