PID diagram
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I would like to ask the experts here: is it necessary to indicate whether the setpoints for PID control are high or low? Are there any specific guidelines regarding this?
Alarm values are generally not indicated; only the function is shown on the PID diagram, with the specific alarm values provided in a separate instrument data sheet. Refer to the data sheet during configuration.
Is there a standard that explicitly requires this? I checked Hg20559, but it doesn’t clearly specify the use of the letters H and L
The specifications do not require it to be marked. It is usually marked for clear reading.
Take a look at HG/T20505-2014.
Generally, the level of a liquid gauge should be indicated to facilitate understanding
The alarm should be marked, and the alarm value can be entered in the work instructions as well as in the system
It must be expressed; otherwise, it’s not clear whether the police have been alerted or not, and there’s a risk of overreporting or underreporting