CURVE  TRACERS

Curve tracers are specialized laboratory instruments that generate and apply voltage sweeps to certain electronic devices, in order to get X-Y output signals to be displayed on an scope that shows a graphic containing one to several curves reflecting the characteristic behavior of a determined electric work area of the device under test.

Before the creation of this instrument, all the characteristic curve graphics were made by hand employing a few galvanometers and writing to tables the multiple readings obtained. Then the data collection was translated to linear or exponential graphic paper. The precision was limited to the readings made.

There are two types of curve tracers of our interest: The transistor curve tracers and the tube curve tracers. Basically, a curve tracer generate a staircase waveform applied to base (or grid) and a pulsed DC waveform applied to collector (or plate) of the device under test. The staircase steps, amplitude and DC level can be varied to meet the testing requirements; the pulsed DC can be varied in amplitude and both may vary in frequency. Different coupling and load resistors are selected to trace curves in a wide range of conditions. There are curve tracers with integrated display and many others that need an external scope.

The curve tracers are professional and specialized instruments. They are indispensable for the research and development of new and better electronic equipment. This means that these instruments are required for the laboratories and engineers, but also for the electronic enthusiast. With this kind of instrument the designer will get the best results ever obtained.

The Tektronix 570 curve tracer, now considered a reference instrument, was the first and only tube curve tracer ever produced; serial numbers above 5000 were improved versions. The Tektronix 575 curve tracer was the first transistor curve tracer. The 576 has been the preferred type for years. The 577 is lightweight and reliable. At present time exist many new expensive digital models and brands that are used only in semiconductor research laboratories.

You should also know that a tube curve tracer may be used to test high voltage transistors, and that a transistor curve tracer may be used with a couple of external supplies to test tubes. The only flaw of using the curve tracers this way is that they must be adapted or "recalibrated” knowing previously the true parameter data from some reference devices, to be able to employ the instrument with certain amount of precision.

Some people think that the first 570 curve tracer is only a museum piece. Nothing more far away of the reality. Will you just predict the different behaviors of the several brands of pentodes when they are taken to their limits? Will you "match" tubes just with a static emission test?

Sophia, an excellent reputation high-end audio manufacturer, sells its own brand tubes. They show the tube datasheets with graphics created with the Sofia (Audiomatica, Italy) curve tracer, but the designers and manufacturers of the tubes as Dr. Liu Zhensheng at his Tianjin factory (full-music dot com) employs the Tektronix 570 on the design, prototyping and manufacturing stages (diyhifisupply dot com/diyhs_tj-factory-trip.htm).

Also AllegroSound, SND tube sales, NY audio repair, Perkins Electro-Acoustic Research Laboratory and many other professionals, have the same Tektronix 570 as an invaluable instrument. Profits for owning and employing such great equipment raise to hundred thousands dollars!

Now is so rare to get a good Tektronix 570 curve tracer, that if you find one, you must be prepared to spend several thousand dollars...