DE4035470C2 - Processing analog signal in combine harvester - processing steep edge of signal to TTL compatible one, with signal counting - Google Patents

Abstract

The analog signals are generated by falling crops onto a sensor, triggering appropriate pulses. The sensor transmits a proportional output signal, corresp. to the crop quantity, via a converter, with a steep rising flank, as well as a wide frequency spectrum with reducing amplitudes. - The steep rising flank of the signal is processed into a TTL signal and counter. Pref. the electric signals are first amplified and rectified, then smoothed and the rising flanks transformed into a needle pulse via a differential member. Simultaneously the d.c. voltage portion is removed from the superimposed signals. The needle pulses trigger an electronic switch, whose output carries narrow, rectangular pulses with constant amplitudes, supplied to a counter.

Description

The invention relates to a method for processing analog electrical signals caused by those falling on impact Harvest components on a sensor triggered impulses arise, and a corresponding device.

Facilities for signal processing are already in various versions known.

DE 20 44 266 C2, for example, is a measuring device to determine grain loss on a combine harvester shown in which a sensor supplies electrical signals, which have a frequency detector and a monostable Multivibrator amplifier circuit containing a measuring device be fed. When crop components hit the sensor becomes a jagged voltage with a certain frequency and amplitude generated. To the sensor is a frequency detector to record the voltages connected, which is designed as a band filter and only lets through those voltages whose frequency is above one determined value. From the frequency detector jagged voltage fed to an amplitude detector that filters out all voltage spikes whose amplitude is less than one predetermined value, so that only the voltage spikes left behind by the impact of grains on the Sensor are caused. From the amplitude detector the tension spikes become a monostable multivibrator supplied, which generates square wave pulses. After The signals of a measuring circuit become pulse amplification fed which is a circuit for forming an average which generates an average voltage through which a Measuring device is applied, the grain throughput optically displays. Because the grain speed in deposition processes and thus the force determining the amplitude upon impact Grains on the sensor is subject to strong fluctuations, it is  difficult to set a defined threshold for that Determine signal amplitude. It also occurs at large Throughputs, especially in the concave area, a partial signal superimposition, so that no clear Detection of the individual excitation pulses is more possible.

The same disadvantages also occur with that from US 36 10 252 known device for measuring the amount of grain, in which the high-frequency vibrations are damped, the signal is amplified, rectified and integrated. Is at the circuit output then an electrical voltage is available that the grain Pulse sequence proportional and dependent on the pulse amplitude is. For monitoring separation processes and automatic control of functional assemblies of combine harvesters are these methods for electronic measurement signal processing can only be used with considerable restrictions.

DE 37 31 080 C2 describes an evaluation device Loss grain sensor of a harvester disclosed in which Signal from the sensor is initially amplified, one Filter element for rejecting interference signals and then one Rectifier is supplied. The rectified signal will fed to a link that the effective value of the Forms voltage signals. In a subsequent trigger stage the RMS signals are converted into counts that finally counted and fed to a display device become. The signals provided by the rectifier are sieved and then in using a comparator Converted digital signals. A disadvantage is that that the choice of the comparator threshold is critical because the signals are very small due to the effective value formation are. If the threshold is too low, there is a fear that Noise signals can be counted if the threshold is too high (smaller) impulses are lost.

US 39 35 866 discloses a grain loss monitor in which the signals generated by a lost grain sensor initially  converted into rectangular pulses using a Schmitt trigger become. The latter are differentiated and a monostable Multivibrator supplied, the output signal in turn one Circuit is supplied which the count signals with respect to Propulsion speed of the vehicle sets. Here it is Output signal of the sensor immediately in a square wave converted so that any amplitude information immediately get lost. The differentiator is only used to control the monostable multivibrators needed.

The aim of the invention is accuracy and Increase reliability of signal processing.

The invention has for its object the electrical Process signals from a sensor so that the pulses triggered by individual grains, especially at very short episode, clearly recognized and in one Successor device can be evaluated electronically.

According to the invention, this is achieved by the teaching of claims 1 and 3 solved.

According to the invention, the electrical signals are first reinforced and rectified, then smoothed and over one Differentiator the rising edges in a needle pulse shaped, at the same time the DC voltage component of superimposed signals is eliminated. Trigger the needle pulses an electronic switch, narrow at the output Rectangular pulses with constant amplitudes are present, which one Counter  be fed. The amplitudes of the needle impulses must exceed a threshold so the electronic switch is not switched by noise signals.

The respective electrical signals have a steep increase flank and a wide frequency spectrum with decaying amplitude the on. The signal width is approximately 1 to 2 ms. That arise the needle pulses correspond to the steep edges of the signals and an excitation pulse. The needle pulses are known in Way, for example with a cut trigger or comparator converted into narrow TTL-compliant rectangular pulses that give you a di gital counter or processed in another way become.

The signal processing according to the invention has the advantage that Output signal regardless of the amplitude of the sensor signal is due to different separation conditions and erntegu t-dependent peculiarities is influenced. The output signal only sets a proportional value to the number of Sensor hitting grains. It is therefore not necessary with changing Harvesting conditions the need for constant new calibration of the Measuring system. Another advantage is that even at very high hen crop throughput quantities the number of hits on the sensor grains can be determined exactly. That from the pulse sensor coming and processed according to the invention behaves in entire measuring range linear to the quantity of grains triggering the signal.

The invention is illustrated below using an exemplary embodiment explained. In the accompanying drawings:

Fig. 1: a block diagram of the signal processing and

Fig. 2: the circuit arrangement of the device for pulse shaping.

A sensor 1 converts the structure-borne sound waves that occur when grains impact into an electrical signal. The signal reverberates due to reflections from these waves. The respective settling time depends on the impact force of the grains and on the acoustic properties of sensor 1 . A voltage curve corresponding to oscillogram 2 is created . The amplifier 3 amplifies the signal for further processing. Oscillogram 4 shows the voltage curve. After the rectifier 5 there is a signal curve according to oscillogram 6 . The sieve stage 7 smoothes the signal so that in the oscillogram 8 the waveform of the envelope corresponds to a half wave of the sensor signal. A zero potential is present at the output of the differentiating element 9 and is interrupted by needle pulses. The needle pulses, which can be seen from the oscillogram 10 , correspond to the steep edges of the sensor signal. The needle pulses switch a trigger 11 , at the output of which there are narrow square-wave signals. The rectangle signals shown in the oscillogram 12 are fed to a digital counter 13 .

A circuit arrangement which is preferably implemented is shown in FIG. 2. In this circuit, the signal coming from sensor 1 is fed to an operational amplifier 14 , which is connected to diodes 15 ; 16 works as an active rectifier in the negative feedback branch. The required gain is set with a controller 17 . A capacitor 18 smoothes the rectified te signal. Another capacitor 19 represents the differentiating element 9. Positive needle pulses are present at the resistor 20 . If their voltage is greater than the reference voltage set by a voltage divider 21 , the operational amplifier 22 operating as a comparator is switched over. The reference voltage is set greater than zero volts to suppress noise signals. The voltage level of the resulting rectangular pulses, which correspond to the operating voltages at the output of the operational amplifier 22 , are determined by the diodes 23 ; 24 limited to 0 and +5 volts. At the output of this circuit there are narrow right corner pulses which are fed to the counter 13 . The width of these pulses depends on the rise time of the signal edges. In the variant he executed, the pulse width is 0.2 ms, so that up to 2500 grains per second can be counted.

List of the reference symbols used

1

sensor

2nd

Oscillogram

3rd

amplifier

4th

Oscillogram

5

Rectifier

6

Oscillogram

7

Sieve stage

8th

Oscillogram

9

Differentiator

10th

Oscillogram

11

Trigger

12th

Oscillogram

13

Counter

14

Operational amplifier

15

;

16

Diodes

17th

Regulator

18th

;

19th

capacitor

20th

resistance

21

Voltage divider

22

Operational amplifier

23

;

24th

Diodes

Claims (3)

1. A method for processing analog electrical signals which are generated by the components triggered by falling crop material impulses on a sensor ( 1 ), the sensor ( 1 ) via a converter output signal proportional to the detected crop quantity with a steep rising edge and a subsequent emits a wide frequency spectrum with decreasing amplitudes, the electrical signals of the sensor ( 1 ) are initially amplified and rectified, then smoothed and the rising edges of the smoothed signals are shaped into needle pulses by means of a differentiator ( 9 ), the DC voltage component of the signal being removed at the same time, and the rising edges of the needle pulses are processed into a TTL-compliant signal and counted. 2. The method according to claim 1, wherein the needle pulses trigger an electronic switch ( 11 ), at the output of which there are narrow rectangular pulses with constant amplitudes, which are fed to a counter ( 13 ). 3.Device for processing analog electrical signals which are caused by the components triggered by falling crop material impulses on a sensor ( 1 ), the sensor ( 1 ) via a converter an output signal proportional to the detected crop quantity with a steep rising edge and a subsequent one emits a wide frequency spectrum with decreasing amplitudes, the electrical signals from the sensor ( 1 ) are first amplified by means of an amplifier ( 3 ) and rectified by a rectifier ( 5 ), then smoothed in a sieve stage ( 7 ) and the rising edges are transmitted via a differentiating element ( 9 ) are formed into needle pulses, at the same time the DC voltage component of the signal is removed, and the rising edges of the needle pulses trigger an electronic switch ( 11 ) which processes them into TTL-compliant rectangular pulses with constant amplitudes, which are fed to a counter ( 13 ).