Choosing the Right Ground Resistance Testing Equipment
There are many ground resistance testers available from various manufacturers, and while it may be tempting to just buy the cheapest ground resistance tester available, it can very often be a very false economy. With a wide range of functions and specifications, it can sometimes be difficult for the end user to decide why certain types of testing require different functions and why some instruments are capable of achieving far better results than others.
For some users, a two pole or three pole ground resistance tester is quite sufficient for their needs as they may only be required to test existing earth installations. For other users, a four pole machine is essential, especially if undertaking design or testing on new installations, where soil resistivity is required to be measured. For this kind of ground resistance testing, a method known as The Wenner Method is normally used, although the Schlumberger method can also be employed if required. The Wenner Method of ground resistance testing can only be achieved by using a four pole ground resistance tester. Some of these testers can also calculate soil resistivity automatically, eliminating the need for the soil resistivity to be manually calculated. Finally, some ground resistance testers, such as the AEMC 6471, the AEMC 6472 and the Sonel MRU-200 are multifunction units, which means that they can undertake all of these tests from a single instrument. In addition to the standard tests, undertaken with earth stakes some of these ground resistance testers can also employ the two clamp method of ground resistance testing, which eliminates the requirement to disconnect the earth and is fast and simple. However, care should still be taken when using the two clamp method of testing, as it is not suitable for all electrical installations.
While a number of manufacturers have ground resistance testers in their product line up, we primarily distribute ground resistance testers from AEMC and Sonel. the reason for this is because the current output from these instruments is superior to many other brands, and while this may seem like a trivial matter, it is arguably the most important feature to look for, especially with the ground conditions in many parts of Australia being dry and rocky, which tends to make the current generated by the ground resistance tester of paramount importance. Too small a current will prevent the meter being able to get a meaningful reading, or in fact any reading at all in some cases. Both AEMC and Sonel ground resistance testers can generate a test current of 200mA and above, and this will allow a more accurate reading to be obtained in a range of different soil conditions.
The most popular model, the AEMC 6471 is supplied complete in a ground testing kit with leads and spools, twin clamps, software, earth stakes and everything required for testing in Australian conditions. This is the kit which we are asked for more than any other and with very good reason. The AEMC 6471 is a 250mA ground resistance tester, which works well here in Australia and it is capable of performing all types of ground resistance testing, which means that you can select which test is best and utilise the 6471 to undertake any of these tests. With the AEMC 6471 or the Sonel MRU-200 there are no types of ground resistance tests that these units cannot perform, so whatever the conditions, you can be confident in having a ground resistance meter that will enable you to be able to undertake testing in more or less any conditions.
Here at Test Equipment, we can advise on any aspect of ground resistance testing, including product selection and application. We are happy to train customers on any aspect of using one of the ground resistance testers which we supply, so please ask us and we will be more than happy to assist you to the best of our ability.