The echo pulse-generator has prevailed far beyond just the ignition. Without being prone to breaking down, it creates in a simple manner, an RPM and rotational position detection, of course without friction or any form of wear and tear. However, in contrast to the inductive pickup, it requires a voltage supply, thus, it is a passive sensor, which makes it metrological and somewhat more complicated to manufacture.
The echo-IC receives its tension supply, and delivers the 'echo- voltage' through its three connections. This, however, only if the path of the magnetic force lines to the IC is unrestricted. There, the electrons are diverted from their usual path and generate a voltage on the control circuit (green). However, should the metallic screen be positioned between the magnet and the echo-IC, the voltage drops to zero. As can be seen in the above animation, in contrast to the inductive pickup, a rectangular signal develops. The above illustration shows a segment rotor with a magnet on its left inside and the echo-IC on the outside.
Test- and measuring conditions in a TZH-system
Under no circumstances may the echo-pickup be measured using an Ohm-meter, because even this voltage can be too high.
The voltage supply of 5 V can be measured on the two outside pins of the distributor plug.
The echo-signal can be measured on the center pin of the (connected!) echo-plug using an oscilloscope.
The center pin (signal circuit) is manually clocked to earth. Should a spark jump across, then the following circuits/components are functional.
The measuring of throughflow-, earth- and plus-circuit on the leads, can be carried out with the help of an Ohm-meter.
Active or passive sensor ... There is hardly anything as contradictory as this classification. As far as I'm concerned, it seems unfavourable that from the word go, it is suggested that it is quite clearly, that when dealing with a certain sensor, e.g., a Hall-sensor, it is an active device. The principle is valid, that a sensor which requires a power supply, must be a passive device. Should it itself generate voltage, then it could be described as being active. This is how I understand the following text. There is indeed, also a second definition: If the sensor transfers the signal unprocessed, the definition “passive” is valid. If the signal is processed, e.g., by changing it for the CAN-Bus, it would then be “active”. There is however literature, particularly in the case of the former, where exactly the opposite is maintained …