13
Control
Example:
aWD 10
(create a watchdog with 10 ms timeout for instrument A)
To disable the watchdog
:
unit_id
WD 0
Hold Valve Position / Resume Flow
The controller valve can be held at any percentage of full drive (controllers only).
To hold the valve at a particular drive percentage
:
unit_id
HPUR
valve_drive
valve_drive
is the percentage of full drive, a floating-point value from 0–100 percent.
Example:
aHPUR 10
(holds the valve for instrument A at 10% of full drive)
To resume closed loop control
:
unit_id
C
The valve will be returned to normal closed loop flow control.
Loop Control Gains
The loop control variables determine how the instrument will maintain the flow rate
(controllers only).
To read the closed loop control gains
:
unit_id
LCG
To set the closed loop control gains
:
unit_id
LCG
pgain igain
pgain
is the value to use for the proportional closed loop gain. It is an integer from 0–65535.
The larger the pgain, the faster the controller will predict necessary future corrections
based on the current rate of change in the system. A larger p gain may result in overshoot
and oscillations.
igain
is the value to use for the integral closed loop gain. It is an integer from 0–65535.
The larger the igain, the more aggressively the controller will correct errors between the
commanded setpoint and the measured process value.
Example:
aLCG 500 5000
(sets pgain to 500 and igain to 5000 for instrument A)
Reference Temperature
The reference temperature is used to calculate standard or normal mass flow.
To read the temperature reference
:
unit_id
RT
To set the temperature reference
:
unit_id
RT
ref_temperature
ref_temperature
is the reference temperature. It is a floating-point number in °C.
Example:
aRT 22
(sets the temperature reference to 22°C for Instrument A)
Readings Averaging
Averaging smooths the reading response for a rapidly changing flow
To read the averaging time constant for flow readings
:
unit_id
DCA
To set the averaging time constant for flow readings
:
unit_id
DCA
average_tc
average_tc
is the averaging time constant, the time required for the reported value to reach
63.2% of the final value when there is a step change in the reading. The value is an integer
from 0–9999 milliseconds.
Example:
aDCA 400
(sets the time constant to 400 ms for instrument A)
Configure Measurement Triggering
Measurements can be triggered based on one or more events (controllers only).
To read the current triggering mode
:
unit_id
MT
To set the current triggering mode
:
unit_id
MT
mode
mode
determines how a measurement will be triggered, per the table below:
