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LOGO! functions
4.4 Special functions list - SF
4.4.19

Analog watchdog

Short description
This special function saves the process variable of an analog input to memory, and sets the
output when the output variable exceeds or drops below this stored value plus a configurable
offset.
Symbol in LOGO!
* AI1...AI8: 0...10 V corresponds with 0...1000 (internal value).
Gain and offset parameters
For more information on gain and offset parameters, refer to topic "Calculating the gain and
offset of analog values (Page 117)".
170
Wiring
Description
Input En
A positive edge (0 to 1 transition) at input En saves
the analog value at input Ax ("Aen") to memory and
starts monitoring of the analog range Aen - Δ
Aen+ Δ
Input Ax
You apply the analog signal to be monitored at input
Ax.
Use the analog inputs AI1...AI8
AM1...AM6, the block number of a function with ana-
log output, or the analog outputs AQ1 and AQ2.
Parameter
A: Gain
Range of values: ±10.00
B: Zero offset
Range of values: ±10,000
Δ
1
on/off threshold
Range of values: 0-20,000
Δ
Aen: on/off threshold
Range of values: 0-20,000
p: Number of decimals
Range of values: 0, 1, 2, 3
Retentivity:
/ = No retentivity
R = The status is retentive in memory
Output Q
Q is set/reset, depending on the stored analog value
and the offset.
1
:Difference value above Aen:
Difference value below
2:
Manual, 10/2017, A5E01248535-AA
to
2
*
, the analog flags
(
)
LOGO!

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