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The latest feature which was implemented in the  Pocket Science Lab Android app is the data exporting feature which was implemented in almost each and every sensor. Now in addition to sensors now the data saving functionality is also implemented in Multimeter and this blog is regarding how the data exporting functionality was implemented for multimeter.

For implementing the data exporting feature first the Toolbar was implemented in the PSLab Android App.

Implementing the Toolbar[1]

For implementing the firstly the front-end of multimeter was changed and the Toolbar was added to it.

<android.support.design.widget.AppBarLayout
  android:id="@+id/top_app_bar_layout"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:theme="@style/AppTheme.AppBarOverlay">

  <android.support.v7.widget.Toolbar
      android:id="@+id/multimeter_toolbar"
      android:layout_width="match_parent"
      android:layout_height="?attr/actionBarSize"
      android:background="?attr/colorPrimary"
      app:popupTheme="@style/AppTheme.PopupOverlay"
      app:title="Multimeter" />

The above xml codes shows the implementation of toolbar.

Figure (1): Showing the implementation of multimeter toolbar

• Backend

For implementing the toolbar the onCreatemenu  was implemented for multimeter

@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.multimeter_log_menu, menu);
this.menu = menu;
return true;
}

For the same a separate menu was created for multimeter

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item
android:id="@+id/record_pause_data"
android:icon="@drawable/record_icon"
android:title="@string/record_csv_data"
app:showAsAction="always" />
<item
android:id="@+id/delete_csv_data"
android:icon="@drawable/delete_icon"
android:title="@string/delete_csv_data"
app:showAsAction="ifRoom" />
<item
android:id="@+id/record_csv_data"
android:icon="@drawable/menu_icon_save"
android:title="@string/save_csv_data"
app:showAsAction="never" />
<item
android:id="@+id/settings"
android:title="@string/nav_settings"
app:showAsAction="never" />
</menu>

Figure(2): Showing Toolbar of Multimeter

Thus through this the basic UI of the toolbar was implemented.

Implementing the Data Export Feature[2]

After implementing the toolbar for multimeter the multimeter the data exporting feature was implemented through the toolbar. The data export feature was implemented in such a manner that the user can start data recording by clicking on the record button after which the recording starts.

Figure(3):Showing snackbar after the data recording is started

and then when the user wants to end the experiment he may click on the pause button after which he gets an option either to export the data in csv format or either to delete the data.

Figure(4):Showing the menu bar for exporting data in csv

After clicking on the export data button the snacker appears which finally tells the user that the data is exported in this particular location (mentioned in the snackbar)

Figure(5):Showing the snackbar for showing location of the CSV folder

Further going to the csv folder we get the excel sheet in which the data is exported

Figure(6):Showing the excel sheet of data recorded

And this is how the data exporting feature was implemented in the PSLab android app. The users can use this functionality to perform experiments using multimeter in PSLab.

Resources

1. Medium, Android Toolbar for AppCompatActivity:
   https://medium.com/@101/android-toolbar-for-appcompatactivity-671b1d10f354
2. Code Project, Exporting data in CSV format:
   https://www.codeproject.com/questions/491823/read-fwritepluscsvplusinplusplusandroid

The Pocket Science Lab Android app has got various functionality such as voltmeter, resistance measurement, capacitance measurement, frequency measurement as well as Count pulse measurement , one of the missing functionality among these is the Ammeter, currently in PSLab there is no direct way of measuring current. In this blog I will be discussing an indirect method of measuring current in PSLab.

Basics of measuring current

Generally in all multimeters , current is measured using  an Ammeter which uses the property of galvanometer to measure to measure current in PSLab. But as the PSLab doesn’t has any such embedded Galvanometer we cannot have a seperate Ammeter in it, but there is another method to measure the current, which is using the famous OHm’s law i.e V/I = R

In PSLab we can measure the voltage across any elements, plus we can also measure  the resistance of any circuit element in PSLab, the theory used for measuring current is stated as follows.

1. We connect the current-source to any known resistant(or any resistance) and then measure the voltage across the resistor.
2. Finally using ohm’s law the current will be voltage / resistance.[2]

Step-by-step guide on measuring the current

Here is the step by step guide on how to measure the current in PSLab:-

1. Take any arbitrary resistor and measure it’s resistance. To measure the resistance follow these steps :-
   1. Take a resistance and connect it to any two pins of breadboard
   2. Connect one end to the sen pin and the other end to the GND pin of PSLab device.
   3. Now go to the Android app and select multimeter instrument.
   4. Now in the multimeter instrument set the knob to resistance, in the measure section
   5. Now click on the read button and then it will show the resistance of the resistor
2. Now that you have measured the resistance of the resistor, now connect the current source across the resistors.
3. Now finally measure the voltage across the resistor. To measure the voltage follow these steps.
   1. Take two male to male wires and connect it’s two individual ends to the two ends of the resistor.
   2. Now connect one of the other two ends of the wire to the any one of the CH1, CH2 or CH3 and the other end to GND respectively.
   3. Now go to the Android app and select multimeter instrument.
   4. Now in the multimeter instrument set the knob to the channel which you have selected i.e CH1, CH2 or CH3 , in the voltage section.
   5. Now click on the read button and then it will show the voltage across the resistor.
4. Now using the using ohm’s law the current will be voltage / resistance.

Thus using these steps one can find the current in PSLab Android App.

Images for the Experiment

Figure (1): Showing resistance measurement

Figure(2) Showing voltage measurement

Resources

1. Using-a-Multimeter, dengarden.com:
   https://dengarden.com/home-improvement/Using-a-Multimeter
2. Wikipedia, Ohm’s Law:
   https://en.wikipedia.org/wiki/Ohm%27s_law

The Pocket Science Lab Android app has various functionalities implemented in it, one of the major implemented functionalities is the knob in the multimeter, In my previous blog I have mentioned about the knobs and how exactly it has been implemented, one the major problems in the knob is that it doesn’t fits correctly in all layouts, even though constraint layout is used , as it has different text-views positioned in a circular constraint in which exact circular radius has to be mentioned (which cannot be constrained), mentioned in my previous-blog there comes the idea of creating different layouts for different-screens in android.

Need to create multiple layouts for different screen

There arises this question of the use of creating multiple layouts for different screens when you can create a flexible layout using tools such as constraint layout. The answer to this question is that in some cases such as as the case of circular constraint or using a linear-layout  one has to use use hard-coded dimensions which thus makes difference in various screens on, there comes the need of using size and orientation quantifiers i.e making layout according to screen sizes. Als

Figure 1:Screenshot

Figure 1 shows how different layouts are made for multimeter according to the screen-size.

Size quantifiers in android

Size quantifier is a name that specifies an individual configuration (in this case size) corresponding to which resources can be used.

For example, here are some default and alternative resources:

res/
   drawable/
       icon.png
       background.png
   drawable-hdpi/
       icon.png
       background.png

In this case -hdpi is a size quantifier, there are default size quantifiers at the drawable folder.

Making different layouts according to size-quantifiers[1][2]

This blog will give a step by step guide on how to make layouts using size quantifiers.

1. Right click the res folder in android studio and select New-> Android Resource directory.
2. A screen like below will appear
3. Change the resource type to layout.
4. From the available quantifiers select the quantifier which you would require, (in our case it is size).
5. After selecting the quantifier click the >> button after which the following screen will get displayed.
6. Now select the screen-size and click ok to make the directory, note that only one directory can be made in a single go.
7. After this make different layouts according to the screen-sizes and then save the respective alternative resources in this new directory. The resource files must be named exactly the same as the default resource files.

Thus by following these steps one can make different layouts according to screen-sizes in android.

Resources

1. Support different screen sizes, Android developers https://developer.android.com/training/multiscreen/screensizes#TaskUseSizeQuali (Link to repo)
2. App resources overview, Android developers https://developer.android.com/guide/topics/resources/providing-resources#ScreenSizeQualifier