Minor deviations within a percentage tolerance are allowed, of course. The allowed deviations for the various test methods are stipulated in our calibration forms.
These are high-precision calibration resistors with a high temperature stability and endurance. All calibration resistors for high test currents are installed in dissipators. Therefore the heat that occurs at high test currents as well as long-term measurement can be well dissipated. This is a pre-condition for a good temperature stability. In addition to these good characteristics the resistors are designed with low capacities and low inductances.
All resistances for high test currents and low test voltages are designed in four-wire-technology. This means that they have a separated current and voltage path. Thus the resistors can be used as high-precision shunts. The flowing current is calculated via a voltage-drop-measurement by means of the external calibration measuring device. Only this guarantees the optimum application as calibration resistor.
The resistors are installed in 4-wire technology in a dissipator. Microhm Electronics' MVR2321-4, MVR3825-4, MVR4618-4 are typical 4-terminal calibration resistors. Two connections are for the current input and two for the voltage-drop measurement. 4mm safety plugs as well as free lead ends can be connected. The highly-stressable calibration resistors are used to run and to calibrate the PE-resistance test. Depending on the model, the resistances are intended for 10A- or 30A continuous current.
