DE4135381A1 - Level sensor with set of Hall sensors - activates sensors contained in non-magnetic tube using float with mounted magnet - Google Patents

Abstract

The level sensor has a row (5) of sensors (4.1-4.n) arranged in a non-magnetic tube and activated by a magnet (3) which is mounted in a float (2) which moves freely along the tube. The individual sensors each comprise a Hall sensor and control circuit (8) in a modular unit. A counter circuit determines which of the sensors is activated by the magnet. Pref. only one Hall sensor at a time is activated. The sensors are arranged on solid or flexible circuit boards with a separation of 1 to 30 mm. ADVANTAGE - Small spacing of Hall sensors gives increased accuracy.

Description

The invention relates to a fill level sensor a Hall sensor chain in a protective tube made of magnetic neutral material that is actuated by a magnet which moves freely along the protective tube Float located.

In the previously known processes (DE-PS 35 10 198) Electrodes formed from reed switches with contacts be paired with resistors. This makes it possible to generate a resistance signal proportional to the level. Another known arrangement (DE-PS 40 11 858) forms one Electrode, also made of reed switches, each with 8 reed Assigns a shift register to switches.

The known methods have the disadvantage that for Er version of the float position reed switches with contacts be used. These reed switches are subject to wear subjected to mechanical vibrations especially in the resonance area of the contact blades due to their glass tube structure, the tendency to break glass and allow only a minimum in the reed switch electrode distance of 5 mm. Hence the accuracy of the reed switch electrode.

The purpose of the invention is to overcome the disadvantages of the reed switch Switch off electrodes and especially the measuring accuracy increase.

This solves the problem on which the invention is based solved that to detect the float position Hall Sensors consisting of Hall switch and integrated Control module at a defined distance on one Carrier material arranged and together to form an electrode be switched. With a periodic counter circuit is determined which Hall switch by the Magnet of the float is actuated. Through the hall control modules assigned to switches is guaranteed that the Hall switches are queried one after the other. The advantage of the invention is that the Hall sensors in  a distance of 1mm and possibly smaller can, resulting in a high measuring accuracy of the arrangement results. Thus, the use is also for the "calibrator Traffic "is also possible. In addition, all other traffic will also be reduced parts of the reed switch electrodes removed. Through the absolute digital data acquisition is not a comparison required. Ensure the switching of the Hall sensor chain ensures that only one Hall switch of the electrode is ever used is switched on. The required operating current is thereby very low.

In an embodiment with the associated undersigned Fig. 1- Fig. 3, the invention will be explained in more detail. It shows

Fig. 1 shows the structure of a Hall sensor with Füllstandsmeßwertgebers chain,

Fig. 2 shows the internal circuit of the patent according to the Hall sensor,

Fig. 3 shows the arrangement of the Hall sensors in a sensor chain.

In Fig. 1 the level sensor is shown, which consists essentially of the junction box 1 , the float 2 with the magnet 3 , the Hall sensor chain 5 and the magnetically neutral protective tube 6 . A Hall sensor 4 is actuated by the magnet 3 .

Fig. 2 shows a single Hall sensor 4 composed of the Hall switch 7, the control unit 8 and the switching transistor 9.

The operating principle of the Hall sensor is to chain 5 will be explained consisting of n Hall sensors 4.1, 4.2 to 4 .n reference to FIG. 3.

At the start of the query, the control units 8 of the Hall sensors 4 are reset by means of the H level on the reset line. Since the data input D of the first Hall sensor 4.1 is connected to the reset line, the logic "1" of the reset line is transferred to the output Q _{D of} the first control unit 8 by a pulse of the clock line, while the following control units are still blocked by the reset signal. Due to the L level at the inverting output of the first control unit 8 , the power supply for the Hall switch 7 in the Hall sensor 4.1 is switched on via the switching transistor 9 . After the level of the reset line has changed to logic "0" corresponding to the L level, the control units are no longer blocked. With the next pulse on the clock line, the logical "1" that is still present at the output Q _{D of} the first Hall sensor 4.1 is switched through to the output Q _{D of} the control unit 8 in the Hall sensor 4.2 and the L level at the inverting output switches the power supply of the Hall switch 7 in the Hall sensor 4.2 . The logical "0" of the reset line with the system-related delay time of the control unit 8 is switched through to the output Q _{D of} the first Hall sensor 4.1 by the same clock pulse and the switching transistor 9 switches off the power supply of the Hall switch 7 in the Hall sensor 4.1 .

With each clock pulse, the next Hall switch 7 is activated and the previously active one is switched off.

An external magnetic field acts on a Hall switch 7, an output transistor of the Hall switch 7 pulls the common Q _S -Leitung to "1" when the driving unit 8 through the power supply of the Hall switch 7 is turned on. The position of the magnet 3 is determined by counting the clock pulses until an L level appears on the Q _{S line} . The length of the sensor chain 5 is determined by counting the clock pulses until the logical "1" appears at the output Q _{D of} the last Hall sensor 4. n.

If the Hall sensors 4 are arranged at regular intervals, the sensor chain 5 can be used as an electrode for digital length measurement.

Reference numerals

1 junction box
2 swimmers
3 magnet
4 Hall sensor
5 Hall sensor chain
6 protective tube
7 Hall switches
8 control unit
9 switching transistor
+ V _S line supply voltage +5 V to +15 V
GND line ground potential 0 V
C line clock
R Reset line
Q _S line common switching output
D Line data input control unit
Q _D Data output line control unit
FF flip-flop function of the control unit

Claims (4)

1. Level transmitter with a sensor chain arranged along the measuring path, which is housed in a protective tube made of magnetically neutral material and which is actuated by a magnet which is located in a float which is freely movable along the protective tube, characterized in that the individual Sensors ( 4.1 to 4. n) of the sensor chain ( 5 ) are formed from a structural unit comprising the Hall switch ( 7 ) and the control unit ( 8 ). 2. Level transmitter according to claim 1, characterized in that it is determined by a counter circuit which of the sensors ( 4.1 to 4. n) of the sensor chain ( 5 ) is actuated by the magnet ( 3 ) of the float ( 2 ). 3. level transmitter according to claim 1 and 2, characterized in that only one Hall switch ( 7 ) of the sensors ( 4.1 to 4. n) of the sensor chain ( 5 ) is activated. 4. level transmitter according to claim 1 to 3, characterized in that the sensors ( 4.1 to 4. n) of the sensor chain ( 5 ) can be arranged on rigid or flexible printed circuit boards at intervals of 30 mm to 1 mm.