Oscilloscope and other Equipment
================================

The first thing that appears when you open the ExpEYES GUI program is an Oscilloscope window. The graphs of the four channel scope appears on the left side. On the right side we have the Buttons, Sliders etc. to control the scope and most of the hardware features of ExpEYES, like DC supplies, waveform generators etc. To understand ExpEYES, one should start  with the Input/Output trerminals and their functions as expleined below.

.. figure:: pics/top-panel.png
   :width: 300px
   
Input/Output Terminals
----------------------

- CCS: :math:`1.1\ mA` Constant Current Source.
   If you connect a resistor from this terminal to ground, a current of 1.1mA will flow irrespective of the value of the resistor. The maximum allowed value of the resistor is :math:`2k\Omega`. Using the Check-Button given on the GUI, you can ennable CCS.
   
- PVS: Programmable Voltage
   The output of this terminal can be set anywhere from 0V to +5V, using software. The voltage can be verified by connecting a voltmeter between PVS and ground. The voltage can be set from the GUI, using Sliders or Text-Entry widgets. 
   
- SQ1: Square Wave Generator
   This terminal can generate a Square wave that changes continuously from :math:`0` to :math:`5\ V`. The frequency can be set from the GUI from 1Hz to 5kHz, but it can be programmed to generate 0.1Hz to 1MHz. SQ1 has a :math:`100\Omega` series resistor so that LEDs can be directly connected.

- SQ2: Square Wave Generator
   SQ2 is similar to SQ1 but has no series resistor. 

- OD1: Digital Output
   The output of this terminal can be set to either :math:`0` or :math:`5\ V`. Using the Check-Button given on the GUI, you can change the voltage level at OD1.
   
- SINE: Sine wave output
   This is an oscillator giving a sine wave with an amplitude of around 4 volts and frequency around 150hz.

- IN1: For measuring Capacitance
   This has a built-in capacitance meter. By connecting between IN1 and ground, you can measure capacitance values ranging from few picoFarads to 5000 picoFarads. A Push-Button on the GUI is provided for measurement. This terminal also functions as a 0 to 5V range analog input.
   
- IN2: Frequency counter for logic signals
   This terminal can measure the frequency and dutycycle of digital signals, swinging
   between :math:`0` and :math:`3` to :math:`5\ V`. A Push-Button provided for measurement.
   This terminal also functions as a 0 to 5V range analog input.
   
- SEN: Input for measuring resistance
   This is actually a voltage measurement terminal that is is internally connected to :math:`3.3\ V` via a :math:`5.1\ k\Omega` resistor. We calculate the value of the externally conencted load by using Ohm's law. This terminal is mostly used for connecting resistive sensors like photo-transistors, for time interval measurements.
  
- A1 and A2: Voltage measurement terminal
   Functions as voltmeter and oscilloscope inputs. Maximum Input range  :math:`\pm\ 5\ V`. 
   The display range is selectable from pull down menu. Input A2 is another input similar to A1.

- MIC: Microphone output
   A Condenser microphone is fixed on the box. Its output is available on MIC output.

-  Inverting Amplifier
   An inverting amplifier with a maximum gain of -51 is available. It's gain can be reduced by feeding the signal through a series resistor.
  
Graphical User Interface
------------------------
  
The GUI menubar consists of several pulldown menus for different categories of experiments. 
The left side of the the screen is the four channel oscilloscope window. On the right side there are Buttons, Sliders and Text Fiields for accessing the hardware features explained earlier.
      
Oscilloscope Controls
---------------------

- Channel Selection
   The four channels A1, A2, IN1 and IN2 can be selected for display using the Check buttons on lower half of the right side.

- Volatge Display Range
   Pulldown menus are provided against each channel for selecting the voltage display range.

- Amplitude and Frequency    
   Check buttons on the right side of the range selection menu enables mathematical fitting of the captured data using a Sine function. The calculated Amplitude and Frequency are displayed.
   
- Time base Slider
   The time base slider is for selecting the duration of the X-axis. The allowed full range can be set from 2mS to 500mS.  
   
- Trigger Controls
   A digital storage oscilloscope digitizes periodically captures the input for a given duration and displays the result. To get a stable trace, the amplitude and slope of the input and the beginning of each capture operation should be kept same. This starting value is decided by the trigger level setting.
  
- Saving Data
   The data of the traces can be saved to a file in text format. The time and voltage values of each selcted trace will be written to a file.
   
- Cursor
   A vertical cursor can be enabled to view the instantaneous values of each channel at the cursor position along with time.
  

- Fourier Transform
    The Fourier transform converts the data from time domain to frequency domain. The amplitudes of the frequency components will be displayed. The value of the fundamenta frequency will be displayed.

Other Controls and Readbacks
----------------------------

- On the top right side there are Check boxes labelled A1, A2, IN1 and IN2. Selecting them will display the instantaneous values of the voltages at those terminals. These are useful for measuring DC volatges only.

- The value of the resistance connected to **SEN** is displayed below the DC voltage displays.

- Next is a Button for measuring the capacitance connected to IN1.

- A Button is available for measuring the frequency of a digital pulse at IN2. The signals should be swinging from zero to 5 volts.

- Two CheckButtons are provided for selecting OD1 and CCS.


- There are four vertical sliders on the left side of the GUI. They are used for horizontally shifting the traces. This is useful in experiments like the study of logic gates.

