On Sun, Sep 9, 2012 at 4:23 PM, John Kasunich <[email protected]> wrote: > Not long after Nixon was president, Tektronix had roughly the same > idea, and called it the TVC-501. It is one of the TM500 series > modular instruments. There are two counters just like you describe, > taking turns counting. Their approach to handling the resulting > data stream was clever. Each cycle of the input results in a number > in a counter, representing a time interval. They subtract an adjustable > offset from that number, then scale it and send it to a DAC. You > connect the output to your scope. So the result is a waveform with > a scale of 1uS, 10uS, 100uS, etc, all the way to 1 second per > division. The offset value can be hundreds of divisions, so for > example you can measure the period of a 100Hz square wave with > resolution of 1uS per division. > > You can use whatever triggering capabilities your scope might have, > but instead of looking at voltage, you are looking at time. The > unit has two input connectors, and you can measure either the period > of the A input, the pulse width on the A input, or the delay from > the A input to the B input. Very nice for looking at things like > the transient response of a PWM based regulator - because the time > values look just like any other analog signal. > > I lucked out and got mine during a lab cleanup - nobody knew what > it was or how to use it. I've seen them on ebay on rare occasions, > for half a kilo-buck or more. > > In these days of inexpensive software based FPGA+USB oscilloscopes, > I think it would be neat to see someone do roughly the same thing. > They could leave out the DAC though - simply write the numbers from > the counter to data memory as if they had come from a channel > sampling ADC. With even a cheap FPGA it would be easy to have 100nS > resolution, 10nS is not at all out of reach. > > > -- > John Kasunich > [email protected]
In fact, there's two of 'em up on Fleabay right now. At $600 a pop. ;-) Mark ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
