alicat 0.9.0

Python driver for Alicat mass flow controllers.

alicat

TCP/Serial driver and command line tool for Alicat Laminar DP and BASIS mass flow devices.

If you are using Analyt-MTC flow controllers, go to this repository for more info. This driver does not currently support CODA devices.

Example Connections

Type	Usage
The standard DB9 cable connected directly to a computer (unix: /dev/ttyS0, windows: COM1).	Good with older computers that still have the connector.
The cable connected to a computer through a USB converter (unix: /dev/ttyUSB0, windows: COM1).	Good for newer computers and maker boards such as Raspberry Pis.
Multiple cables connected to one port via a splitter and Alicat's addressing (A-Z).	Good when number of ports is limited.
Cables routed through a TCP device server (192.168.1.100:23).

Installation

pip install alicat

Usage

Command Line

For basic tasks, this driver includes a command-line interface. Read the help for more.

alicat --help

Python

This uses Python ≥3.5's async/await syntax to asynchronously communicate with an Alicat. For example:

import asyncio
from alicat import FlowController

async def get():
    async with FlowController(address = "com_port", unit = "unit_id") as flow_controller:
        print(await flow_controller.get())

asyncio.run(get())
#  If there is already an event loop (e.g. Jupyter), replace the above line with:
#  sawait get()

A similar format can be used to communicate with a BASIS device.

import asyncio
from alicat.basis import BasisController

async def get():
    async with BasisController(address = "com_port", unit = "unit_id") as basis_controller:
        print(await basis_controller.get())

asyncio.run(get())

If the flow controller is communicating on the specified port, this should return a dictionary of the form:

## Standard Devices
{
  'setpoint': 0.0,         # Setpoint, either mass flow rate or pressure
  'control_point': 'flow', # Either 'flow' or 'pressure'
  'gas': 'Air',            # Can be any option in `flow_controller.gases`
  'mass_flow': 0.0,        # Mass flow (in units specified at time of purchase)
  'pressure': 25.46,       # Pressure (normally in psia)
  'temperature': 23.62,    # Temperature (normally in C)
  'total_flow': 0.0,       # Optional. If totalizer function purchased, will be included
  'volumetric_flow': 0.0   # Volumetric flow (in units specified at time of purchase)
}

## BASIS Devices
{
  'setpoint': 0.0,         # Mass Flow Setpoint
  'gas': 'Air',            # Can be Air, Ar, CO2, N2, O2, N2O, H2, He, CH4
  'mass_flow': 0.0,        # Mass flow (in SCCM or SLPM)
  'temperature': 23.62,    # Temperature (normally in C)
  'volumetric_flow': 0.0   # Volumetric flow (in CCM or LPM)
}

On flow controllers, you can set the flow or pressure setpoints.

await flow_controller.set_flow_rate(1.0)
await flow_controller.set_pressure(20)

Gas Type

You can set the gas type by name or by index. For more on setting by index, see the gas table in your Alicat's manual.

await flow_controller.set_gas('N2')
await flow_controller.set_gas(8)

For firmware 5v and greater, you can create and set gas mixes. Mixes can contain up to five gases and are stored in gas indices 236-255.

await flow_controller.create_mix(mix_no=236, name="Mix1", gases={'N2': 50, 'O2': 30, 'CO2': 20})
await flow_controller.set_gas(236)
await flow_controller.delete_mix(236)

PID Parameters

For flow controllers, read and write PID loop settings for device tuning.

await flow_controller.set_pid(p=4000, i=4000, d=10, loop_type='PD2I')
print(await flow_controller.get_pid())
{
    'loop_type': 'PD2I',
    'P': '4000',
    'I': '4000',
    'D': '10',
}

Other Features

Additional features include override commands to increase device functionality.

await flow_controller.lock()            # Lock the front display.
await flow_controller.unlock()          # Unlock the front display.
await flow_controller.hold()            # Hold the valve in its current position.
await flow_controller.cancel_hold()     # Cancel the valve hold.
await flow_controller.tare_volumetric() # Tare volumetric flow.
await flow_controller.tare_pressure()   # Tare pressure.
await flow_controller.reset_totalizer() # Reset totalizer, if totalizer functionality included.

Addressing

You can have multiple controllers on the same port by using Alicat's A-Z addresses and an RS-232 splitter.

flow_controller_1 = FlowController(address='A')
flow_controller_2 = FlowController(address='B')

await flow_controller_1.set_flow_rate(1.0)
await flow_controller_2.set_flow_rate(0.5)

await flow_controller_1.close() # /dev/ttyUSB0 is still open!
await flow_controller_2.close()

Breaking changes

0.5.0

• Support only asyncio. The last version with synchronous code was 0.4.1.
• Rename address/-a to unit/-u to match Alicat's documentation
• Rename -u to -ul (for --unlock)

0.4.1 Remove TCP support. Use pip install alicat==0.3.1 if needed