Pearson Electronics, Inc. Capacitive Voltage Divider VD-500A

The Model VD-500A capacitive voltage divider is intended for the measurement of voltage amplitude and wave-shape of ac signals at high potential. It has a nominal division ratio of 10000:1, and the exact measured ratio is printed on the name-plate. This ratio is measured in insulating oil at 35oC, and is accurate to ±5%. The division ratio is temperature compensated to ±1% over the range of 20o to 80oC. Calibration for other ratios or for use in air is available from the factory for an additional charge. The unit consists of two capacitors connected in series. The high voltage center electrode forms a capacitor with a guarded pickup ring located in the lower metal cylinder. This pickup ring is connected to the center conductor of the output connector via a 50ω resistor. The low-voltage capacitor connects the pickup ring to the outer conductor of the connector. The output voltage is thus a fraction of the input voltage determined by the ratio of the capacitances. Typically, the divider is placed in high-voltage insulating oil, such as Shell Diala AX, along with other components of the high-voltage circuit being measured. The case has drain holes to allow oil to enter or drain out as the unit is inserted or removed from the oil bath. The standard calibration is for use in oil, which has a dielectric constant of about 2.3. If the unit is used in air, its division ratio will be approximately 23000:1, but if this is the intended use, a factory calibration of 10000:1 in air would be more accurate and desirable. The maximum pulse voltage rating for use in air is 90 kV. These ratings are for pulses up to 5 µseconds duration. Consult Pearson engineering for voltage derating for longer pulses.