AW Gear Meters EMO-1005 - Manual (Page 27)

AW-Lake Company 8809 Industrial Drive, Franksville, WI 53126  web: www.awgearmeters.com
 Tel: 262-884-9800  Fax: 262-884-9810  Email: [email protected]
REV. 1a 05/98 EMO-1005 Manual.DOC
26
CLOSED LOOP CONTROL MODE (CLC)
The CLC mode has been adapted to the EMO-1005 for extremely slow closed loop applications. In
some applications (fluid) where the distance between the I/P converter and the regulator is more than
40 feet and the pneumatic system is not quick enough in response, the standard PI loop will not do the
job. The CLC mode has one major difference to the standard PI mode in that the corrections are done
by a percentage to the error rather than proportionally.
For example:
If a set value (Analog In) is calling for a flow rate of 20 liquid ounces but the feedback frequency is
only 18.2 liq.oz. when sending out 10mA's, then the CLC would correct the Analog Output as
follows:
Set Value - Current Value
New Analog Out=Old Analog Out + * A
Set Value
where,
A is the highest value of the Analog Output. (Usually 5VDC)
After making the corrections, the CLC waits until the mellow frequency (average) catches up with the
actual frequency. After the catch-up has been achieved, within the death band limits, the CLC is then
ready for a new round of calculations.
There are a great many applications which show a lag time before any reaction in the system can be
seen. To take care of this problem, a programmable lag time factor has been added to the CLC mode.
In the CLC mode, a change at the Analog Input will immediately cause a change in the Analog
Output. Again, the change on the output is based on a percentage.
CLC Parameters
Totalizer Limit # 2 = Initial kick (205=4mA...1023=20mA)
Totalizer Limit # 1 = Lag time (0100 - 0255)
Sample amount = Average (005 -040)
Cutoff = Death band (100=1Hz...255=2.55Hz)
Analog In Gain = Scales Analog Input
The initial kick is used to start a system regulating. See the section "THE EMO-1005 PID
OPERATIONS", page 20, for more information about the initial kick.
The Cutoff is used to stop the unwanted hunting of the CLC mode. When Cutoff is set, the number in
the Cutoff is translated into a frequency. The number in the Cutoff is the margin where the EMO-1005
will stop regulating and will hold a steady Analog Output.
By increasing the Sample amount, the Lag time reaction becomes slower.
By increasing the Death band the unwanted hunting will be avoided.
** CAUTION ** Changing from one mode to another changes some of the inputs to outputs therefore,
please make sure which mode the channel card is in before hooking up external signals.