7912

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.

• http://w140.com/kurt/7912_gpib_examples.zip
• http://130.226.56.153/rispubl/reports_INIS/RISOM2873.pdf