The ITS Team will be performing maintenance on Confluence beginning at 6:00 pm Tuesday, Apr 8. During this time the service may go offline. It should be available again by 8:00 pm. Please refrain from editing pages during this time to avoid losing your work.
LINK TO MEASURING VI
LINK TO RESPONDING VI
LINK TO RUNNING
Introduction
In order to measure the amount of liquid helium in the system at any given moment, a user interface with the platform LabVIEW is needed. The level of liquid helium is controlled by the position of the run valve, which allows it to flow from the separator to the nose (for more information on this process, follow THIS LINK and find Low Temperature: Cryogenics). The run valve has can have any position between 0 and 3 "turns", with 0 turns being completely closed and 3 turns being completely opened. LabVIEW is used to provide a means of automatically measuring and responding to the helium level inside the tank. This is done by running two separate Virtual Interfaces in unison, a Measuring VI and a Response VI.
- The Measuring VI uses a predetermined equation to estimate the current level of the tank based on the valve position. It takes into account randomness of flow and a constant rate of evaporation.
The Response VI controls the run valve position. It reads the current level from the Measuring VI, and reacts in order to ensure that the level stays near a user-specified target level. This is the larger of the two VIs and it interacts with the instrumentation involved, like the run valve itself.
The two VIs communicate through the use of text files, which are set by the user. One text file produces data by the Measuring VI with the standard date and time stamp, flow rate, valve position and new level with each iteration. The other text file produces data from the Response VI including the enoch time stamp, the level as read by the Response VI and the new valve position.
******ppl who need to modify the code, and ppl who just need to run it in order to get the fridge working*******
Measurement VI
Interface
When the VI is first opens up, the first panel to appear is the interface. This panel is where you can comprehensively see how full the tank is at any given moment, and can change a few control factors of the code.
One of the controls that will need to be set before the VI can run is the file path (see below). You should set this to a location on your computer's hard drive.
Next, you will need to set the standard deviation of the flow rate randomness curve. In order to provide a more realistic measurement of the level, randomness was introduced into the flow rate equation to account for small variations in flow. Also included in the interface are indicators for certain values pertaining to the system at that iteration. For instance, above the standard deviation control there is a "theoretical flow rate" indicator, (in other words, the flow rate calculated before randomness was applied) and below it there is a "realistic flow rate" indicator (the flow rate with randomness taken into account). The blue tank is comprehensive indicator for the level at each iteration. It is measured in percentages of 0 - 100 % full.
To the right of this section of the interface there are indicators for the current valve position, the current iteration number and the new level as calculated by the VI. These values are calculated every 1 second.
Code
- explain
Response VI:
Interface
Code
- explain
- understand all the sections
- visas
Running the VIs
- Power Supply Box
- Step Motor Driver
- indications on Paul's VI
- equations on mine
- how they communicate?