RigExpert AA-230PRO
Time Domain Reflectometer mode
Time domain reflectometers are electronic instruments used for locating faults in transmission lines.
A short electrical pulse is sent over the line, and then a reflected pulse is observed. By knowing the delay between two pulses, the speed of light and the cable velocity factor, the DTF (distance-to-fault) is calculated. The amplitude and the shape of the reflected pulse give the operator idea about the nature of the fault.
Instead of a short pulse, a “step” function may be sent over the cable.
Unlike many other commercially-available reflectometers, the RigExpert AA-230PRO does not send pulses into the cable. Instead, another technique is used. First, R and X (the real and the imaginary part of the impedance) are measured over the whole frequency range (up to 230 MHz). Then, the IFFT (Inverse Fast Fourier Transform) is applied to the data. As a result, impulse response and step response are calculated.
(This method is often called a “Frequency Domain Reflectometry”, but the “TDR” term is used in this document since all calculations are made internally and the user can only see the end result.)
The vertical axis of the resulting graphs displays the reflection coefficient: Γ=-1 for short load, 0 for matched impedance load (ZLoad=Z0), or +1 for open load. By knowing the cable velocity factor, the horizontal axis is shown in the units of length.
Single or multiple discontinuities can be displayed on these graphs. While the Impulse Response graph is suitable for measuring distance, the Step Response graph helps in finding the cause of a fault.
See the examples of typical Step Response graphs:
A short electrical pulse is sent over the line, and then a reflected pulse is observed. By knowing the delay between two pulses, the speed of light and the cable velocity factor, the DTF (distance-to-fault) is calculated. The amplitude and the shape of the reflected pulse give the operator idea about the nature of the fault.
Instead of a short pulse, a “step” function may be sent over the cable.
Unlike many other commercially-available reflectometers, the RigExpert AA-230PRO does not send pulses into the cable. Instead, another technique is used. First, R and X (the real and the imaginary part of the impedance) are measured over the whole frequency range (up to 230 MHz). Then, the IFFT (Inverse Fast Fourier Transform) is applied to the data. As a result, impulse response and step response are calculated.
(This method is often called a “Frequency Domain Reflectometry”, but the “TDR” term is used in this document since all calculations are made internally and the user can only see the end result.)
The vertical axis of the resulting graphs displays the reflection coefficient: Γ=-1 for short load, 0 for matched impedance load (ZLoad=Z0), or +1 for open load. By knowing the cable velocity factor, the horizontal axis is shown in the units of length.
Single or multiple discontinuities can be displayed on these graphs. While the Impulse Response graph is suitable for measuring distance, the Step Response graph helps in finding the cause of a fault.
See the examples of typical Step Response graphs:
