Here are examples of an analog Input and Output interface for Printer Port. There are two visual basic demo programs with source to test out idea.
Analog Interface for PC Ports
USB and wireless interface to PC may be more in vogue, but a higher speed is possible in printer-port. For analog and digital fast data acquisition, PC cards to full Access to PC bus are the best choice.
The Sensors and Actuators interfaced with a computer form a basic automation system or even a robot. So learning to interface Sensors (input devices like a thermocouple or pH sensor) and Actuators (output devices like a motor or heater) with a PC is the best way to start. It is by studying examples and experimenting cautiously can one learn the science, book reading alone will never help.See the Hardware Book connector details, cables, adapters, etc. The RS232-Serial Port, The Parallel- Centronics port, The USB-firefire port are good to start with. Then you can interface by LAN or Wireless- LAN or TCP/IP-Internet to make Robots or Automation extend to multiple places and computers. The possibilities are endless, imagination is the limit for students. But entrepreneurs need to be practical and only make equipment that have a utility and sensible market scope.
The circuits and code have some errors, The documentation is not complete.
DVM = digital volt meter MVS = milli volt source