# Precision Measurement

Smallest resistance to measure less than the resistance of the measuring terminals themselves – a challenge! Each connection has a resistance! Micro Ohm meters are designed to measure the ohmic resistance in very low. The error of measurement, which only occurs through insertion of a measuring system must be considered when measuring small resistances. A 4-wire measurement a remedy here. A micro ohm meter is a measuring instrument with the smallest resistances can be measured, for example to measure the resistance at switches, relays or screwed connections, as well as the conductivity of welding points, but also to the continuity of ring bus systems. The principle of resistance measurement is very simple, the ohmmeter can flow a known power over two lines through the test object and the integrated DC voltmeter detects the voltage drop (hence the name 4-wire measurement method) over two more lines. From these two values is the resistive The unknown resistance calculated Act. An ohmmeter combines power and volt meter in a single housing. With a 2-wire measurement the resistance of the measuring leads is measured necessarily with.

Due to the fluctuating contact resistance in the terminals, the test lead resistance can not simply be deducted from the Messgergebnis! Apart from that, this is generally unknown because of different cable lengths. Determination of very small resistances, this leads to high deviations. It is very clear in the following: the measurement of the resistance of a relay of which 25 milliohms is an ordinary ohmmeter can view 125 milliohms because added the line and contact resistances by 100 milliohms. Using a 4-wire digital micro-ohm meter, 3001, which is available at the PCE Germany GmbH, are for example the PCE-MO eliminates these measuring errors. Here the Prufleitungs – and contact resistance are almost meaningless because two lines, for the power supply and, separately, two more are responsible for the measurement of the voltage drop. The power supply of a constant current source, which defined current value, regardless of the resistance is regulated. Since the volt meter have a high input impedance, the current flowing through the lines, very small and therefore the voltage drop is negligible. Smallest resistance to measure less than the resistance of the measuring terminals themselves – a challenge! Thanks to the 4-head measuring method of micro Ohm meters PCE-MO 3001 can such resistance measurements are carried out smoothly and precisely.