Re: What calibration items to buy.


Good morning, gentlemen;

Calibration. What a subject to discuss. A few of things:

(1.) I have Leo Bodnar's device. It has proven useful. When propagation has been relatively stable, a comparison with WWV has shown the device to be adequately close for at least my simple requirements.

(2.) One other device that I have, which is described as a small. portable, battery operated device for quickly checking the operation and calibration (to some level of accuracy and precision) of an oscilloscope that you may be considering for a purchase. This is the "Pyramid Generator," an "Oscilloscope Calibrator and Tester," available from BP Magnetics, 1705 Stonehenge Drive, Tustin, California 92780. Still quoting from the printing on the front of the small box, there is an e-mail address of; REED714@....

While it does claim to have a 5 V p-p square wave output, and a 3 V p-p triangular wave into a 1 MegOhm high impedance load, and a 0,3 V p-p into a low impedance 50 Ohm load, it seems to be mainly useful for checking the horizontal sweep time base and the linearity of the time base. I do not have any figures for the accuracy of the "pyramid" waveform, but it does give an indication of the linearity of the vertical amplifier, in addition to the time base.

For my limited application, it does seem to be useful, and at least it does give me some confidence in my own equipment for my limited purposes. Anyone else have any information or commentary on what certainly is at least a useful small portable checking device for an oscillograph or oscilloscope?

(3.) For my checks of the vertical amplifier, I can use a variable voltage DC power supply monitored by a John Fluke 885A DC Differential Voltmeter. That should be enough in looking at an oscillograph CRT screen to work with the limited resolution of my long out of calibration eyeball.

(4.) There is a Tek Type 105 here also, but clearly it is "well out of calibration" by now. Assuming that it is still somewhat linear, at least it does show that my vertical amplifiers are still working, and there is an obvious and approximate step change in the vertical trace as a function of the voltage selected.

For my purposes, the main utility for my collection of Tek oscilloscopes is in looking at the shape of a signal or waveform.

Finally, I do have some calibration references around here that do give me some confidence in what I am doing. I cannot claim to have any "calibration standards" here, because I know what that implies. Normally the best accuracy that I will claim is limited to about four (4) significant figures. For almost all of my work now, that is certainly enough for those tasks. For frequency I can go out quite a bit more. That is a little easier.

Enjoy, and 73;

Ralph Javins, N7KGA
Latte Land, Washington

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