Electrical engineering students and hobbiests work with signals that are within the range of both these instruments. In industry,the instruments are suitable for power, control and audio measurements. The scope bandwidth is 2MHz, so the scope is not suitable for looking at signals higher than this frequency, which include video, high-frequency digital and radio frequency signals.

2. The DSO-101 includes the ability to print out a waveform to a postscript file, for printing or inserting into a document. Analog scopes don't have this capability, and for digital scopes it's often a pricey option. (In one case, the option to print waveforms is double the entire cost of our oscilloscope.)

3. The DSO-101 is small enough to fit into a pocket. If you have a laptop computer handy, then the DSO-101 is a convenient way to have an oscilloscope available.

4. You might have specialized requirements that require additional signal processing and types of displays. It's possible to modify the software - the source code is open and included on CDROM with the instrument - and runs under the both the Windows and Linux operating systems. The modifications can appear as additional controls on the oscilloscope. For example, it took us approximately 2 hours to add a histogram display to the software. It would be straightforward to add signal processing and mathematical functions, such as multiplying the two waveforms to display power. As well, the programming interface is described in the 30 page technical manual included with the oscilloscope.

2. Analog function generators generally divide up the output frequency of the instrument into a series of ranges, each a decade apart. You can manually sweep the frequency continuously over a range of 10:1, then you have to change ranges.

The WGM-101 has one frequency control slider which can sweep the frequency over the entire range, from 1Hz to 100kHz. Or you can set upper and lower limits on the frequency range. For example, if you set the upper and lower limits at 20Hz and 20kHz, then you can sweep the frequency over the audio band.

3. The WGM-101 is capable of producing an arbitrary waveform. You can define the waveform by generating a file of data points. For example, you could create a cardiograph waveform and then use it to test cardiograph instrumentation.

4. If mobility is important, the WGM-101 is small enough to be stuffed into a pocket - and it works from USB power, no wall adaptor required.

5. You can modify the software - which is provided with the instrument - to create other features. For example, it would be possible to add a repetitive frequency sweep to the control software.

A school, to set up a very low-cost electronics lab.

Engineers and technicians who need a highly portable oscilloscope and generator.

Someone putting together a low-cost data-acquisition system for some specialized purpose.

They can explore circuit ideas and operating the test equipment more extensively.

In the same way that the personal computer had a dramatic effect on programming skills, this equipment will have a dramatic effect on student circuit design and debugging skills.

It improves the learning among the students by allowing them to pursue the subject in off-hours and off-campus.

Students are better prepared when attending a scheduled lab period.

Students practice construction and debugging skills on their own.

Q14.

The Tcl/Tk programming language is easily learned and very effective for this type of application. The programs are in text form (no binaries or linked libraries required) and are interpreted by the Tcl/Tk language. As a consequence, reading and modifying existing programs, or developing new ones, is a relatively simple process.

Any program that can communicate ASCII characters to the serial port can communicate with these instrument modules. During development, we have used Matlab for this purpose as well as a simple terminal emulator and various small Tcl/Tk programs.

For the waveform generator:
Variable duty cycle pulse
Automatic frequency sweep

For both instruments:
Network analyser for audio frequencies
Device curve tracer

Microsoft Windows keeps track of each individual USB device using its serial number. Each Syscomp USB instrument has a unique serial number such that Windows will assign each device its own COM port. This COM port will remain reserved for the device regardless of the order in which different devices are attached.

The Linux operating system (we use Suse 9.3) does not bind or reserve specific ttyUSB ports for a device. Instead, it assigns the ports in order. That is, the first USB-serial device that is plugged in will appear on ttyUSB0. The next device to be connected will appear as ttyUSB1, and so on.

When a Syscomp USB instrument GUI is started, it attempts to connect to the device using the port specified in the .cfg file. In the 2.4 version of the Linux kernel, the operating system does not lock a USB serial port when it is opened. For this reason, it is important that each Syscomp instrument configuration file point to a different USB serial port. For example, if an oscilloscope is running on ttyUSB0 and a function generator GUI is started which attempts to open ttyUSB0, both programs will crash. A workaround to this problem is outlined below:

1. Plug the first instrument into a USB port
2. Run dmesg to determine which port the instrument was assigned to (typically ttyUSB0)
3. Select Hardware->Port Settings in the GUI for that device and select the port from step 2.
4. Click 'Save and Exit' to save the serial port settings. The program will connect to the device.
5. Do not plug in the second device. Instead, open the GUI for that device and use Hardware->Port Settings to select the next available port (i.e. ttyUSB1).
6. Click 'Save and Exit' and close the program.
7. Plug in the device and ensure that it has been assigned the correct port using dmesg.
8. Start up the GUI and it will connect to the new device.