Introduction
The Cable Distance Meter is a unique, handheld
instrument, primarily used for the measurement of the
height of overhead cables.
The Cable Distance
Meters measure up to 6 cables.
The CDM-50 model measures to a height of up to
50 feet (15m). The CDM-75 model has an increased
range of up to 75 feet (23m).
The unit operates by transmitting an ultra-sonic signal
towards the wires, and measuring the time it takes to
pick up the echo from that signal. It automatically
compensates for the fact that the speed of sound
varies with temperature by monitoring the ambient
temperature using the internal temperature sensor.
The display continuously shows the ambient
temperature reading. Because the temperature sensor
reacts relatively slowly to large temperature changes, it
is necessary to wait about a minute after taking the
meter suddenly from a warm to a cold environment
before taking a measurement, e.g. taking the unit from
inside a warm vehicle to outside.
To make a measurement
1. Select the required measurement units by setting
the switch at the back of the unit to display in feet and
inches (
I
) or meters (
M
).
2. Set the Calibrate switch to the
CABLE
position.
2. Press the
ON
key to power on the unit.
3. Position unit directly under the cable(s) to be
measured.
4. Press the
MEASURE
key to take a measurement.
The distance to the first cable is shown in the
Height
Measurement
location in the display. If there is more
than one cable present, the difference in height
between each cable is stored in memory.
5. Press the
READ
CABLES 1-6
key to display each of
the cable height differences stored in memory (
Stored
Measurements
).
The unit will automatically turn off 3 minutes after the
last key has been pressed.
Hints & Guidelines
Position the unit on the ground, directly underneath the
cable to be measured. Align the unit in the direction of
the cable, with the cone pointing towards the cable, as
shown.
When taking cable measurements, ensure that
there are no walls or buildings within a distance
of 7 feet (2m) on either side of the meter, as
reflections from these will distort the readings.
Also ensure there are no trees or other
overhanging objects in the vicinity.
When measuring more than one cable, ensure
that none of the cables are outside the sonic
beam, as shown in the Performance section of
this manual. If the cables are not vertically above
one another, this could be the case. In this
instance, it will be necessary to take a number of
separate readings from different positions.
Water and moisture can cause the Cable
Distance Meter to malfunction. Therefore, the
meter should not be used in rain or snow. If
water does get into the cone, leave it upside
down in a dry, warm area.
If the display shows - - -.- - -, this indicates a
“poor target” and normally happens when the
cables are moving due to wind, etc. Wait until
the wind dies down to get an accurate reading.
Calibrate Mode
The Calibrate mode switch allows the user to
periodically check the unit to ensure that it is still
operating within specification. For cable distance
measurement, this switch should be in the
CABLE position. When the switch is put to the
WALL position, horizontal measurements to
large objects, e.g. walls, can be taken.
When the unit is first used, a horizontal reading
to an object, e.g. wall, from a fixed position
should be taken. The reading should be entered,
together with the date, into the table below.
Whenever the unit is to be checked for accuracy,
a reading should be taken from the same point,
noting the result and date in the table. If the
reading is outside of specification, the unit
should be returned to HD Electric for calibration.
Date
Reading
