3M 2550 Manuale Utente

 22 

78-9000-0192-2 Rev C

 

− If the continuity of the circuit is very good (the reading on the display is less than 

3K Ω. and a solid tone from the transmitter is heard) all frequencies can be used to 

locate. Always use the lowest frequency available (for example, 577 Hz). Lower 

frequencies are less likely to ‘bleed over’ to other cables in the same area, and are 

very good for tracing over long distances.

 

− If the circuit reads more than 3K Ω., but less than lOK Ω (indicated by a beeping 

tone from the transmitter) it will be necessary to use a higher frequency than 

577 Hz in order to locate the cable/pipe.

 

− If the circuit reads more than lOK Ω., it will be necessary to use an RF signal such 

as 33 kHz, 82 kHz or 200 kHz.

 

− If there is no tone and the transmitter indicates that there is an open circuit (OL 

in the display) this could be an indication of a poor ground, or an open-ended 

cable or pipe. Use one of the higher frequencies available, at high or maximum 

output power level. If it is an open-ended cable or pipe, the receiver's response will 

decrease suddenly at the site of the clear or severed end.

and volts. When displaying ohms, the flag over the Ω symbol will be visible. When 

If a high AC voltage is detected, a rapid beeping tone will be heard.
•  Press Trace [T-3] repeatedly until the desired frequency appears on the display. Note 

that the number that flashes alternately with the selected frequency is called the 

relative current. This number can be useful in identifying the target cable/pipe and 

is discussed more in 8. Depth and Current Estimate and 10. Locating in Directional 

Peak Mode.

•  Press Output Level [T-5] to select high, or maximum, output power level for longer 

tracing distances or deep pipe/cable.