In this project, Java is used for reading data from a multimeter that has an RS232 port (such as the Voltcraft model 3850d). Java MultiMeter (JMM) has a very simple design. The main window displays the measurement value, the range and a bargraph (a semi-analogue measurement bar), plus a number of buttons. The READ button at the lower right is used to read in a value, while the START and STOP buttons can be used to control repetitive measurements at an adjustable interval that can be set using a slider (Sequence). At the top of the window there is a menu bar that has two options in the Window menu, namely Plot and Log. If you click on Log, a logging window appears that displays all measured values and the time of each measurement. This can be useful for looking at what happened in the past. In addition, the information in the log window can be stored for subsequent processing, for example using a spreadsheet program. If you click on Plot, a plot window appears that displays the measured values in graphic form. This plotting function works in a fairly advanced manner. The scale is automatically adjusted after each new measurement point is added. You can use the mouse to draw a rectangle over part of the plot, and then zoom in by moving the mouse down and to the right, or zoom out by moving the mouse up and to the left. If you press the Fill button, the full set of data is displayed again. Several plot windows can be open at the same time. New measurement data are always entered in the most recently opened window.
||Free to try
||serial port, multimeter