JPH075992A - Analog signal input device - Google Patents

Abstract

(57) [Abstract] [Objective] In an analog signal input device which converts an analog data signal a into a digital data signal and outputs the digital data signal, the temperature t in the device is detected to improve the reliability of the output data signal. Let A temperature detection unit 16 for detecting an ambient temperature T and a reference voltage value V corresponding to each ambient temperature T when the internal temperature t is equal to the ambient temperature T are stored as expected voltages Vs. The expected voltage table 18 is provided to calculate the deviation voltage ΔV between the expected voltage corresponding to the detected ambient temperature and the actual A / D-converted reference voltage, and the calculated deviation voltage is set to the temperature with respect to the ambient temperature. Convert to characteristics and output. Also, when the calculated deviation voltage exceeds the allowable limit, an alarm is output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention collects various analog data signals indicating the operating state of each device from plant equipment in a factory or the like, converts them into digital signals, and outputs them to a higher-level device such as a process control device. The present invention relates to an analog signal input device for sending.

[0002]

2. Description of the Related Art In a process control device for controlling the operation of plant equipment, process data (data signals) indicating the operation state from various equipments constituting a plant is collected and a predetermined process data is collected for the collected process data. The control calculation is performed to calculate the operation amount for each device and send it to each device.

Since the process control device is generally composed of a small computer, it is necessary to once convert a large number of analog data signals output from each device into digital data signals and then input them into the process control device.

An analog signal input device having such a function is constructed, for example, as shown in FIG. The analog data signal a output from each sensor 1 attached to each equipment of the plant is collected by the terminal block 3 in the monitoring control room via the signal line 2 and the analog signal input device via the dedicated cable 4. Analog signal input card 5
Is input to. The data signal a output from each sensor 1 has a current range of 4 to 20 mA and a voltage range of 1 to 5V.

The data signal a input into the analog signal input card 5 is applied to the first to 16th input terminals of the multiplexer 6. An analog reference voltage V is applied from the reference voltage circuit 7 obtained by dividing the control voltage Vc by the variable resistance 7a and the fixed resistance 7b to the 17th input terminal.

The multiplexer 6 is a microprocessor 8
From the selection signal b sent from the photocoupler 9 through the photocoupler 9, one signal designated in order at a constant cycle is selected and sent to the next amplifier 10. The amplifier 10 amplifies each of the data signals a and the reference voltage V, which are selected in order, to a predetermined signal level and sends the amplified data signal to the A / D converter 12 via the next isolation amplifier 11. The isolation amplifier 11 has a function of insulating the signal system power supply from the microprocessor system power supply.

The A / D converter 12 converts each input data signal a or reference voltage V into a digital data signal a or digital reference voltage V. The digital data signal a or the digital reference voltage V output from the A / D converter 12 is input to the microprocessor 8. Since the sampling cycle in the A / D converter 12 is synchronized with the cycle of the selection signal b input to the multiplexer 6, the microprocessor 8 causes the microprocessor 8 to sequentially input the digital data signal a and the digital reference voltage V. It is possible to capture each separately.

The microprocessor 8 performs a predetermined processing on the input digital data signal a, and then sends it to an upper device 15 composed of a process controller or the like via an interface 13 and an upper exclusive bus 14. To do.

Further, the microprocessor 8 has an original function of A / D-converting each data signal a collected from each sensor 1 and transmitting the data signal a to the higher-level device 15, as well as the reference voltage V converted by A / D. A function of monitoring the value and, when the reference voltage V is out of a preset allowable range, determining that the A / D converter 12 has failed and sending a failure detection signal to the host device 15. Have.

[0010]

However, the analog signal input device configured as shown in FIG. 4 still has the following problems to be solved. That is, A
When the / D converter 12 does not operate at all or outputs an abnormal value, the failure of the A / D converter 12 can be detected by the method described above.

However, a large number of electronic parts for handling analog signals such as the amplifier 10, the isolation amplifier 11 and the A / D converter 12 are incorporated in the analog signal input device. The reference voltage circuit 7 is, of course, an electronic component that handles analog signals. Generally, analog signals are susceptible to temperature changes.

Of course, when the temperature inside the device is greatly increased and the electronic parts are thermally destroyed, the above-mentioned A / D
Since the converted reference voltage V shows an abnormal value, the microprocessor 8 can detect this abnormal situation. However, it is not judged as abnormal unless the electronic parts are destroyed by heat.

Generally, each electronic component has an allowable temperature range in which its characteristics can be guaranteed. However, even if the temperature inside the device deviates from the permissible temperature range, the characteristics are deteriorated but the material is not thermally destroyed. As described above, when the temperature inside the device is out of the allowable temperature range in terms of the characteristics, but no warning is output when the temperature does not rise to the thermal destruction temperature, the upper device 15 always outputs correct digital data. It is not possible to obtain confirmation that the signal is being output from the analog signal input device.

It is also important to know the temperature characteristics of the analog signal input device during operation in order to properly use the analog signal input device and to perform temperature compensation on the output data signal.

The present invention has been made in view of the above circumstances, and is provided with a temperature detecting section for detecting the ambient temperature, and the inside of the apparatus is based on the deviation amount of the reference voltage corresponding to the ambient temperature from the expected voltage. It is an object of the present invention to provide an analog signal input device capable of detecting the temperature of the device, ensuring the reliability of the output data signal, and grasping the temperature characteristic of the device during operation.

[0016]

In order to solve the above problems, the present invention takes an analog data signal input from the outside and a reference voltage output from an internal reference voltage source with a multiplexer at regular intervals. A / D conversion is performed to output the data signal as a digital data signal, and an analog signal input device that monitors an abnormal operation of the A / D conversion operation with the A / D converted reference voltage is used to detect the ambient temperature. Corresponding to the detected ambient temperature, the temperature detection unit to detect, the expected voltage table that stores each reference voltage value corresponding to each ambient temperature when assuming that the device internal temperature is equal to the ambient temperature, as each expected voltage Deviation voltage calculation means for calculating a deviation voltage between the expected voltage and the reference voltage actually A / D converted, and the calculated deviation voltage as a temperature characteristic with respect to the ambient temperature. It is obtained and a temperature characteristic output means for outputting the conversion.

Further, in another invention, in place of the temperature characteristic output means in the above-mentioned invention, an alarm output means for outputting an alarm when the deviation voltage calculated by the deviation voltage calculation means exceeds an allowable limit is provided. There is.

[0018]

According to the analog signal input device constructed as described above, the reference voltage also changes when the temperature inside the device rises.
The expected voltage corresponding to the ambient temperature is read from the expected voltage table. Then, the deviation voltage between the A / D converted reference voltage and the expected voltage is calculated. That is, this deviation voltage has a value corresponding to the temperature difference between the internal temperature of the apparatus and the ambient temperature. Therefore, it is possible to convert the calculated deviation voltage into a temperature characteristic with respect to the ambient temperature and output the temperature characteristic.

For example, assuming that the ambient temperature is room temperature, the temperature rise characteristic from room temperature is obtained. Further, in another invention, when the internal temperature of the device is not largely different from the ambient temperature, the A / D converted reference voltage is not significantly different from the expected voltage corresponding to the ambient temperature. Therefore, since the deviation voltage is small, no alarm is output. However, when the temperature rises to such an extent that the characteristics of each electronic component cannot be guaranteed, the deviation voltage exceeds the allowable limit and an alarm is output.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an analog signal input device of the embodiment. The same parts as those of the conventional analog signal input device shown in FIG. 4 are designated by the same reference numerals. Therefore, detailed description of the overlapping portions is omitted.

In the apparatus of this embodiment, a temperature detector 1 for detecting the ambient temperature is provided outside the analog signal input card 5.
6 is provided. The temperature detecting unit 16 converts the detected ambient temperature T into a digital signal having, for example, an 8-bit structure and sends it to the microprocessor 17 in the analog signal input card 5.

In the microprocessor 17, FIG.
The expected voltage table 18 shown in is stored. In the expected voltage table 18, the device internal temperature t, that is, the temperature in the analog signal card 5, is shown for each ambient temperature T detected by the temperature detection unit 16, for example, from 10.0 ° C. to 40.0 ° C. Each expected voltage Vs in the case where it is assumed that it is equal to the ambient temperature T (t = T) is stored.

The temperature characteristic table 19 stores the relationship between the deviation voltage ΔV (V-Vs) between the actual reference voltage V after A / D conversion and the expected voltage Vs and the temperature change amount ΔT with respect to the ambient temperature T. Has been done.

In such an analog signal input device, each analog data signal a output from each sensor 1 shown in FIG. 4 is input to the multiplexer 6 in the analog signal input card 5 in FIG. The reference voltage V from the reference voltage circuit 7 is input to the multiplexer 6 in addition to each data signal a. The multiplexer 6 selects one signal which is sequentially designated at a constant cycle by the selection signal b from the microprocessor 17 and sends it to the next amplifier 10.

1 time-division multiplexed by the multiplexer 6
The data signals a and the reference voltage V from No. 16 to 16 are
Amplified by amplifier 10 and A / D via isolation amplifier 11
After being converted into each digital data signal a and the reference voltage V by the converter 12, it is input to the microprocessor 17.

The microprocessor 17 executes a predetermined processing on the input digital data signal a, and then sends it to the host device 15 composed of a process controller or the like via the interface 13 and the host dedicated bus 14. To be done.

Further, the microprocessor 17 has an original function of A / D converting each data signal a collected from each sensor 1 and transmitting the A / D converted data signal to the higher-level device 15, as well as the A / D converted reference voltage V. The value is monitored, and if this reference voltage V is outside the preset allowable range, the A / D converter 12
Has a function of sending a failure detection signal to the higher-level device 15 upon determining that the failure has occurred.

Further, the microprocessor 17 executes the monitoring processing of the internal temperature t of the analog signal input card 5 according to the flow chart shown in FIG. When the flow chart is started and the digital reference voltage V is input from the A / D converter 12 at the above-described constant period (P1), the temperature detection unit 16
The digital ambient temperature T output from is read. Then, the expected voltage table 18 is searched with the read ambient temperature T to read the corresponding expected voltage Vs. The deviation voltage ΔV is obtained by subtracting the expected voltage Vs from the reference voltage V.

ΔV = V-Vs Further, the temperature change ΔT corresponding to the corresponding temperature deviation ΔV is read from the temperature characteristic table 19 to calculate the internal temperature t of the apparatus.

T = T + ΔT The calculated device internal temperature t is sent to the host device 15 (P
2). Next, it is checked whether the calculated in-apparatus temperature t is higher or lower than the operation reference temperature of the electronic device and the electronic element such as 25 ° C. (P3). If it is high, the calculated deviation voltage ΔV
However, the multiprocessor 6, the amplifier 10, the isolation amplifier 11, and the A / D converter 1 that constitute this analog signal input device
2. When the allowable temperature range Vm corresponding to the allowable temperature range determined by the characteristics of each electronic component such as the reference voltage circuit 7 is exceeded (P4), the internal temperature t of the host device 15 is within the allowable temperature range. The alarm is sent when the upper limit of is exceeded.

On the other hand, in P3, when the in-apparatus temperature t is lower than the operation reference temperature, and when the deviation voltage ΔV is less than the allowable voltage Vm (P4), the in-apparatus temperature t with respect to the host apparatus 15 is
Sends an alarm when the temperature falls below the lower limit of the allowable temperature range.

In the case of the analog signal input device configured in this way, the internal temperature t of the analog signal input device is
Using the reference voltage V of the existing reference voltage circuit 7 and the temperature T detected by the temperature detector 16 attached to the outside, the temperature is measured at a constant cycle and transmitted to the host device 15.

Therefore, the host device 15 can always grasp the accurate internal temperature t of the analog signal input device. Therefore, it is possible to perform temperature correction on the digital data signal a received from the analog signal input device, if necessary.

Further, when the temperature t in the apparatus of the analog signal input apparatus is out of the allowable range of the characteristics of each electronic component constituting the apparatus, an alarm is sent to the host apparatus 15. Therefore, when the host device 15 receives the alarm, it performs processing such as discarding the data signal a input during that period to prevent the control operation processing based on the erroneous data signal a. It becomes possible.

[0035]

As described above, according to the analog signal input device of the present invention, the temperature detecting portion for detecting the ambient temperature is provided, and the reference voltage corresponding to the ambient temperature is determined based on the deviation amount from the expected voltage. The temperature inside the device is detected. Then, when it is out of the allowable range, an alarm is output. Therefore, the reliability of the output data signal can be ensured and the temperature characteristic in the device during operation can be grasped.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an analog signal input device according to an embodiment of the invention.

FIG. 2 is a diagram showing an expected voltage table and a temperature characteristic table set in the apparatus of the embodiment.

FIG. 3 is a flowchart showing the operation of the apparatus of the embodiment.

[Explanation of symbols]

1 ... Sensor, 3 ... Terminal block, 5 ... Analog signal input card, 6 ... Multiplexer, 7 ... Reference voltage circuit, 10 ... Amplifier, 11 ... Isolation amplifier, 12 ... A / D converter, 13 ...
Interface, 15 ... Host device, 16 ... Temperature detection unit,
17 ... Expected voltage table, 18 ... Temperature characteristic table.

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[Procedure amendment]

[Submission date] October 4, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 4

[Correction method] Added

[Correction content]

FIG. 4 is a block diagram showing a schematic configuration of a conventional analog signal input device.

Claims (2)

[Claims] 1. An analog data signal input from the outside and a reference voltage output from an internal reference voltage source are taken in at a constant cycle by a multiplexer and A / D converted, and the data signal is converted into digital data. In an analog signal input device that outputs a signal and monitors an abnormal operation of an A / D conversion operation with an A / D converted reference voltage, a temperature detection unit that detects an ambient temperature and an internal temperature of the device are equal to the ambient temperature. An expected voltage table that stores each reference voltage value corresponding to each ambient temperature under the assumption that they are equal as each expected voltage, an expected voltage corresponding to the detected ambient temperature, and an actual A / D converted reference voltage. A deviation voltage calculating means for calculating a deviation voltage between the temperature difference and a temperature characteristic output means for converting the calculated deviation voltage into a temperature characteristic with respect to the ambient temperature and outputting the temperature characteristic. Analog signal input device including. 2. An analog data signal input from the outside and a reference voltage output from an internal reference voltage source are taken in at a constant cycle by a multiplexer and A / D converted, and the data signal is converted into digital data. In an analog signal input device that outputs a signal and monitors an abnormal operation of an A / D conversion operation with an A / D converted reference voltage, a temperature detection unit that detects an ambient temperature and an internal temperature of the device are equal to the ambient temperature. An expected voltage table that stores each reference voltage value corresponding to each ambient temperature under the assumption that they are equal as each expected voltage, an expected voltage corresponding to the detected ambient temperature, and an actual A / D converted reference voltage. And an alarm output means for outputting an alarm when the calculated deviation voltage exceeds an allowable limit. Signal input device.