RU2488771C2 - Strain gauge - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: strain gauge is proposed, which includes a housing in the form of a sleeve with a central hole, on outside surface of which and on the plate from the same material there arranged are active and compensation resistance strain gauges, which are connected to each other as per a bridge diagram, the arms of which have equal electric resistances, a protective casing, in addition, it is equipped with an independent power supply, a set of light-emitting diodes included in composition of the electronic circuit that connects to the network this or that light-emitting diode of the set depending on the bridge resistance. In addition, the electronic circuit includes a Wheatstone bridge consisting of strain gauges, an instrument amplifier, a unit of comparators, a setting device, an indication unit, a timer feeding device, by means of which ignition of a light-emitting diode from the indication unit is provided, which corresponds to load interval.

EFFECT: providing visual monitoring of load on anchors by means of independent sensors that do not require a secondary instrument, functioning in the monitoring network without loss of a function of visual monitoring.

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Description

The invention relates to mining, in particular to instruments for measuring the manifestation of rock pressure, and in particular to sensors for measuring the tension of the anchor.

Known [1] a dynamometer for measuring the loads on the lining of mine workings, consisting of upper and lower covers, bushings, cup spring, rubber gaskets. For remote measurement of plate spring deformations, it is equipped with a photocell.

The main disadvantage of such dynamometers is the instability of the deformation characteristics of the Belleville spring during the measurement process, due to the influence of the shape during thermal quenching and significant sensitivity to a slight temperature change.

It is known [2] an anchor tension control device consisting of two support washers and a compliance element located between them. A capsule is built into the body of the compliance element, in the cavity of which a system of stripped movable contacts connected to a radio transmitter is installed.

The disadvantage of the device is that it is difficult to combine with a single monitoring network system for monitoring the methane gas content, the condition of the anchor support and the edge array. In addition, an elastic malleable element, for example, of vacuum rubber does not have a time-stable load characteristic due to aging of the rubber, as well as due to its eccentric compression.

The closest analogue in technical stability is [3] a strain gauge sensor, which includes a housing with a central hole and flanges at the ends, on the outside of which active and compensation strain gages are connected, connected by a bridge circuit, the shoulders of which have equal electrical resistance.

The main disadvantage of the sensor is that it cannot work without a secondary device in offline mode.

The aim of the invention is the creation of a strain gauge capable of functioning in standalone mode.

To achieve this goal, the strain gauge sensor includes a housing in the form of a sleeve with a central hole, on the outer surface of which and on a plate of the same material active and compensating strain gages are placed, interconnected by a bridge circuit, the shoulders of which have equal electrical resistance, a casing.

The difference is that the strain gauge sensor is additionally equipped with an autonomous power source, a set of LEDs included in the electronic circuit, which connects one or another LED from the set to the network, depending on the bridge resistance. The electronic circuit includes a Wheatstone bridge of load cells, an instrumental amplifier, a comparator unit, a master device, by means of which it provides ignition of the LED from the display unit corresponding to the load interval.

Thus, the introduced features solve the problem of visual monitoring of the load on the anchors by means of autonomous sensors that do not require a secondary device. This strain gauge sensor can also function in the monitoring network without losing the visual control function.

The essence of the proposal is illustrated by drawings.

Figure 1 presents an axial section of the strain gauge sensor.

Figure 2 is a section 1-1 of figure 1.

Figure 3 presents the electronic block diagram of the strain gauge sensor.

The strain gauge sensor includes a sleeve 1 with flanges and an axial hole for the anchor. The space between the flanges and the sleeve encloses the casing 2. On the outer surface of the sleeve 1 mounted active shoulders 3 of the Wheatstone bridge. The compensation arms 4 are located on a plate 5 made of the same material as the steel sleeve 1. Between the flanges of the sleeve 1 there are power supplies 6 with contact substrates 7 and 8. The substrates 8 are mounted on the covers 9, which cover the holes in the sockets of the lower flange of the sleeve 1, through which power supplies are installed 6. Substrates 7 and 8 are contact plates, between which power supplies are installed 6. Between the flanges of sleeve 1, racks are installed - boards 10, on which sets of LEDs 11 are mounted. the window 2 is cut off against the LEDs 11. The windows 12 can be inserted in the windows 12, for example, directly LEDs or quartz glasses through which light from the LEDs is indicated (FIG. 2). The circuit board 13 of the electronic circuit is located in the gap between the sleeve 1 and the casing 2 and between the flanges. The electronic circuit (Fig. 3) includes a Wheatstone bridge 14, a tool amplifier 15, a comparator unit 16, a driver 17, an indication unit 18 with LEDs, a timer-power device 19 with power sources 6.

To connect to the sensor of the monitoring network, the casing 2 of the sensor is equipped with a plug connector 20.

The sleeve 1 is placed an axial hole on the anchor between the nut and the supporting element of the anchor, which form a load on the ends of the sleeve 1 (figure 1).

A change in the load causes a change in the electrical resistance of the bridge 14. The bridge of the strain gages 14 provides a linear change in the output voltage in a certain range, depending on the load on the sensor sleeve 1.

Instrumentation amplifier 15 is designed to amplify the signal and bring it to some standard value. The normalized signal is fed to the input of the comparator unit 16. The reference voltages that specify the switching thresholds of the individual unit comparators are supplied to the other inputs of the comparator unit.

The master 17 generates reference voltages for the block of comparators 16. These voltages create a measurement law (linear, logarithmic, etc.) and switching intervals both uniform and non-uniform. This provides a wider scope for the sensor. For example, two switching thresholds corresponding to the three states of the object under study are sufficient for the control sensor:

- Load below normal

- The load is normal

- The load is above normal.

When you switch one of the comparators of the comparator unit 16, one or more LEDs 11 of the display unit 18 are ignited.

The timer-supply device 19 provides stable power to the measuring bridge, the instrumentation amplifier 15 and the driver 17. For long-term operation of the electronic circuit from an autonomous power supply 6, the timer-supply device 19 provides a repeated short-term supply of voltage to the comparator units 16 and indicators 18.

The strain gauge operates as follows.

After installing power supplies 6 between the contact substrates 7 and 8, the timer-feeding device 19 (TPU) provides a stable supply voltage to the Wheatstone bridge 14. After installing the sensor on the anchor and pre-tensioning it with a nut on the ends of the sleeve 1, the active shoulders of the bridge change the electrical resistance in proportion to the current load . The resulting imbalance in the bridge resistance causes a signal that enters the instrumental amplifier 15. Here the signal is amplified and reduced to a certain standard value is fed to the input of the comparator unit 16.

To another input of the comparator unit 16 from the master 17, reference voltages are supplied that specify the switching thresholds of the individual comparator units.

As a result of comparing the received signal from the IU 15 with the threshold voltages from the memory 17, one or another comparator of the block 16 is turned on, which supplies the voltage to the corresponding LED 11 from the indicator block 18. The LED lights up in the window 12. The color of the LED corresponds to the signal level, proportional to the load in force range up to 20 kN. With increasing load, for example up to 45 kN, the signal level from the bridge will increase. The signal will increase in DI 14. After comparing the increased signal received in BC 16 with threshold voltages from the memory 17 in BC 16, another comparator will turn on, which will supply voltage to the corresponding LED from BI 18. A LED of the corresponding color lights up in the corresponding window 12 of the casing 2 .

When a signal at the boundary of the intervals of values, two LEDs light up.

Changing the load on the sensor in this way leads to the lighting of one or another LED of the corresponding color.

Repeatedly short-term operation of the comparator unit and the display unit allows you to increase the duration of the current source.

Thus, this proposal allows you to implement a strain gauge, which operates offline.

The sensor can also function in a network of monitoring systems.

Analysis of information sources allows us to conclude that this proposal satisfies the sign of novelty and usefulness.

Information sources

1. A.S. USSR 474671.

2. A.S. USSR 191448.

3. RF patent No. 2169901.

Claims (2)

1. The strain gauge sensor, comprising a housing in the form of a sleeve with a central hole, on the outer surface of which and on a plate of the same material are placed active and compensating strain gages connected by a bridge circuit, the shoulders of which have equal electrical resistances, the protective casing is additionally equipped with an autonomous a power source, a set of LEDs included in the electronic circuit, which connects one or another LED from the set to the network, depending on the bridge resistance. 2. The strain gauge sensor according to claim 1, characterized in that the electronic circuit includes a Wheatstone bridge of load cells, an instrument amplifier, a comparator unit, a driver, an indication unit, a timer-feeding device, by means of which the LED is ignited from the indication unit corresponding to the load interval .

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