> For the complete documentation index, see [llms.txt](https://support.powerio.com/hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://support.powerio.com/hub/codesys-hvac/en/hvac-library/functionblocks/monitoring/position3p.md).

# Position3P

## `Position3P` (FB)

FUNCTION\_BLOCK Position3P

### Short description

> Calculation of the current position of a 3-point actuator\
> In addition, a reference position (limit switch) of the actuator can be detected.\
> Typical application: position determination on a 3-point valve actuator

### Representation

<figure><img src="https://2592874069-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FQR4vCFzt6ixgsqlR3pdR%2Fuploads%2Fgit-blob-abf0a197bfe6a121c3357abbb871b35823daea90%2Fimage.png?alt=media" alt=""><figcaption></figcaption></figure>

### Interfaces

#### Inputs

| Name        | Data type | Value range | Initial value | Function                                                          |
| ----------- | --------- | ----------- | ------------- | ----------------------------------------------------------------- |
| *xOutOpen*  | BOOL      |             |               | Input - Enable - Open                                             |
| *xOutClose* | BOOL      |             |               | Input - Enable - Closing                                          |
| *xRefPos*   | BOOL      |             |               | Digital input for detecting the reference position (limit switch) |

#### Outputs

| Name   | Data type | Value range                    | Initial value | Function                             |
| ------ | --------- | ------------------------------ | ------------- | ------------------------------------ |
| *rPos* | REAL      | **rMinLimit** to **rMaxLimit** |               | Display of the current position in % |

#### Setpoints / Parameters

| Name             | Data type | Value range | Initial value | Function                           |
| ---------------- | --------- | ----------- | ------------- | ---------------------------------- |
| **iRefPosition** | INT       | 0 - 100     | 0%            | Reference position of the actuator |
| **rMinLimit**    | REAL      |             | 0.0           | Limit value - Minimum position     |
| **rMaxLimit**    | REAL      |             | 100.0         | Limit value - Maximum position     |
| **tDuration**    | TIME      |             | T#120s        | Actuator runtime                   |

### Functional description

#### General

This function block is used to calculate the current position of a 3-point actuator that does not have position feedback.\
The calculation is based on the duration of the signals at the inputs Input - Enable - Open *xOutOpen* and Input - Enable - Closing *xOutClose*.\
Every rising edge at the digital input *xRefPos* (i.e. the actuator is currently in its reference position) causes a redefinition of the analog output signal *rPos* to the setpoint / parameter **iRefPosition**.

#### Reference position

The digital input *xRefPos* allows readjustment of the position display *rPos* to a predefined value **iRefPosition** (0% = rest position - 100% = maximum position).\
Every rising edge at the digital input triggers a readjustment.

#### Position display *rPos*

It is used to display the current position of the 3-point actuator in the range **rMinLimit** to **rMaxLimit** and is calculated internally.\
Signals at the input *xOutOpen* increase the value of the position display, signals at the input *xOutClose* reduce the value of the position display.

{% hint style="info" %}
**Restrictions / Notes**

The 3-point actuator must move linearly, i.e. perform the same position changes in equal time intervals.\
A position change via a possibly existing manual override - hardware is not recorded.\
To avoid deviations between the calculated and actual position, it is recommended to regularly trigger readjustment of the position display.
{% endhint %}

### CODESYS

InOut:

| Scope       | Name           | Type   | Initial      |
| ----------- | -------------- | ------ | ------------ |
| Input       | `xOutOpen`     | `BOOL` |              |
| Input       | `xOutClose`    | `BOOL` |              |
| Input       | `xRefPos`      | `BOOL` |              |
| Input Const | `iRefPosition` | `INT`  | 0            |
| Input Const | `rMinLimit`    | `REAL` | 0.0          |
| Input Const | `rMaxLimit`    | `REAL` | 100.0        |
| Input Const | `tDuration`    | `TIME` | TIME#2m0s0ms |
| Output      | `rPos`         | `REAL` |              |


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