US3928810A - Electronic analog hold circuit - Google Patents

Electronic analog hold circuit Download PDF

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Publication number
US3928810A
US3928810A US434001A US43400174A US3928810A US 3928810 A US3928810 A US 3928810A US 434001 A US434001 A US 434001A US 43400174 A US43400174 A US 43400174A US 3928810 A US3928810 A US 3928810A
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United States
Prior art keywords
output
generator
hold circuit
input
amplifier
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Expired - Lifetime
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US434001A
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English (en)
Inventor
Mikio Narita
Kiyoto Ohashi
Jun Yamamoto
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Fischer and Porter Co
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Fischer and Porter Co
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C27/00—Electric analogue stores, e.g. for storing instantaneous values
    • G11C27/02—Sample-and-hold arrangements
    • G11C27/024—Sample-and-hold arrangements using a capacitive memory element
    • G11C27/026—Sample-and-hold arrangements using a capacitive memory element associated with an amplifier

Definitions

  • ABSTRACT An electronic hold circuit in which a capacitor is connected between the output of an operational amplifier and an input thereof.
  • a manually-operated device is provided to alter the output of the output of the hold circuit, the device being constituted by a D-C generator connected between a resistor leading to an input of the amplifier and a point of reference potential, the output of the generator being varied by means of a manually-rotatable element whereby by rotating the element, the capacitor is charged with current resulting from the output voltage of the generatonthereby changing the output of the analog hold circuit.
  • This invention relates generally to electronic analog hold circuits, and more particularly to an improved circuit of this type having manually operated means for altering the output thereof.
  • a potentiometer as a manually operated means for adjusting the set point or output of an electronic controller or'of a manual station in a process control system is well known.
  • a complicated and relatively expensive servomechanism is required in order to follow the output of the potentiometer in accordance with a remote set point so as to effect a balanceless, bumpless transfer from remote to local.
  • an electronic analog hold circuit in the setpoint section or in the manual section of the system.
  • a push-button type of manually operated means is included in the analog hold circuit to vary the output thereof.
  • a knob-operated, rotatable multi-contact switch is employed to effect a change in output.
  • an analog hold circuit comprising an operational amplifier and a hold capacitor connected between the output and one input thereof, a manually operated device being provided to alter the output of the circuit.
  • the device is constituted by a D-C generator connected between a resistor leading to an input of the amplifier and a point of reference potential, the output of the D-C generator being varied by a rotatable knob or thumb wheel mechanically coupled to the generator.
  • the generator output is proportional to the derivative of the rotation angle of the knob or wheel
  • the output of the analog hold circuit is proportional to said rotation angle.
  • FIG. 1 is a schematic diagram of an electronic analog hold circuit provided with one known form of manualoperating means to vary the output of the circuit;
  • FIG. 2 is a schematic diagram of another known form of manual-operating means
  • FIG. 3 is a schematic diagram of a first preferred embodiment of an electronic analog hold circuit provided with a manually-operated device in accordance with the invention
  • FIG. 4 is a diagram graphically illustrating the operating principle of the embodiment of the invention shown in FIG. 3;
  • FIG. 5 is a schematic diagram of a second preferred embodiment of the invention.
  • FIG. 6 is a schematic diagram of a third preferred embodiment of the invention.
  • a hold capacitor C is connected between the output terminal and the inverting input terminal of an amplifier
  • the non-inverting input terminal of the amplifier is connected to a potential source having a predetermined level.
  • a push-button S is connected between a voltage source E, and one end of an input resistor R whose other end is connected to the inverting input of the amplifier, the voltage level of source E being lower than said predetermined level.
  • a second pushbutton E is connected between a voltage source E and the inverting input terminal through resistor R the level of source E being higher than said predetermined level.
  • the lower voltage E By pushing button S or S the lower voltage E, or the higher voltage may be selectively applied to the input resistor R
  • a predetermined current (i) is caused to flow into hold capacitor C through resistor R as indicated by the arrow, and the output B, then developed at the output terminal 1 of the amplifier decreases at a uniform rate.
  • the current (i) is caused to flow in the reverse direction with respect to the arrow direction, as a consequence of which the output E increases at a uniform rate.
  • the voltage change in the output is proportional to the operating time of push-button S or S With this push-button type of manual operation, the output E is changed at a uniform rate.
  • knob 2 when knob 2 is turned manually in the counterclockwise direction (a), the movable contact of switch S is rotated in the same direction.
  • the movable contact is connected to input resistor R only after it has been connected to the higher voltage source E Since capacitor C coupled to the movable contact is charged with the higher voltage E in every counterclockwise rotation of switch S this higher voltage is applied to input resistor R
  • a very small current (i) flows into hold capacitor C intermittently through input resistor R in the direction shown by the arrow, as the movable contact of switch S repeatedly rotates in the counterclockwise direction, and hold capacitor C is thereby charged in a stepwise manner.
  • the output E of the analog hold circuit is thereby caused to decrease in a stepwise manner.
  • knob 2 when knob 2 is rotated in a clockwise direction (a), the movable contact of switch S then proceeds to rotate repeatedly in the same direction, as a result of which the lower voltage E is repeatedly applied to input resistor R causing the output E to increase in a stepwise manner.
  • the change in the output of the analog hold circuit is proportional to the number of rotations of switch S as determined by the rotation angle of knob 2. In this way, the operator can change output E, with a feeling comparable to that experienced when using a potentiometer for manual control.
  • FIG. 3 there is shown a first preferred embodiment of this invention which includes a D-C generator G in place of the rotational switch S and the capacitor C shown in FIG. 2.
  • the output of generator G is varied by means of a knob 2 through a suitable transmission 3,
  • Generator G is electrically connected so as to supply an output voltage Eg between the one end of the input resistor R and the predetermined voltage level common to the non-inverting input terminal of amplifier A
  • knob 2 is rotated counterclockwise, the D-C generator G is rotated 0 in the same direction through transmission 3.
  • an electromotive force proportional to the variation rate of said 0, Le, dO/dt (rad/sec) is generated.
  • the output voltage 15,, of generator G may be expressed by the following equation:
  • the output E of amplifier A decreases in proportion to the rotation angle 0. That is, the output E of the analog hold circuit is altered in proportion to the rotation angle of the generator, i.e., to the rotation angle of the knob 2.
  • FIG. 4 is a diagram illustrating the relationship between E,,, the generator output, and E the circuit output.
  • the waveform (a) shows the output voltage E of the DC generator G while the waveform (b) shows the output E, of the analog hold circuit.
  • FIG. 5 shows a second preferred embodiment ofthe invention in which the analog hold circuit shown in FIG. 3 is applied to a manual station in an electronic controller.
  • the circuit including operational amplifier A acts as a hold amplifier and generates a manual output E in the manner explained in connection with FIGS. 3 and 4.
  • the proportional operational amplifier composed of an amplifier A and a potentiometer R to which a deviation input E, is applied, generates a proportional output E, as a function of input E,-.
  • This output is then applied to the inverting input terminal of the amplifier A, through a parallel circuit of a capacitor C and a variable resistor R
  • the circuit composed of the amplifier A, and capacitor C acts as a proportional-integral operational amplifier.
  • the drift compensating circuit contains a converter AD for converting the output E, to a signal whose frequency corresponds to the output E,,, a clock pulse generator CP, a counter FF to count the frequency of the signal for a predetermined period and a resistor 4 for generating a compensation signal in accordance with the output state (1 or 0) of the counter FF at the end of counting, so that the compensation signal may be supplied to the inverting input terminal of the amplifier A,.
  • the output drift of the analog hold circuit can be made less than 0.1 percent of full scale. From the technical point of view, it will be appreciated that this electronic analog hold circuitry may be used in place of the conventional potentiometer.
  • FIG. 6 shows a third preferred embodiment of this invention, in which the manually operated means in accordance with the invention is applied to an ordinary sample hold circuit.
  • the sample hold circuit is composed of an amplifier A and a capacitor C, connected between the non-inverting input terminal and the reference potential level. Between the output terminal and the inverting terminal of the amplifier A one may provide a circuit so that the output E is fed back directly or through a divider (not shown).
  • the output of generator G which is connected between the inverting input terminal and the non-inverting input terminal of the amplifier A, through resistor R and the parallel circuit of diodes D, and D is applied across these input terminals.
  • the current (i) from generator G flows into the capacitor C through the current-regulating resistor R and the diode D, or D depending on its direction. Also, the current from the low impedance output terminal I flows to generator G.
  • a terminal 5 connected to the non-inverting input terminal of the amplifier A acts to receive input signals to charge the capacitor C other than the manual operating signal produced by generator G.
  • the diodes D, and D act as a switch for separating the circuit including the generator G from both input terminals of the amplifier A and serves to secure an input offset voltage of the amplifier A which is necessary for the amplifiers normal function.
  • the D-C generator included in this invention is the ordinary type adapted to generate positive or negative DC voltage in accordance with the direction of rotation. Accordingly, many commercially available, lowcost D-C generators can be used for this purpose without making any changes therein. Furthermore, since the generator in this invention is not rotated continuously, a highly durable generator is not required.
  • An ordinary D-C generator has a commutator and brushes.
  • a brushless D-C generator containing Hall effect elements and transistorized switching circuits is also applicable to this invention.
  • an A-C generator may be used in place of a D-C generator if a rectifying means and means for detecting the rotating direction are added thereto to produce the necessary D-C output.
  • the operating principle of the circuit in accordance with this invention differs markedly from that of the conventional circuit. That is, in the analog hold circuit of this invention, the alteration of the output E,, i.e., the alteration of the memory of the capacitor C, is brought about by the voltage of the generator G. On the other hand, in the conventional analog hold circuit having push buttons as shown in FIG. 1 or an endlessly rotatable switch as shown in FIG. 2, the alteration of the output E, is caused by the voltage supplied by external voltage sources E,,, E
  • the present circuit may, therefore, be composed of inexpensive components as distinguished from conventional circuits containing a specially-structured rotatable switch as shown in FIG. 2. And, in accordance with this invention, the output E of the circuit can be changed with the same operational feeling as that of the conventional potentiometer.
  • An electronic analog hold circuit comprising:
  • an operational amplifier having a hold capacitor connected thereto and b. a manually operated device to alter the output of the hold circuit, said device including a D-C generator connected between a point of reference potential and an input to said amplifier, said generator being rotated in either direction by means of a manually operated knob or thumb wheel which is mechanically coupled to the generator shaft to cause it to make several turns for each turn of the knob or wheel, whereby the voltage produced by said generator has a polarity that depends on the direction of rotation and gives rise to a current 7 which charges said capacitor to change the output of said analog hold circuit.

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US434001A 1973-01-25 1974-01-17 Electronic analog hold circuit Expired - Lifetime US3928810A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP994173A JPS549862B2 (enrdf_load_stackoverflow) 1973-01-25 1973-01-25

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JP (1) JPS549862B2 (enrdf_load_stackoverflow)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS51126737A (en) * 1975-04-25 1976-11-05 Kawai Musical Instr Mfg Co Ltd Control device of voltage memory element.
JPS5379179A (en) * 1976-12-23 1978-07-13 Yokogawa Hokushin Electric Corp Adjustor meter

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3072856A (en) * 1958-04-15 1963-01-08 Richard N Close Sweep recovery and altitude compensation circuit
US3093784A (en) * 1961-04-26 1963-06-11 Alfred I Mintzer Simplified aided tracking and coasting system
US3511979A (en) * 1968-02-26 1970-05-12 Us Air Force System for measuring area under a curve
US3781628A (en) * 1970-08-07 1973-12-25 Sperry Rand Corp Autopilot pitch attitude control
US3783393A (en) * 1971-05-31 1974-01-01 Fischer & Porter Co Drift-compensated analog hold circuit

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3072856A (en) * 1958-04-15 1963-01-08 Richard N Close Sweep recovery and altitude compensation circuit
US3093784A (en) * 1961-04-26 1963-06-11 Alfred I Mintzer Simplified aided tracking and coasting system
US3511979A (en) * 1968-02-26 1970-05-12 Us Air Force System for measuring area under a curve
US3781628A (en) * 1970-08-07 1973-12-25 Sperry Rand Corp Autopilot pitch attitude control
US3783393A (en) * 1971-05-31 1974-01-01 Fischer & Porter Co Drift-compensated analog hold circuit

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JPS549862B2 (enrdf_load_stackoverflow) 1979-04-27
JPS4998944A (enrdf_load_stackoverflow) 1974-09-19

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