Hitachi L2002 manual 184

Output

freq.

Thresholds

Output

freq.

4–40

Using Intelligent Output Terminals

Frequency arrival output [FA1] uses the standard output frequency (parameter F001) as the threshold for switching. In the figure to the right, Frequency Arrival [FA1] turns ON when the output frequency gets within 0.5 Hz below or

1.5Hz above the target constant frequency. This provides hysteresis that prevents output chatter near the threshold value.The hysteresis effect causes the output to turn ON slightly early as the speed approaches the threshold. Then the turn-OFF point is slightly delayed. The timing is further modified by a small

60 ms delay. Note the active low nature of the signal, due to the open collector output.

Frequency arrival output [FA2] works the same way; it just uses two separate thresholds as shown in the figure to the right. These provide for separate acceleration and deceleration thresholds to provide more flexibility than for [FA1]. [FA2] uses C042 during acceleration for the ON threshold, and C0043 during deceleration for the OFF threshold. This signal also is active low and has a 60 ms delay after the frequency thresholds are crossed. Having different accel and decel thresholds provides an asymmetrical output function. However, you can use equal ON and OFF thresholds, if desired.

Operations and Monitoring

	0.5 Hz						1.5 Hz
				F001					F001
										1.5 Hz
0			0.5 Hz
FA1					ON			ON			t
signal
											t
		60 ms				60 ms

						1.5 Hz
C042	accel.		0.5 Hz
C043	decel.
0
FA2				ON			t
signal
		60 ms			60 ms