Amprobe TDR-400 Manuale - Pagina 3

Sfoglia online o scarica il pdf Manuale per Strumenti di misura Amprobe TDR-400. Amprobe TDR-400 4. Impulse reflectometer

The amplitude on the cursor position can be set to the zero line by pushing the keys 1 and

2 simultaneously. Because the IRM 5 has its highest sensitivity in the area of the zero

line, e.g. the graphical representation of the amplitude on the pulse peak can be seen.

This function can be cancelled by pushing the key 3.

- Start mode: If at a determined resolution the keys 1 and 3 are pushed simultaneously,

this resolution is at switch on of the IRM active.

- Charging: Plug power supply 2-24 V DC or AC on the charging socket 5,5 / 2,1 mm (+pole

inside).

Display of the power supply voltage (12-28 V) and charging monitoring on the display.

Propagation factors:

Mains cable

Coaxial cable with PE-dielectric

Coaxial cable with foam-PE

Air isolation

Determination of the propagation factor (nvp-value) of a cable:

Connect a cable of a known length (e.g. 100 m) on the IRM, set the cursor on the cable length

and change the propagation factor so, that the pulse echo is located behind the cursor.

Measuring principle:

The measuring pulse fed into the cable will reflected by in homogeneity of the cable impedance

(cable faults) and showed on the display.

The distance and the kind of the fault can be determined out of the shape and the time setting of

the reflection.

(Practical experience can be obtained by test measurements).

The Propagation factor (nvp-value) declares the velocity of electrical signals in the cable in

relation to the speed of light.

− The propagation factor of the cable under test must always preset before the length

measurement.

− If the propagation factor is unknown, a approximate value is set and the fault is determined

from both ends of the cable

Fault location:

ATTENTION ! No measurement on live cables ! (electric strength max. 65 V)

At 0 m the positive transmitting pulse can be seen. If the connected cable is open on its end, an

additional positive going pulse appears on the display. In the case of a shorted end of the cable a

negative going pulse appears reflected from the cable end (pulse echo).

Adjust the cursor to the beginning of the pulse and read the cable length.

If the cable is terminated with a resistance equal to the impedance of the cable, no reflexion

occurs when the cable is faultless.

0.49–0.57, (ca. 0.53)

0.66

0.77–0.85