JP2712625B2 - Signal transmitter - Google Patents

Description

The present invention relates to a signal transmitter equipped with a microprocessor and transmitting various process quantities (physical quantities) detected in a process by electric signals. The present invention relates to a signal transmitter capable of continuously outputting a signal of a predetermined accuracy even when the operation of a microprocessor becomes abnormal, thereby ensuring safety and reliability.

<Conventional technology> Process quantities such as temperature, pressure, and flow rate are detected by various sensors, and then a zero point and a span adjustment are performed by a signal transmitter, and the signal is standardized, for example, 4 to 20 mA. And transmitted to the instrument room.

A recent type of such a signal transmitter has a microprocessor mounted therein, and is configured to perform zero point and span adjustments and further necessary operations using its intelligence function. I have.

<Problems to be Solved by the Invention> In this type of signal transmitter equipped with a conventional microprocessor, if the microprocessor malfunctions, an output signal cannot be obtained or upper and lower limit values are set. was there.

The present invention has been made in view of such a point, and an object of the present invention is to provide a signal transmitter that can continuously output an output signal having a predetermined accuracy even when a microprocessor malfunctions.

<Means for Solving the Problems> The present invention for solving the above-mentioned problems includes a sensor unit that outputs a signal to be transmitted, a preamplifier that amplifies an electric signal from the sensor unit, and a signal that is received from the preamplifier. , A conversion amplifier that adjusts the zero point and the span value, an A / D converter that receives a signal from the preamplifier and converts it into a digital signal, and a microprocessor that inputs a signal from the A / D converter A D / A converter that converts an operation output from the microprocessor into an analog signal; a monitoring unit that monitors an abnormal operation of the microprocessor; a signal from the conversion amplifier; and a D / A converter. And a voltage / current converter for converting a signal selected by the switch into a current signal. And.

<Operation> When the operation of the microprocessor is normal, the switch selects the output from the microprocessor. In this state, the conversion amplifier receives the signal from the preamplifier, adjusts the zero point and the span value, and constantly outputs the signal to the switch. At this time, the adjustment of the zero point and the span value is controlled based on the output of the microprocessor.

When the monitoring means detects an abnormal operation of the microprocessor, the switch selects an output signal of the conversion amplifier, and outputs a signal from the output signal to the voltage / current converter via the switch.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration block diagram showing one embodiment of the present invention. In the figure, reference numeral 1 denotes a sensor unit, which exemplifies a sensor that receives a pressure signal, changes the distance between the electrodes to change the capacitance, and converts this into an electric signal to detect the pressure.

Reference numeral 2 denotes a preamplifier that amplifies an electric signal from the sensor unit 1, and 3 denotes a conversion amplifier that receives a signal from the preamplifier 2 and adjusts a zero point and a span value.

An A / D converter 4 receives a signal from the preamplifier 2 and converts the signal into a digital signal. A microprocessor 5 receives a signal from the A / D converter 4, and 6 receives an arithmetic output from the microprocessor 5. This is a D / A converter that converts to analog signals.

Reference numerals 71 and 72 denote memories connected to the microprocessor 5 via a bus, and ROM and RAM are used.

Reference numeral 8 denotes monitoring means for monitoring the operation abnormality of the microprocessor 5, for example, using a watchdog timer. Reference numeral 9 denotes a switch for switching one of the signal from the conversion amplifier 3 and the signal from the D / A converter 6 in accordance with the signal from the monitoring means 8 and outputting the selected signal.

Reference numeral 10 denotes a voltage / current converter (V / I converter) for converting a signal selected by the switch 9 into a current signal. The current signal from the voltage / current converter is a standardized current signal of, for example, 4 to 20 mA. And transmitted to the instrument room. Reference numeral 11 denotes a power supply unit that manages power outages and power restorations and supplies power used internally to each unit. The power supply may have a battery inside,
For example, when the transmission line is configured by a two-wire system, power transmitted from the receiving end via the two-wire transmission line may be used.

FIG. 2 is a block diagram showing a specific configuration of the conversion amplifier 3 in FIG.

31 is an OP amplifier, 32 is a resistor for zero adjustment, and the divided voltage is applied to one input terminal of the OP amplifier 31. Reference numeral 33 denotes a span adjustment resistor connected to the output terminal of the OP amplifier. The voltage divided here is fed back to the other input terminal of the OP amplifier 31.

Here, the resistance 32 for zero adjustment and the resistance for span adjustment
Each of the 33 uses an electronic volume composed of, for example, an EEPROM and a resistor, and is configured to be controllable by a signal from the microprocessor 5.

The operation of the device configured as described above will be described below.

FIG. 3 is a time chart showing an example of the operation.
Here, the operation from the time when the power of the apparatus is turned on is illustrated.

When the power is turned on as shown in (a), the power supply unit 11 detects this, and monitors the power recovery management signal a as shown in (b) when the voltage becomes equal to or higher than the minimum drive voltage of the transmitter. Output to means 8. Upon receiving the power recovery management signal a, the monitoring means 8 outputs the CPU reset signal d (from low level to high level) as shown in (e) and starts the microprocessor 5. The microprocessor 5 outputs a reset signal c to the monitoring means 8 at a constant period T1 as shown in (d) when a normal input / output operation is started after executing the predetermined initial processing. This reset signal (low level signal) c
Is output at a constant period T1 while the microprocessor 5 continues to operate normally.

The monitoring means 8 outputs the output control signal b while the microprocessor 5 outputs the reset signal c at a constant period.
Is set to a low level as shown in (c). The output control signal b is supplied to the conversion amplifier 3, the microprocessor 5, and the switch 9. The switch 9 operates as shown in FIG.
It is connected to the 9A side, selects a signal from the microprocessor 5 via the D / A converter 6, and outputs it via the V / I converter 10.

While the operation of the microprocessor 5 is normally performed, the microprocessor 5 inputs the output of the preamplifier 2 via the A / D converter 4 and adjusts the zero point, span adjustment, linear operation, and temperature. A correction operation or the like is performed, and the operation result is output to the V / I conversion unit 10 via the D / A converter 6 and the switch 9. In addition, the control amplifier 3 outputs a control signal of the zero point adjustment resistor 32 and the span value adjustment resistor 33 to the conversion amplifier 3.

Here, the output of the preamplifier 2 is, for example, a voltage of 1 V to 5 V while the sensor unit 1 detects a pressure of 0 to 20 kgf / cm.

Then, when the measurement range of 0 to 10 kgf / cm is set, the microprocessor 5
The gain is doubled, and the value of each resistor is controlled so that a voltage of 1 to 5 V is output for the output of 1 to 3 V of the preamplifier 2.

When the operation of the microprocessor 5 becomes abnormal from the state of normal operation, the reset signal c is not output from the microprocessor 5 to the monitoring means 8 as indicated by the broken line in (d).

When the reset signal c is not output at a constant period, the monitoring means 8 detects an abnormal operation of the microprocessor, sets the output control signal b to a high level as shown in FIG. As shown, the CPU reset signal d is output to the microprocessor 5 at a constant period T2, and the operation of the microprocessor 5 is waited for.

When the output control signal b becomes high level, the switch 9
Is connected to the contact 9B side, selects the output from the conversion amplifier 3 and outputs it to the V / I converter 10.

Here, when the measurement range of 0 to 10 Kgf / cm has already been set, the conversion amplifier 3 applies a control signal from the microprocessor 5 to the output 1 to 3 V of the preamplifier 2.
Since the value of each resistor is set so as to output a voltage of 1 to 5 V, a value close to the operation result from the microprocessor 5 (operation accuracy is reduced) will be continuously output.

With the above operation, even if the operation of the microprocessor 5 becomes abnormal, the V / I converter 10 can continue to output an output signal of a certain accuracy by the conversion amplifier 3. In addition, since the output signal from the microprocessor 5 and the output signal from the conversion amplifier 3 have substantially the same value, this switching can be performed smoothly without causing a large bump in the output signal.

When the operation of the microprocessor 5 recovers normally, the microprocessor 5 again outputs the reset signal c to the monitoring means 8 as shown in (d),
Upon receiving this, the monitoring means 8 sets the output control signal b to the low level as shown in (c), the switch 9 is connected to the contact 9A side as shown in (f), and outputs the output from the microprocessor 5 to D. The signal is output again via the / A converter 6 and the switch 9.

In the above-described embodiment, the sensor unit 1 detects the pressure signal based on a change in capacitance. However, various sensors can be used according to the measurement process amount.

<Effects of the Invention> As described above in detail, according to the present invention, even if the operation of the microprocessor becomes abnormal due to any cause, the operation of the conversion amplifier can continue to output an output signal with a constant accuracy. Thus, a highly reliable signal transmitter can be provided.

INDUSTRIAL APPLICABILITY The present invention is extremely effective when applied to a nuclear power plant requiring high reliability at a relatively low cost or a signal transmitter used in an important plant.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
FIG. 3 is a block diagram showing a specific configuration of the conversion amplifier in FIG. 1, and FIG. 3 is a time chart showing an example of the operation. 1 Sensor part 2 Preamplifier 3 Conversion amplifier 4 A / D converter 5 Microprocessor 6 D / A converter 71, 72 ROM, RAM 8 Monitoring Means 9 Switch 10 Voltage / current converter (V / I converter) 11 Power unit

Claims (1)

(57) [Claims] 1. A sensor for outputting a signal to be transmitted, a preamplifier for amplifying an electric signal from the sensor, a conversion amplifier for receiving a signal from the preamplifier and adjusting a zero point and a span value; An A / D converter that receives a signal from the preamplifier and converts the signal into a digital signal; a microprocessor that receives a signal from the A / D converter; and an arithmetic output from the microprocessor that converts an arithmetic output from the microprocessor into an analog signal A D / A converter, a monitoring unit that monitors an abnormal operation of the microprocessor, a signal from the conversion amplifier, and a signal from the D / A converter, according to a signal from the monitoring unit. A switch for switching and outputting; and a voltage / current converter for converting a signal selected by the switch into a current signal, wherein the conversion amplifier adjusts a zero point and a span value. Is controlled based on the output of the microprocessor, and when the monitoring means detects an abnormal operation of the microprocessor, the output of the conversion amplifier is output to a voltage / current converter via a switch.