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The Tektronix 7912 is a high-speed digitizer that takes one 7000-series vertical plug-in | |||
and one 7000-series horizontal plug-in. There is a 7912AD which has 500MHz bandwidth | |||
and a 7912HB which is 750MHz bandwidth. These instruments contain a special internal | |||
CRT-based digitizing tube that is not visible from the outside. The signal goes from | |||
the vertical plug-in to the vertical amplifier to the digitizing tube where it deflects | |||
a beam of electrons. The electrons hit a small flat rectangular target inside the tube. | |||
This target is a solid state image sensor, conceptually similar to that in a digital camera. | |||
The trace is read from the target by electronics in the 7912AD, digitized, and stored in memory. | |||
The reading of the target is asynchronous from the sweep and therefore the tube can be considered | |||
a form of scan converter. Three output methods are provided: NTSC-out, X-Y low-speed analog, and GPIB. | |||
The resolution of the target is 512x512, giving 512 points in the time domain and 9-bit linear | |||
quantization of the input voltage. Skipping the vertical amplifier, the 7912 can provide a | |||
bandwidth of 1GHz with a sensitivity of 4V/division. | |||
With aftermarket modifications to the electronics, 7912AD | |||
bandwidths have been extended above 2GHz in special cases. With a 7B92 sweeping the whole X-axis | |||
in 5ns, and the 7912AD capturing 512 samples in that sweep, the 7912AD performs the function of a | |||
100Gsamp/sec ADC. The technology was designed at Tektronix in the 1970's and sold through the 1980's. | |||
They were expensive. | They were expensive. | ||
* http://w140.com/kurt/7912_gpib_examples.zip | * http://w140.com/kurt/7912_gpib_examples.zip |