JPS63310098A - Multipoint input signal converter - Google Patents

Abstract

PURPOSE:To arbitrarily mix a different types of input sensors and to measure in the same circuit by previously combining the resistance of a bridge circuit and the gain resistance constant of an amplifying circuit according to the request for mixedly using the sensor in a multipoint input signal converter. CONSTITUTION:At the time of mixing the different types of J.E.K even in the same thermocouple, as for constituting a conversion circuit, only the gain of the operating amplifier AMP of the amplifying circuit 5 is adjusted, thereby, the different types of the sensors can be mixed and stored. When the different types of the sensors are arbitrarily mixed and stored such as the thermocouple and a resistance thermometer bulb, the resistance thermometer bulb and the thermocouple are disposed at the arbitrary input channel position of a specification required by the customer and the bridge circuits R1-R4 of the detection part 1 are arranged according to the type of the sensors. For instance, at the time of sensing the resistance thermometer bulb, the resistance R4 of the bridge circuit is opened and a terminal CM is connected to a reference voltage VEE2. In the case of a thermocouple sensor, the circuit R2 is opened, the R3 is short circuited, the R1 is defined to be a high resistance for detecting a burn out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-point input signal conversion device, and more specifically, it is capable of processing analog input signals supplied from a large number of measurement points using a microcomputer or the like. The present invention relates to a multi-point input signal conversion device capable of converting into a digital signal and further converting the digital signal into an optical digital signal.

[Conventional technology]

At present, there is no known low-friction, low-power, and highly flexible multi-point input signal conversion device that allows measurements to be made by arbitrarily mixing a plurality of different types of sensors.

[Problem that the invention seeks to solve]

Therefore, the present invention enables measurement by arbitrarily mixing different types of input sensors at multi-point input points in one converter. It is an object of the present invention to provide a multi-point input signal conversion device having excellent features such as the following.

The reason why there has not been a multi-point input signal converter until now is that: ■ If you try to handle different types of input sensors with one multi-point input signal converter, for example, for input 1, A Each circuit must be equipped with its own conversion circuit, such as three circuits for input 2 and a C circuit for input 6, which has the drawback of extremely high cost.

■ Different types of input sensors can be used at any input location;
In other words, if either the A sensor or the B sensor can be used for input 1, there is a problem in that the conversion circuit is likely to become extremely complex.

■ Eliminating and adjusting errors for each input channel of the measurement conversion circuit is expected to be complicated and troublesome, and is likely to be avoided.

This is thought to be due to the following reasons. [Means for solving the problem] A detection means that is connected to a sensor that detects a physical quantity to be measured to form a bridge circuit and whose connection mode can be changed according to the sensor type, and the detection means A signal extracting means provided correspondingly and sequentially extracting the sensor signal and the abuse signal, a plurality of amplifying means whose gain is adjustable according to the sensor type and amplifying the signals from the signal extracting means, and from each of the amplifying means. a selection means for sequentially selecting the output signals of the amplification means; a conversion means for converting the output of the amplification means via the selection means into a number of pulses; A calculation means for converting each digital signal into a digital signal and a communication means for converting the digital signal into an optical digital signal and transmitting the optical digital signal to a host device are provided.

[Effect]

By combining the resistance of the bridge circuit and the gain resistance constant of the amplifier circuit in response to the demand for mixed use of Kanekome sensors, it is possible to mix and measure different types of input sensors in the same circuit with a simple and minimal configuration. It is an attempt to close the gap. Furthermore, by simplifying the conversion circuit, the cost can be reduced, and by using CMO8iC frequently and reducing circuit current consumption, it is possible to realize a low-power multi-point input signal conversion device.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, 1 is a detection section, 2 is a primary filter, 3 is a diode, 4 is an analog switch, 5 is an amplifier circuit, 6 is a multiplexer, 7 is a voltage/frequency (V/F) conversion circuit, 8 is a counter, 9 and 10 are flip-flops (FF)
, 11A, 11B are inverter gates, 12 is a Nant gate, 15 is a control bus circuit, and 14 is an arithmetic and control unit (CP
U), 15 is optical/electrical (0/E) interface, 16
teeth! An air/optical (Elo) interface, 17 an optical unit, 18 an optical fiber, and 19 a reference junction compensation circuit serve as a sensor input signal source, here a resistance temperature detector.

Although thermocouples or large mV inputs are assumed, general analog input signal sources can be handled. In other words, regarding the mixed use of sensors, (a) different types of the same thermocouple (for example, J
, E, etc.) (b) When different types of sensors such as thermocouples and resistance temperature sensors are arbitrarily mixed, two types can be considered. Regarding (a), from the point of view of configuring the conversion circuit, the operational amplifier AM of the amplifier circuit 5
By simply changing the gain adjustment of P, different types of sensors can be mixedly accommodated. Specifically, if the resistor R6 is constant for every sensor in Figure 1, then only the resistor R5 needs to be arranged for each sensor. Therefore, any combination of sensors can be used according to the specifications requested by the customer. A multi-point input signal conversion device can be realized using only the combination of resistor R5. The linearity correction calculation etc. for each sensor will be described later, and the explanation will be limited to the outline in . The bridge circuit of the detection section 1 may be arranged according to the sensor type. The linearity correction for each sensor in this case will also be described in detail later.

VEE is a stabilized power supply voltage, which is supplied by a low power regulator iC (not shown).

In addition, the operational amplifier AMP of the amplifier circuit 5 should be of a low-power type with low friction, and the reference power supply voltage vEE should be set so that the bridge circuit as well as the current flowing to the amplifier circuit 5 can be reduced as much as possible. In addition to keeping it low, try to save power and lower power overall by using high-level resistors, etc. Furthermore, a low-power CMOS type iC is used for the CPU 14, and an 0/E interface 15. Regarding the E10 interface 16 as well, when the power on the circuit is reduced, low power is realized as a minimum configuration, and low friction is achieved.

Channel 1 will be explained below, but it goes without saying that the same applies to other channels. (1) When using a resistance temperature sensor as a sensor, open the resistor R4 of the bridge circuit of the detection section 1, Connect terminal CM to reference voltage VEE2. Note that the reference voltage VgE2 is generated from a reference voltage of a V/F circuit 7, which will be described later. The bridge circuit includes VEE 4 R1-+ R-
+ Current i flowing through CM4 Vjg2, and 7EB −+ R2-b R34CM 4 V EE2
Current flowing through 12 and Ashi, i, X R (sensor resistance)
The electromotive force v1 generated by 12XR5 and the electromotive force (reference voltage) V2 generated by 12XR5 are respectively
．． It is applied to an analog switch 4 via a diode 3.

Here, R1=R2. Although v2 always maintains a constant potential, (1) R increases or decreases depending on the temperature detected by the resistance temperature sensor, so vl takes a value that varies depending on the object to be measured. Therefore, since v2 becomes a reference potential, vl-v2 becomes a voltage value that substantially depends on temperature. Note that the primary filter 2 is provided to remove noise, and the diode 5 is provided to absorb input surges. Since the analog switch 4 is switched between A and B alternately at a predetermined period, the voltage v
1 and V2 are applied to the amplifier circuit 5, where they are amplified and converted into voltage values within a predetermined range.

The amplifier circuit 5 includes an operational amplifier AMP, resistors R5 and R6 for forming a gain, a filter capacitor C1, a noise killer capacitor (not shown), and the like. Amplification circuit 5
The amplified voltage is selected by a CMOS type analog multiplexer 6, and then the voltage -
It is converted into a pulse signal, and the magnitude of the resistance [R] of the resistance temperature detector is converted into the magnitude of the pulse interval.

FIG. 2 shows a specific example of the V/F circuit, and FIG. 3 shows its operating waveforms. As shown in FIG. 2, the V/F circuit 7 is composed of a comparator 71, an FF 72, a reset circuit 73, an analog switch 74, an integrator 75, a buffer amplifier 76, etc. , more controlled.

The buffer amplifier 76 generates the VEE2 voltage υ from the reference voltage Vs, and the integrator 75 integrates the reference voltage Vs to generate sawtooth wave voltages as shown in FIGS. 3(A) and 3(E). This sawtooth voltage is applied to the output Wi from the amplifier circuit 5 at the comparator 71.
n, and when this exceeds the voltage Min, the outputs of the comparator 71 and the FF 72 rise as shown in tJ3 diagrams (b), (c) and (f), ()), respectively. The reset circuit 73 is activated by the Q output and outputs a reset signal for resetting the FF 72 after a predetermined time, so the FF 72 is reset after a predetermined time from its rise, which closes the switch 74, so that the integrator 75 is reset by discharging its capacitor C. In this way, one pulse is formed, and by repeating this, a pulse train signal corresponding to the input voltage Vin is obtained.

In addition, in Fig. 3 (a) to (d), when the input voltage is 1V,
(E) to (H) respectively show cases where the input voltage is 3V. Further, (d) and (h) of the same figure show the Q output waveform of the FF 72.

The pulse train signal generated by the V/F circuit 7 is input to the counter 8 shown in FIG. 1 and divided into channels. This counter 8 is CP
It is reset by the control signal S given from U14 via the inverter gates 11A and 11B, and from this point on, counting of the pulse train signal from the V/F circuit 7 is started, and for example, the frequency is divided into 1/8 and 1/128. Let's do it. 1/8
Frequency division output to FF9, and 1/128 frequency division output to FF1
0 respectively and set them. The outputs of FF9 and FF10 are applied to the Nant gate 12, and the logical product of both outputs is taken. In other words, the FF9.10 and the gate 12 form a constant interval (time width signal) proportional to the V/F output, and during this time the CPU4
V/F depends on how many reference clocks are counted.
A pulse curran proportional to the input or output is obtained.

FIGS. 4A and 4B show the above operation. FIG. 4A is an example when the input voltage is 1V, and FIG. 4B is an example when the input voltage is 3V. Also, Figures 4A and 4
In figure B, a is the output of the V/F circuit 7, b and d are the 1/8 and 1/128 divided outputs of the counter 8, and c and e are the FF9
．． 10, f is the output of the Nandt gate 12, CL is the reference clock, and CT is the count box. Figures 4A and 4
As is clear from a comparison with diagram B, the Nandt gate output f is the magnitude of the input voltage, that is, the output a of the V/F circuit 7.
It changes depending on the pulse interval of the CPU 14 during this period.
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 times the reference clock CL is counted by a counter (not shown).

Note that the CPU 14 can identify the start time of counting of the reference clock as the rising edge of the signal f, and the end timing as the falling edge of the signal f.
It is possible to count the clock CL.

CPU14-1' total! The generated pulse count is treated as a digital box by the internal software (program in the narrow sense), and the input ZERO (Z0) v!
Various processes such as 4,5 PAN (Suba/) tone, lJ nearing, etc. are performed. For linearity correction, set the linearity points in advance within a range sufficiently large to meet the accuracy standard, and prepare the correction amount at each linearity point in advance by creating a table in the CPU's memory (ROM). It is controlled so that it is referenced when controlling software calculations. All linearity correction tables are prepared for each sensor, and the software is configured to determine which correction table to refer to depending on which sensor is used for each channel. In other words, as explained separately, which channel uses which type of sensor can be determined by using the converter's CPU memory, both from the converter side and from the host system side, so the memory information can be referred to. However, linearity correction is possible using the correction table of the sensor.

In addition, the CPU 14 is a one-chip microcomputer with internal RO
Although a device equipped with M, RAM, 16-bit counter, etc. is selected, the present invention is not limited to this, and a small, inexpensive, low-power arithmetic and control device can be used.

The digital measurement values obtained in this way are given commands from the host system via a single-core optical fiber 18, and then via the optical unit 17 → 0/E interface 15 → PU 14 route based on commands from the host system. By this,
This is sent to the host system as an optical digital signal. That is, CPU 14 → E10 interface 16 → optical unit 1
7→optical fiber 18 route. In this way, the optical unit 17 uses the -core optical fiber cable 18 to branch the optical signal in order to transmit the optical digital signal.

In FIG. 1, a control port signal P1 is output from an output port included in the CPU 14 and controls the multiplexer 6.

Further, the control bus circuit 13 controls the analog switch 4 based on a signal P2 from the CPU 14, and is composed of, for example, a decoder circuit. The electromotive voltage V 1 * V 2 applied to the analog switch 4 was explained earlier, and the switching of the analog switch 4 is performed at a constant cycle, and the electromotive force V 1 due to the temperature sensing resistor and
The reference voltage V2 is grasped. Note that the reason why the analog switch 4 is switched at an appropriate timing and v2 is determined appropriately is because offset fluctuations occur in the operational amplifier AMP of the amplifier circuit 5 due to temperature rise or fall of the surroundings or the conversion circuit, so it must be adjusted in advance. This is because there is a risk that the zero point that was previously set may change.

Zero adjustment and span adjustment are performed as tA adjustments during measurement, but these adjustments must be performed in advance for each channel by, for example, reading the rotary switch number (not shown) into the CPU 14. be. The zero adjustment data and span adjustment data during this adjustment are each stored in a predetermined location in a memory (RAM) not shown, and are referred to during straightening measurement. However, if the zero point fluctuates due to temperature, a temperature error will occur. For this reason,
It automatically determines the zero point during measurement and performs control to eliminate errors. Furthermore, the temperature correction of the span is suppressed to be within the temperature error of the set standard, taking into account the temperature factor of the elements used in the circuit. Note that these operations are performed using software of the CPU 14.

In this way, measurement using a resistance temperature detector as a sensor becomes possible.

(2) When connecting a thermocouple, resistor R2 is opened and resistor R3 is shorted. R
1 is a high resistance (for example, 22 MΩ) for detecting burnout.

Note that FG is an external ground line, and when using a sensor with a ground shield, A12. in FIG. A
22. Each terminal of A32... can be directly read. This makes it possible to share the input terminals of the resistance temperature detector and the thermocouple.

At this point, resistor R4 is used as a current limiting resistor so that the current does not flow into VEE2 through VEX→R1→thermocouple ■→O. -t'', V/
Since the F conversion circuit and the like are the same as in the case where the resistance temperature detector is a sensor, a description thereof will be omitted. However, in the case of a thermocouple, it is necessary to perform reference junction compensation, unlike in the case of a resistance temperature detector. For this reason, a reference junction compensation circuit 19 is provided to obtain a compensation value based on the external temperature. That is, by making the outside temperature proportional to the voltage, the reference junction compensation voltage is added to the V/F circuit 7 and converted into a pulse signal, and the CPU performs calculations for the voltage compensation using the software.

This circuit generally uses a copper resistor or temperature-sensitive resistor, and a method is adopted that takes advantage of the temperature and linearity dependence of the resistance value (a relationship in which the higher the temperature, the higher the resistance value is proportionally). However, this N uses the 9 degrees and the linearity dependence of the voltage across the diode when a constant current is passed through an epitaxial planar silicon diode to reduce costs and save power. ing. Furthermore, since such reference junction compensation is necessary, it is necessary to inform the CPU 14 which channel the thermocouple is attached to. For this reason, a memory inside the CPU is used to distinguish the sensor arrangement, and this memory information is referred to during the measurement cycle to determine whether or not reference junction compensation is to be performed. In this section, you will be able to read and write memory using the following two methods.

One is to prepare in advance a transmission protocol (communication procedure) for rewriting the memory from the host system, and then set the memory information to be referenced according to predetermined operations. is the CPU on the conversion device side.
This method uses 14 input/output ports to operate switches and use a simple display to set memory information to be referenced during adjustment.

As described above, once the installation positions of the sensors of different companies are appropriately determined, zero adjustment and span adjustment are performed for each channel via the rotary switch as described above according to the specifications of the sensor. In this way, it becomes possible to perform measurements by arbitrarily mixing different types of sensors with one converter. Moreover, the conversion device according to the present invention has a simple configuration, and avoids realizing it by complicated combinations of analog amplifiers as in the past, and instead uses the software control function of the CPU 14 as much as possible. We are trying to make it cheaper. In addition, since we do not use expensive A/D converters and use only a single circuit to reduce power, low power can be achieved, making it possible to create a low-cost multi-point input signal converter. becomes.

〔Effect of the invention〕

According to the present invention, various input sensors can be mixed in any channel by using a combination of the bridge circuit design, the constant setting of the amplifier circuit, and the control function of the CPU.

In addition, it generally does not use expensive A/D converters, etc., and the circuit configuration is simple, resulting in lower costs.There are no circuit elements that consume a large amount of power, so low power can be achieved. . Furthermore, by achieving low power, it becomes possible to apply it to intrinsically safe explosion-proof applications that require suppression of electrical energy.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing an embodiment of the present invention, Figure 2 is a V/F
A circuit diagram showing a specific example of the circuit, FIG. 6 is a waveform diagram of each part to explain its operation, and FIGS. 4A and 4B are both K.
It is a waveform diagram of each part for explaining the conversion operation which converts the output of a V/F circuit into the number of pulses. Symbol explanation 1...detection section, 2...1st order filter,
3...Diode, 4.74-...Analog switch, 5...Amplification circuit, 6...
・Multiplexer, 7...--■/F circuit, 8...
... Counter, 9, 10, 72 ... Flip-flop, 11A, 11B ... Inverter gate, 12 ... Nant gate, 13 ...
・Control bus circuit, 14... Arithmetic control unit (CP
U), 15...0/E interface, 16.
... E10 interface, 17 ... Optical unit, 18 ... Optical fiber, 19 ...
...Reference junction compensation circuit, 71...Comparator, 73...Reset circuit, 75...Integrator, 76...Buffer amplifier, S...・・・
・V/F start control signal, P1+P2... Control boat signal. Agent Patent Attorney Akio Namiki Agent Patent Attorney Kiyokatsu Matsuzaki 2 Diagram

Claims (1)

[Scope of Claims] A plurality of detection means that are connected to a sensor that detects a physical quantity to be measured to form a bridge circuit and whose connection mode can be changed depending on the type of sensor, and a plurality of detection means that are provided corresponding to the detection means. a signal extracting means for sequentially extracting a sensor signal and a reference signal; a plurality of amplifying means whose gain is adjustable according to the sensor type and amplifying the signals from each of the signal extracting means; and an output from each of the amplifying means. a selection means for sequentially selecting signals; a conversion means for converting the output of the amplification means via the selection means into a number of pulses; and a conversion means for controlling a conversion start time by the conversion means to calculate the number of pulses corresponding to each physical quantity from a plurality of sensors. A multi-point input signal conversion device comprising: arithmetic control means for converting the digital signal into a digital value; and communication means for converting the digital signal into an optical digital signal and transmitting it to a host device.