JP2719815B2 - Analog output type measuring instrument - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial application field> The present invention is to input a sensor signal such as a rotation pulse from a rotation sensor,
The present invention relates to an analog output type measuring device that calculates a measurement value such as a flow rate and a passage time and outputs the calculation result as an analog amount of voltage or current.

<Conventional technology> To keep the rotation speed of the roller driven by the motor and the peripheral speed of the belt conveyor constant, use an analog output type measuring device and respond to the rotation speed or the peripheral speed measured by this measuring device. The analog output is fed back to the control unit of the motor to control the rotation speed of the motor.

Analog output type measuring instruments used for such purposes are
Conventionally, a pulse signal from a rotation sensor or the like is converted into an analog voltage or current value by a frequency-voltage converter and output.

<Problems to be Solved by the Invention> However, in a measuring instrument provided with a frequency-voltage converter, good linearity is obtained over a wide range from a low speed to a high speed of an object to be measured, from a general characteristic of the converter. It is difficult to realize, especially in a low-speed region, and there is a disadvantage that linearity is deteriorated and a large fluctuation (ripple) occurs in an analog output due to a long input interval of a pulse signal.

Also, when the number of pulse signals generated per rotation of the measured object changes, or when resetting the maximum and minimum rotation speeds, operate several operation means such as DIP switches. It was necessary to switch the frequency range, and the handling was troublesome.

To deal with this, it is possible to digitally process the input sensor signal using a digital measuring instrument, obtain digital data corresponding to the measured value, convert this digital data into an analog quantity with a D / A converter, and output it. Conceivable.

As described above, once digital data corresponding to a measured value is created and then converted to an analog output, good linearity can be expected over a wide range from low speed to high speed.

However, a conventional general digital measuring instrument digitally displays a measurement result at a relatively long cycle (1/4 to 1 second) so that the measurement result can be confirmed by human eyes. It is performed in a long period that is almost synchronized.

Therefore, when trying to use the measurement output of such a measuring instrument, the response of the analog output to the fluctuation of the input sensor signal tends to be delayed, and the analog output that follows the fluctuation of the movement of the measured object cannot be obtained. Feedback control becomes impossible.

Here, if the calculation cycle is shortened in order to enhance the followability, the display cycle is correspondingly shortened, and the digital display of the calculation result becomes difficult to see, so that the digital display unit no longer plays its original role.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and creates digital data corresponding to a measured value based on an input sensor signal, and then converts the digital data into an analog amount, thereby obtaining an analog signal. To obtain good linearity over a wide range from low speed to high speed of the measuring object, improve the followability to fluctuations of the input sensor signal, and do not interfere with the digital display of the calculation result. As an issue.

<Means for Solving the Problems> In order to achieve the above object, the present invention provides an input unit for inputting a sensor signal as shown in FIG. First digital calculation means for calculating a measurement value based on the input signal of the first digital calculation means, a digital display unit for displaying a calculation result of the first digital calculation means, setting means capable of setting at least a measurement range, and the input unit A second digital calculation means for calculating a measurement value in a shorter period than the first digital calculation means in a measurement range set by the setting means based on an input signal from the second digital calculation means; An analog output type measuring device is provided with a D / A converter for converting digital data corresponding to the measured value into analog data and outputting the converted data to the outside.

<Operation> In the above configuration, the sensor signal is transmitted to the first through the input unit.
And the second digital operation means.

The first digital calculation means calculates the measurement value at a relatively long cycle, and displays the calculation result on the digital display unit at a long update cycle that can be confirmed by human eyes.

On the other hand, the second digital calculation means calculates the measurement value at a shorter cycle than the first digital calculation means. The digital data as the calculation result is converted into an analog quantity by a D / A converter and output.

Therefore, the analog output follows the fluctuation of the sensor signal. Further, since the second calculating means calculates the measured value based on the setting data from the setting means, an analog output having the set range as a full scale can be obtained as in the case where the frequency range is switched.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 2 is a circuit block diagram of an analog output type measuring instrument according to one embodiment of the present invention.

As shown in FIG. 1, an analog output type measuring instrument according to this embodiment includes a main body 1 and an input / output adapter 2 attached to the main body 1.
And an appendage 3 connected via the.

The main body 1 includes a digital display 4, a setting key 5, and a first key.
Microcomputer 6 as digital operation means
A waveform shaping input interface 8 as an input section of a rotation pulse from the rotation sensor 7 which is a sensor signal;
An EE-PROM 9 as an external memory is provided. Reference numeral 10 denotes a rotating body as a measured object.

The microcomputer 6 includes a CPU, a program ROM, a work RAM, a timer for generating a reference time for inputting a clock pulse, and a counter for counting a rotation pulse input via the input interface 8. Is used, and specifically, μPD75116 is used.

The microcomputer 6 counts the number of rotation pulses input within the reference time To created by the timer with a counter, and further, after the reference time To elapses, sets a period Ta until the first rotation pulse is input to the timer. , And the total period T (= To + Ta) in which an integer number (n) of rotation pulses are input is measured.
The number of rotations is calculated from the number n of rotation pulses during that time and the number of pulses P generated per rotation of the rotating body. Each time the calculation result is calculated, the display on the digital display 4 is updated. In the microcomputer 6, the reference time To is set to a relatively long time (about 1/4 to 1 second). Therefore, the measurement cycle is long, and the display update cycle on the digital display 4 is also a cycle that can be confirmed by human eyes.

On the other hand, the appendix 3 includes a microcomputer 11 as a second digital operation means,
A serial-parallel converter 12 for converting serial data output from 11 into parallel data, and a photocoupler 13 interposed between the serial-parallel converter 12 and an output unit of the microcomputer 11
A D / A converter 14 for converting parallel data from the serial-parallel converter 12 into an analog amount, a voltage output amplifier 15 for amplifying the output of the D / A converter 14, and a voltage output amplifier 15 And a current output amplifier 16 connected to the output stage. 17 is a voltage output terminal, and 18 is a current output terminal.

The microcomputer 11 receives a rotation pulse through the input interface 8 of the main unit 1 and the adapter 2 and communicates with the microcomputer 6 of the main unit 1 through the adapter 2. As with the microcomputer 11 of the body 1, the microcomputer 11 of the attachment 3 includes a CPU, a program ROM, a work RAM, a timer for generating a reference time for inputting a clock pulse, and an input interface 8. A counter having a counter for counting the number of input rotation pulses is used.

Similarly to the microcomputer 6 of the main body 1, the microcomputer 11 of the appendage 3 measures the total period T (= To + Ta) in which an integer number (n) of rotation pulses are input, and calculates the total period T The number of rotations is calculated from the number of rotation pulses n and the number of pulses P generated per rotation of the rotating body 10. The reference time To of the microcomputer 11 is calculated by the microcomputer 6 of the main body 1. It is set shorter than the reference time (specifically, about 10 msec), and the calculation result is calculated in a short cycle.

 Hereinafter, the operation of the above configuration will be described.

FIG. 3 is a flowchart showing a routine in which the microcomputer 6 operates when the power of the main body 1 is turned on.

In step S1, it is determined whether or not the attachment 3 is connected to the main body 1 via the adapter 2. If the attachment 3 is connected, communication with the attachment 3 is performed in step S2.
Since a different type of accessory from the illustrated accessory 3 may be connected to the main body 1, it is checked in step S 3 whether the connected accessory 3 is the specified accessory 3 as illustrated.

If the predetermined attachment 3 is connected, the setting data (the number of rotation pulses per rotation, the maximum rotation number, the minimum rotation number, etc.) stored in the EE-PROM 9 is attached in step S4. It is transmitted to the body 3, and in step S5, it is confirmed whether or not all the setting data has been received by the attachment 3.

FIG. 4 is a flowchart showing a routine when the setting data is changed by operating the setting key 5 in the main body 1.

In step T1, it is determined whether or not the setting data has been changed by operating the setting key 5. If there is a change in the setting data, in step T2, the changed setting data items (the number of pulses per rotation, Rotation speed, minimum rotation speed, etc.)
Is determined, and in step T3, the setting data of each item is reset.

In step T4, it is determined whether the setting is completed. If the setting is completed, in step T5, communication is performed with the attachment 3 connected to the main body 1, and The type is queried, and in step T6, it is determined whether or not the appendage 3 connected to the main body 1 is the predetermined appendage 3. If the appendage 3 is the predetermined appendage 3, the setting is reset in step T7. The attached data is transmitted to the appendix 3.

In step T8, it is checked whether or not all the setting data has been received by the appendix 3.

FIG. 5 is a flowchart showing the operation of the microcomputer 11 of the appendage 3 and shows routines related to the routine of the main unit 1 shown in FIGS. 3 and 4.

In step U1, the transmission data from the main body 1 is received,
In step U2, it is determined whether or not the transmission is an inquiry about the type of the appendage 3, and if the transmission is an inquiry about the type of the appendix,
In step U3, the type of the appendage 3 is transmitted to the main body 1 side.

In step U2, when it is determined that the transmission from the main body 1 is not an inquiry of the appendage type, in step U4, it is determined whether or not the transmission data from the main body 1 is the setting data. The setting data is checked for each item, and in step U6, it is determined whether or not the setting data is correct. If there is no defect, in step U7, a reply indicating that the setting data has been received is transmitted to the main body 1 side. And then
In step U8, a measurement routine is entered.

As described above, this measurement routine counts the number of rotation pulses input within the reference time To created by the timer with a counter, and further, after the elapse of the reference time To, the cycle until the first rotation pulse is input. Ta is measured by a timer, thereby measuring an entire period T (= To + Ta) in which an integer number (n) of rotation pulses are input.
The number of rotations is calculated from the number n of rotation pulses during that period and the number of rotation pulses P generated per rotation of the rotating body.

If it is determined in step U4 that the transmission data from the main unit 1 is not the setting data, the process proceeds to step U9 to transmit that a reception error has occurred on the main unit 1 side.

<Effects of the Invention> As described above, according to the present invention, the input sensor signal is digitally processed, and once digital data corresponding to the measured value is created, the digital data is converted into an analog amount and output. Good linearity can be obtained over a wide range from low speed to high speed of the measured object.

In addition, the second digital operation means calculates the measured value in a shorter cycle than the first digital operation means and outputs a voltage or a current corresponding to the operation result. Output is obtained, followability is improved, and accurate feedback control becomes possible.

Further, the first digital calculation means calculates the measurement value at a relatively long cycle and displays the calculation result on the digital display unit. Therefore, the display is updated at a long cycle that can be confirmed by human eyes. As a result, the display is not obstructed.

In addition, since the second digital calculation means calculates the measurement value based on the setting data from the setting means, an analog output having the set range as a full scale can be obtained in the same manner as switching the frequency range. In addition, the trouble of switching frequency ranges is eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a circuit block diagram of one embodiment of the present invention, and FIGS. 3 and 4 are flowcharts showing the operation of the microcomputer on the main body. FIG. 4 shows a routine when the power is turned on, and FIG. 4 shows a routine when the setting data is changed. FIG. 5 is a flowchart showing the operation of the microcomputer on the appendage side. 1 ... body, 3 ... attachment, 4 ... digital display, 5
…… Setting keys, 6,11 …… Microcomputer, 8 ……
Input interface, 14 ... D / A converter.

Claims (1)

(57) [Claims] 1. An input section for inputting a sensor signal, first digital calculation means for calculating a measured value based on an input signal from the input section, and a digital display for displaying a calculation result of the first digital calculation means. A display unit, setting means capable of setting at least a measurement range, and the first measurement range set by the setting means based on an input signal from the input unit.
A second digital calculating means for calculating a measured value in a shorter cycle than the digital calculating means, and a D / D converter for converting digital data corresponding to the measured value obtained by the second digital calculating means into an analog signal and outputting it to the outside An analog output type measuring instrument comprising an A converter.