Special Applications; When To Use 8 Khz Vs. 33 Khz Frequency; Locating Non-Metallic Pipes And Sewer Lines; Taking Depth And Current Measurements - Amprobe UAT-600 Serie Mode D'emploi

4. SPECIAL APPLICATIONS

4.1. When to Use 8 kHz vs. 33 kHz Frequency

As a general rule, 8 kHz will provide the best compromise between clarity of signal and effects of "bleed off" to
other services. However, there are times when the higher 33 kHz frequency will be beneficial:
1. Locating pot ended cables: Pot ended cables are generally not grounded. This means that the signal will
not readily travel to the pot end. Using a higher frequency will encourage signal current to flow.
2. Small diameter cables: Higher frequencies tend to flow better on small diameter cables, although the rule
"first try 8 kHz" still applies.
3. Locating old cast iron pipes: These pipes tend to have mechanical connections between sections which rust
over time and prevent an electrical connection between pipe sections. The 33 kHz signal will tend to jump
across these joints and continue down the line.
4. Poorly grounded cables: Generally, higher frequencies will travel along a poorly grounded cable better than
lower frequencies.

4.2. Locating Non-Metallic Pipes and Sewer Lines

The UAT-600 locator can indirectly trace non-metallic conduits and pipes.
1. Insert fish tape or wire inside the conduit or pipe. For sewer lines, use the sewer drain cleaning machine to
insert a cleaning cable.
2. Follow steps as described in the Direct Test Leads Connection Mode – Tracing an Individual Pipe or Cable
section 3.5. Connect the red test lead to the fish tape or the drain cable.
The Receiver will pick up the signal conducted by the fish tape or wire, indicating the location of the non-metallic pipe.

4.3. Taking Depth and Current Measurements

Depth and current measurements are only available when the
Receiver is set to 8 kHz or 33 kHz frequency. The mode is NOT
available in 50/60 Hz or Radio Modes.
To take a depth and current measurement, first pinpoint the
position of the line. Place the tip of the Receiver on the ground
making sure it is vertical and across the line. Press and hold the
" " button until the screen changes to display a dialog box.
The current measurement feature is useful for confirming that
the detected signal is radiating from the traced line. If the signal
is "bleeding off" onto other services, the resulting signals will
generally be less than that of the originating signal. However,
care should be taken as the signal current will gradually reduce over the length of the line. A sudden drop in
current over distance indicates that either:
1. There is a ground fault on the line which is shunting signal to ground.
2. There is a "T" off from the mainline.
3. The operator has migrated from the connected line to a line which has some signal that has bled off from
the main line.
Checking for depth errors due to signal distortion
One way to determine if the depth measurement is likely to have been affected by distortion is to take a depth
reading at ground level, then raise the Receiver a known distance off the ground (such as one foot). Retake
the depth reading at the new depth and confirm that the depth has increased by this amount. If the depth has
changed by something other than the actual change, then the readings should be treated as suspect.
Distorted signals will cause the located line position to be displaced from the actual position. The errors are
more pronounced using the arrows in Null Mode than the Peak Mode bar graph. Hence, if the arrow/null
position and peak bar graph position indicate differently, the signal likely distorted and the readings should be
treated with caution.
�WARNING
Never mechanically dig over the path of a buried pipe or cable. Always dig carefully.
8kHz
33kHz
50Hz
Radio
18
262
3'11"
3.45mA