Rent, buy or lease CISPR 16-1-2 High impedance and capacitive voltage probes. The EMC Shop stocks calibrated test equipment for radio disturbance and immunity measuring.
Figure 6 shows a circuit which is used to make voltage measurements between a mains conductor and reference ground. The probe consists of a blocking capacitor C and a resistor such that the total resistance between line and earth is 1 500 Ω. The probe may also be used to make measurements on other lines and for certain applications its impedance may need to be increased to avoid excessive loading of high impedance circuits. An inductor may have to be connected across the input of the measuring apparatus, for safety reasons; its inductive reactive, Xc, to be much greater than R.
The capacitive voltage probe is used for measurements of conducted disturbances in the frequency range 150 kHz to 30 MHz with an almost flat frequency response in the frequency range of interest. The voltage division factor, which is defined as the ratio of the disturbance voltage on the cable to the input voltage at the measuring receiver, depends on the type of cable. This parameter should be calibrated over a specified frequency range for each cable type, using the method described in Annex G.