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LANGER
EMV-Technik
DE-01728 Bannewitz
[email protected]
www.langer-emv.de
E1
Figure 8: S31 sensor with an IC mounted (top) and without IC (bottom).
Pulse stretching
Which fast transient disturbances the S31 sensor of the E1 can detect depends on the IC mounted. The
pulse widths of these disturbances may be in the nanosecond range. Due to the low limit frequency of the
optical system (5 MHz), such short disturbances cannot be transmitted. A pulse stretching circuit which
stretches short pulses to 100 ns is integrated in the sensor. The optical fibre is then able to transmit these
pulses. Neither can the optical system of the sensor transmit frequencies above 5 MHz. The same sensor
circuit reduces frequencies > 5 MHz to 5 MHz.
Without this circuit, the optical system would not be able to transmit anything. It would assume a high or low state.
The circuit ensures that fault states are transmitted from the device under test.
2.3.1
Principal mode of operation of the sensor
The sensor is integrated in the device under test and connected to the line of interest. A three-pole socket
(included in the scope of delivery) is glued to the device under test with super glue in the immediate
vicinity of the interesting signal line, if possible at the input, and wired with a short CuL wire; the ground, 3-
5 V voltage and sensor input are also wired before the sensor is connected (Figure 9). The wiring should be
short and laid directly on the module's surface so as to prevent the formation of loops where magnetic or
electric fields could couple in.
The S31 sensor is supplied with a 3 to 5 volt voltage from the device under test. If this is not possible, a
battery module can be used (not included in the scope of delivery).
Figure 9: S31 sensor connected to an IC in the device under test, for example, via a three-pole socket.
ICs which have been damaged
during the measurement can be
easily replaced.
