The transmitter is the most misunderstood piece of equipment that a locator operates in his day to day work. The transmitter determines quality and strength of a signal, which can either work for you or against you.
If the unit is hooked up incorrectly or the earth-stake is placed in an incorrect position, this may affect the quality of the signal and make it difficult to locate or even confuse the operator.
Another major factor in performance is your earth return; the better the earth return, the better the signal going out and the further you will locate. All these factors can work against a locator.
An understanding of basic electronics helps explain what a transmitter does. Ohm’s law states that the current through a conductor between two points is directly proportional to the potential difference across the two points.
When using a transmitter you are creating a circuit and your transmitter is the power source for the signal to be pushed down. In any circuit you have resistance; resistance is determined by the type of cable and type of ground and is a factor that a transmitter has no control over.
Current
Current, or Amps and Voltage, is controlled from your transmitter. The amount of current that can be pushed through a cable is determined by the resistance in the cable and voltage is how hard the transmitter is working to push the current out through the cable.
Wattage
Wattage refers to the rate of power the transmitter has to do its work and is determined by the manufacturer, hence there are standard one, three, five and ten watt transmitters in the industry. Don’t base assumptions of quality solely on wattage, quality of components has a lot to do with how much power and current a transmitter can push through a pipe even at high resistance. To relate this to car engines, you have two factors that relate to performance, power and torque. Some engines can have equal power but one engine might have half the torque and would struggle more with heavy loads than the motor with more torque. One significant factor that is always overlooked is how much power can be output on a pipe due to the resistance – sometimes a 10 watt transmitter is no better than a 1 watt transmitter in these circumstances.
Frequency
Having the right frequency can assist with improved location. Frequencies can affect what type of signal is output and capacitance abilities of the frequency; generally high frequencies 65 kHz-200 kHz
tend to have higher capacitance ability and will jump off the cable or pipe quicker, medium frequencies of 8 kHz-51 kHz are good all-rounders and will travel further than higher frequencies and low frequencies are normally the best – around 500 Hz-4 kHz – but will only work on the right cable or pipe due to the low capacitance abilities of these frequencies and because they require a good earth return.
For companies that already have locators and would like to learn more, NULCA have a fully accredited, industry-standard, two day course that covers transmitter theory and practicality. NULCA will soon be introducing a one day, in-depth practical course in the first quarter of 2013 for new or infrequent users; this course would also be an excellent option for operators who may have never had formal training from experienced trainers. The course will be practically-orientated and teach the user the correct use of transmitters.
For more information visit nulca.com.au.