Loop Controllers: Lone Logic is More Connected
作者:Mark T. Hoske 发表时间:2005-12-05
handle less than 20% of their control loops; 13% said 20-39% of control loops, 12% said 40-59% of control loops, 7% said 60-79% of control loops, 9% said 80-89% of control loops, 5% said 90-100% of control loops, and 7% didn't know.

More daily attention is given to keeping control loops running closed loop in 2005 than in 2003. Asked how often respondents check if stand-alone loop controllers are running in open or closed loop, 24% said daily, 13% weekly, 7% monthly, 16% several times a year,

and 41% didn't know. In 2003, 20% said daily, 17% weekly, 8% monthly, 12% several times a year, and 42% didn't know.

Respondents in 2005 and 2003 were nearly identical on how they program and configure most loop controllers: 52% do so on the device; 37% connect locally; and 11% connect remotely.

Looking at I/O channels in 2005 (descending order for each):

  • For PC-based controllers, the most numerous categories selected were: 2 or 3 analog inputs; 4 or 5 analog outputs; 21+ discrete inputs; and 21+ discrete outputs.
  • For electronic single-loop controllers, the most numerous categories were: 1 analog input; 1 analog output; 2 or 3 discrete inputs; and 2 or 3 discrete outputs.
  • For electronic multiple-loop controllers, the most numerous categories were: 2 or 3 analog inputs; 2 or 3 analog outputs; 4 or 5 discrete inputs; and 3-way tie between 2 or 3, 4 or 5, and 11-20 discrete outputs.
  • For pneumatic loop controllers, the most numerous categories were: 1 analog input; 1 analog output; 21+ discrete inputs; and (tie) 2 or 3, 4 or 5 discrete outputs.

Loop controller products

For more manufacturers, see www.cesuppliersearch.com, for integrators with expertise with controllers, go to www.controleng.com/ integrators. For more on products, visit the Web sites below.

Single-loop controllers or more

Users can select a traditional Bulletin 900 Single Loop Temperature/Process Controller or I/O device with integrated logic to do PID or other process-related tasks, or various PLC or a progr

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