Megger TDR1000 Manuel Utilisateur page 7

As a pulse is transmitted down a cable, the size and shape of that pulse is gradually attenuated by losses in the cable: the pulse gets smaller
in height and more spread out. The level of attenuation is determined by the cable type, the condition of the cable and any connections along
its length. The limit of how far you can see is determined by the point beyond which you will not discern a reflection. To maximise the
instruments range, the TDR1000 has an adjustable gain setting on its input to allow you to discern a reflection from farther away. By combining
this variable gain with increasing pulse widths, the TDR1000 can discern faults up to 3 Km away.
The MEGGER TDR1000 can be used on any cable consisting of at least two insulated metallic elements, one of which may be the armouring
or screen of the cable. The TDR1000 has internal matching networks to allow testing of 25 Ω, 50 Ω, 75 Ω and 100 Ω cables. (These correspond
to power, coaxial data and data/telecoms cable). The instrument can be closely balanced to the cable using the balance control; this allows
long lengths of cable to be easily tested. The velocity factor can be adjusted to match the cable, thus allowing an accurate distance
measurement to be directly read from the instrument. To enable a wider range of faults to be detected, the gain of the instrument is adjustable;
this allows more minor faults to be identified along the entire length of the cable. Other setting options include changing the distance units
between metres and feet, changing the propagation velocity units between a ratio and a distance per microsecond. Display contrast is fully
adjustable to compensate for all viewing conditions. A backlight aids viewing in low ambient light conditions.
The batteries to power the instrument are housed in the compartment on the case back, the cover is held in place with two screws. The batteries
are held in a carrier, which hold the batteries securely, and allow a quick change of rechargeable battery packs. The instrument can be powered
by manganese-alkali, nickel-cadmium or nickel-metal-hydride batteries. All cells must be of the same type.
7