Emerson Process Management 1500 manual 7.5Overshoot compensation

Configuring the Filling and Dosing Application

Table 7-4Valve control parameters – Two-stage discrete fill

Flow option	Default	Description
Open Primary	0.00% of target	Enter the quantity or the percent of the target at which the primary valve will
		open.
		Either Open Primary or Open Secondary must be set to 0. If one of these
		parameters is set to a non-zero value, the other is set to 0 automatically.
		Before a fill of this type can be started, the primary valve must be assigned to
		a discrete output. See Section 7.4, Step 4.
Open	0.00% of target	Enter the quantity or the percent of the target at which the secondary valve will
Secondary		open.
		Either Open Primary or Open Secondary must be set to 0. If one of these
		parameters is set to a non-zero value, the other is set to 0 automatically.
		Before a fill of this type can be started, the secondary valve must be assigned
		to a discrete output. See Section 7.4, Step 4.
Close Primary	100.00% of target	Enter the percent of the target, or the quantity to be subtracted from the target,
		at which the primary valve will close.(1)
		Either Close Primary or Close Secondary must be set to close when the target
		is reached. If one of these parameters is set to a value that is not the target,
		the other is adjusted accordingly.
Close	100.00% of target	Enter the percent of the target, or the quantity to be subtracted from the target,
Secondary		at which the secondary valve will close.(1)
		Either Close Primary or Close Secondary must be set to close when the target
		is reached. If one of these parameters is set to a value that is not the target,
		the other is adjusted accordinly.

(1) See the definition of Configure By in Table 7-3.

Table 7-5Valve control parameters – Three-position analog fill

Flow option	Default	Description
Open Full	0.00% of target	Enter the quantity or the percent of the target at which the valve will transition
		from partial flow to full flow.
Close Partial	100.00% of target	Enter the percent of the target, or the quantity to be subtracted from the target,
		at which the valve will transition from full flow to partial flow.(1)

(1) See the definition of Configure By in Table 7-3.

7.5Overshoot compensation

Overshoot compensation keeps the actual quantity delivered as close as possible to the fill target by compensating for the time required to close the valve. Without overshoot compensation, there will always be some amount of overfill because of the time required for the transmitter to observe that the target has been reached and send the command to close the valve, and then for the control system and valve to respond. When overshoot compensation is configured, the transmitter issues the valve close command before the target is reached. See Figure 7-6.

62 Micro Motion® Model 1500 Transmitters with the Filling and Dosing Application