Amphenol Temposonics MH Series Посібник з експлуатації - Сторінка 14

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Temposonics

MH Analog

Operating Manual

5.3 Insulation checks

Part of the testing performed on off-road mobile machinery can be insulation checks. During these checks, high voltages are applied to deter-

mine the dielectric strength of the cables against the housing (insulation resistance). For testing, all connecting cables must be disconnected

from the sensors. Otherwise, stray voltage flowing through the sensor protective circuitry against ground can cause damage or failure of these

components and of the sensors.

5.4 Welding

After installing the cylinder in machines, welding work on adjacent components can be necessary. If a grounding tong is

applied directly or too closely to the cylinder, welding currents can be transmitted to the sensor via the cylinder and cause

burning of the sensor pipe or damage of internal sensor components. Cylinders mostly consist of two assemblies: the lower

part with the cylinder pipe (Figure, shown in dark gray) and the piston with the piston rod (light gray). These components are

isolated electrically from each other by gaskets, bearings and slide rails. This means that, normally, no current flow is pos-

sible. With cylinders, however, the welding current may be transmitted from the piston to the cylinder pipe. In this case, an

electrical connection causes the entire welding current to flow through the sensor pipe and the sensor head, thus damaging

the electronics. Moreover, the cylinder and/or the gaskets are destroyed.

For this reason, the instructions given below must be followed:

• Cut or disconnect all sensor connections during welding.

• Never fasten the grounding point at the piston rod or at the cylinder pipe.

• Never perform welding work on a part of the cylinder, if a sensor has been installed.

• Never perform welding work near a cylinder, if a sensor has been installed.

• Due to isolating bearings, plastic slide bearings or grease in the contact points, electric potentials/voltages can build up at

every bearing point of machines. Accordingly, similar effects as on hydraulic cylinders can be produced.