Check that the spigot around the sensing aperture of the JCI 140 is properly engaged into the hole in the baseplate of the Voltmeter unit and sits fully up into the mounting hole. The JCI 140 may be easily removed from the unit by depressing the spring supporting fingers either at the front or by the lever extension at the back. If a spark breakdown occurs the discharge current may be quite large and will contain very high frequency transient signals. These could cause damage or interference. After earth bonding the high voltage connector may be inserted and connected to whatever source is to be tested.
Care needs to be taken about the selection and routing of the high voltage lead.
The lead should have a suitably low leakage dielectric covering and have sufficient dielectric strength to avoid electrical breakdown to the highest voltages which may occur. None the less it is wise to route the lead away from other equipment, instruments and earthy surfaces. It is also desirable to avoid any rubbing of the cable against surfaces and to minimise any flexing. These actions are liable to generate static charges on the outside of the cable and this can couple into the connecting lead and degrade the quality of observations. JCI 140 and JCI 140F instruments may be used with an external power supply for long term continuous monitoring observations.