Pole-zero PZ cancellation

Connect the UNIpolar pulse output to the oscilloscope. Check that the oscilloscope is DC coupled. 

Now adjust the PZ screw control or controls so that the trailing edge returns to the baseline with no undershoot or overshoot. It is easier to do this from the overshoot situation, that is, the pulse tail dipping below the baseline the adjustment from this position is made by turning the screw clockwise. Some amplifiers have separate coarse and fine controls of PZ some, such as the Tennelec 245, have LEDs indicating the direction of the adjustment. 

There are three ways in which this adjustment can be made. 

This method, similar to the method above bnt nsing a square wave instead of detector pulses, is said to be more sensitive. Consult the amplifier manual for details of how to apply this method. 

A few more recently introduced amplifiers allow an anto-matic PZ cancellation simply by pressing a bntton on the front panel. No oscilloscope is needed bnt, if one is available, examining the amplifier output wiU allow the user to watch the correction as it happens. The anthor, notoriously sceptical of automatic procedures, has been pleasantly surprised by the accuracy of such corrections  

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