User Manual

LOGO! functions
4.4 Special functions list - SF
LOGO!
192 Manual, 06/2014, A5E33039675
4.4.21
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!
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
2
to
Aen+ Δ
1
Input Ax Input Ax is one of the following analog signals:
• AI1 to AI8 (*)
• AM1 to AM64
• NAI1 to NAI32
• AQ1 to AQ8
• NAQ1 to NAQ16
• Block number of a function with analog output
Parameter A: gain
Range of values: -10.00 to 10.00
B: zero offset
Range of values: -10,000 to 10,000
Δ
1
: difference value above Aen:
on/off threshold
Range of values: 0 to 20,000
Δ
2
: difference value below Aen:
on/off threshold
Range of values: 0 to 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.
* 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 130)".