Flow Controller

Overview

A FlowController oversees a bank of mass flow controllers with an optional pressure sensor. Drivers typically support two operating modes: holding each channel at a fixed flow rate, or maintaining a constant ratio of flow rates while regulating the total flow to sustain a target pressure read by an integrated sensor. Blackchirp records the names and setpoints of all enabled gases at the start of an experiment, and reads flow rates and pressure as auxiliary data throughout the run.

The number of flow channels is configurable per profile through the numChannels setting. Changing the value from the device dialog rebuilds the per-channel array on accept; data for channels that still exist is preserved.

Settings

Most settings are exposed in the hardware dialog with inline labels and tooltips supplied by the settings registry. A few items are worth highlighting:

  • numChannels sets the number of mass flow channels the controller manages. It defaults to 4 and is registered as an Important setting, so the per-channel channels array is rebuilt as soon as the new value is saved; data for channels that still exist is preserved.

  • pUnits (the pressure-units string used for display and file output) is registered at the FlowController base class and defaults to kTorr. Drivers that need a different default (for example, the Python flow-controller bridge) override only this key; users still see the same setting in the dialog.

  • intervalMs is the timer period between successive readback queries. Each tick advances by one channel through the channel list, so the effective per-channel update rate scales with the configured channel count.

  • The per-channel channels array (chUnits, chMax, chDecimals) controls display formatting only. Maximum values are advisory: Blackchirp does not clamp setpoints to chMax before sending them to the device.

The rolling and auxiliary display for flow data is rendered in the gas-flow status panel of the main window. Channels with no name and a zero setpoint are hidden so that small experiments do not waste vertical space; channels become visible automatically as soon as either a name or a non-zero setpoint is assigned. Each row carries the live flow value, a status LED indicating an active setpoint, and a tooltip summarizing the current setpoint with units. The pressure row at the top of the panel uses the registry-supplied pressure units and decimal places for formatting.

Drivers

Virtual

A dummy 4-channel driver that echoes setpoints back as flow readings. Useful for offline UI testing.

MKS 647C

A 4-channel device with a built-in PID controller for maintaining a target pressure. The communication protocol is RS232. The driver maintains an internal table of supported gas-correction factor ranges and pressure ranges; both are selected automatically based on the configured maxima.

MKS 946

A modular platform from MKS supporting different combinations of mass flow controllers and pressure sensors. The Blackchirp driver assumes 4 flow channels and 1 pressure channel and adds three driver-specific settings (address, offset, and pressureChannel) for matching the controller’s RS-232 address and the physical slot numbers of the MFC and pressure inputs. The communication protocol is RS232.