Alicat P Series Pressure Gauge - Manual (Page 35)

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Sending a Set-point via RS-232 / RS-485 (PC and PCR-Series only):
To send a set-point via RS-232 / RS-485, “Serial” must be selected under the
“Input” list in the control set up mode. To give controllers a set-point, or change
an existing point, simply type in a number between 0 and 65535 (2% over
range), where 64000 denotes full-scale pressure, and hit “Enter”.
The set-point column and pressure rates should change accordingly. If they do
not, try hitting “Enter” a couple of times and repeating your command. The
formula for performing a linear interpolation is as follows:
Value = (Desired Set-point X 64000) / Full Scale Pressure Range
For example, if your device is a 50 psig full-scale unit and you wish to apply a
set-point of 12.5 psig you would enter the following value:
16000 = (12.5 psig X 64000) / Full Scale Pressure Range
If the controller is in polling mode as described in Changing from Streaming
Mode to Polling Mode, the set-point must be preceded by the address of the
controller. For example, if your controller has been given an address of D, the
set-point above would be sent by typing:
D16000 followed by “Enter”
To adjust the Proportional and Differential (P&D) terms via RS-232 / RS-485
(PC and PCR-Series only):
Type *@=A followed by “Enter” to stop the streaming mode of information.
To adjust the “P” or proportional term of the PID controller, type *R21
followed by “Enter”.
The computer will respond by reading the current value for register 21 between
0-65535. It is good practice to write this value down so you can return to the
factory settings if necessary. Enter the value you wish to try by writing the new
value to register 21. For example, if you wished to try a “P” term of 220, you
would type *W21=220 followed by “Enter” where the bold number denotes the
new value.
The computer will respond to the new value by confirming that 21=220. To
see the effect of the change you may now poll the unit by typing A followed
by “Enter”. This does an instantaneous poll and returns the values once. You
may type A “Enter” as many times as you like. Alternately, you could resume
streaming mode by typing *@=@ followed by “Enter”. Repeat step 3 to remove
the unit from the streaming mode.
To adjust the “D” or proportional term of the PID controller, type *R22 followed
by “Enter”.
The computer will respond by reading the current value for register 22 between
0-65535. It is good practice to write this value down so you can return to the
factory settings if necessary. Enter the value you wish to try by writing the new