DE1538496C3 - Electronic regulator - Google Patents

Description

The invention relates to an electronic controller, the actuator of which by means of a two-position switch optionally in a first position on the output of the controller for automatic control in Depending on the control deviation or in a second position on the output of a control device to adjust the manipulated variable z. B. by hand, is switchable, with an amplifier whose input is over a series input impedance can be subjected to a voltage corresponding to the control deviation, with a feedback network including a feedback resistor between the output and the input of the amplifier and with a capacitor which is in the first switch position of the Two-position switch Part of the feedback between the output and the input of the Amplifier is and in the second position on a dependent on the manipulated variable and the control deviation Voltage is chargeable.

Such a regulator is known from US Pat. No. 68,387. In this known regulator is For example, the actuator is switched on by means of an electric

motor operated valve. The known control system also contains an amplifier with an input resistor and a feedback. A switch can be used to switch between a hand-operated Control and automatic regulation can be selected. There is feedback during the regulation of the amplifier from the series connection of a feedback resistor with capacitor to achieve of an integral rule behavior. This capacitor is used during manual control mode is used, a corresponding to the difference between the control deviation and the manipulated variable To save voltage in order to enable a bumpless switch back to automatic operation. the known arrangement is however due to a high number of changeover contacts which makes a relay necessary as well as the requirement of an additional magnetic amplifier and the position of the motor indicating transducer very expensive. In a further embodiment of this known controller is In addition, a device is provided that also enables smooth switching from the automatic to the Should enable manual operation. This setup requires two motorized potentiometers as well a servo amplifier and is therefore extremely complex and extensive.

The invention is therefore based on the object of creating a controller of the type defined at the outset, in which the switching process takes place smoothly in each direction with little effort.

This object is achieved in a regulator of the type mentioned in that in the first position of the two-position switch (automatic mode) the series input impedance and the feedback resistance are connected to a first input of the amplifier via a common connection point, that the capacitor is between a first output and a second output of the amplifier and a second capacitor are connected between the first and second output of the amplifier, and that in the second position of the two-position switch (manual operation) the common connection point of series input impedance and feedback resistor isolated from the first input of the amplifier and instead the first capacitor between the first Output of the amplifier and said connection point is connected, while the second output of the amplifier is fed back to the first output and the second capacitor between the first Output of the amplifier and its second input are switched. .

While the controller regulates the controlled variable in automatic operation, the variable is the control voltage simultaneously impressed on a storage circuit with the second capacitor, which its respective Is able to maintain charge over relatively long periods of time. >

When the two-position switch is out of its first position is switched to its second position (manual mode), one side of the mentioned second capacitor via a switch contact directly connected to the second amplifier input. Another switch contact connects at the same time the first amplifier input via a feedback line to the amplifier output. There this'output at the moment before switching the potential of said side of the second capacitor the two amplifier inputs essentially have at the first moment after switching same potential. The voltage output by the amplifier is therefore during the switchover and held essentially constant immediately after switching to manual control mode, so that the controlled process sequence experiences no disturbance as a result of the switchover.

Furthermore, after switching to manual control mode, the second capacitor is between the one Output and one input of the amplifier switched on, so that the amplifier generated feedback effect is aimed at the second capacitor in the on its original Keep voltage charged state, thereby minimizing displacement effects will.

While the controller is switched to manual mode, however, the first capacitor serves as a memory, the the actual value of the controlled variable compared to its setpoint and the ratio of this actual value to the saves the actual manually set control signal.

When the two-position switch is returned to its first position (automatic mode), there is practically no potential difference between the Amplifier inputs present as the first capacitor and the connection point between the series input impedance and the feedback resistor directly to one another through a changeover contact were connected. Since the voltage of the first capacitor during manual operation on the correct value reflecting both the control deviation and the control signal output by the controller has been held, the capacitor voltage does not cause an immediate change in the amplifier input voltage after switching to automatic mode, so that switching without changing the control voltage going on.

Particularly useful refinements of the invention emerge from claims 2 to 8.

In the following the invention will be explained using an exemplary embodiment with reference to the drawings explained in more detail. It shows

F i g. 1 a simplified circuit diagram of a controller with a two-position switch,

F i g. 2 is a detailed circuit diagram of the power supply circuit with the setpoint signal generating device

F i g. 3 and 4 together a circuit diagram showing details of the controller according to FIG. 1 illustrates. According to FIG. 1, the controller has three input terminals 10, 12 and 14, which are connected to one another via two Resistors 16 and 18 lying in series are connected to one another. Via terminals 10 and 12 and the Resistor 16 (500 Ω) flows a setpoint current, but normally of a fixed magnitude of, for example, 2 to 10 mA, while a measuring current of for example via terminals 12 and 14 and resistor 18 (100 Ω) 10 to 50 mA flows, the size of which is proportional to the value of the process state to be controlled. This Both currents flow, indicated by the arrows, in opposite directions, so that the at the Resistors Ί6 and 18 generated voltages have opposite polarity.

The circuit described so far provides a Input comparison circuit, which supplies a deviation voltage between terminals 10 and 14, the size of which

is proportional to the control deviation and whose polarity is determined by whether the actual value is above or is below the setpoint. If the measured controlled variable corresponds exactly to the setpoint, it is Deviation voltage equal to zero. However, if the measuring current changes across the resistor 18, it changes the potential of the terminal 10 compared to that of the terminal 14 accordingly. To provide a reference base for the To create different potentials present in the controller, the terminal 14 can for the sake of simplicity as "Circuit earth" and the line 20 connected to it are referred to as "reference line". If the Setpoint current is set to its mean value of 6 mA via the resistor 16, the at the Terminal 10 is any value between - 2 V and + 2V compared to the Own reference line, the exact value of course being dependent on the determined value of the Controlled variable depends.

The deviation voltage is applied via a series input impedance 22 (100 kΩ) and a section 70a of a two-position switch 72 to the input 24 of an AC amplifier 26 with a high gain. This amplifier, which will be explained in more detail later, can have an advance gain of 2000, for example. The output lines 28 and 30 of this amplifier are connected to the two ends of a potentiometer 32 (600 Ω), the lower end of which is connected to the reference line 20 at the same time. The tap 34 of the potentiometer 32 supplies a feedback voltage which is fed to the amplifier input 24 via a feedback resistor 36 (100 Ω). The current flows "upwards" through the potentiometer 32, so that the potential at the amplifier input 24 with respect to the reference line 20 is negative.

It can be seen that the resistors 22 and 36 form a voltage divider with a division ratio of 2: 1. Since the amplifier 26, as will become more apparent from the following detailed description, practically no current is required in its input circuit, are those via the resistors 22 and 36 flowing currents are the same and therefore the potential is at the junction between these two Resistances in the middle between the voltages present at the ends. For example, if the Deviation voltage at terminal 10 is zero and the potentiometer 32 to supply a voltage of -3 V is set at tap 34, the amplifier input 24 is at -15 V.

The potentiometer tap 34 is also made up of two series resistors 40 and 42 second voltage divider 38 is connected to the reference line 20. The junction 44 of this voltage divider is connected to a feedback circuit consisting of an adjustable resistor 46 (for example 100 Ω) and a downstream capacitor 48, the junction point 50 between the resistor 46 and the capacitor 48 via the section 706 of the two-position switch 72 to the second amplifier input 52 is connected. The other plate of capacitor 48 is over one Switch 54 is connected to the reference line 20. As can be seen from the precise description with reference to FIGS. 3 and 4 As will become even clearer, the switch 54 is actually not required, but is shown in FIG. 1 only to simplify the explanation.

The voltage difference between the two amplifier units 24 and 52 determines the size of the current flowing through the output lines 28 and 30. When both inputs are at the same potential the current supplied by the amplifier is typically set to its mean value, i. H. on a value which produces a voltage drop of 9 volts across potentiometer 32. If the from The amplifier output voltage changes over its full range, the voltage drop varies over the Potentiometer 32 between 3 and 15 V. A voltage rise at the amplifier input 24 has an increase of the current flow through the potentiometer 32 and vice versa. The maximum deviation of the Amplifier output voltage from its mean value becomes when the input voltage changes of about 1 mV is achieved.

The circuit according to FIG. 1 works as follows: First it is assumed that the terminal 10 lying deviation voltage is zero and that all other voltages of the circuit are stabilized; in In this state, an increase in the measuring current across resistor 18 produces a positive deviation voltage at the terminal 10, whereby the potential at the amplifier input 24 seeks to increase. Consequently increases the current flowing through the potentiometer 32 and leaves the potential of the potentiometer tap 34 fall off. However, the capacitor 48 prevents an immediate change in the potential of the second amplifier input 52 and the feedback effect is initially due to the influence of the feedback resistance 36 brought out to the first amplifier input 24.

As an exaggerated example, assume that the potential of terminal 10 is +1 V when the Measurement current across the resistor 18 suddenly increased by 10 mA, for example from 30 mA to 40 mA. If that The potential of the potentiometer tap 34 was initially -3 V, such an increase in the deviation voltage by 1 V with the result that the potential of the potentiometer tap 34 to a new lower Shifts potential and seeks to bring the potential of the amplifier input 24 to its original Worth keeping. Obviously, this new lower potential must be -4V; H. a decrease the deviation voltage by 1 V requires a reduction in the feedback voltage at the potentiometer tap 34 by 1 V, since the division ratio ensured by the resistors 22 and 36 the potential of the amplifier input 24 can only be kept constant when the Voltages at the ends of the voltage divider by equal amounts and in opposite directions to change. Of course it is not possible to exactly match the input 24 of the amplifier to the original To hold voltage, since there is a voltage change between its two inputs 24 and 52 must be increased by the amount required to shift the potential of the potentiometer tap 34 by 1 V. To generate amplifier output current. However, the gain of the amplifier is so high that this change in the input potential versus the change in the deviation signal and the feedback voltage is practically negligible. .

A control signal circuit 56 is connected to the amplifier 26, which is shown in FIG. 1 symbolically than to the Output line 28 connected individual line is indicated. This circle is attached to a remote actuator, like a valve not shown or the like. Connected

and supplies it with an actuating signal corresponding to the current through potentiometer 32. In the case of the FIG. 3 4 and 4 regulator shown in greater detail as it is actually used, this circuit 56 is essential more complicated than in FIG. 1, but essentially operates in a conventional manner to generate an actuating signal in the order of magnitude of 10 to 50 mA, while the potentiometer 32 flowing current is in the range of 5 to 25 mA. When the offset voltage goes from zero to 1 V, the control signal in circuit 56 initially increases accordingly.

After the initial change in the potential of the potentiometer tap 34, a further and continuous change occurs as a result of the gradual change in the Potential of the other amplifier input 52, which results from a charge or discharge of the capacitor 48. More precisely, if the potential of the Potentiometer tap 34 changes from -3 V to -4 V in the manner previously described, this shifts Potential of junction 44 of voltage divider 38 from -1.5 V to -2 V, so that the capacitor 48 correspondingly from -13 V towards -2 V begins to charge This drop in the potential of the capacitor 48 leads to an increase in the Voltage difference between the two inputs 24 and 52 of the amplifier, so that the amplifier output current seeks to increase accordingly.

Of course, the charging of the capacitor 48 takes place as a result of the large time constant of the Resistor 46 and capacitor 48 are normally relatively slow. This time constant can be up to 30 minutes for procedures with a relatively long time delay. Besides that the initial change in the control signal in circuit 56 results in a corresponding change in the setting of the actuator, which in turn causes the controlled variable to begin to return to the setpoint. As a result, the deviation voltage appearing at the terminal 10 is reduced accordingly, which is the Tends to counteract the increase in the actuating current as a result of the feedback effect. These various effects of the circuit act in a dynamic manner together and ensure, as the end result, a perfect control effect, which the controlled variable with considerable speed and minimal overflow stabilized on the setpoint

The setting of the potentiometer 32 determines the P-range of the controller, i. H. the size of the change in Voltage supplied by the amplifier for a given change in the deviation voltage. Every change the potential of the terminal 10 is determined by an equal and opposite change in the potential of the potentiometer tap 34 correspond, while the corresponding change in the current flow on the Lines 28 and 30 depends on the setting of the potentiometer 32

In many processes it is desirable that the control signal also contains a component which determines the rate of change of the to be measured State is proportional. In the case of the controller described, this is indicated by an upper measuring resistor 18 lying rate-of-change-dependent circuit 60, which consists of a capacitor 62 and a direct current amplifier 66 in series one connecting the branch point between these two elements to the reference line 20 adjustable resistance 64 (1ΜΩ) consists. the Capacitor 62 and resistor 64 cooperate and produce a across resistor 64 Voltage which is essentially proportional to the speed with which the resistance moves

S 18 generated measuring voltage changes. The two entrances of DC amplifier 66, which has a gain of approximately 1: 5, are connected to the two Ends of resistor 64 are connected, and the two outputs of the amplifier are between the Capacitor 48 and the reference line 20 turned on, so that when the short-circuit switch 54 is open amplified speed voltage from amplifier 66 to input 52 of main amplifier 26 in series with the feedback voltage across the capacitor gate 48 is fed in.

The following describes how to switch the controller to manual control. While the controller at automatic operation controls the controlled variable, the size of the control voltage is also stored in a memory circle impressed with a second capacitor 74, which is able to maintain its respective charge over relatively long periods of time. More precisely, one plate of the capacitor 74 is via the contact 70c of the two-position switch 72

2 $ connected to the second output 30 of the amplifier 26, while the other plate is connected directly to the first output 28, which in turn is connected to the reference line 20. The capacitor 74 is therefore directly parallel to the Potentiometer 32 so that it is always on the from The voltage output by the amplifier is maintained. More specifically, it will be the potential of the lower plate of the capacitor is held at the negative potential of the top of the potentiometer 32.

When the two-position switch 72 is moved from its position shown in the figures to in the following When the position known as the "manual control" position is switched over for non-automatic operation, the lower plate of capacitor 74 across the switch contact 70c is directly connected to the second amplifier input 52. At the same time, the switch contact 70a connects the first amplifier input 24 via a feedback line 80 to the amplifier output 30 and to the upper end of the potentiometer ters 32. Since this output shows the potential of the lower plate of the Capacitor 74 had the two amplifier inputs 24 and 52 in the first moment after the Switching essentially the same potential. On then the difference between the inputs changes The voltages are of course negligible, for example by a fraction of a millivolt, which is due to the Is due to the feedback effect of the line 80, which causes the output from the amplifier Voltage is held at this value, and thus an adjustment between the potential of the amplifier output 30 and that through the capacitor 74 dem Amplifier input 52 impressed potential ensures the voltage output by the amplifier thus essentially during the switchover and immediately after the switchover to "manual control" kept constant so that the process sequence does not experience any disturbance as a result of the switchover especially to point out that this result without Requirement for a balancing process during the Switching is achieved.

It should be noted that the second capacitor 74 after switching to "Handstcuer" mode

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between the output 28 and the input 52 of the amplifier 26 is switched on. The through this The feedback effect produced by the amplifier tends to reduce the capacitor 74 in on its keep original voltage charged state, minimizing displacement effects be reduced.

If the control current supplied by the controller is to be changed, the capacitor only needs to be charged 74 because the feedback effect of line 80 reduces the output voltage of the Amplifier 26 then changes accordingly. This change in the capacitor charge can be seen in illustrated embodiment by actuating the movable contact 76 of a switch 78 on a of two positions 82 or 84 cause.

In position 82, switch 78 switches amplifier inputs 24 and 52 to one of one current limiting resistor 86 and a DC power source 88 existing circuit, while the Storage capacitor 74 as a result of the feedback effect with a by the time constant of the from the Capacitor 74 (2 μΡ) and the current limiting Resistor 86 (10 ΜΩ) existing circuit at a certain speed gradually discharges. So long the switch 78 is held in the position 82, the capacitor 74 discharges with practically constant slow speed, whereby the control current supplied by the controller decreases accordingly.

When the switch 78 is flipped to its other position 84, the actuating current increases with practically constant slow speed, since in this switch position a direct current source 90 instead of the Current source 88 is switched on in the circuit, which opposite the current source 88 polarity is reversed owns.

When switch 78 is returned to its central position, capacitor 74 is off Voltage sources 88 and 90 separate and is its Aufbzw. Discharge interrupted. As a result, the Actuating current at a constant value corresponding to the capacitor charge.

Switching from manual to automatic mode is explained in more detail below. As long as the Controller is switched to "manual control", the contact 706 of the two-position switch 72 connects the upper plate of the capacitor 48 directly with the junction between the two resistors 22 and 36 of the feedback circuit, so that the capacitor voltage is constantly the difference between that of the Control deviation corresponding input voltage at terminal 10 and the manually set, corresponds to the control voltage represented by the potential of the potentiometer tap 34. During the Controller is switched to manual control, the capacitor 48 thus serves as a memory for the actual value of the controlled variable compared to its setpoint and the ratio of this actual value to the actual value manually set control signal "remembered".

When the two-position switch 72 is reset to its "automatic" position, it is in the first Immediately after switching, there is practically no potential difference between the amplifier inputs 24 and 52 are present because the capacitor 48 and the connection point between the resistors 22 and 36 were directly connected to one another by the changeover switch contact 70ό. Since the tension of the Capacitor 48 during the "manual control" operation on the correct, both the control deviation and the value reproducing the control signal output by the controller has been maintained, the condensate

gate voltage no immediate change in the amplifier input voltage after switching to automatic operation, so that switching without any substantial Change of control voltage is going on. If the actual value is then not equal to the setpoint,

d. H. if the input 10 carries a voltage corresponding to a control deviation, the controller works Of course, in his own way, the controlled variable quickly and smoothly back to the setpoint to adjust.

It is particularly important to note that even in the presence of the rate of change the control deviation dependent circuit 60 before switching back to automatic operation bumplessly goes, even if the short-circuit switch 54 is open and the controlled variable at the moment of Toggle changes. Under these conditions, the change in the controlled variable is triggered by a corresponding Output voltage of amplifier 66 reproduced, (' However, both before and after switching back in series with the one corresponding to the control deviation Voltage and the capacitor voltage and therefore none at the moment of switching back Has an influence on the voltage fed into the amplifier 26. After switching, the

Rate of change corresponding voltage of course, the intended influence on the guarantee of a perfect automatic regulation of the controlled variable.

The following is the structure of the controller of the embodiment of the invention in more detail described.

The in F i g. The preferred embodiment of the invention shown in FIG. 3 has two input terminals 10 and 12a, via which the setpoint current is fed to the resistor 16, via which a corresponding setpoint voltage is generated. One end of the resistor 16 is connected to the series input impedance 22 via a cascade switch 100 and the contact 102a of a coupled changeover switch 104, while the end of the resistor 16 connected to the terminal 12a via two other contacts 1026 and 102c of the changeover switch is connected to the measuring voltage resistor 18, which is fed from the terminals i2b and 14 with measuring current. These last-mentioned terminals are typically connected by a two-wire transmission line to a conventional transducer, for example one which generates a current corresponding to a temperature of the process. The measurement voltage generated across the resistor 18 is thus in series with the setpoint voltage across the resistor 16 and is opposite to this, so that these resistors, together with the circuit assigned to them, form a comparison circuit. The difference between the two compared voltages represents the deviation voltage, which is proportional to the difference between the actual value and the setpoint value.

The lower end of the input comparison circuit formed by the resistors 16 and 18 is connected to the circuit ground formed by the reference line 20 via the contact 102d of the changeover switch 104, while the deviation voltage appearing at the upper end of the comparison circuit is

input impedance 22 is fed to the input 24 of the amplifier 26, the details of which are shown in FIG. The current delivered by this amplifier flows via the output lines 28 and 30 as well as a filter 112 drawn in the upper right corner of FIG The tap 34 of the potentiometer 32 is connected on the one hand via the feedback resistor 36 to the amplifier input line 106 and on the other hand to the voltage divider 38 formed by the resistors 40 and 42 (100 kΩ each), in which an adjustment potentiometer 116 (10kΩ) is switched on, the tap 44 of which at the same time forms the junction 44 of the voltage divider 38. The potential of point 44 is applied to capacitor 48 (18 μί) via a fixed-value resistor 118 (390 kH) and the adjustable resistor 46 (100 ΜΩ) in series with it, the upper plate of which has a two-position via one contact 7Qb Switch 72 is connected to a line 124 which leads to the other input 52 (FIG. 4) of the amplifier 26.

The measurement voltage generated across the resistor 18 is also applied to one input 126 of a speed-sensitive circuit 60 applied, the other input 130 with the reference line 20 The input 126 of this circuit is connected to the capacitor 62 (100 mF), its other Plate is connected to the resistor 64 via an off switch 134, which in this embodiment consists of a fixed-value resistor 138 (2.2 kΩ) in Series with an adjustable resistor 140 (1 ΝΩ) consists. When the measurement voltage across the resistor 18 is constant, no voltage occurs across the resistor 64, since the capacitor 62 is on the Measurement voltage charges up As soon as the measurement voltage changes, however, occurs across the resistor 64 one of the Rate of change of the measuring voltage proportional voltage, the size of which is determined by the ÄC time constant of the circuit elements 62 and 64 is determined and with the help of the adjustable Resistance 140 can be changed at will.

The voltage generated across resistor 64 is fed to the two directly coupled transistors 142 and 144 having amplifier 66 is fed, which has two according to F i g. 2 to a conventional 43 V DC power source 150 connected lines 146, 148 is fed with working current and its output is positive is biased so that with an input voltage of 0 V at terminal 152 an output voltage of approximately 20 V. that fluctuates between approximately 0 and 40 V under operating conditions

If the influence of the rate of change on the control signal is to be switched off, the Off switch 134 turned to its OFF position, connecting the capacitor 62 to the reference line 20 through a resistor 154 (^ Ω), whereby the capacitor 62 is always charged to the potential of the measurement voltage across the resistor 18 remains and switching to ON can take place without disrupting the process flow. Resistance 154 is provided to prevent deterioration in the speed of response of the controller, such as it could occur if the capacitor 62 is connected directly across the measured value resistor 18 would.

An instrument 156 is connected to the left end of the resistor 22, which measures the size of the Shows control deviation. Since not only the nominal value and the measuring current flows through the resistors 16 and 18, but also a small additional current based on the feedback voltage at the potentiometer tap 34, the control deviation cannot simply be obtained in such a way that the display instrument 156 is switched directly across the resistors 16 and 18. To compensate for this small additional current is rather, the lower terminal of the display instrument 156 via a resistor 158 (600 Ω) to the Reference line 20 and connected to potentiometer tap 34 via a further resistor 169 (100 kΩ), which are matched to each other that the voltage drop across the resistor 158 through the additional current through the resistors 16 and 18 caused an additional voltage drop across them Resistances accurately compensated so that the instrument 156 only shows the actual offset voltage indicates.

The upper end of the potentiometer 32 is via the contact 70c of the two-position switch 72 with the one plate of a capacitor 74 (2 μΡ) connected, the other plate of which is connected to the reference line 20 via a stabilizing resistor 164 (100 kΩ) is. The live plate of the capacitor 74 is also connected to the selector arm 76 of a five-position switch 78a, the middle mating contact of which is dead. Usually lies the selector arm 76 against this central mating contact, so that the voltage of the capacitor 74 always exactly the output voltage of the amplifier 26 follows and a "storage" of the size of the control voltage which is then used when the controller switches from automatic to manual mode will.

If the two-position switch 72 is switched to the "manual control" position, disconnects the contact 70a of this switch (Fig. 4) the line 106 from the amplifier input 24, so that the amplifier the deviation voltage is no longer supplied. At the same time, the capacitor 74 is across the contact 70c of the switch 72 is connected to the amplifier input 24 in order to generate the control voltage supplied by the regulator to the value present immediately before switching to manual control. Since the However, capacitor 74 is charged to the control voltage, it has a much too high potential to can be connected directly to the amplifier input, since the amplifier is immediately on its Limit would be driven. According to the invention, however, this effect is achieved by a circuit arrangement prevents the size of the when switching the two-position switch 72 to manual control Capacitor voltage compensated so that the voltage supplied by the amplifier is on its previous one Value is held.

In the illustrated embodiment of the invention, this circuit arrangement consists of one Feedback line 80 which, when the switch 72 is switched to manual mode, the amplifier input 24 connects via the changeover switch contact 70a to the amplifier output line 30, so that the from The voltage supplied to the amplifier is automatically maintained at its previous value, since the feedback effect of the line 80 reduces the amplifier output voltage adjusts to the value that corresponds to the potential of the

Holds output line 30 at the same level as the potential of capacitor 74; H. on the value, which these parts had before switching. Switching to manual control is therefore possible without Disturbance of the process flow ahead. This is what the feedback effect of the amplifier 26 seeks thereafter, to maintain the original charge on capacitor 74, so that all displacement effects reduced to a minimum for a certain period of time.

If the control voltage supplied by the controller is to be changed during manual operation of the system, the operator sets the switch 78a to the contact 82 or 84, whereby the movable switch contact 76 via the respective resistors 86a or 86b (each 10 ΜΩ) that limit the charging speed. is applied to a positive or negative supply voltage 88 or 90 of, for example, 3 V; the circuit is closed via a resistor 92 and a common return line 94. Details of the power supply 168 concerned are shown in FIG. 2 shown. The current supplied by the voltage source 88 or 90 charges or discharges the capacitor 74 gradually to a new value, the control voltage supplied by the regulator changing accordingly. In order to enable the capacitor charge to be changed very quickly, the switch 78 is provided with two further contacts 170 and 172, which are connected directly to the positive and negative voltage sources 88 and 90, bypassing the limiting resistors 86a and 86b.

During manual operation of the system, the contact 70b of the two-position switch 72 connects the upper plate of the capacitor 48 to the branch between the resistor 22 and the feedback resistor 36, so that the capacitor on one of the difference between the differential voltage at terminal 10 ( possibly plus the voltage dependent on the rate of change if the state changes) and the voltage corresponding to the voltage represented by the potential of the potentiometer tap 34 remains charged Control value supplied by the controller, so that the controller can be switched back to automatic operation at any time without disturbing the process.

When the system is switched back to automatic operation, section 706 of two-position switch 72 reconnects capacitor 48 to lower amplifier input 52, while contact 70a connects the other amplifier input 24 to the branch between resistors 22 and 36. Since the capacitor and this branch were connected to one another immediately before switching to automatic operation and therefore had exactly the same potential, the two amplifier inputs obviously also have the same potential immediately after switching back. For this reason, the control voltage output by the controller does not need to be changed in order to achieve a stable state, so that the switch back to automatic operation takes place without disturbing the process sequence.

Switching to automatic operation occurs smoothly even when the controlled variable changes, so that a speed-dependent voltage is generated at the output of amplifier 66. This is because the output of amplifier 66 is connected in series with capacitor 48 both before and after switching to automatic operation. The charging of the capacitor is therefore kept at the value that is required when switching back to automatic operation in order to ensure a practically zero voltage difference between the amplifier inputs 24 and 52, regardless of any control deviations occurring at the moment of switching.
After switching to automatic operation, the controller regulates again in the normal way, ie if a control deviation occurs, the control signal or the control voltage is automatically changed to a value that resets the actuator in such a way that the controlled variable quickly and smoothly back to the setpoint is brought.

The setpoint current applied to terminals 10 and 12a is determined by a device shown in FIG. 2 with a full-wave rectifier 202, the secondary voltage of which is applied to a voltage-regulating Zener diode 206 via an AC filter 204. The DC voltage determined by this diode is impressed on the actual current-carrying circuit of the SoH value generator, which consists of a fixed-value resistor 208, an adjustable "range" resistor 210, the emitter and collector of a transistor 212, the setpoint terminals 10 and 12a and a fixed value resistor. Resistor 214 (100 Ω) exists, which supplies a display voltage for a remote display device or for other control functions

The magnitude of the current flowing through the transistor 212 is set by a setpoint potentiometer 216, the tap of which taps a control voltage for the base of the transistor a second Zener diode 222 is connected. The latter is fed via two compensation diodes 224 and a fixed-value resistor 226, which is connected in series with the first Zener diode 206.The diode 222 supplies a very precisely regulated voltage for setting the potential of the base of the transistor 212 .

An advantage of this set-point generator 200 consists in its relation to comparable, currently available circuits simple Eichbarkeit For this purpose, the tap of the set value potentiometer 216 is first set to low potential and zero resistance 218 so that through the transistor 212, a current of 2 mA flows. Then the tap of the potentiometer 216 is set to high potential and the range resistor 210 is set so that a current of 10 mA flows through the transistor ensure mA; in any case, however, the calibration is quick. It should also be noted that with this arrangement the setpoint potentiometer 216 need not be a precision resistor as the calibration settings compensate for any inaccuracy in the actual resistance value. The only requirement is that the change in resistance when the potential

meter setting is consistent and consistent.

With the help of the cascade switch 100, a remote-controlled setpoint voltage can be fed into the controller that are, for example, the output of a similar controller regulating a second controlled variable is removed. This setpoint voltage is applied to terminals 180 and 182 and generated via a Resistor 184 (100 Ω) a corresponding current flow of, for example, 10 to 50 mA. The one above this Resistance tapped voltage is measured via a compensation resistor 186 (400 Ω) and the cascade switch 100 is applied to contacts 102a and 1020 of switch 104; H. the one at the resistance 18 generated measuring voltage connected in series with reversed polarity. The ohmic resistance of the Resistors 184 and 186 are chosen equal to that of resistor 16 to ensure that the the deviation indicating instrument 156 provides an accurate indication.

The changeover switch 104 reverses in the usual way the control voltage output by the ao regulator at a predetermined one Change either the measuring voltage or the nominal voltage by. More precisely, has one position this switch increases the measuring current with the result that the potential of the potentiometer tap 34 becomes more negative, while an increase in the measuring current in the other position of the switch does The potential of the potentiometer tap 34 can be more positive.

When the controller is switched to automatic operation is, according to FIG. 4 to the amplifier inputs 24 and 52 via lines 106 and 124 and the Contact 70a of the changeover switch 72 is fed a voltage that allows a current to flow through a T-filter network 300, which creates a winding 302 of a transformer 304 and two semiconductor diodes 306 and 308. This Diodes, which in practice can consist of transistors connected as diodes, work in the non-conductive mode Range of their characteristic and introduce a capacitive resistance, the size of which corresponds to the applied voltage.

The general operation of diodes 306 and 308 to control amplifier 26 is disclosed in the United States patent 29 56 234 described in more detail. In short, these diodes form part of a variable attenuator. fungsnetzes in a positive feedback resonant circuit around the amplifier 26 and regulate the amount of damping in such a way that the amplitude of the vibrations is fed to one of the DC voltage corresponding value is set. This capacitive diode arrangement is special advantageous because it ensures an extremely high input impedance for the amplifier 26, whereby again, a number of important advantages to the design and operation of the controller guaranteed.

The vibrations generated in the amplifier 26 are generated by a resonance circuit 310, for example tuned to a frequency of 130 kHz. The vibrations generated in this circle are carried through the transformer 312 of a direct coupled two stage transistor amplifier unit 314 fed in. Each transistor of this unit is assigned over Load resistors 316 and 318 connected to a DC supply line 320 with working power This feed line is in turn connected via a resistor 322 which causes a voltage drop the positive terminal 324 of a 65 V power supply 325 is connected, the negative terminal 326 of which in F i g. 2 is shown.

The alternating voltage supplied by the amplifier unit 314 becomes a via a capacitor 328 further directly coupled two-stage transistor amplifier amplifier unit 330 is fed. The first transistor this unit is fed with direct current through a load resistor 332, while the second transistor Via a load resistor 334 and two coupling circuits 336 and 338 connected in series with current is supplied. The first of these circles, namely circle 336, contains the primary winding 340 of one Transformer 342, whose secondary winding. 344 a Power amplifier stage 346 feeds. The coupling circuit 336 includes a tuning capacitor and a Load resistance that work in the usual way. The other coupling circuit 338 contains the primary winding 348 of a transformer 350 whose secondary winding 352 is connected to two positive feedback lines 354 connected. This coupling circuit 338 includes a tuning capacitor and a load resistor as well as two counter-connected diodes 356, which limit the amplitude of the positive Serve feedback voltage to ensure better stability properties.

The positive feedback lines 354 carry those in the secondary winding 352 of the transformer 350 generated AC voltage back to winding 358 of transformer 304 in the amplifier input circuit, the other winding 302 of which has two center taps 360 and 362 which become a balance adjustment potentiometer 364 lead, whose tap to complete the AC input circuit connected to transformer 312 when the DC inputs 24 and 52 of amplifier 26 no voltage is impressed, diodes 306 and 308 have the same capacitance the potentiometer 364 is set so that it unbalances the AC input circuit so far brings that the amplifier with one between the limits of the design range of the amplitude changes lying amplitude oscillates If the inputs 24 and 52, however, a DC voltage is fed, the diodes 306 and 308 receive different capacities, depending on the Polarity of the fed-in direct voltage increases or decreases the amplitude of the oscillations

The power amplifier 346 has two transistors 366 and 368, the bases of which are connected to one and the other, respectively End of transformer winding 344 are connected so that the two transistors alternate to be activated. The emitters of these transistors are connected to one or the other end of a winding 370 an output transformer 372 is connected. The center tap 374 of this winding is with the negative output 376 of the controller connected, while the positive output 378 of the controller via a Instrument 380 displaying the control voltage generated by the controller to power supply terminal 324 connected. The controller load switched on between outputs 376 and 378 can consist of one or consist of several units of different types: the total ohmic resistance of this load can be up to be about 600 Ω.

The regulator output load circuit includes power supply terminal 324 which is indicative of the control voltage Instrument 380, the regulator load (not shown), one or the other of the two halves of the

Transformer winding 370, the transistor 366 or 368, the resistor 382 or 384, a series resistor 386 (100 Ω) and the negative power supply terminal 326. In this load circuit, the transistors 366 and 368 conduct alternately, the magnitude of the direct current flow being the amplitude of the over the transformer 342 corresponds to AC voltage applied to these transistors.

It has been shown that the strength of the current delivered by the regulator both in terms of its minimum their maximum value should also be limited. In some cases it is desirable to adjust the regulator output current while limiting it to its normal intended operating range in others Cases where the controller is used, for example, to provide a cascade setpoint voltage for another Regulator is used, it may be desirable to reduce the regulator output current to a narrower range for example, from 25 to 75% of its normal range. The current ao output by the regulator limiting device should therefore be adjustable. It has also been shown that this facility does so it should be arranged that it distinguishes the current from the voltage supplied by the regulator must be kept within a desired range since the output load is in a range of up to 600 ohms can be and a voltage limit to different results with different Loads. These features are represented by the circuit elements to be described below guaranteed

In parallel with the transistor 366 and the resistor 382 connected downstream of it, there is a further transistor 388, the base of which is kept at a fixed but adjustable potential by a biasing network 390. This network has a regulating Zener diode 392, which is fed from the power supply terminals 324 and 326 via a resistor 394 which causes a voltage drop. The potential applied to transistor 388 is so great that it normally blocks. However, if the current delivered by the regulator drops to a predetermined lower limit value of, for example, 10 mA, at which the voltage drop generated across the series resistor 386 falls below the potential of the base of the transistor 388 , this transistor becomes conductive, the one flowing through this transistor Current bypasses power transistor 366 and provides sufficient current to the regulator load to prevent the total load current from dropping below a predetermined lower limit.

To set the upper limit value, a further transistor 396 is connected between the base of the power transistor 368 and the negative power supply terminal 326. The base of the transistor 396 is supplied with a fixed but adjustable potential from the network 390. With this arrangement, when the load current across the series resistor 386 reaches a predetermined upper limit value of, for example, 50 mA, a current flows through the emitter-collector circuit of the transistor 396, but only at successive peaks of the alternating current flowing through the transformer 342, whereby these tips will be clipped and the energization of transistor 368 will be decreased. This clipping is presumably based on the effective internal resistance of the transformer 342, for example due to saturation or on a voltage drop across the resistor (, of the transformer winding. In either case, the effect is that the current delivered by the regulator is kept at the predetermined maximum limit value the emitter of the transistor 396 are fed from both ends of the transformer winding 344 ; in this case a corresponding isolating diode (not shown) is switched on in each line, which ensures full-wave operation of the transistor 3% and a corresponding limitation at both output transistors 366 and 368.

The in connection with F i g. 3 is fed by the secondary winding 398 of the transformer 372, the AC voltage of which is fed to a full-wave rectifier circuit 400 for this purpose, which feeds the lines 28 and 30 with DC voltage in order to produce the desired DC supply of the feedback circuit. Obviously, the size of this direct current corresponds to the current that can be drawn from the controller outputs 376 and 378 .

For this purpose 4 sheets of drawings

Claims (8)

Patent claims: 1. Electronic controller, the actuator of which by means of a two-position switch optionally in one first position on the output of the controller for automatic control depending on the Control deviation or in a second position on the output of a control device for adjustment the manipulated variable, e.g. B. by hand, is switchable, with an amplifier whose input has a A voltage corresponding to the control deviation can be applied to the series input impedance, with a feedback network including a feedback resistor between the output and the input of the amplifier and with a capacitor which is in the first switching position of the two-position switch part of the feedback between the output and the input of the Amplifier is and in the second position to one of the manipulated variable and the control deviation dependent voltage is chargeable, thereby characterized that in the first position of the two-position switch (72) (automatic mode) the series input impedance (22) and the feedback resistor (36) over a common one Connection point are connected to a first input (24) of the amplifier (26) that the Capacitor (48) between a first output (28) and a second input (52) of the amplifier (26) and a second capacitor (74) between the first (28) and second (30) output of the amplifier (26) are switched, and that in the second position of the two-position switch (72) (manual operation) the common connection point of the series input impedance (22) and the feedback resistor (36) from the first input (24) of the Amplifier (26) separated and instead the first capacitor (48) between the first output (28) of the Amplifier (26) and said connection point is connected, while the second output (30) of the amplifier (26) is fed back to the first input (24) and the second capacitor (74) are connected between the first output (28) of the amplifier and its second input (52). 2. Regulator according to claim 1, characterized in that a device (78, 88, 90, 74) for Generation of a setting voltage of the desired polarity is provided in the latter Position of the two-position switch (72) is connected to the amplifier input (24, 52) and sets the manipulated variable according to the set voltage. 3. Regulator according to claim 2, characterized in that the device for generating the Setting voltage contains the second capacitor (74), which in the first-mentioned position of the Two-position switch (72) is connected to the amplifier output (30) that its Voltage follows the value of the manipulated variable, and which is in the second position of the two-position switch keeps the manipulated variable at the voltage to which the capacitor immediately before the Switching to the second position was charged. 4. Regulator according to claim 3, characterized in that the two-position switch (72) in its second position the amplifier input (24) impresses a negative feedback voltage that the the voltage impressed by the second capacitor (74) on the amplifier input is equal to and is opposite, such that the moment of switching to the second switch position the The voltage impressed on the amplifier input is practically zero and the manipulated variable is practically none Changes. 5. Regulator according to claim 3 or 4, characterized in that the device (78, 74, 88, 90) a manually adjustable switch (78) with a neutral position to generate the setting voltage and has two operating positions, the second capacitor (74) in its one operating position with a voltage source (88) and in the other operating position connects to an oppositely polarized voltage source (90). 6. Regulator according to claim 3, 4 or 5, characterized in that the changeover switch (72) in its second position the second capacitor (74) between the amplifier output and the amplifier input turns on. 7. Regulator according to one of the preceding claims, characterized in that an input comparison circuit (16,18) is provided and that at this one of the rate of change of the control deviation dependent circuit (62, 64, 66) is connected, the output of which is in the first position of the Two-position switch (72) in series with the first capacitor (48) and the amplifier input and in the second position of the two-position switch in series with the first capacitor and the series input impedance (22) is connected. 8. Controller according to claim 7, with an amplifier having two inputs, characterized in that that the two-position switch (72) in its first position both the one Output of the input comparison circuit (16, 18) and the feedback resistor (36) with the first amplifier input (24) and that of the rate of change of the control deviation dependent circuit (62, 64, 66) in series with the second capacitor (48) with the second amplifier input (52) connects.