4
5
©2017 SAT-Kabel GmbH
©2017 SAT-Kabel GmbH
The
IRM 20
operates based on the reflections of electric pulses on open or closed cable ends.
These electric pulses are send out in time constant intervals.
The device calculates the length of the cable by measuring the time between the sending of
the impulse and his return.
This depends on the velocity factor of the cable which is considered in the calculation.
The velocity factor (v/c or pulse velocity) declares the propagation of electrical signals in the
cable in relation to the speed of light. It depends on the used type of coaxial cable and can be
found, for example, in the manufacturer's data sheet for the cable in question. Alternatively it
has to be determined "at the place" (locally).
To make work easier the
IRM 20
has a persistent memory with 20 predefined cable types and
their corresponding velocity factors. These can be modified.
3. Functional principle
3. Operation
3.1 Switch on/ off
3.2 Measuring
3.3 Velocity factor
3.3.1 Set a velocity factor
Press the key briefly
Press the Key briefly
Press the key briefly
and change values ongoing
Long press the key
and move the cursor
press an hold key
for 5 seconds …
… until MENU appears
Press the key for
2 seconds
Press the key briefly again
BATTERY INDICATOR
IRM 20
operate
IRM 20
switched of
Without any key pressed the
IRM 20
turns off automatically after 2 minutes to save battery.
If the battery voltage becomes lower than 5,8 V a battery icon appears in the display.
At a battery voltage of 5,5 V the
IRM 20
switches off.
On switch on again the IRM 20 shows the last
used memory entry.
With the IRM 20 switched on press the key
briefly to select a memory entry between P1
and P30.
P0 … P9
P9 … P0
The cable to be measured must be connected only after selecting the required shortening
factor. Then read the length of the cable in the display. If there is a short circuit in the
cable, the cable length appears
>>K<<
in the display.
Notes
!
the velocity factor of the cable has always to be selected before
the measurement of the length
!
if the velocity factor is unknown, choose an approximate value
and determine the fault from both ends of the cable
!
if a terminating resistor is installed which corresponds to the wave
impedance of the cable a length measurement is not possible
(the send pulse will not be reflected at the cable end)
!
to minimize measuring errors determine the cable from both ends
The velocity factor declares the propagation of electrical signals in the cable in relation to
the speed of light. It affects the accuracy of the measurement significant. The velocity
factor is in general:
Electric cable
0,49–0,57
(ca. 0,53)
Telephone cable
0,58–0,65
(ca. 0,62)
Coaxial cable with PE dielectric
0,66
Coaxial cable with foam PE
0,77–0,85
(ca. 0,83)
Air insolation
0,88–0,92
After 8 s display
OFF
PROGRAMMING MENU
MEMORY ENTRY
P0 … P9
1| MEMORY ENTRY ON/OFF
2| VELOCITY FACTOR
(two decimal places 0,xx)
