JPH0731758B2 - Strain measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain measuring device, and more particularly to a strain measuring device which measures the strain of the ground to prevent landslides and automatically collects the measured data in a master station.

[0002]

2. Description of the Related Art A long pipe is vertically embedded in the ground, and a large number of pairs of resistance wire strain gauges are attached to the opposing surfaces of the pipe at a certain interval in the vertical direction. A strain measuring device has been conventionally known in which a bridge circuit is composed of two constant resistors, a measuring DC voltage is applied to the input side of the bridge circuit, and a change in the DC voltage is taken out from the output side.

In such a strain measuring device, when the strain gauge comes into contact with moisture in the ground, there is a problem in that a charging function such as a lead wire causes a polarization action, which deteriorates the measurement accuracy. In order to eliminate the effect of this polarization effect, it is known to provide a polarity switching device for the DC power supply for measurement that is supplied to the strain gauge, and take the average value of the result measured with a positive voltage and the result measured with a negative voltage. ing.

[0004]

On the other hand, when the output of the strain gauge is transmitted to a remote monitoring station, the output value is A
There are the following problems when the digital value is converted into a digital value and transmitted by using the / D conversion measuring instrument.

That is, a general industrial A / D conversion measuring instrument is manufactured so that it operates when the applied voltage is a positive voltage, but does not operate when the applied voltage is a negative voltage.

However, if the voltage applied to the strain gauge is switched to a negative voltage in order to eliminate the influence of the above-mentioned polarization action, the output value becomes a negative voltage, so that even if this is converted into a digital value, A / D conversion is performed. There is a problem that the measuring instrument does not work.

Therefore, the present invention provides the industrial A as described above.
An object of the present invention is to enable A / D conversion without any problem even if a negative voltage is applied to the strain gauge when the / D conversion measuring instrument is used.

[0008]

In order to achieve the above object, the present invention provides an A / D conversion measuring device for converting the output of a strain gauge into digital value data for each slave station, and the A / D conversion device is provided. In a strain measuring device in which the digital value data converted by the conversion measuring device is transmitted to the CPU of the master station through the CPU of the slave station, a DC power source for measurement is connected to the input side of the strain gauge through a polarity switch. Connected to the output side of the strain gauge, a DC bias power supply having a positive voltage with an absolute value larger than the absolute value of the negative voltage output value is connected, and the CPU of the master station is instructed to transfer data for each slave station. Means, a means for transmitting a switching signal for operating the polarity switcher of each slave station, and a means for arithmetically processing and averaging data before and after transmission of the switching signal.

[0009]

In the above strain measuring device, the CPU of the master station
When a data transmission command is sent to a specific slave station, the A / D conversion measuring instrument of the corresponding slave station takes in the data of the strain gauge belonging to that slave station and converts it into digital value data. A slave station number and digitized data are arranged in the order of strain gauge installation to form a signal string of a predetermined format and transmitted to the master station. When receiving the data, the master station transmits a switching signal to the slave station, activates the polarity switcher on the slave station side, and sends a data transfer command again. Then, the data collected by switching the polarity of the DC power source for measurement is transmitted to the CPU of the master station. At this time, even if the measuring DC power supply has a negative voltage, a positive voltage is applied to the A / D conversion measuring instrument by adding the bias voltage of the slave station.

The data converted into the digital value in this way is again transferred to the CPU of the master station, and the CPU of the master station performs arithmetic processing for averaging the previous data and the subsequent data, and the bias voltage of the slave station. The calculation result with the minutes removed is output.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 and 2, the strain measuring apparatus of the embodiment has a public telephone line 3 between a monitoring station 1 and a master station 2.
, And data communication is performed between them.

The monitoring station 1 has a CPU 4, a modem 5 and a CRT 6
And a printer 7. Further, the master station 2 includes a CPU 8, a modem 9 and a control unit 10. CPU of master station 2
4, the control unit 10 and each slave station 11 are connected by a loop-shaped communication line 12 using an optical fiber.

An AC power line 13 is provided between the control unit 10 and each slave station 11, and a switch 14 for each slave station 11 is provided on the master station 2 side so that the AC power can be turned on and off.

Each slave station 11 has an A / D conversion measuring instrument 15,
It is composed of a plurality of measuring units 16. As shown in FIG. 2, the A / D conversion measuring instrument 15 is a CPU of the slave station 11.
17 and an A / D converter 18 are provided and are configured to operate only when the input is a positive voltage, as described above.

Each measuring unit 16 of the slave station 11 comprises a switching regulator 19, a polarity switcher 20, a bridge circuit 21, a bias power supply 22 for the bridge circuit 21, and an amplifier 23.

The switching regulator 19 converts the AC power (100V) supplied from the master station 2 into a stabilized predetermined DC voltage (2.5V) and outputs it.

The polarity switching device 20 is composed of a switching relay 24 and two switching contacts 25 and 25 thereof, and each switching contact 25 and 25 is interposed in a circuit connecting the switching regulator 19 and the bridge circuit 21. . The switching relay 24 is operated by a switching signal transmitted from the master station 2 via the A / D conversion measuring instrument 15.

The bridge circuit 21 includes a strain gauge 26 on the compression side.
And a strain gauge 27 on the extension side and a combination of two constant resistors 28, 28, and the amplifier 23 is connected to the circuit on the output side. The output side of the amplifier 23 is input to the A / D converter 18. Further, one output end of the bridge circuit 21 is grounded via a bias power source 22 of positive polarity. The voltage of the bias power source 22 is set to have an absolute value larger than the absolute value of the negative voltage appearing on the output side when the negative voltage is applied to the bridge circuit 21 via the polarity switcher 20. That is, when a positive voltage is applied to the bridge circuit 21, a positive bias voltage is added to the bridge circuit 21 and output, and when a negative voltage is applied, the difference between it and the positive bias voltage is output as a positive voltage. Has become
In either case, a positive voltage is input to the A / D conversion measuring instrument 15.

The strain measuring apparatus of the embodiment is as described above, and its operation will be described below.

From the monitoring station 1 through the CPU 4 to the master station 2
When a data transfer command is output via the public telephone line 3, the CPU 8 of the master station 2 calls a predetermined slave station 11 via the control unit 10 and closes the corresponding switch 14 to switch the AC power supply to the slave station. Send to 11.

In the corresponding slave station 11, a DC power for measurement is supplied to the bridge circuit 21 through the switching regulator 19, and an output voltage obtained by adding a bias voltage to the measurement result at that time is input to the amplifier 23. The output data (analog value) amplified by the amplifier 23 is input to the A / D converter 18, where it is converted to digital value data and input to the CPU 17 of the slave station 11.

Since the CPU 17 of the slave station 11 also receives the data from the other measurement units 16 belonging to the slave station 11, these are arranged in sequence and the slave station 1 as the transmitting station is further arranged.
A signal sequence of a predetermined format numbered 1 is constructed and transmitted to the CPU 4 of the master station 2 through the communication line 12.

The master station 2 then transmits a polarity switching signal to the slave station 11. As a result, the switching relay 24 of the slave station 11 is excited, the switching contact 25 thereof is activated, and the polarity of the DC voltage input to the bridge circuit 21 is switched, and the output at that time is sent to the CPU 4 of the master station 2 in the same manner as described above. Send.

The CPU 4 of the master station 2 controls each measuring unit 16
For each of the two types of data, a negative sign is attached to the data measured in the negative polarity, and the arithmetic processing of adding and averaging the two types of data is performed. That is, assuming that the output of the amplifier 23 before switching the polarity (to be a positive voltage) is C, the output of the bridge circuit 21 is A, and the bias voltage is B, the output C is C = A + B, and after the polarity switching. Amplifier 2
When the output of 3 is C ', the output of the bridge circuit 21 is A', and the bias voltage is B, the output C'is C '= BA'.
Therefore, the CPU 4 performs addition averaging with the sign of C ′ being negative, as in {C + (− C ′)} / 2 = (A + A ′) / 2. As a result, the influence of the bias voltage B can be eliminated.

The above calculation result is sent from the master station 2 to the monitoring station 1 through the public telephone line 3, is displayed on the CRT 6 of the monitoring station 1, and is printed out on the printer 7.

[0026]

As described above, according to the present invention, when an A / D conversion measuring instrument that operates only at a positive voltage is used, a positive voltage and a negative voltage are applied to the strain gauge in order to eliminate the effect of polarization. Even when switching and adding, the bias voltage is added to the output as the measurement data, so a positive voltage is always applied to the A / D.
It can be input to the conversion measuring instrument and does not interfere with its operation. Further, the influence of the bias voltage can be eliminated by averaging the measured data before and after switching the polarity.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment.

FIG. 2 is a partial detailed block diagram of the same as above.

[Explanation of symbols]

 1 Monitoring Station 2 Parent Station 3 Public Telephone Line 4 CPU 5 Modem 6 CRT 7 Printer 8 CPU 9 Modem 10 Control Unit 11 Slave Station 12 Communication Line 13 AC Power Line 14 Switch 15 A / D Converter 16 Measuring Unit 17 CPU 18 A / D converter 19 Switching regulator 20 Polarity switch 21 Bridge circuit 22 Bias power supply 23 Amplifier 24 Switching relay 25 Switching contact 26 Compression side strain gauge 27 Extension side strain gauge 28 Constant resistor

Claims (1)

[Claims] 1. An A / D conversion measuring instrument for converting the output of a strain gauge into digital value data is provided for each slave station, and the A
In the strain measuring device in which the digital value data converted by the D / D conversion measuring instrument is transmitted to the CPU of the master station through the CPU of the slave station, the input side of the strain gauge is used for measurement via the polarity switching device. A DC power supply is connected, a DC bias power supply having a positive voltage with an absolute value larger than the absolute value of the negative voltage output value is connected to the output side of the strain gauge, and data is transferred to the CPU of the master station for each slave station. And a means for transmitting a switching signal for operating the polarity switching device of each slave station and a means for arithmetically processing and averaging data before and after transmission of the switching signal.