AL-40 ALUMINOTHERMIC WELDING TESTER

Micro ohmmeter Welding Joint Tester

AL-40 Micro ohmmeter. Joint Tester.
The AL-40 allows a precise and easy quality control of aluminothermic welded joints. 
The instrument measures the electrical resistance resulting of the fusion of the welding with the conductors. 
The advantage of this method is that it gives a measurement and not just a visual appreciation.
The AL-40 is equipped with a probe designed specifically for aluminothermic welding, and that uses the four-points measuring method. This technique consists of injecting a known current through two current contacts, then to measure the voltage with the help of two voltage contacts placed in between.
Measuring an aluminothermic joint
The AL-40 takes a measuring automatically as soon as the four contacts are pressed against the
welding.

The electrical resistance value of a good aluminothermic welding is around ten micro ohms, and the difference between a good and a bad welding can be as low as one micro ohm. 

The accuracy and resolution of the tool used to perform such a measuring are then very important, in order to be able to make the difference. Plus, these joints are welded in the field, so it requires a tool that is portable and easy to use.
The AL-40 is alone in this category.

A unique probe
The AL-40 is equipped with a probe designed specifically for aluminothermic welding, and that uses the four-points measuring method. This technique consists of injecting a known current through two current contacts, then to measure the voltage with the help of two voltage contacts placed in between. The current is read as well, to eliminate the contact-resistance factor. 
The instrument is also equipped with a microprocessor that eliminates offsets and parasite voltages. 
Thanks to its unique filtering system, the AL-40 can be used in presence of intense magnetic fields.

Quality control of aluminothermic welding
The quality of energy and grounding networks joints is of prime importance for the companies who produce or use high power electric energy (power plants, substations, railways, aluminum foundries, etc). A bad quality joint provocates a decay of the network’s performances, that soon translates into excess of maintenance. The traditional method to check aluminothermic welding used to be a visual inspection, but this method is now considered ineffective because a lot of factors escape to this type of control: conductors oxidation, insufficient preheating temperature or traces of humidity can all result in a solid, good looking welding which resistance value is still too high. 
Measuring the resistance value of such welding with the AL-40 enables you to make the difference.

Quick and easy measuring

The measuring is done automatically when the probe is pressed against the welding.
Once the AL-40 has detected the presence of the four contacts, the result is displayed instantly. 
Additional measuring can be made by lifting the probe and pressing it back against the welding.

Technical specifications
Four points measuring method