Indicating the conditions of the insulation of electrical networks and equipment is an important element for ensuring efficient protection against electric shocks. Recently, the company, SONEL S.A., has been working hard on the development and production of state-of-the art devices for such testing. A number of models with test voltages up to 5 kV and to 10 kV have been implemented. Due to extended measurement functions and immunity to electric fields and other interferences, they are one of the leading products used in professional power engineering for complex and advanced insulation resistance testing. Common insulation resistance tests carried out in receiving end of the electrical grids do not require such extended measurement functions, as this leads to an increase in the overall dimensions of the device. Therefore, with a large group of electricians in mind who test receiving end electrical systems in the broadly defined municipal infrastructure, industries, office buildings or private housing – Sonel MIC-2501, a new insulation resistance tester has been designed and launched onto the market.