JPH0431680Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Purpose of the Invention] (Field of Industrial Application) The present invention relates to a meter reading device, and particularly to a meter reading device suitable for remote meter reading using a water meter or the like as a terminal.

(Prior art) Fig. 1 is a schematic configuration diagram when a conventional meter reading device is applied to a water meter, in which 1 is the main body of the meter reading device, 2 is the water meter as a terminal, and 3, 4, and 5 are A signal line consisting of a 3-core cable connecting the main body 1 and the water meter 2, 6 a constant current source that generates a constant current, 7 the output end of the constant current source 6 as an input, and converts the input voltage into a digital value. An analog-to-digital converter (hereinafter referred to as an A-D converter) for conversion, 8 a power supply, 9 a clock pulse generation circuit, 10 a data display for displaying the output of the A-D converter 7, 16 a data display for displaying the output of the A-D converter 7; A resistor group 11A to 14A with a tap that receives current supply from the constant current source 6 through the signal line 3 operates in accordance with each digit of the pointer of the water meter 2, and is a changeover switch that switches the tap of the resistor 16. , 11 to 14 are digit switching transistors that ground the taps of the resistor group 16 selected by the changeover switches 11A to 14A via the signal line 4, and 15 are connected to the clock pulse generation circuit 9 via the signal line 5.
In response to signal input from the transistors 11-
This is a switching circuit that sequentially and selectively turns on 14.

In this configuration, constant current I from constant current source 6 is applied to resistor group 16 of water meter 2 via signal line 3. On the other hand, the clock signal from the clock circuit 9 is transmitted to the switching circuit 1 via the signal line 5.
5, which sequentially switches transistors 11-14 into conduction.

Assuming that the transistor 11 is now selectively turned on as described above, the constant current source 6, the signal line 3, the resistor group 16, the changeover switch 11A,
A circuit is formed that connects the transistor 11, the signal line 4, and the ground, and a constant current I flows through the resistor on the signal line 3 side from the changeover switch 11A in the resistor group 16. In the example of Figure 1, this resistance value is 2r, but
The output terminal voltage V ₁ of this time constant current source 6 is the resistance value
The value is 2r multiplied by constant current I, that is, V ₁ =I×2r (1). This voltage V ₁ becomes an input to the AD converter 7.

By the way, the A-D converter 7 converts the applied input voltage V ₁ into a digital signal as described above, and outputs the digital signal to the changeover switch 1 of the data display 10.
Display this on the digit corresponding to 1A.

Note that after this operation, the switching circuit 15
The transistor 12 is turned on, and the data given by the changeover switch 12A is similarly displayed on the corresponding digit on the data display 10, and the data given by the changeover switches 13A and 14A are also displayed in the same way. This is displayed on each corresponding digit on the display 10.

The operations described above are performed repeatedly at high speed by the action of the switching circuit 15. Therefore, the data corresponding to each of the switching switches 11A to 14A of the water meter 2, that is, the index of each digit of the pointer, is displayed on the data display 10. This can be confirmed as digital 4-digit data above.

(Problem to be solved by the invention) Now, in the configuration shown in FIG. 1, if it is assumed that the transistor 11 has failed and entered the conduction mode, the constant current I from the constant current source 6 will flow through the transistors 11 to 14. Transistor 1 regardless of switching
1, so the other changeover switch 12A
Even if the transistors 12 to 14 corresponding to 14A become conductive and try to obtain data, it becomes impossible to obtain true data corresponding to that digit.

In addition, when the signal line 3 is used as a bus line and is also connected to other terminals, there is a problem that the true value of the data is not displayed for the other terminals as well, resulting in erroneous meter readings.

The operation of the configuration in Figure 1 is also shown in the time chart in Figure 2, where a shows the digit switching clock timing, and b shows the A-D conversion when transistors 11 to 14 are normal. The input data of the converter 7 and c indicate the input data to the A/D converter 7 when the transistor 11 fails in the conduction mode. Incidentally, in the time chart of FIG. 2, 17 indicates the timing of the clear pulse for returning the output of the switching circuit 15 to "0", and 18 indicates the timing of the digit switching pulse.

As is clear from Figure 2, transistor 1
If transistor 1 fails, other transistors 12 to 13
Even if A-D becomes conductive, the resistance value of the resistor group 16 selected by the changeover switches 12A to 13A corresponding to these transistors is bypassed by the transistor 11 in the example of FIG. The input voltage of the converter 7 is fixed to the voltage obtained when only the transistor 11 is conductive.

For this reason, conventionally the transistor 1 for digit selection
There has been a strong demand for a device that can prevent erroneous needle reading even in the case of failures in conduction modes 1 to 14.

Therefore, in view of the above-mentioned problems of the prior art, the purpose of the present invention is to detect double connection before data collection when a double connection is detected due to a conduction mode failure of a digit selection transistor. An object of the present invention is to provide a meter reading device that takes measures to prevent erroneous meter readings, such as erasing the display.

[Structure of the idea]

(Means for solving the problem) The meter reading device of the present invention has a resistor group with a tap that receives constant current from a constant current source, and a tap that can be switched and selected for each digit in conjunction with each digit of the pointer. A changeover switch is provided corresponding to the changeover switch, a switching element for digit selection is connected to each changeover switch, and the output voltage of the constant current source is measured in conjunction with the switching operation of the switching element, and data for each digit is measured. and double connection detection means for detecting double connection by comparing the output voltage of the constant current source with a reference voltage at the timing of opening all the switching elements.

(Function) In the meter reading device according to the present invention configured as described above, when all the switching elements are normal and open, the output voltage of the constant current source measured and taken out by the taking out means is the reference voltage. On the other hand, when a certain switching element is faulty in the conduction mode, the output voltage of the constant current source measured by the extraction means is determined by the changeover switch connected to the faulty switching element. The value is proportional to the resistance value of the resistor corresponding to the selected tap. As a result, if the reference voltage is appropriately selected, double connection can be determined by comparing the output voltage of the constant current source with the reference voltage by the double connection detection means at the timing when all the switching elements are opened. will be possible.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 3 is a block diagram of a meter reading device according to an embodiment of the present invention, in which reference numeral 21 indicates that there is a failure in the conduction mode among the transistors 11 to 14 based on the input voltage of the A-D converter 7. A double connection detection circuit 22 for detecting this is a flip-flop that latches the output of the double detection circuit 21 and erases the display on the data display 10.

The operation of this configuration will be explained according to the timing chart shown in FIG. 4, where a shows the digit switching clock timing and b shows the transistor 11.
~14 is the input data of the A-D converter 7 when it is normal, c is the input data of the A-D converter 7 when the transistor 11 fails in the conduction mode, and d is the output signal of the double connection detection circuit 21. are shown respectively.

Now, if all transistors 11 to 14 are normal, the analog data input to the A-D converter 7 changes in the range of 0 to 9r x I (V) corresponding to the positions of the changeover switches 11A to 14A. However, due to the clear pulse 17, the transistor 11
During the period t in FIG. 4b when all of the circuits 14 to 14 are turned off, the constant current I from the constant current source 6 is cut off, and therefore the analog data is 9r×I.
(V).

On the other hand, if any of the transistors 11 to 14 becomes a conduction mode failure, the constant current I will flow through the failed transistor even during period t. Therefore, the analog data during period t falls within the range of 0 to 9r×I(V).

The double connection detection circuit 21 in FIG.
The analog data in the period is compared with an appropriately set voltage V such that V>9r×I (2), and when the analog data in the period t is lower than the set voltage V, the double voltage shown in FIG. It outputs a connection detection signal.

Now, in the arrangement shown in Figure 3, transistor 1
When transistors 1 to 14 are all normal, all transistors 11 to 14 are off during period t in FIG. 4b, so that the input analog data of double connection detection circuit 21 exceeds the set voltage. Therefore, data collection and display are performed normally, but the specific operation is exactly the same as the configuration shown in FIG. 1.

On the other hand, if the transistor 11 fails in the conduction mode now, the transistor 11 remains conductive during period t in FIG. 4b, so the input analog data of the double connection detection circuit 21 becomes 2r×I , below the set voltage V. Therefore, during the period t, the double connection detection circuit 21 outputs the double connection detection signal shown in FIG.

The output of the flip-flop 22 is applied to a data display 10, and the display on the display 10 is erased to prevent erroneous reading of erroneous data.

As mentioned above, even if a tap in a resistor group is selected twice due to a failure in a digit switching transistor, this is detected before data collection and measures such as erasing the display are taken, thereby increasing reliability. It is possible to perform high meter readings.

In the above embodiment, the display on the data display 10 is erased when a double connection is discovered, but the implementation of the present invention is not limited to this, and it is possible to avoid misreading. It goes without saying that a configuration such as issuing a warning to prevent this is also applicable.

[Effect of idea]

As described above, according to the present invention, when reading water meters, etc. that are arranged as terminals and connected by bus lines, double connections due to equipment failure can be detected in advance and the data displayed. Since it is possible to take measures such as prohibition, it is possible to sufficiently deal with terminal failures, which were difficult to judge objectively in the past, and it is possible to obtain a meter reading device that can significantly improve the reliability of remote meter reading. It is something.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a conventional meter reading device, Fig. 2 a, b, and c are time charts explaining the operation of the configuration shown in Fig. 1, and Fig. 3 is a diagram of a meter reading device according to an embodiment of the present invention. The schematic configuration diagrams in FIGS. 4a, b, c, and d are time charts for explaining the operation of the configuration in FIG. 3. 1... Meter reading device body, 2... Water meter, 3,
4, 5...3-core cable, 6...constant current source, 7...
...A-D converter, 8...Power supply device, 9...Clock pulse generation circuit, 10...Data display, 11
~14...Digit switching transistor, 11A~14
A...Switching switch, 15...Switching circuit, 21...
...Double connection detection circuit, 22...Flip-flop.

Claims (1)

[Scope of utility model registration request] A resistor group with a tap that receives constant current from a constant current source, a changeover switch provided for each digit to switch and select the tap in conjunction with each digit of the pointer, and a changeover switch provided for each digit of the pointer. A switching element for selecting a digit connected to each, an extraction means for measuring the output voltage of the constant current source and extracting data for each digit in conjunction with the switching operation of the switching element, and opening all the switching elements. A meter reading device comprising: double connection detection means for detecting double connection by comparing the output voltage of the constant current source with a reference voltage at a timing when the meter reading device detects a double connection.