These sensors are used to amplify the very low level PD signals and transmit them via coaxial cable to the Model 831 and Model 832B units. The 834B is a split core high frequency CT with 66mm window. For transformer testing a good choice is the 835B ultrasonic sensor which has a strong magnetic base capable of gripping the steel tank of the transformer.
Rejecting spurious signals is important when performing PD tests, and for this purpose we have the 836B noise sensor. This sensor picks up and amplifies ambient electrical noise with its aerial, and the signal is then sent to the 831 or 832 so they can discard any apparent PD which occurs at the same time which may be due to noise.
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