Bill's Tektronix 453 and 454 Info Pages
Probe High Frequency Compensation Adjustment
The probe and input circuit of a scope together form a resistor/capacitor voltage divider, of the form shown to the right. The resistor ratio is 9:1 for a 10X probe (9M ohms in the probe and 1M ohm in the scope input circuit). The scope input also has capacitance to ground. A capacitor is included in the probe, in parallel with the 9M ohm resistor.
In order for the instrument to have the same sensitivity at all frequencies, the impedance ratio of the two capacitors must be 9:1 just like the resistors. (Since impedence goes down as capacitance goes up, we need a ratio of 1:9 for the capacitance values.)
To adjust the attenuator high frequency compensation, connect the probe to the scope's calibrator signal (a 1KHz square wave with a 1 Volt amplitude). Adjust the sweep rate and triggering for a stable display of a few pulses on screen, as shown to the right.
Using a small (ideally non-metallic) screw driver, adjust the compensation trimmer capacitor (usually in the probe connector body). The best adjustment corresponds to the flattest square waves on screen.
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