JPH0769999B2 - Multi-point input signal converter - Google Patents

Description

The present invention relates to a multipoint input signal conversion device, and more specifically, for example, an analog amount of input signals supplied from a large number of measurement points can be processed by a microcomputer or the like. A multi-point input signal conversion device that can convert digital signals into digital signals and can convert the digital signals into optical digital signals, especially detecting the presence or absence of each wire connection of multiple sensors and the presence or absence of a wire breakage that occurs afterwards in the wire connection part. The present invention relates to a multipoint input signal conversion device capable of

[Conventional technology]

A system shown in FIG. 7 is known as a systematic system of this kind of multipoint input signal converter. In the figure, each remote scanner corresponds to a multipoint input signal converter for converting an analog signal of multipoint input into a digital signal.

Conventionally, the connection / non-connection of the input signal line in each remote scanner as such a multi-point input signal converter is identified by the point number (tag number) of each measurement point from the data key of the central control display. It is necessary to give a definition in advance, and on the assumption that the definition is fulfilled, determination of whether or not to measure each input point of each remote scanner and determination of an abnormal input point such as disconnection detection of the measurable point are performed. I am trying to do it.

[Problems to be solved by the invention]

However, such a multi-point input signal converter requires a great deal of human labor because it must be manually specified from the above-mentioned data key based on a table prepared in advance as shown in FIG. In addition, if the number of input measurement points increases, the irrationality of equipment and systems, inefficiency, and the labor cost for measurement will increase significantly.

Therefore, the present invention provides a multi-point input conversion device capable of automatically determining whether or not each measurement point is connected / unconnected at power-on, and further, when a disconnection occurs at a connection point, The purpose is to be able to detect this quickly.

[Means for solving problems]

When a bridge circuit is formed by being connected to a sensor that detects a physical quantity to be measured, a plurality of detection means whose connection mode can be changed according to the sensor type, and a sensor signal and a reference signal provided corresponding to the detection means , A plurality of amplifying means capable of adjusting the gain according to the sensor type and amplifying the signals from the respective signal extracting means, and a selection for sequentially selecting the output signals from the respective amplifying means. Means, a converting means for converting the output of the amplifying means through the selecting means into a pulse number, and an arithmetic control for controlling a conversion start timing by the converting means and converting the pulse number corresponding to each physical quantity from a plurality of sensors into a digital value. Means, wire connection identifying means for identifying the presence / absence of each wire connection of a plurality of sensors at the time of power-on, and wire disconnection identification for identifying the existence / non-existence of wire breakage in the wire connection part. And means, connected, and communication means converts the data indicating the occurrence of unconnected and disconnected to the optical digital signal and transmits it to the host device provided.

[Action]

By automatically registering the connected / unconnected input of multiple points of the multi-point input signal converter, it is possible to detect disconnection when it occurs later in the connection part and improve reliability. Try.

〔Example〕

FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram showing an example of a measurement system using a multipoint input signal conversion device according to the present invention.

In FIG. 1, 1 is a detector, 2 is a primary filter, 3 is a diode, 4 is an analog switch, 5 is an amplifier circuit, and 6
Is a multiplexer, 7 is a voltage / frequency (V / F) conversion circuit, 8 is a counter, 9 and 10 are flip-flops (FF), 11
A and 11B are inverter gates, 12 is a NAND gate, 13 is a control path circuit, 14 is an arithmetic and control unit (CPU), 15 is an optical / electrical (O / E) interface, and 16 is an electrical / optical (E / O) interface. Face, 17 is an optical unit, and 18 is an optical fiber. The multipoint input signal converter shown in FIG. 1 is connected to a master station (upper device) via an optical fiber and a star coupler as shown in FIG. 2, for example.

As the sensor input signal source, here we assume a resistance temperature detector, a thermocouple, or mV input, but we can handle analog input signals in general. In other words, regarding the mixed use of sensors, (a) when the same thermocouple is mixed with different types (for example, J, E, K types, etc.) (b) Different sensors such as thermocouple and resistance thermometer There are two types of cases where the two are arbitrarily mixed. Regarding (a), after all, only the difference in gain of the operational amplifier AMP of the amplifier circuit 5 becomes a problem. More specifically, if the resistor R6 is constant for any sensor in FIG. 1, only the resistor R5 needs to be arranged according to the sensor. Therefore, an arbitrary sensor-mixed multi-point input signal converter according to the specifications required by the customer can be realized only by the combination of the resistor R5.
On the other hand, with regard to (b), the resistance temperature detector and the thermocouple may be arranged at arbitrary input channel positions according to the customer's required specifications, and the contact circuit of the detection unit 1 may be arranged according to the sensor type.

V _EE is a regulated power supply voltage, and is supplied from a low power regulator ic (not shown). In addition, as the operational amplifier AMP of the amplifier circuit 5, a low-power type low-priced one should be used, and the amplifier circuit 5 as well as the bridge circuit should be used.
The standard power supply voltage V _EE should be kept low so that the current flowing through can be reduced as much as possible, and a high-level resistor should be used to achieve overall power saving and low power consumption.
In addition, the CPU14 is a low-power CMOS type ic
The power of the O / E interface 15 and the E / O interface 16 is also reduced by using, and the low power and low cost are achieved as the minimum configuration.

Hereinafter, the channel 1 will be described, but it goes without saying that the same applies to other channels.

(1) When using a resistance temperature detector as a sensor Open the resistor R4 of the bridge circuit of the detector 1 and connect it to the terminal.
Connect CM to reference voltage V _EE2 . This reference voltage V _EE2 is created from the reference voltage of the V / F circuit 7 described later. The Buritsuji circuit, a current i ₁ flowing through the _{V EE → R1 → R → CM} → V EE2, there is a current i ₂ flowing through the _{V EE → R2 → R3 → CM} → V EE2, i 1 × R ( sensor resistance the electromotive voltages V ₁ generated by), i ₂ × electromotive voltage (reference voltage generated by R3) V ₂ and each primary filter 2 is supplied to the analog switch 4 via the diode 3. Here, R1 ＝
It is R2. Further, V ₂ always maintains a constant potential, but V ₁ has the resistance R increased or decreased depending on the temperature detected by the resistance thermometer,
V ₁ changes depending on the temperature to be measured. Therefore, since V ₂ becomes the reference voltage, V ₁ −V ₂ becomes a potential value that substantially depends on the temperature. The primary filter 2 is provided to remove noise, and the diode 3 is provided to absorb input surge. Since A and B of the analog switch 4 are switched alternately at a predetermined cycle, the voltages V ₁ and V ₂ are applied to the amplifier circuit 5, and are amplified by this so as to be converted into a voltage value within a predetermined range. The amplifier circuit 5 includes an operational amplifier AMP, resistors R5 and R6 for gain formation, a filter capacitor C, a noise killer capacitor (not shown), and the like. Amplifier circuit 5
The voltage amplified by is converted into a voltage pulse signal by the V / F circuit 7 after being selected by the CMOS type analog multiplexer 6, and the resistance value R of the resistance temperature detector is converted into the pulse interval. It is becoming like this.

FIG. 3 shows a concrete example of the V / F circuit, and FIG. 4 shows its operation waveform. The V / F circuit 7 has a comparator 7 as shown in FIG.
1, FF72, reset circuit 73, analog switch 74, integrator 75, buffer amplifier 76, etc.
It is controlled by the V / F start control signal S.

Buffer amplifier 76 creates a more V _EE2 voltage reference voltage V _S, the integrator 75 Figure 4 integrates the reference voltage V _S (i), making such sawtooth wave voltage (E). The sawtooth voltage is compared with the output V _in from the amplifying circuit 5 in the comparator 71,
If this exceeds the voltage V _in, the comparators 71 and FF72
The output of Fig. 4 is (b), (c) and (c), respectively.
Stand up like (G). Since the reset circuit 73 is activated by the output and outputs the reset signal for resetting the FF72 after a predetermined time, the FF72 is reset after a certain time from the rising edge, and the switch 74 is closed by this, so that the integrator 75 is closed. The capacitor C is discharged and reset. In this way, one pulse is formed, and by repeating this, a pulse train signal corresponding to the input voltage V _in is obtained. Incidentally, FIG. 4 (a) to (d) of the input voltage V _in is 1V
In the case of (e) to (h), the input voltage is 3V. Further, (d) and (h) in the figure show the output waveform of the FF72.

The pulse train signal generated by the V / F circuit 7 is input to the counter 8 of FIG. 1 and divided. This counter 8 is CPU14
Is reset by the control signal S given from the inverter gates 11A and 11B. From this point, the V / F circuit 7 is reset.
Counting of the pulse train signal from is started, and for example, 1/8 frequency division and 1/128 frequency division are performed. And 1/8 frequency division output to FF9,
In addition, 1/128 frequency division output is introduced to FF10 and these are set. The outputs of FF9 and FF10 are applied to the NAND gate 12 and the outputs of these outputs are logically ANDed. That is, FF9,
FF10 and NAND gate 12 form a constant interval (time width signal) proportional to V / F output, and CP
V / F depends on how many reference clocks are counted by U14.
The pulse count value is proportional to the input or output.

5A and 5B show the above operation. FIG. 5A shows an example when the input voltage is 1V, and FIG. 5B shows an example when the input voltage is 3V. Further, in FIGS. 5A and 5B, a
Is the output of the V / F circuit 7, b, d is the 1/8, 1/128 divided output of the counter 8, c, e is the output of FF9, FF10, f is the output of the NAND gate 12, CL is the reference clock, CT Indicates the count value. As is clear from a comparison between FIG. 5A and FIG. 5B, the NAND gate output f changes according to the magnitude of the input voltage, that is, the pulse interval of the output a of the V / F circuit 7. A count value CT proportional to the pulse interval of the output a of the V / F circuit 7 can be obtained depending on how many reference clocks CL are counted by a counter (not shown). The clock CL can be counted by causing the CPU 14 to identify the reference clock counting start time as the rising edge of the signal f and the ending time thereof as the falling edge of the signal f.

The pulse count value counted by the CPU 14 is handled as a digital value by its internal software (a program in a narrow sense), and various processing such as ZERO (zero) adjustment, SPAN (span) adjustment, and linearization of the input is performed. To be done. The CPU 14 is, for example, a one-chip microcomputer, and has an internal ROM, R
It is assumed that an AM and a 16-bit counter are provided, but the present invention is not limited to this, and a small, inexpensive, low-power arithmetic and control unit can be used.

The digital measurement value obtained in this way is passed through the optical fiber 18 of one core based on the command from the host system, and then the route of the optical unit 17 → O / E interface 15 → CPU 14 is used to host the device (master in Fig. 2). When a command is given from the station, this is sent to the host system side as an optical digital signal. That is, a signal is transmitted through the route of CPU14 → E / O interface 16 → optical unit 17 → optical fiber 18. In this way, the optical unit
Reference numeral 17 branches the optical signal in order to transmit the optical digital signal using the one-core optical cable 18.

In addition, in FIG. 1, the control port signal P ₁ is CP.
It is output from the output port provided in U14 and controls the multiplexer 6. Further, the control path circuit 13 is the CPU 1
The analog switch 4 is controlled by the port signal P ₂ from 4 and is composed of, for example, a decoder circuit. Although the electromotive voltages V ₁ and V ₂ applied to the analog switch 4 have been described above, the switching is performed at a constant cycle, and the electromotive voltage V ₁ by the resistance temperature detector and the reference voltage V ₂ thereof are changed. Figure out It should be noted that the reason why V ₂ is appropriately grasped by switching the analog switch 4 at an appropriate timing is that an offset variation or the like occurs in the operational amplifier AMP of the amplifier circuit 5 due to the temperature rise or fall of the surroundings and the conversion circuit, and it is adjusted in advance. This is because the set zero point may change.

Zero adjustment and span adjustment are performed as adjustments at the time of measurement, but these adjustments need to be executed in advance for each channel by, for example, reading the number of a rotary switch (not shown) in the CPU 14. The zero adjustment data and span adjustment data during this adjustment are stored in the memory (RA
M) is stored at a predetermined position and is referred to at the time of measurement. However, if the zero point fluctuates due to temperature, a temperature error will occur. Therefore, the zero point at the time of measurement is automatically known, and control is performed to eliminate the error. Further, the temperature correction of the span is suppressed so as to be within the temperature error of the set standard in consideration of the temperature factor of the element used in the circuit. Note that these are performed using the software of the CPU 14.

In this way, the measurement can be performed when the resistance temperature detector is used as the sensor.

(2) When sensing a thermocouple: Open resistor R2 and short resistor R3. R1 is a high resistance (for example, 22 MΩ) for detecting the burnout. In addition, FG is an external earth line, and when using a sensor with a shield for earthing, A12, A22, A32, ...
Can be connected to each terminal. As a result, the resistance temperature detector and the input terminal of the thermocouple can be shared. Here, resistor R4 is used as a current limiting resistor so that current does not flow into V _EE2 through V _EE → R1 → thermocouple →. The other V / F conversion circuits and the like are the same as in the case of the resistance temperature detector, and the description thereof is omitted. However, in the case of a thermocouple, a reference junction compensation circuit is indispensable,
Although this is actually provided between the multiplexer 6 and the V / F circuit 7, it is not shown here because it is not directly related.

Next, a description will be given of identification of connected and unconnected and disconnection.

(3) Unregistered / automatic registration of connections Whether it is a temperature resistor input, thermocouple input, or mV input, if it is not connected, the amplifier of amplifier circuit 5 will saturate and V / F circuit 7
Does not generate an output pulse. Therefore, even if the V / F conversion command signal S is given from the CPU 14 immediately after the power is turned on, the CPU 14 cannot detect the rising edge signal from the NAND gate 12 by a certain period of time, so that the CPU 14 can treat it as unconnected. . At this time, it is impossible for the converter according to the present invention to erroneously generate an excessive input and saturate the amplifier. This means that depending on the input range used, the input of the amplifier may be the input signal overflow (for example 120% of span) or underflow (for example −120 of span).
%) And the input range is designed with a margin, so it is not possible for the input value to suddenly exceed the value that causes the input range to overflow or underflow. Generally, in case of temperature sensor etc., the response of the sensor is extremely slow, so if the software is programmed to identify connected / unconnected within the response speed, identification after power-on is possible. Is. Even if an excessive input etc. comes in in the connection state, the amplifier is in the unsaturated region until the response speed is reached, so the CPU 14 can identify the connection state and then the input is abnormal. Can be detected by overflow or the like.

On the other hand, in the case of no connection, the response speed of the conversion circuit is much faster than the response speed of the sensor, so that it can be immediately determined that the amplifier exceeds the saturation region. That is, V /
The F circuit 7 generates a rectangular wave pulse by comparing the integrated reference voltage with the input voltage, and further generates the pulse with the flip-flop, so no pulse is generated if the amplifier of the first-stage amplifier circuit is saturated. So CPU1
Even if the V / F conversion command S is given from 4, if the rising edge signal of the output of the NAND gate 12 is not returned to the CPU 14, it can be identified as unconnected.

(4) Detection of disconnection In the conventional manual registration method, if the key operation is mistaken and a free number is entered, the input point cannot be measured. In other words, it was the method of detecting disconnection only for those registered manually. On the other hand, according to the present invention, since the information is automatically registered, it is possible to detect whether or not a wire that has been connected without error is subsequently broken. This is because the connected / unconnected information is stored in the memory inside the CPU when the power is turned on, and a program that refers to this memory at a fixed cycle determines whether or not there is a disconnection in the connected part only by software during subsequent measurements. It can be checked periodically.

First, in the case of a thermocouple, if the compensating lead wire (not shown) is broken during measurement, the operational amplifier of the amplifier circuit 5 is saturated by the burnout resistance R1, so that the CPU 14 outputs V / F at regular intervals.
Even if the start control signal S is given, since the rising edge signal of the NAND gate output does not return to the CPU 14 by a certain timing, the disconnection can be identified.

On the other hand, in the case of the breakage of the lead wire (not shown) in the case of the resistance temperature detector, the breakage can be detected because the operational amplifier is saturated even if any wire is broken.

As described above, when the processing of (3) and (4) is represented on the time axis, the sixth
It becomes like the figure. It should be noted that these connected / unconnected information can be sent out as an optical digital signal to notify the host system. In addition, by programming the input channel information currently being measured to be sequentially stored in the memory of the CPU, when a disconnection occurs, the information on the disconnection location and the disconnection occurrence are provided to the host device (master station in FIG. 2). ) Can be informed.

The processing procedure of the above-mentioned connection / non-connection identification and disconnection identification will be described with reference to the flowchart shown in FIG.

First, immediately after the power is turned on, in step (S1), the output value from the sensor is measured for a certain fixed period to determine whether or not it is overscale.

When the CPU 14 gives a V / F conversion command S and the CPU 14 cannot detect the rising edge signal from the NAND gate 12 within a certain time, that is, in the case of overscale, it can be treated as an unconnected state. So
In step (S2), unconnected wiring is registered.

If there is no overscale, it is treated as a wire connection state, and the wire connection is registered in step (S3). The measurement of the connection registered in this way starts the measurement in step (S4).

Next, in step (S5), it is determined whether or not overscaling occurs at regular intervals. Here, the V / F conversion command S is given from the CPU 14, and the NAND gate 1
If the rising edge signal from 2 is returned, the measurement is repeated without disconnection. If the edge signal is not returned to the CPU 14, treat it as if a wire break occurred during measurement after registering the wire connection, and then step (S6).
In step 3, the upper device is notified of the occurrence of disconnection.

[Effects of the Invention] According to the present invention, since connected / unconnected can be automatically registered by the CPU after power-on, it can be omitted and the overall operating cost and management cost can be significantly reduced. It becomes possible to do. Further, since disconnection detection can be performed by using the same conversion circuit configuration, cost merit arises and the reliability of the conversion device is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram showing an example of a measurement system using a multipoint input signal converter according to the present invention, and FIG. 3 is a specific example of a V / F circuit. Fig. 4 is a circuit diagram showing the
5A and 5B are waveform charts for explaining the conversion operation for converting the output of the V / F circuit into the number of pulses, and FIG. 6 shows the timing of the connected / unconnected identification operation and the disconnection identification operation. Explanatory diagram for explaining, FIG. 7 is a schematic diagram showing a conventional example of a system using a multipoint input signal converter, FIG.
The figure is an explanatory diagram for explaining the remote scanner setting table,
FIG. 9 is a flow chart for explaining a processing procedure for identifying connected / unconnected and disconnection identification. Explanation of symbols 1 ... Detector, 2 ... Primary filter, 3 ... Diode, 4,74 ... Analog switch, 5 ... Amplifier circuit, 6 ...
… Multiplexer, 7 …… V / F circuit, 8 …… Counter,
Flip-flop (FF), 11A, 11B ... Inverter gate, 12 ... NAND gate, 13 ... Control path circuit, 14 ... Arithmetic control unit (CPU), 15 ... O / E interface , 16 …… E / O interface, 17 …… Hikari unit, 1
8 …… Optical fiber, 71 …… Comparator, 73 …… Reset circuit, 75 …… Integrator, 76 …… Buffer amplifier, S ……
V / F start control signal, P ₁ , P ₂ ... Control port signal.

Claims (1)

[Claims] 1. When a bridge circuit is formed by being connected to a sensor for detecting a physical quantity of an object to be measured, a plurality of detecting means whose connection mode can be changed according to the sensor type and provided corresponding to the detecting means. Signal extracting means for sequentially extracting the sensor signal and the reference signal, a plurality of amplifying means capable of adjusting the gain according to the sensor type and amplifying the signals from the respective signal extracting means, and output signals from the amplifying means. Selecting means for sequentially selecting, the converting means for converting the output of the amplifying means through the selecting means into the number of pulses, the conversion start timing by the converting means, and the number of pulses corresponding to each physical quantity from a plurality of sensors is digitally changed. A calculation control unit that converts the value into a value, a connection identification unit that identifies the presence or absence of each connection of multiple sensors when the power is turned on, and a presence of a disconnection that occurs after the connection A disconnection identifying means for identifying nothing and a communication means for converting data indicating presence / absence of disconnection, disconnection and disconnection into an optical digital signal and transmitting the optical digital signal to a host device are provided. Point input signal converter.