More cables, the better?
Resistance measurement is a special challenge. As you know, there is no method of direct measurement of this parameter, so you need to use the so-called indirect measurement through determination of the values of the voltage drop that occurs when the flow through the test the current element with a given (known) intensity, it's easy to calculate the resistance value using the immortal Ohm's law (R = U / I). That's the theory – but practice, as usual, some surprising nuances. So, in the case of very small values of resistance (e.g., ground loops), i.e. of the order that the maximum individual ohms measurement is strongly perturbed, the resistance of the wires of the multimeter and pin probes (electrodes) with the conclusions of the element. Therefore, the more expensive measuring earth resistance and devices laboratory uses a method czteroprzewodową in which two wires are for the "flow" of the nominal current, and the other two "collect" voltage drop directly from these conclusions.
Testers and parameters LC
In this category you will find several interesting offers devices, which are ideal in measurements performed both in the home and in the field. Measuring resistance and capacity unit type UT601 allows accurate resistance measurement in the range from 20? to 2 G? and the capacity ranges from 200 PF to 20 MF. In addition, it offers the function to check bipolar transistors (NPN/PNP), voltage and conductivity of semiconductor diodes and detect short circuits and interruptions (buzzer). In turn, resistance meter UT602 inductance and offers similar features, with the difference that instead of the capacity measures the inductance in the range of discharges from 2 mH-200 H.
Testers of insulation and grounding
Resistance meter unit type UT526 provides a measurement of loop resistance short-circuit method two-wire system in the range of from 0.01 to 2 k?, and the accuracy of measurement small values at the bottom of this compartment provides the calibration function (by shorting between the probes before the measurements correctly). In turn, the measurement of ground resistance can be performed through high-voltage tests – UT526 the meter provides voltage for testing ranges: 100 V, 500 V and 1 kV, which allows to make measurements in the range 50 k? up to 500 M?. The device allows, in addition, voltage measurement DC and AC (up to 440 V) and frequency (20 ~ 100 Hz).
