JPS6058402B2 - Servo recorder - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in the electrical circuitry of servo recorders.

A servo recorder has a pen and a slider of a potentiometer mechanically interlocked, and feedback is provided from the potentiometer to an amplifier that drives the pen. The typical configuration of a conventional example is shown in Figure 1. Shown below.

That is, in FIG. 1, Vin is the recorder input, which is amplified by an amplifier Al and configured to drive a motor M mechanically coupled to the pen. The motor M is mechanically interlocked with the slider of the potentiometer VRI, and generates a voltage VA by dividing the reference voltage Es applied to the potentiometer VR. Further, another potentiometer VR2 for determining the zero point is connected to this same reference voltage, and a divided voltage VB is obtained at this slider. These two voltages VA and VB are coupled to two inputs of a differential amplifier A2, and the output Vf of this differential amplifier A2 obtains a voltage Vf=VA-VB, which is the voltage of the pen drive amplifier Al. It is fed back to the positive input.

In such a structure, the potentiometer VR, that is, the pen moves until the feedback voltage Vf becomes equal to the input voltage Vin, so the gain of the amplifier Al has an excellent property of not causing a display error. However, in such a servo recorder, when the differential amplifier A2 obtains the difference between the voltages VA and VB, the gain error immediately becomes a display error.

,R. Precision resistors must be used for and R. In a practical device, metal film resistors are used for these four resistors in order to cope with aging, temperature changes, and the like. This is expensive, and the accuracy of the meter is determined by these four resistors, which is not desirable for a precision meter. Figure 2 is also a configuration diagram of the conventional device.
Connect the reference voltage FEEs to the internal common power supply +E (e.g. 15V)
In this case, resistors Rl, R6, R7, R8 and R9 need to be precision.

FIG. 3 is also a block diagram of a conventional device, which is constructed to reduce the number of precision resistors.

In this example, the three resistors Rl, R6 and R7 need only be precision. However, for this purpose, the diodes D1 and D2 must generate positive and negative constant voltages with respect to each other, and it is necessary to select diodes having the same temperature coefficient. FIG. 4 is also a structural diagram of a conventional device, which was designed to eliminate precision resistors.

In this example, the reference voltage Es is completely floating from ground potential.
Here are the two potentiometers VRl and V
R2 is connected, and a common potential point is determined at an arbitrary dividing point using a potentiometer VR2. This example does not require a precision resistor, but in order to obtain a current source S'' that is completely floating from the ground, a separate winding is prepared for the power transformer, and a rectifier circuit and a smoothing circuit are installed just for this power source Es''. The circuit becomes complicated. Furthermore, such a power supply that is completely floating from the ground is susceptible to noise and generates large hum or spike noise from the commercial power supply, making it impractical. The present invention was made against such a background. To provide a practical servo recorder that does not require a power supply completely floating from ground, which requires precision resistors, tends to become a noise source, and has a complicated circuit configuration.

In the present invention, a constant voltage obtained from a power source in the device is applied to two potentiometers, the negative input of the slider of one potentiometer is used, the positive input is used as a common potential point, and the output is coupled to the constant voltage. A voltage (1)8 is generated by a differential amplifier, and a voltage (2) and (f) is obtained from the slider of the other potentiometer and applied to the positive input of a differential amplifier for driving the pen.

This will be explained in more detail with reference to Examples. FIG. 5 is a circuit diagram of a first embodiment of the present invention.

Al, A2, AG are differential operational amplifiers, VRl,
VR2 is a potentiometer, and R1 to Rl4 are resistors. D indicates a zener diode, and M indicates a motor for driving the pen. The input signal Vin is input to the amplifier A1 via the resistor R1.
is connected to the negative input of The output of this amplifier A1 is subjected to negative feedback through a resistor R2. This output is configured to drive a motor M. On the other hand, the zener diode D has a resistor R connected to the power supply +E in the device.
A current flows from the output of lO and the amplifier input through the resistor Rl4, which is connected from the resistor Rll and the output of the amplifier A2 to the power supply IE, and the current flowing through the zener diode D is It is configured to be controlled to a constant current by a dynamic operational amplifier and resistors Rl2 and Rl3. The voltage across the Zener diode D is connected to both fixed ends of the two potentiometers R1 and VR2, and the negative potential point of this voltage is coupled to the output of the differential operational amplifier. . The potential of the slider of potentiometer VR2 is connected to the negative input of this amplifier. The positive input of the amplifier ~ is connected to a common potential point. Also, the slider of the potentiometer R1 is configured to mechanically interlock with the motor M and the pen (not shown).
It is electrically coupled to the positive input of amplifier A1. To explain the operation of such a device, since the Zener diode D is controlled so that a constant current flows,
The voltage Es across these ends remains constant.

The potential of this voltage A S with respect to a common potential point is a potential located midway between the power supply E in the device, but it changes depending on the position of the slider of the potentiometer VR2. That is, since the differential operational amplifier ~ is provided with sufficient negative feedback via the slider of the potentiometer VR2, this amplifier ~
Within the normal operating range, the potentials of the positive and negative input terminals are controlled to be equal, and the potential of the slider of potentiometer VR2 is equal to the common potential point. Therefore, amplifier A
If the potential difference between the output potential of amplifier A2 and the slider of potentiometer R1 is VAl, or the potential difference between the output potential of amplifier A2 and the slider of potentiometer VRl is VB, then the common potential of the slider of potentiometer VRl is The potential with respect to the potential point is Vf=VA-■8.

Since this is applied to the positive input of the amplifier A1, the motor M follows so that this potential Vf becomes equal to the input signal Vin, and operates as a servo recorder. Potentiometer VR2 is for initial zero point setting. In the circuit of Fig. 5, there is no need for a precision resistor between the slider of potentiometer R1 and the positive input of amplifier A1, and between the potentiometer VR2 and the negative input of amplifier A2. Precision resistors are also not required.

Therefore, a precision resistor is not required in the circuit that calculates the difference between the voltage (6) and VB. Further, the voltage Es generated across the Zener diode D is obtained from the power supply engineer E within the device.

Although this is not a completely floating supply from common potential, potentiometer VR2 becomes the negative feedback path for amplifier A2, forcing the slider of VR2 to the common potential point. That is, according to this circuit, the reference voltage Es
does not have to be a completely floating voltage. Since the value of the reference voltage Es is determined by the Zener diode D, the resistors RlO-Rl4 do not need to be precise. The resistor RlO or Rll can be selected within a wide range depending on the output capacitance of the amplifier.

For example, make their resistance values infinite (RlO, Rll
) is also possible.

However, in that case, all of the current flowing through the resistors Rl2 and Rl flows out of the output of the amplifier A3 and flows into the output of the amplifiers. FIG. 6 is a circuit diagram of a second embodiment of the present invention.

In this example, a constant current applied to the Zener diode D is obtained by a transistor Q and resistors R15 to R17, and the other components are the same as the example shown in FIG. In this case too, no precision resistor is required. It also does not require a power supply completely floating from a common potential point. 7th
The figure is a circuit diagram of a third embodiment of the present invention.

In this example, compared to the second embodiment shown in FIG.
With potentiometer R2 in the figure fixed at the lowest point, the positive input terminal of amplifier A2 is connected to -V from another reference voltage.
It is configured to give B. With this configuration, it is necessary to generate two types of reference voltages, +Es and upper s'', and the circuit becomes somewhat complicated, but the amplifier ~
Since there is no need to use precision resistors around the circuit, this circuit is considerably advantageous compared to the conventional example shown in FIG. In this case, -VB may be supplied from another variable constant voltage source without necessarily using the potentiometer (R2).
As described above, according to the present invention, since a precision resistor or a metal film resistor is not used, the device is economical and there is no measurement error caused by changes in resistance value such as aging. It will be done.

Furthermore, since a reference voltage completely floating from the common potential point is not required, a device with a simple circuit configuration and low noise can be obtained. In the above embodiment, the slider of the potentiometer VR is mechanically interlocked with the pen, and the slider of the potentiometer R2 is used to adjust the zero point, but these two potentiometers are mutually linked. Even if it is replaced with , the operation and characteristics are the same, and the present invention can be carried out in the same manner.

[Brief explanation of the drawing]

1, 2, 3, and 4 are circuit configuration diagrams of a conventional device, FIG. 5 is a circuit configuration diagram of a first embodiment of the present invention, and FIG. 6 is a circuit diagram of a second embodiment of the present invention. Example device) Device circuit configuration diagram, No. 7
The figure is a circuit configuration diagram of a device according to a third embodiment of the present invention. Al, ~, A3... Differential operational amplifier, M... Motor, VRl, VR2... Potentiometer, Dl, D2
9D9D''... Zener diode, R1~Rl8...
·Resistor.

Claims (1)

[Claims] 1. A first potentiometer VR_1 whose slider is mechanically connected to the pen, a second potentiometer VR_2 whose slider is arranged for zero point setting, and Means for commonly applying a constant voltage Es to each fixed terminal of the potentiometer, a negative input connected to the slider of the second potentiometer VR_2, a positive input connected to a common potential point, and an output of the constant voltage Es The slider potential of the first differential operational amplifier A_2 and the first potentiometer VR_1 connected to one potential point of A servo recorder equipped with a second differential operational amplifier A_1 guided by a driving motor. 2 A first potentiometer VR_1, a means for applying a constant voltage Es to the fixed terminal of this potentiometer, a means for generating a variable voltage -V_B, and a negative input and an output connected to the fixed terminal of the first potentiometer VR_1. The first differential operational amplifier A_2 is connected to one side and its positive input is connected to the variable voltage -V_B, and the slider potential point of the first potentiometer VR_1 is guided to the positive input and input to the negative input. A servo recorder comprising a second differential operational amplifier A_1 to which a signal Vin is guided and whose output is guided to a motor M for driving a pen.