SIM900_for_CMP

This repository is for use in the Carnegie Mellon University Department of Physics Modern Physics lab on Condensed Matter Physics (CMP). Please see this manual for a summary of the status of the physical experiment

There are two main "bulks" of work: the code to communicate with the SIM900 from TeachSpin via Pyvisa as well as a Tkinker-dependent temperature visualization.

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Communicating with the SIM900

Utilizing Pyvisa, one can interact with the SIM900, specifically the SIM922 Diode Temperature Monitor, by creating a SRS_Device object, as shown in my example file, to be called from the command line.

The functions of serial_talking.py are well documented and easy to use.

There are two things a user can do: either get temperature/voltage data, or configure things to get accurate data.

Code takes minimal input and takes no knowledge of RS-232 communication:

from serial_talking import SRS_Device

if __name__ == "__main__":    
    #Creating obect representing commmunication channel to device
    chan = SRS_Device()
    #Who are we talking to?
    chan.get_idn()
    
    #Syntax for getting data goes as chan.get_temp(n) or chan.get_volt(n), where
    #   'n' represents the SIM922 channel in question (1-4)

    #Call to get temperature for diode on line 1
    chan.get_temp(1)
    #Call to get voltage for diode on line 2
    chan.get_volt(2)

All other functions are to store and maniluate "calibration curves," which the SIM internally uses to read out temperatures from its measurement of voltage.

Note that one can manually determine voltage / temperature conversion, described in Chapter 4 of the TeachSpin Cryostat manual, or via the code in the /temperature_fitting_code directory. The wind.py does have a converter built in for quick PID conversions.

Look at example_code.py for an intro to using the command line.

To use the command line, open a terminal and cd path.to.SIM_Code (change directory to the SIM_Code repository). From there, assuming you're on the computer in MA326, one needs to active the venv virutal environment with the command venv\Scripts\Activate, and now all required libraries are accessible and one can simply call python com_line.py or python wind.py to have the desired files run.

Visualizing Temperature

To give some functionality to this repository, wind.py has been created to accomplish 2 tasks:

1. temperature to voltage conversion, to be used with the TeachSpin PI Temperature Controller.
2. live plot of temperature from diodes connected to the SIM922. The tkinker program lives in wind.py, yet it is based on code from multiple other files, using the SRS_Device as described in the secion above.

The wind.py file is admitidly a mess as it is creating the required objects to populate the Tkinker, but one can understand and manipulate functionality via the "command" functions at the top of the file, as well as the graphing.py file.

Note: the "user defined" curve, mentioned in the tkinker window, requires knowledge of the SRS_Device handling to initially add points to.

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While a user of this code need only know how to use the command line to open the wind.py application, it will take a little reading of documenation in the serial_talking.py to be comfortable with adding calibration curves, and quite a bit more digging into the SIM922 manual to understand how you can manipulate the SRS_Device code. However, a lot of future improvements can be made though updating wind.py functionalities.

Specific Improvement Ideas:

• Visualize Multiple Thermometers at the same time (really just storing two sets of data and plotting on the same axis twice)
• Set up curve calibration points from tkinker window
• update the name wind.py to window.py becuase two more characters really clears things up