Quote:
Originally Posted by Pinörkel
Does anybody here know what exactly these modules do or how to calibrate without using these modules? I do not expect that any of these calibration fixtures are still available.
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One way to set up most of the attenuator settings is initially to terminate the input with a 50R terminator on a T connector. Feed a perfectly rectangular pulse in (I use the Tek PG506 generator). On max sensitivity the attenuator is bypassed, and you can set up the frequency compensation components in the vertical amplifiers for a flat response, with at least 70 to 80% deflection on the CRT. After that, you start to increase the attenuation and increase the drive amplitude. As each section of the attenuator kicks in, you can adjust its compensation capacitors (sometimes resistors too) for a flat response until you have done them (all but one) up to the minimum sensitivity on the attenuator knob.
The effect of the input adjustment capacitor immediately on the scope's input then comes into play when the 50R terminator is removed and you plug on your scope probe. (When the 50R was there its effects are largely deactivated).
Generally the resistance there is 1Meg and the parallel capacitance around 10 to 15pF depending on the probes it was designed for. This is where a normalizer box would be used to normalize the response for some intended probe.
One quick way around this (without a normalizer box) is to just match the probe to a similar scope's input R & C values, by setting up a x10 probe's compensation adjustments (on another scope in your workshop with a similar bandwidth), then transfer the probe and adjust the scope's input compensation capacitor at the attenuator input to match that probe. Then of course that probe is ready to use on more than one scope in your workshop without having to re-tweak its compensation capacitor when you use it on different scopes, which is one advantage to not doing it with a normalizer box. So one of your scopes becomes the "normalizer"