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.
LOGO! 9 and later versions support two data types: integer (16-bit) and float (32-bit).
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Connection |
Description |
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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 +- Delta. |
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Input Ax |
Input Ax is one of the following analog signals (integer or float):
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Parameter |
Value range |
Integer |
Float |
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Gain |
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-3.402823E38 to +3.402823E38 |
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Offset |
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Threshold 1 (Difference value above Aen, on/off threshold) |
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Threshold 2 (Difference value below Aen, on/off threshold) |
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p (Number of decimals) |
0, 1, 2, 3 |
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Output Q |
Q is set/reset, depending on the stored analog value and the offset. |
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1 If the data type of Ax is integer and the data type of this FB is configured as float, LSC will convert Ax into 32-bit receivable float data. 2 If the data type of Ax is float and the data type of this FB is configured as integer, LSC will cut off the decimal numbers of Ax and convert it into 16-bit receivable integer data. 3 AI1 to AI16: 0 to 10 V corresponds with 0 to 1000, 0 to 4095 or 0 to 10000 (internal value). 4 AI1 to AI8: 0 to 10 V corresponds with 0 to 1000 (internal value). |
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Parameters Threshold 1 and Threshold 2
The two threshold parameters Threshold 1 and Threshold 2 can be provided by the actual value of another already-programmed function:
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Analog comparator: Ax - Ay
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Analog threshold trigger: Ax
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Analog amplifier: Ax
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Analog multiplexer: Aq
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Analog ramp: Aq
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Mathematic instruction: Aq
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PI controller: Aq
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Up/Down counter: Cnt
For the 0BA7 and later version devices, you can additionally use the actual values of the following already-programmed functions:
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On-delay: Ta
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Off-delay: Ta
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On-/off-delay: Ta
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Retentive on-delay: Ta
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Wiping relay(pulse output): Ta
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Edge triggered wiping relay: Ta
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Asynchronous pulse generator: Ta
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Stairway light switch: Ta
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Multiple function switch: Ta
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Stopwatch: Aq
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Analog filter: Aq
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Average value: Aq
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Max/Min: Aq
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Threshold trigger: Fre
For the 0BA8 and later version devices, you can additionally use the actual values of the following already-programmed functions:
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Float/Integer converter: eAq
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Integer/Float converter: eAq
For the LOGO! 9 and later version devices, you can additionally use the actual values of the following already-programmed functions:
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Float calculation instruction: Aq
You select the required function by the block number.
The thresholds are represented by the symbol Δ on the LOGO! Base Module and in the timing diagram below.
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0BA4: Gain: Range of values: 0.00 to 10.00 |
Parameter p (number of decimals)
Parameter p applies only to the display of Aen, Ax, Threshold 1 and Threshold 2 values in a message text.
Timing diagram
Description of the function
A 0 to 1 transition at input En saves the value of the signal at the analog input Ax. This saved process variable is referred to as "Aen".
Both the analog actual values Ax and Aen are multiplied by the value at parameter A (gain), and parameter B (offset) is then added to the product, as follows:
(Ax * gain) + offset = Actual value Aen, when input En changes from 0 to 1, or
(Ax * gain) + offset = Actual value Ax.
Output Q is set when the signal at input En = 1 and if the actual value at input Ax is out of range of Aen + Threshold 1 / Aen - Threshold 2.
Output Q is reset, when the actual value at input Ax lies within the range of Aen + Threshold 1 / Aen - Threshold 2, or when the signal at input En changes to lo.
Particular characteristics to be noted when configuring
Refer to the help on analog block parameters in the Analog value processing section.