Method for adjusting a measuring device for non-contact detection of electrically conductive parts

Abstract

Method for adjusting a measuring device for the non-contact detection of electrically conductive parts (3), wherein the electrically conductive parts (3) are guided through a conveying line (2) which is enclosed by a ring coil (5) which interacts with a capacitor (6) as a resonant circuit within an oscillator circuit (7), wherein the electrically conductive parts (3) cause a detuning of the resonant circuit within the oscillator circuit (7) and thereby events (21, 22) in the form of frequency and / or amplitude peaks, and wherein an evaluation circuit (8) is provided for detecting the events (21, 22) in an output signal of the oscillator circuit (7), wherein the evaluation circuit (8) detects the magnitude of the frequency and / or amplitude peak.compares with at least one switching threshold and, using a first signal generator (9), outputs a signal depending on whether a highest switching threshold has been exceeded, and the first signal generator (9) can assume different states (18, 28, 29, 30, 31) and indicates how reliably one of the parts (3) to be detected was detected when passing through the ring coil (5), characterized in that, after a switch-on signal (17), the measuring device initially assumes an operational state and the first signal generator (9) outputs a standby signal (18), and for signal evaluation, a measurement (19) and an evaluation of the frequency and / or the amplitude of the oscillator circuit (7) are continuously carried out by a microprocessor of the evaluation circuit (8), wherein a first comparison (23a) of a first event (21) with the value of a lower switching threshold (24) is carried out and, if the lower switching threshold (24) is not exceeded,the measurement (19) is continued, otherwise a classification as an event (22) is performed, wherein a second comparison (23b) of the classified event (22) is made with a second switching threshold (32), which is a sum of the lower switching threshold (24) and a potentiometer offset (25), and wherein, in the case that the second switching threshold (32) is exceeded, it is recognized as part (3), otherwise it is classified as a minor event (28), wherein, in the case of the detection of a significant frequency and / or amplitude peak, and thus as part (3), a difference between the measurement (19) and a mean rest signal (20) is stored, wherein a third comparison (23c) of the classified event (22) is made with a first switching threshold, which is a sum of the second switching threshold (32) and a switching reserve offset (26),and wherein the potentiometer offset (25) can be influenced by means of a first potentiometer (11) and / or the switching reserve offset (26) can be influenced by means of a second potentiometer, wherein the first signal generator (9) continuously displays the last detected part (3) and the display of the first signal generator (9) also changes to match the last detected part (3) when the first potentiometer (11) is actuated.

Description

[0001] The present invention relates to a method for adjusting a measuring device for the non-contact detection of electrically conductive parts, wherein an electrically conductive part is guided through a conveying line enclosed by a ring coil which interacts with a capacitor as a resonant circuit within an oscillator circuit, wherein the electrically conductive parts cause a detuning of the resonant circuit within the oscillator circuit and thereby events in the form of frequency and / or amplitude peaks, and wherein an evaluation circuit is provided for detecting the events in an output signal of the oscillator circuit, wherein the evaluation circuit detects the magnitude of the frequency and / or amplitude peak.compares with at least one switching threshold and, using a first signal generator, outputs a signal depending on whether a highest exceeded switching threshold has been crossed, and the first signal generator can assume different states and indicates how reliably a part to be detected was recognized when passing through the ring coil.

[0002] Such a measuring device is already known from DE 10 2005 045 711 B4. Further prior art is also known from DE 10 2020 107 100 A1, which allows electrically conductive components, in particular screws, nuts, pins, small ironware of all kinds, or the like, to be moved through an electrically non-conductive hollow body. The measuring device uses a ring coil to generate an electric field inside the hollow body. As soon as one of the electrically conductive parts enters the electric field, it changes and causes a detuning of the resonant circuit formed by the ring coil and a capacitor. Such measuring setups and the measuring method are also described in DE 10 2014 016 217 A1, on whose technical principles the measuring device described here is based.

[0003] The measuring device itself consists of a housing in which the aforementioned ring coil is arranged. The ring coil comprises a wire winding made of at least one, and generally a plurality, turns. The electric field is generated by the wire winding of the ring coil. The resonant circuit formed by the ring coil and the capacitor is set into periodic oscillation by the oscillator circuit.

[0004] The electrical design and operation of such an oscillator can also be found in DE 10 2014 016 217 A1. As soon as a disturbance in the electric field occurs due to a falling, electrically conductive part, this event is detected by an evaluation circuit. The measured frequency and / or amplitude peaks can be further analyzed and stored by the evaluation circuit, so that the measuring device can be used to count the falling parts.

[0005] Such measuring devices are known with either static or dynamic signal evaluation. As the electrically conductive parts travel through the conveying line, which can be a pipe or a hose, they are only briefly inside the sensor, resulting in only a short, measurable event. The pause between events is comparatively long. For the reliable detection of particularly small metal parts, the dynamic evaluation method is more advantageous. It only evaluates the signal change relative to a mean resting signal, thereby eliminating effects caused by temperature and long-term drift. For further improvement, known measuring devices can incorporate a potentiometer to adjust the sensitivity of the switching threshold to the specific requirements.A setting that is too sensitive can lead to reliability problems, while a setting that is too insensitive can cause parts to sometimes no longer be detected.

[0006] With measuring devices using such a dynamic evaluation method, the user must ensure that a large number of parts pass through the device continuously so that the user can decide, based on the device's response, whether to further adjust the potentiometer. A drawback is that such devices use only a single LED as a signal source, which flashes briefly when the part to be detected passes through the ring coil. This provides the user with no information about whether the signal amplification is set too sensitively or too insensitively. Even if the amplification is incorrectly set, this error is difficult to detect because the LED only flashes briefly. Faulty circuits during the adjustment process are hard to spot, making the adjustment process time-consuming and inaccurate due to the high number of repetitions required and the limited information provided.

[0007] Against this background, the present invention is based on the objective of providing a method for adjusting a measuring device for the non-contact detection of electrically conductive parts guided through a conveying line, which allows for quick and accurate adjustment of the measuring device with minimal effort.

[0008] This problem is solved by a method for adjusting a measuring device according to independent claim 1. Meaningful embodiments of the adjustment method can be found in the subsequent dependent claims.

[0009] A method is provided for adjusting a measuring device for the non-contact detection of electrically conductive parts, wherein an electrically conductive part is guided through a conveying line enclosed by a ring coil which interacts with a capacitor as a resonant circuit within an oscillator circuit, wherein the electrically conductive parts cause a detuning of the resonant circuit within the oscillator circuit and thereby events in the form of frequency and / or amplitude peaks, and wherein an evaluation circuit is provided for detecting the events in an output signal of the oscillator circuit, wherein the evaluation circuit detects the magnitude of the frequency and / or amplitude peak.The method compares the measured value with at least one switching threshold and, using a first signal generator, outputs a signal depending on whether a highest switching threshold has been exceeded. The first signal generator can assume different states and indicates how reliably a part to be detected was recognized when passing through the ring coil. According to the invention, such a method is characterized in that, after a switch-on signal, the measuring device initially assumes an operational state and the first signal generator outputs a standby signal. For signal evaluation, a measurement and evaluation of the frequency and / or amplitude of the oscillator circuit is continuously performed by a microprocessor of the evaluation circuit. A first comparison of a first event with the value of a lower switching threshold is performed, and if the lower switching threshold is not exceeded, the measurement is continued.Otherwise, a classification as an event is performed, wherein a second comparison of the classified event with a second switching threshold, which is a sum of the lower switching threshold and a potentiometer offset, is carried out, and wherein, in the case that the second switching threshold is exceeded, it is recognized as a part, otherwise it is classified as a minor event, wherein, in the case of the detection of a significant frequency and / or amplitude peak, and thus of a part, a difference between the measurement and a mean rest signal is stored, wherein a third comparison of the classified event with a first switching threshold, which is a sum of the second switching threshold and a switching reserve offset, is carried out, and wherein the potentiometer offset and / or the switching reserve offset can be influenced by means of a first potentiometer and / or by means of a second potentiometer.wherein the first signal generator continuously displays the last detected part and, by actuating the first potentiometer, also changes the display of the first signal generator to match the last part.

[0010] By using different switching thresholds and displaying them via the first signal generator, the user can accurately determine how well the measuring device is already adjusted after guiding a part through the circular coil. They can then verify the effect of further changes with additional measurements and fine-tune the settings based on the first signal generator.

[0011] Setting up the measuring device is considerably faster and easier for the user than with previous technology, and the result of the setting process is more reliable. After switching on the sensor, the user simply drops an object through it, preferably the smallest object that needs to be reliably detected. Based on the response of the first sensor, the user can then adjust the switching sensitivity by turning the adjustment potentiometer and subsequently verify the response with another object.

[0012] A particular advantage is that the last signal output can be displayed using the first signal generator until the next frequency and / or amplitude peak occurs, or for a delay period. This makes it easy to identify the last signal and allows the use of simple signal generators, which can then employ easily recognizable flashing sequences to provide feedback on the signal strength of the event or the magnitude of a frequency and / or amplitude peak.

[0013] In a specific embodiment, it can also be provided that the evaluation circuit is reset immediately after the detection of a frequency and / or amplitude peak, regardless of the delay time, with a second signal generator preferably indicating a ready state of the evaluation circuit. By using two signal generators, for example, two LEDs, the user can verify whether the measuring device is ready for use and can perform further data acquisition, and can also view the result of the last acquisition, i.e., the last event and its evaluation.

[0014] Preferably, the signal from the first sensor can be adjusted by changing the second switching threshold using a first potentiometer and / or the first switching threshold using the first and / or second potentiometers. This allows the user to directly observe the effect of their adjustments on the first sensor. This simplifies the setup process to the point of measuring a single part by passing the part through the ring coil and then adjusting the first potentiometer until the frequency and / or amplitude peak is just above the first switching threshold. Typically, one attempt is sufficient to correctly adjust the sensor. Previously, the user required a continuous flow of objects passing through the ring coil to make any adjustments, and even then, they had no information on whether the detection was too weak or too strong.

[0015] Furthermore, the evaluation circuit can be designed to relate the frequency and / or amplitude peak to the average idle signal before evaluation. This allows, in particular, the elimination of temperature and long-term drift effects.

[0016] Furthermore, it can be provided that frequency and / or amplitude peaks above the lower switching threshold are recorded in a memory along with the height of the respective frequency and / or amplitude peak and preferably with the time of their occurrence. This allows the measuring device to be used for counting tasks, in particular for counting and recording the corresponding times of occurrence of the described events.

[0017] Finally, it may be provided that a fourth comparison of the classified event is also carried out with a sum of the second switching threshold and a maximum offset.

[0018] The invention described above will be explained in more detail below using an exemplary embodiment.

[0019] They show Fig. 1 a measuring device in an installed state on a conveying line in a lateral partial section, Fig. 2 the measuring device in a detached state with the ring coil open, as well as Fig. 3. A schematic flowchart of a measurement using the measuring device.

[0020] Fig. Figure 1 shows a measuring device 1 through which electrically conductive parts 3, in particular screws, nuts, pins, small ironware of all kinds, or the like, are moved through an electrically non-conductive conveying line 2. The conveying line 2 is designed as a pipe or hose, and the transport direction of the parts 3 can be arbitrary. Since the sheathing of the conveying line is made of an electrically non-conductive material, an electric field can form inside the conveying line 2 due to a current-energized ring coil 5 of the measuring device 1. As soon as one of the electrically conductive parts 3 passes through the electric field, it changes, and a resonant circuit formed by the ring coil 5 and a capacitor 6 connected to it is detuned.

[0021] The measuring device 1 consists structurally of a housing 4 in which the ring coil 5 is arranged. The ring coil 5 comprises a wire winding made of a multitude of turns and shaped so that it can be cut open as needed to be placed around the conveying line 2. The housing 4 is additionally secured to the conveying line 2 by means of a securing band 14 to provide sufficient mechanical support.

[0022] The electric field is generated by the wire winding of the ring coil 5. For this purpose, the ring coil 5, together with the associated capacitor 6, forms part of an oscillator circuit 7. For clarity, the resonant circuit consisting of capacitor 6 and ring coil 5 is shown next to the oscillator circuit 7 in the diagram. An evaluation circuit 8 is also provided, the function of which will be discussed below. Data evaluation and power supply to the measuring device are provided via a connection 16.

[0023] Provided that the oscillator circuit 7 and, via it, the ring coil 5 are supplied with voltage, a uniform electric field will develop within the conveying line 2. An average value of this electric field is used as the rest signal 20 for further measurements. If an electrically conductive part 3 now enters the area of ​​the ring coil 5 within the conveying line 2, its electric field will change, and the resonant circuit formed by the ring coil 5 and the capacitor 6 will be detuned. This generates a changed output signal at the oscillator circuit 7. Since the passage of the part 3 is short, a correspondingly short voltage spike results, which can be selectively detected as a frequency and / or amplitude spike by an evaluation circuit 8 connected to the oscillator circuit 7.Depending on the setting of a first potentiometer 11 and the size and speed of the parts 3, the frequency and / or amplitude peak is shaped and has a corresponding height. Such an event is evaluated by the evaluation circuit 8 and compared with various switching thresholds. Depending on which switching threshold was last exceeded, a signal 28 to 31 is output via a first signal generator 9, in this case an LED. The sensitivity of the switching threshold can now be adjusted using the first potentiometer 11, so that the counting of the parts 3 to be detected can be carried out reliably. For this purpose, the evaluation circuit 8 stores the already detected events and their associated frequency and / or amplitude peak heights in a dedicated memory (not shown separately), whereby the first signal generator 9 maintains the current signal 28 to 31 until a new event occurs.This also allows adjustments to be made using the first potentiometer 11 while a reading is already being displayed via the first signal generator 9. The signal generator 9 is not provided with the constant signal 28 to 31, but rather with the measured frequency and / or amplitude peak, so that a change in the setting of the first potentiometer 11 also results in a change in the signal 28 to 31. Therefore, the setting can be applied retrospectively to the measurement, meaning that, as a rule, only a single measurement is required to fully calibrate the measuring device 1.

[0024] In order to ensure time-saving and structurally simple yet reliable assembly and disassembly of the measuring device 1 on the conveying line 2, the housing 4 has according to Fig. 2. A toroidal coil 5 with two half-shells, which can be separated from each other both mechanically and electrically in a separation position. Inside the housing 4, the toroidal coil 5 with the wire winding is provided, so that when the housing 4 is separated into the two half-shells, the respective turn of the wire winding is also separated.

[0025] To enable such separation of the windings, a plug and a corresponding socket are provided in the separation position. Each winding is thus electrically connected to a plug and a socket. The housing 4 is designed such that the separation position is diametrically opposite a hinge 12. The hinge 12 allows the housing 4 to be folded around its axis of rotation and placed around the conveying line 2. Since each winding in the area of ​​the hinge 12 must exhibit elastic deformation to accommodate the rotational movements of the housing 4, each winding in this area is connected to an elastically deformable circuit board.The coupling of the windings takes place diametrically opposite the hinge 12 in the area of ​​a closure 13 and by means of plugs and couplings, creating an electrically and mechanically detachable connection.

[0026] Since the ring coil 5 and the associated part of the housing 4 are not suitable for mechanical stress, a retaining strap 14 is provided, as already described in Fig. Figure 1 shows that this can be detachably connected to the housing 4 on one or both sides using a locking element 15. Specifically, this is a rubber band with fastening openings, which can be fixed to the housing 4 on one side and secured on the other side by inserting the locking element 15, in the form of a locking pin, through one of the fastening openings. This also mechanically secures the device to the conveying line 2.

[0027] Fig.Figure 3 schematically illustrates the setup process of the measuring device 1 according to the invention. After a power-on signal 17, the system initially assumes an operational state, and the first signal generator 9 outputs a standby signal 18. The measuring device 1 has a total of two LEDs: the first signal generator 9 as a status LED and a second signal generator 10 as an information LED. The second signal generator 10 can be a single-color yellow LED that only indicates the state of the switching output, or it can be multi-colored. For example, a blue LED can indicate that an operating voltage is present, yellow that the switching output is activated, and red can symbolize an error message.

[0028] However, the first signal generator 9 is essential here. This can assume various states 18, as well as 28 to 31 and indicates how reliably a part 3 to be detected was recognized when passing through the ring coil 5.

[0029] For signal evaluation, a measurement 19 and evaluation of the frequency and / or amplitude of the oscillator circuit 7 are performed continuously by a microprocessor of the evaluation circuit. If a significant peak is detected in the signal, it is assigned to a detected part 3, and the difference of the peak to the average signal level, i.e., a rest signal 20, is stored. A difference between the measurement 19 and the rest signal 20 yields the height of the frequency and / or amplitude peak and thus, as soon as a first relevant part 3 traverses the ring coil 5, a first event 21. In a first comparison 23a, this first event 21 is compared with the value of a lower switching threshold 24. If the value of the first event 21 is less than the value of the lower switching threshold 24, the measuring device 1 remains in its initial state, and the next measurement 19 is performed. If no peak or amplitude has been detected after the sensor is switched on, the measurement device 1 remains in its initial state, and the process continues with the next measurement 19.Part 3 is detected; the status LED, i.e., the first signal transmitter 9, is off but flashes briefly at regular intervals. A duty cycle of 0.1 is preferred, meaning the LED is on for 500ms and off for 50ms.

[0030] If the value is greater, however, event 22 is classified. A second comparison 23b is then performed with a second switching threshold 32, which is derived from the value of the lower switching threshold 24 and a potentiometer offset 25. A signal exceeding the second switching threshold 24 is a signal that triggers a count as part 3, but without any switching reserve; that is, a signal that is just barely valid. If the aforementioned second comparison 23b between event 22 and the second switching threshold 32 shows that the sum of these values ​​is less than the peak of event 22, the state of the first signal generator 9 changes to a minor event 28. The peak is so weak that the second switching threshold 32 is not reached, and the first signal generator 9 is off.

[0031] If the threshold is exceeded, the next, third comparison 23c takes place, now with a sum of the second switching threshold 32 and a switching reserve offset 26. This sum corresponds to a first switching threshold. If it is not exceeded, a peak has been detected with a signal amplitude such that the second switching threshold 32 has just been reached, i.e., an event without switching reserve 29. Then the LED of the first signal transmitter 9 flashes, preferably with a duty cycle of 0.5, meaning the LED is on for 500 ms and off for 500 ms.

[0032] If this switching threshold is also exceeded, a fourth comparison 23d is performed with the sum of the second switching threshold 32 and a maximum offset 27. This is an upper switching threshold. If this is not exceeded, the part 3 is optimally detected, whereby the switching threshold is exceeded with a signal reserve. The LED of the first signal transmitter is permanently switched on with a switching reserve 30 in such an event.

[0033] If this upper switching threshold is also exceeded, a peak has been detected, but with a signal amplitude that is far too high, so that the LED of the first signal transmitter 9 is on, but with short interruptions. A preferred duty cycle for such a maximum event 31 would be 0.9, so the LED would be on for 500 ms, off for 50 ms.

[0034] Alternatively, some of the aforementioned states can be omitted. At a minimum, states 28 and 30 are sufficient for the sensor to function; the additional states 18, 29, and 31 simplify operation by also displaying information about the reliability of the detected signal.

[0035] Based on the display of the first signal generator 9, the user can now adjust the sensor's signal gain using the first potentiometer 11 and / or the switching threshold using a second potentiometer, ensuring that the event and its associated frequency and / or amplitude peak remain within a safe evaluation range. The first signal generator 9 continuously displays the last detected part 3, and adjusting the first potentiometer 11 also changes its display to reflect the last detected part 3.

[0036] The switching output is only activated as long as part 3 is within the range of the ring coil 5, i.e., as long as the received signal is above the lower switching threshold. The current state of the switching output is indicated by the LED of the second signal transmitter 10. Since this process can be very brief, it is possible to extend this short switching pulse by means of an adjustable switch-off delay.

[0037] The above describes a method for adjusting a measuring device for the non-contact detection of electrically conductive parts guided through a conveyor line, which allows for quick and accurate adjustment of the measuring device with minimal effort. REFERENCE MARK LIST 1 measuring device 2 Conveyor line 3 electrically conductive part 4 cases 5 ring coil 6 Capacitor 7 Oscillator circuit 8 Evaluation circuit 9 first signal transmitter 10 second signal transmitter 11 first potentiometer 12 hinge 13 Closure 14 securing tape 15 locking element 16 connection 17 Switch-on signal 18 Idle signal 19 Measurement 20 Rest signal 21 first event 22nd event 23a first comparison 23b second comparison 23c third comparison 23d fourth comparison 24 lower switching threshold 25 Potentiometer offset 26 Switching reserve offset 27 Maximum offset 28 minor events 29 events without switching reserve 30 events with switching reserve 31 Maximum event 32 second switching threshold

Claims

[1] Method for adjusting a measuring device for the non-contact detection of electrically conductive parts (3), wherein the electrically conductive parts (3) are guided through a conveying line (2) which is enclosed by a ring coil (5) which interacts with a capacitor (6) as a resonant circuit within an oscillator circuit (7), wherein the electrically conductive parts (3) cause a detuning of the resonant circuit within the oscillator circuit (7) and thereby events (21, 22) in the form of frequency and / or amplitude peaks, and wherein an evaluation circuit (8) is provided for detecting the events (21, 22) in an output signal of the oscillator circuit (7), wherein the evaluation circuit (8) detects the magnitude of the frequency and / or amplitude peak,compares with at least one switching threshold and, using a first signal generator (9), outputs a signal depending on whether a highest exceeded switching threshold has been exceeded, and the first signal generator (9) can assume different states (18, 28, 29, 30, 31) and indicates how reliably one of the parts (3) to be detected was detected when passing through the ring coil (5), , characterized by, that the measuring device initially assumes an operational state after a switch-on signal (17) and the first signal generator (9) outputs a standby signal (18), and for signal evaluation a measurement (19) and an evaluation of the frequency and / or the amplitude of the oscillator circuit (7) is continuously carried out by a microprocessor of the evaluation circuit (8), wherein a first comparison (23a) of a first event (21) with the value of a lower switching threshold (24) is carried out and if the lower switching threshold (24) is not exceeded, the measurement (19) is continued, otherwise a classification as an event (22) is carried out, wherein a second comparison (23b) of the classified event (22) with a second switching threshold (32), which is a sum of the lower switching threshold (24) and a potentiometer offset (25), is carried out and wherein, in the case that the second switching threshold (32) is exceeded, a recognition as part (3),Otherwise, a classification as a minor event (28) is performed, wherein, in the case of the detection of a significant frequency and / or amplitude peak, and thus as part (3), a difference between the measurement (19) and a mean rest signal (20) is stored, wherein a third comparison (23c) of the classified event (22) is performed with a first switching threshold, which is a sum of the second switching threshold (32) and a switching reserve offset (26), and wherein the potentiometer offset (25) and / or the switching reserve offset (26) can be influenced by means of a first potentiometer (11), and the switching reserve offset (26) can be influenced by means of a second potentiometer, wherein the first signal generator (9) continuously displays the last detected part (3) and, by actuating the first potentiometer (11), also changes the display of the first signal generator (9) to match the last detected part (3). [2] Method according to claim 1, characterized by, that the last output signal is displayed using the first signal generator (9) until the occurrence of the next frequency and / or amplitude peak or for a delay period. [3] Method according to claim 2, characterized by that the evaluation circuit (8) is reset immediately after the detection of a frequency and / or amplitude peak, regardless of the delay time, preferably signaling a ready state of the evaluation circuit (8) by means of a second signal generator (10). [4] Method according to any one of claims 1 to 3, characterized by , that the signal of the first signal generator (9) is adjusted when the second switching threshold (32) is changed using the first potentiometer (11) and / or the first switching threshold is changed using the first potentiometer (11) and / or the second potentiometer. [5] Method according to any one of claims 1 to 4, characterized by, that the evaluation circuit (8) puts frequency and / or amplitude peaks into a ratio to the mean rest signal (20) before their evaluation. [6] Method according to any one of claims 1 to 5, characterized by , that frequency and / or amplitude peaks above the lower switching threshold (24) are recorded in a memory together with a height of the respective frequency and / or amplitude peak and preferably with a time of its occurrence. [7] Method according to any one of the preceding claims, characterized by , that a fourth comparison (23d) of the classified event (22) is also performed with a sum of the second switching threshold (32) and a maximum offset (27).

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