Siemens 420 manual Wire breakage monitoring

Issue 07/04 3 Functions

NOTE

When the filter time constant P0753 (ADC-PT1) is increased, this smoothes the ADC input signal therefore reducing the ripple. When this function is used within a control loop, this smoothing has a negative impact on the control behavior and immunity to noise (the dynamic performance deteriorates).

Wire breakage monitoring

The wire breakage monitoring (refer to Fig. 3-25) is set using parameters P0756 and P0761. If the input signal of the analog input falls below the wire breakage threshold (0.5 * P0761), then after the time in P0762 expires, fault F0080 is output and the status bit is set in parameter r0751.

Analog input	V
	10
P0761
0,5 ⋅ P0761
	0		t
Signal loss
r0751 1			t
	0
	P0762		Fault acknowl.
	1	F0080
	0		t
Act. ADC after scaling
r0755
	0		t

Fig. 3-26 Wire breakage monitoring

The following secondary conditions/limitations apply to the wire breakage monitoring:

The monitoring function must be activated using parameter P0756 Width of the ADC dead zone P0761 > 0

Wire breakage monitoring if the ADC input quantity ≤ 0.5 * P0761

Note

The wire-breakage monitoring function is only possible for unipolar analog inputs.

Input range 0 to 0.5 * P0761 of the analog input must be excluded when activating the wire breakage monitoring for normal operation.

MICROMASTER 420	Operating Instructions
6SE6400-5AA00-0BP0	93