[en] This report describes a method for testing neutron sensor response time to meet the provisions of ISA S67.06, IEEE Std 338-1977, and NRC Regulatory Guide 1.118. The method requires the perturbation of the high voltage from the power supply to the neutron sensor and measurement of the signal response from the sensor. The method can potentially be applied on-line, does not require reactor shutdown or other interference with plant operation, does not require installation of special sensors, and only minor sensor modification. The high voltage perturbation method uses a mercury-wetted contact relay switch (designed and constructed in this study) to turn on the high voltage bias to the sensor in less than 10 nanoseconds. This provides an effective step and facilitates measurement of the sensor step response. Evaluation of the technique was made through simulated detector and cable degradation. The boron lined chamber response was investigated for two different fill gases: nitrogen (i.e., normal fill gas) and xenon. The fission ion chamber response was investigated for a sensor in a normal state and one with known failure of the seal between the chamber and signal cable