This instrument may look like one form a DIY shed, but it is not.
The testers used for trouble shooting & fault finding are very specialised
and require knowledge & skill to use correctly.

WARNING: Do NOT operate anything electrical with the internal workings exposed.
Lethal voltages are present and IT COULD KILL YOU.

Special instruments like this are required to measure the low (and high) resistances found in electrical circuits.
The instruments themselves cost about the same as a high end laptop and need to be calibrated at least once a year to ensure accuracy. The cost of calibration is much higher than the cost of a cheap tester from one of the DIY sheds! When we issue certificates for nearly all electrical work, the serial number of the instrument used is noted on the certificate.

Another special instrument with it's own calibration certificate.

Another test in progress.

The fault can be complicated to find, or fairly obvious as in this case.

In order to find a broken cable buried in the wall or under the floor without dismantling the whole house, it is necessary to use advanced equipment and non destructive test techniques. This collection of test gear consists of two wireless transmitters, tuned to different channels connected to either end of the broken cable and a hand held receiver. The receiver is used to follow the signal from one end of the cable until the receiver detects the transmission from the opposite transmitter. The point where both transmitters can be detected indicates the location of the fault.

"X" marks the spot!