We did one for a 2nd year engineering project.
We used an 8bit microcontroller. for us we chose the a 20Mhz microchip 16F876 (although there are other better alternatives) because it had a decent amount of RAM to be used as a buffer for sampling at high frequencies. although the 16F876 has an internal ADC we used an external ADC that communicated with the micocontroller via an SPI port. this allowed us to sample at higher frequencies, and because it was a serial ADC it was cheap.
we used an amplifier to ofset the incoming signal so it was always a +ve signal so the ADC could correctly sample the wave. we used a buffer to increase the devices impedance giving a better signal.
the device communicated with the PC through the serial port. this turned out to be the largest bottle neck in the product, however was cheap and overcome using the buffer mentioned above.
a simple gui was built in vb and the device was Calibrated using a real oscilliscope.
we were able to obtain an accuracy of within 1% with the voltages the timebases.
trigering and auto-triggering implementations was trival as we other features like printing and rulers. the slew rate of the external adc was good so we were able to measure any type of wave without a problem. all this was done for about A$80 = US$40 including the case.
we found that using vb to write the gui provided an additional bottleneck as the serial comms implementation in vb wasnt all that good - and we had a relatively slow computer. so one written in C or C++ would have been nice.
So it can be done well, quite easily and cheaply.
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We did one for a 2nd year engineering project.
We used an 8bit microcontroller. for us we chose the a 20Mhz microchip 16F876 (although there are other better alternatives) because it had a decent amount of RAM to be used as a buffer for sampling at high frequencies. although the 16F876 has an internal ADC we used an external ADC that communicated with the micocontroller via an SPI port. this allowed us to sample at higher frequencies, and because it was a serial ADC it was cheap.
we used an amplifier to ofset the incoming signal so it was always a +ve signal so the ADC could correctly sample the wave. we used a buffer to increase the devices impedance giving a better signal.
the device communicated with the PC through the serial port. this turned out to be the largest bottle neck in the product, however was cheap and overcome using the buffer mentioned above.
a simple gui was built in vb and the device was Calibrated using a real oscilliscope.
we were able to obtain an accuracy of within 1% with the voltages the timebases.
trigering and auto-triggering implementations was trival as we other features like printing and rulers. the slew rate of the external adc was good so we were able to measure any type of wave without a problem. all this was done for about A$80 = US$40 including the case.
we found that using vb to write the gui provided an additional bottleneck as the serial comms implementation in vb wasnt all that good - and we had a relatively slow computer. so one written in C or C++ would have been nice.
So it can be done well, quite easily and cheaply.