JPH06243549A - Method and instrument for measuring tension - Google Patents

Abstract

PURPOSE:To easily perform the measurement of tension without deteriorating the measuring accuracy even when a voltage more than an analog max. input voltage is given to an A/D converter and to obtain the tension measuring instrument required for no gain adjustment of an amplifier. CONSTITUTION:Tension given to a tape T is measured by a sensor part 110, and a signal SS concerning the obtained tension from this sensor part 110 is amplified by an amplifier part 106, and then an amplified signal AS amplified by this amplifier 106 is analog/digital-converted by an analog/digital converter part 108. At this time, when the amplifier signal AS having a voltage more than the max. input voltage of the analog/digital converter part 108 is inputted from the amplifier part 106 to the analog/digital converter part 108, subtraction control is performed on the signal SS concerning the tension obtained from the sensor part 110, so that the amplified signal AS is suppressed not to exceed the max. input voltage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention measures the tension applied to a long object such as a tape of a VTR device.
The present invention relates to a tension measuring device also called a tension analyzer and a tension measuring method.

[0002]

2. Description of the Related Art A conventional tension measuring device of this type is set, for example, in a VTR device as shown in FIG. The magnetic tape T used in this VTR device passes through the guide 14 and contacts the outer periphery of the rotary drum 10, and further the guide 16
To reach the tension detector 60. The magnetic tape T passes from the guide roller 20 of the tension measuring device, the tension measuring roller 24, and the guide roller 22.

When tension is applied to the magnetic tape T, the tension measuring roller 24 produces a torque F as indicated by an arrow. The resistance value of the strain gauge RX shown in FIG. 5 changes according to the torque F. Due to the change in the resistance value of the strain gauge RX, the balance of the resistance bridge circuit 70 to which the DC power source 34 is applied is lost,
An output is generated in the differential amplifier 37. This differential amplifier 37
The output voltage of is subjected to analog / digital conversion through the AD converter 39 and recorded in the computer 41.

[0004]

However, in order to accurately measure the tension of the tape in such a structure, the amplifier gain N of the differential amplifier 37 is increased so that the tension of the differential amplifier 37 is increased with respect to the tension. It is possible to increase the output voltage.

However, a large tension is caused by the magnetic tape T.
Or when the amplifier gain N of the differential amplifier 37 is set too high, the AD converter 39
Exceeds the maximum input voltage (maximum allowable input voltage) of, and the output code is fixed to the maximum input. Therefore, in such a case, in order to enable measurement, it is necessary to lower the amplifier gain N of the differential amplifier 37 and lower the measurement point from A to the measurement point B for measurement. However, when the amplifier gain of the differential amplifier 37 is lowered in the measurement as described above, there arises a problem that the measurement accuracy of the tension is lowered.

Therefore, in the differential amplifier 37 of the conventional tension measuring instrument shown in FIG.
By selecting any one of 6 and 48, the amplifier gain can be changed from N1 to N2. The output voltage amplified by the differential amplifier 37 by the selected amplifier gain is analog / digital converted by the AD converter 39 and input to the computer 41 such as a microcomputer.

FIG. 6 shows how the output voltage E0 of the differential amplifier 37 changes when the tension of the tape T increases and the torque F increases. For example, when a very large torque Fmax is applied to the strain gauge RX, or when the amplifier gain N of the differential amplifier 37 is large N2, the differential amplifier 37.
6 will exceed the analog maximum input voltage (Emax) of the AD converter 39, as shown by the broken line in FIG.

Thus, the output voltage SO of the differential amplifier 37
Exceeds the analog maximum input voltage Emax of the AD converter, it is necessary to reduce the amplifier gain N. That is, by switching the switch 54 based on a command from the computer 41 shown in FIG. 5, the feedback resistor 48 is switched to the feedback resistor 46. As a result, the large amplifier gain N2 is reduced to the small amplifier gain N1. As a result, the point A at which the maximum analog input voltage Emax is exceeded on the straight line for the large amplifier gain N2 is reduced to the point B on the straight line for the small amplifier gain N1. As a result, the point B is made smaller than the analog maximum input voltage Emax.

By the way, the output voltage SO of the differential amplifier 37
The measured value of E is E0, that is, the input voltage (Volt / g · cm) to the AD converter, and the quantization error of the AD converter 39 is X (Volt / bit). Therefore, the accuracy S is X / It can be expressed by E0 (g · cm / bit). It can be seen that in order to improve the accuracy S, the inclination of the straight line in FIG. 6 should be increased.

Here, E0 (Volt / g · cm) is
The voltage aF (a is a constant) proportional to the torque F is multiplied by the amplifier gain N. That is, the differential amplifier 37
The measured value E0 of the output voltage SO of Eq.

[0011]

[Equation 1]

For example, assuming that the measured value E1 of the output voltage of the differential amplifier 37 when the amplifier gain is N1 and the measured value E2 of the output voltage of the differential amplifier 37 when the amplifier gain is N2, these measured values E1 And E2 are Equation 2 and Equation 3, respectively.

[0013]

[Equation 2]

[0014]

[Equation 3]

These accuracies S1 and S2 are given by equations 4 and 5, respectively.

[0016]

[Equation 4]

[0017]

[Equation 5]

Therefore, the ratio between the precisions S1 and S2 is expressed by the equation (6).

[0019]

[Equation 6]

Therefore, when the amplifier gain is switched from a large N2 to a small N1 as shown in FIG. 6, the accuracy becomes N.
There is a problem that the tension measurement accuracy is deteriorated because of 1 / N2 times. Moreover, as described above, FIG.
The differential amplifier 37 entering the AD converter 39 shown in FIG.
It is necessary to adjust the amplifier gain of the differential amplifier 37 according to the magnitude of the output voltage.

The present invention has been made in order to solve the above-mentioned problems, and a large tension is applied to a long object, so that the analog maximum input voltage is exceeded to the AD converter. It is an object of the present invention to provide a tension measuring device and a tension measuring method that can easily perform the measurement without lowering the tension measuring accuracy even when a large voltage is applied and does not require the gain adjustment of the amplifier.

[0022]

According to the present invention, there is provided a sensor section for measuring a tension applied to a long object and outputting a signal relating to the tension.
A tension measuring device comprising: an amplification unit that amplifies a signal related to tension obtained from the sensor unit and outputs an amplified signal; and an analog / digital conversion unit that performs analog / digital conversion on the amplified signal from the amplification unit. Yes, when the amplified signal having a voltage exceeding the maximum input voltage of the analog / digital conversion unit is input from the amplification unit to the analog / digital conversion unit, with respect to the signal related to the tension obtained from the sensor unit. And a control means for controlling the voltage of the amplified signal so as not to exceed the maximum input voltage of the analog / digital conversion unit.

In the present invention, preferably, the control means is configured to operate when the amplified signal having a voltage exceeding the maximum input voltage of the analog / digital converter is input from the amplifier to the analog / digital converter. A signal output means for outputting a control signal for making the amplified signal the maximum input voltage, and a subtracting means for subtracting a signal relating to the tension obtained from the sensor section by the control signal of the signal output means. Prepare Further, in the present invention,
Preferably, the elongated object is a tape for recording information.

Further, in the present invention, the above object is as follows.
The tension applied to the long object is measured by the sensor unit, the signal related to the tension obtained from the sensor unit is amplified by the amplification unit, and the amplified signal amplified by this amplifier is converted by the analog / digital conversion unit to analog / digital The tension obtained from the sensor unit when the amplified signal having a voltage exceeding the maximum input voltage of the analog / digital conversion unit is input from the amplification unit to the analog / digital conversion unit during digital conversion. By the subtraction control for the signal related to, the tension measurement method that suppresses the amplified signal so as not to exceed the maximum input voltage,
To be achieved.

[0025]

According to the above construction, when the amplified signal of the tension-related signal obtained from the sensor section is analog / digital converted by the analog / digital conversion section, analog / digital conversion is performed.
When an amplified signal with a voltage exceeding the maximum input voltage of the digital conversion unit is input to the analog / digital conversion unit from the amplification unit, subtraction control is performed on the signal related to the tension obtained from the sensor unit, and the maximum Make sure that the amplified signal with a voltage exceeding the input voltage does not exceed the maximum input voltage.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The examples described below are preferred specific examples of the present invention, and therefore, various technically preferable limitations are given, but the scope of the present invention particularly limits the present invention in the following description. Unless otherwise stated, the present invention is not limited to these modes.

FIG. 1 shows a portion of a VTR device with a preferred embodiment of the tension measuring device of the present invention. In this VTR device, a rotary drum 110 and guides 114, 11 for recording / reproducing on / from the magnetic tape T are used.
Have six. The rotary drum 110 is rotatable about 112 and includes a magnetic head (not shown).

The magnetic tape T is guided along the rotary drum 110 via the guide 114, and is further guided to the tension detector 160 of the tension measuring device 118 via the guide 116. Then, the magnetic tape T passes through a guide roller 120 of a tension measuring device 118, a tension measuring roller 124, and a guide roller 122, and is guided to the next stage.

When a tension is applied to the magnetic tape T, the tension measuring roller 124 produces a torque F as indicated by an arrow according to the magnitude of the tension. The resistance value of the strain gauge RX shown in FIG. 2 changes corresponding to the torque F.

The tension measuring circuit shown in FIG. 2 includes a sensor section 110, a control means 120, an amplifying section 106 and an AD.
The converter 108 is provided. Preferably, only the bridge circuit 170 of the sensor unit 110 is included in the tension detecting unit 160 of the tension measuring device 118.

The sensor section 110 comprises a resistance bridge circuit 170, a DC power source 134 as a signal source, and a differential amplifier 104 also called an amplifying section. The resistor bridge circuit 170 includes resistors R1 and R2 and a reference resistor R3,
And it is composed of a strain gauge RX. The DC power supply 134 includes a connection point P1 between the resistors R1 and R2 and a resistor R1.
3 and the strain gauge RX are connected between a connection point P2. In addition, the differential amplifier 104 of the sensor unit 110
Is connected between a connection point P3 between the resistors R2 and R3 and a connection point P4 between the resistance R1 and the strain gauge RX.

In FIG. 1, when a tension is applied to the magnetic tape T and a torque F is generated, the resistance value of the strain gauge RX changes accordingly. As a result, the balance of the resistance bridge circuit 170 is lost, so that a minute voltage change occurs and the differential amplifier 104 generates a signal SS relating to tension.

Next, the control means 120 will be described.
The control means 120 includes a computer 124 such as a microcomputer, the computer 124, a DA converter, and a subtraction circuit 138. The subtraction circuit 138 is provided on the output side of the amplifier 104 and the amplifier 106.
It is provided between the input side of. The subtraction unit 138 is connected to the computer 142 via a DA converter, and the subtraction unit 138 is connected to the AD converter 108 via the amplification unit 106. This AD converter 10
8 is connected to the computer 142. Amplifier 10
The amplifier gain of 6 is fixed to N or fixed.

If the control means 120 outputs an amplified signal AS having a voltage exceeding the maximum allowable input voltage of the AD converter 108 from the amplifier 106 to the AD converter 108.
When the input signal is input to, the signal SS related to the tension obtained from the sensor unit 110 is controlled. As a result, the voltage of the amplified signal AS is changed to A
The maximum allowable input voltage Emax of the D converter 108 can be set to be smaller or smaller.

The computer 142 uses the AD converter 1
Amplified signal A having a voltage exceeding the maximum input voltage Emax of 08
When S is input from the amplifier 106 to the AD converter 100, the DA converter is made to output the control signal SR for setting the amplified signal AS to the maximum input voltage Emax. In this way, the DA converter 136 outputs the control signal SR to the subtraction circuit 138 to subtract the signal SS relating to the tension from the amplification unit 104.

Next, the operation of the above structure will be described.
When tension is applied to the magnetic tape T in FIG. 1, torque F is applied to the roller 124 for tension measurement.
Occurs. In response to this torque F, the resistance value of the strain gauge RX shown in FIG.
The balance of 0 is lost. When this balance is lost, the amplification unit 104 outputs the tension-related signal SS to the amplification unit 106 via the subtraction circuit 138. The amplifying unit 106 amplifies by an amplifier gain N times and outputs an amplified signal AS to the AD converter 108. AD
The converter 108 performs analog / digital conversion on the amplified signal AS and stores it in the computer 142.

By the way, when a large tension is applied to the magnetic tape T, for example, a signal SS relating to a large tension is applied from the differential amplifier 104 to the amplification section 106. As a result, the amplified signal AS from the amplifier 106 to the AD converter 108 is changed to the AD converter 108.
May exceed the inherent maximum allowable input voltage of the.

When the maximum allowable input voltage peculiar to the AD converter 108 is exceeded, the amplified signal AS
The computer 142 detects that the voltage exceeds the maximum allowable input voltage Emax of the AD converter 108, and immediately D
A digital control amount is given to the A converter 136.
The DA converter 136 converts the digital control amount from digital to analog, and outputs the analog control signal SR to the subtraction circuit 138. This subtraction circuit 138
A signal S related to the tension corresponding to the control signal SR
Subtract S.

As a result, the signal SS related to the tension applied to the amplification section 106 becomes small, and the amplification section 106 is reduced.
The voltage of the amplified signal AS output from is preferably AD
It is equal to the inherent maximum allowable input voltage Emax of converter 108.

For example, as shown in FIG. 3, the amplified signal AS which is the input voltage E0 to the AD converter 108 is AD
When the maximum allowable input voltage Emax of the converter 108 is exceeded, for example, when the point A on the extension of the straight line 200 is reached, the control signal SR of the DA converter 136 is gradually increased to be indicated by the point B. Thus, preferably, the amplified signal AS (the input voltage E0 of the AD converter) becomes equal to the maximum allowable input voltage Emax, and the amplified signal AS that is the output value of the AD converter 108 is fixed. The value of the DA converter 136 at that time is (+ a).

At that time, the point A can be expressed by Equation 7. Formula 7
In, the input voltage E0 of the AD converter 108 is the maximum input voltage Emax and a constant (value of the DA converter 136+
a) and multiplied by N.

[0042]

[Equation 7]

In this way, the amplifier gain N of the amplifying section 106 is fixed or fixed, and the amplified signal AS is preferably input to the maximum allowable level without any adjustment of the amplifier gain of the conventional amplifying section. Since the offset can be automatically adjusted to be equal to the voltage Emax, the tension can be automatically measured with high accuracy without impairing the accuracy S (g · cm / bit). In this way, it is also preferable to set the amplified signal AS to the maximum allowable input voltage E.
By automatically adjusting the offset to be equal to max, the tension can be measured most accurately by taking advantage of the maximum capacity of the AD converter 108.

Although the amplified signal AS is equal to the maximum allowable input voltage Emax in the above embodiment, the amplified signal AS may be automatically offset-adjusted so as to be smaller than the maximum allowable input voltage Emax. . In this way, for example, by feeding back this value in accordance with the value of the tension measured accurately, it is possible to adjust the rotation speed of the rotary drum and control the reproduction sensitivity of the tape, for example.

The present invention is not limited to the above embodiment. For example, the present invention can be applied not only to magnetic tapes but also to measuring tension applied to other types of long objects. Further, although the strain gauge RX is used for torque detection in the above embodiment, the present invention is not limited to this, and other types of sensors for measuring pressure or force may be used. Also, the bridge circuit is not limited to the resistance-voltage conversion circuit, and other types can be applied.

[0046]

As described above, according to the present invention, when a large tension is applied to a long object, an amplified voltage exceeding the maximum input voltage is applied to the analog / digital converter. Even when added, the tension can be measured without lowering the accuracy without lowering the gain of the amplification section. Further, it is not necessary to adjust the gain of the amplification section.

[Brief description of drawings]

FIG. 1 is a V to which a tension measuring device of the present invention is applied.
The figure which shows a part of TR apparatus.

FIG. 2 is a diagram showing a circuit of the tension measuring device of FIG.

FIG. 3 is a diagram showing characteristics with respect to the torque F in FIG. 2 and an input voltage E0 to the AD converter side.

FIG. 4 is a diagram showing a part of a VTR device provided with a conventional tension measuring device.

5 is a diagram showing a circuit of the conventional tension measuring device of FIG.

6 is a diagram showing a relationship characteristic between a torque F and an input voltage E0 of an AD converter in the conventional circuit of FIG.

[Explanation of symbols]

104 amplification section (differential amplifier) 106 amplification section 108 AD converter (analog / digital conversion section) 110 sensor section 118 tension measuring instrument 120 control means 124 tension measurement roller 136 DA converter (signal output means) 138 subtraction circuit (subtraction means) ) 142 computer (signal output means) 170 resistance bridge circuit Rx signal related to strain gauge SS tension AS amplified signal as input voltage E0 to AD converter SR control signal

Claims (4)

[Claims] 1. A sensor section for measuring a tension applied to a long object and outputting a signal related to the tension, and an amplification section for amplifying a signal related to the tension obtained from the sensor section and outputting an amplified signal. And an analog / digital converter for analog / digital converting the amplified signal from the amplifier, wherein the amplified signal has a voltage exceeding the maximum input voltage of the analog / digital converter. From the amplifier to the analog /
In order to control the tension-related signal obtained from the sensor unit so that the voltage of the amplified signal does not exceed the maximum input voltage of the analog / digital conversion unit when input to the digital conversion unit. And a control means for controlling the tension. 2. When the amplified signal having a voltage exceeding the maximum input voltage of the analog / digital converter is input from the amplifier to the analog / digital converter, the control means outputs the amplified signal to the maximum value. The signal output means for outputting a control signal for setting the input voltage, and the subtraction means for subtracting the signal related to the tension obtained from the sensor section by the control signal of the signal output means. Tension measuring instrument. 3. The tension measuring device according to claim 1, wherein the elongated object is a tape for recording information. 4. A tension applied to a long object is measured by a sensor unit, a signal related to the tension obtained from the sensor unit is amplified by an amplification unit, and the amplified signal amplified by this amplifier is analog / digital. When the analog / digital conversion is performed by the converter, when the amplified signal having a voltage exceeding the maximum input voltage of the analog / digital converter is input from the amplifier to the analog / digital converter, the sensor unit Performs subtraction control on the signal related to the tension obtained from
A tension measuring method, characterized in that the amplified signal is suppressed so as not to exceed a maximum input voltage.