Analog to Discrete Value Conversion
Full Name
Lib.Mervis.v1_0.AnalogToDiscrete
Required Project References
- Lib.Mervis
Description
A block used for converting continuous values (e.g., voltage or resistance) that encode binary values based on their magnitude.
Usage in ST
program test
var
a2d: lib.mervis.v1_0.AnalogToDiscrete;
end_var
a2d(Value := ..., Weights := [1, 2, 4, 8, 0, 0, 0, 0], Output0 => D0, Output1 => D1);
end_program
Inputs
| Name | Data Type | Allowed Range | Retain | Mandatory Connection | Meaning |
|---|---|---|---|---|---|
| Value | real | No | Yes | Input analog value | |
| Weights | array[0..7] of real | Each element greater than or equal to zero | No | No | Weights of individual inputs. Must be sorted in ascending order, zero at any position ends the calculation. |
| Tolerance | real | 0..100 % | No | No | Tolerance for comparing the weights of individual inputs |
Outputs
| Name | Data Type | Meaning |
| Output0..Output7 | bool | Values of individual bits (0 - lowest weight = LSB, 7 - highest weight = MSB) |
| CombinedOutput | usint | Outputs Output0..Output7 combined into one 8-bit number |
Detailed Function Description
The block is used to convert a continuous variable (e.g., voltage or resistance) that encodes binary values based on its magnitude. Its main use is for utilizing analog inputs to expand the number of digital inputs or to save wiring between the sensor and the controller.
Usage Examples:
- A module with 6 digital inputs that converts to 0-10 V voltage.
The first input has a weight of 5 V, the second 2.5 V, and so on, the last has a weight of 0.15625 V. The resulting voltage is the sum of these weights. To convert back to the states of the digital inputs, this function block can be used by filling in the weights from the smallest: Weights = [0.15625, 0.3125, 0.625, 1.25, 2.5, 5, 0, 0].
- Another possibility is transmitting multiple digital contacts over just two wires using appropriately chosen resistor values for the given contacts.
For example, choosing values of 120 Ohms, 240 Ohms, 390 Ohms, and 820 Ohms allows us to distinguish 16 different resistance values and thus 4 switching contacts.