| The Directional
Impulse Detector ( D.I.D.) is a compact handheld detector used to locate
primary cable faults by sensing the magnetic field generated by the current
pulse from a high voltage discharge device (thumper). A meter deflection
indicates the intensity of the received signal. No deflection indicates
that you have walked beyond the fault or away from the cable.
The high sensitivity of the DID reduces stresses to the cable by locating the fault while thumping at the minimum voltage required to flashover at the fault. It is particularly effective on shorted faults that produce no audible response and in noisy environments.
The DID saves time since manholes do not need to be pumped prior to fault locating. It is powered by a standard 9v transistor battery.
The DIRECTIONAL IMPULSE DETECTOR employs a voltage gradient measurement technique to accurately pinpoint primary cable failures. The output pulse of the "thumper" used to locate primary cable faults developes a voltage gradient in the earth between the cable fault and the "thumper" ground return. Because of the unique design of the input circut, the DIRECTIONAL IMPULSE DETECTOR is able to detect low energy pulses from "thumpers" through primary ground faults. This allows you to "thump" cables at lower voltages avoiding higher voltages which put the cable at risk of further damage.
The voltage gradient signal is received through an antenna connected to the detector by a 2 foot sheilded cable. The detector contains dual differential amplifiers which produce a meter deflection indicating the relative position of the antenna to the cable route and fault. Since the detector senses the voltage gradient in the earth, holding the antenna perpendicular to the earth will allow you to follow the cable route and indicate which side of the route you are on by the meter deflection.. Continuing probing along the cable route until the signal weakens or a null (no meter deflection) is located indicates you have passed the fault. Back up slowly until the meter shows an indication and you are at the fault location.