https://github.com/electronsandstuff/py-pfeiffer-vacuum-protocol

Python implementation of the Pfeiffer vaccum protocol for vacuum gauge control
https://github.com/electronsandstuff/py-pfeiffer-vacuum-protocol

Last synced: 4 months ago
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Python implementation of the Pfeiffer vaccum protocol for vacuum gauge control

Host: GitHub
URL: https://github.com/electronsandstuff/py-pfeiffer-vacuum-protocol
Owner: electronsandstuff
License: bsd-3-clause
Created: 2020-05-17T02:36:11.000Z (about 6 years ago)
Default Branch: master
Last Pushed: 2025-01-15T05:14:50.000Z (over 1 year ago)
Last Synced: 2025-01-15T07:12:51.134Z (over 1 year ago)
Language: Python
Homepage:
Size: 195 KB
Stars: 16
Watchers: 1
Forks: 2
Open Issues: 0
Metadata Files:
- Readme: README.md
- License: LICENSE.txt

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README

# Pfeiffer Vacuum Protocol
[![](https://img.shields.io/pypi/v/pfeiffer-vacuum-protocol.svg)](https://pypi.org/pypi/pfeiffer-vacuum-protocol/)
[![](https://img.shields.io/pypi/pyversions/pfeiffer-vacuum-protocol.svg)](https://pypi.org/pypi/pfeiffer-vacuum-protocol/)
[![](https://img.shields.io/pypi/l/pfeiffer-vacuum-protocol.svg)](https://pypi.org/pypi/pfeiffer-vacuum-protocol/)

A python interface for controlling Pfeiffer vacuum gauges over RS485.

## Installation, Testing, and Dependencies
This library is available on pip. Please install it with the following command.
```
pip install pfeiffer-vacuum-protocol
```
Testing is done with python's unit testing framework. You can verify the current branch is working with the following command run from the root of this repo.
```
$ python -m unittest
...............................
----------------------------------------------------------------------
Ran 31 tests in 0.006s

OK
```
The only required dependency is your favorite serial library. This package was developed and tested against `pySerial`. However, it should be compatible with any library that implements python's IO interface.
## Description and Hardware Compatibility

This library was created to communicate with a Pfeiffer vacuum PPT 100 over its RS485 interface. These gauges can be purchased cheaply from ebay and this library enables simple readout of pressure from the gauges through python.

![gauge](https://raw.githubusercontent.com/electronsandstuff/py-pfeiffer-vacuum-protocol/master/assets/gauge.jpg)

To correctly do this, you'll need to make a quick custom cable for the device. Please follow the pinout in the PPT 100 manual reproduced here. On this particular gauge, V DC is 24 V.

![pinout](https://raw.githubusercontent.com/electronsandstuff/py-pfeiffer-vacuum-protocol/master/assets/pinout.png)

Cheap RS485 adapters exist that allow the gauge to be directly connected to a PC. Currently, only functions relevant to the PPT 100 are implemented in the library. The following is a table of compatibility for other models reproduced from the PPT 100 manual. If you are interested in other gauges, then please consider contributing.

![compatibility](https://raw.githubusercontent.com/electronsandstuff/py-pfeiffer-vacuum-protocol/master/assets/compatibility.PNG)

## Quickstart Guide
The library is designed for and tested against the `pySerial` interface for communicating with the gauges. However, because it can technically be used with any serial interface that implements python's IO interface, I have decided against imposing which library to use in the dependencies of this project. To use pySerial as in this example, please installit through pip with `pip install pySerial`.

The most common operation is to read out pressure from the gauge. The following example will read out pressure from a gauge attached to COM port 1 with address 1 on the RS485 network. The pressure returned will be in bar.

```python
import serial
import pfeiffer_vacuum_protocol as pvp

# Open the serial port with a 1 second timeout
s = serial.Serial("COM1", timeout=1)

# Read the pressure from address 1 and print it
p = pvp.read_pressure(s, 1)
print("Pressure: {:.3f} bar".format(p))
```

## Invalid Character Filter
Some users have reported invalid characters coming from their serial device. Sometimes this can be resolved by simply ignoring those extra characters. The library comes with a filter built in. This is kept off by default to properly display errors to the user. However, it can be enabled/disabled by running one of the following function after import.
```python
import pfeiffer_vacuum_protocol as pvp
pvp.enable_valid_char_filter() # Filter on
pvp.disable_valid_char_filter() # Turn it off again
```
The filter can also be overridden on a per-function basis. The relevant functions have an optional argument called `valid_char_filter` which can be set to `True` or `False` to enable or disable the filter in a more targeted way.

## Package Reference

##### read_error_code(s, addr, valid_char_filter=None)

Reads Pfeiffer's low level error code on the gauge. This appears to be useful for diagnosing failure of the transmitter itself.

###### Parameters