JP3123038B2 - Signal transmitter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal transmitter for converting a physical quantity to be measured into an electric signal by a sensor, processing the signal by a signal processing circuit, and transmitting the processed signal as a current signal to a load via a transmission line. In particular, the present invention relates to a signal transmitter improved so that a past abnormal state can be analyzed from the trend of the current signal.

[0002]

2. Description of the Related Art A physical quantity such as a differential pressure / pressure is converted into an electric signal by a sensor, and an analog / digital converter converts this into a digital signal and outputs the digital signal to a signal processing circuit including a microprocessor.

The signal processing circuit executes necessary calculations such as non-linearity correction on the input digital signal and transmits the digital signal to an output circuit via a digital / analog converter, where the signal is converted into, for example, a current signal. Then, it is transmitted to the load side via two transmission lines.

Procedures and the like necessary for these calculations are stored in, for example, a non-volatile memory, and data from a sensor or data that needs to be temporarily stored are stored in a volatile memory. And used for the operation.

[0005]

However, in the conventional signal transmitter described above, only the current signal at the time when data is input is monitored, and the output history data at a time before this is not stored. It has not been.

[0006] Therefore, even if the output becomes abnormal before the present time, and if the output abnormality is later noticed, it is necessary to know at what point the abnormality has occurred and what kind of abnormal history has passed and the present has been reached. Can not.

[0007] Further, when a temporary abnormality has occurred in the past and is now restored to the normal state, there is no way to know the abnormality, and it is impossible to investigate the cause of the accident caused by the abnormality. There's a problem.

[0008]

According to the present invention, a physical quantity to be measured is converted into an electric signal by a sensor, processed by a signal processing circuit, and processed through a transmission line. in the signal transmitter for transmitting a current signal to the load side Te, memory means for historical data of the current signal is stored as a trend for each original predetermined time interval of the control of the microprocessor in a predetermined format, external
A receiving resistor that transmits power from a power source along with transmission lines and terminals
Connected to both sides as needed, requesting the history data
Outputs a command under the control of the microprocessor
To display the history data sent out on the display.
And a communication device .

[0009]

In the memory means, history data of a current signal transmitted to the load side is stored in a predetermined format as a trend at predetermined time intervals under the control of the microprocessor. The reference means accesses the history data stored in the memory means as needed, and refers to the past history data.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention.

Reference numeral 10 denotes a detection unit. The detection unit 10 is constituted by a movable electrode provided at the center and a pair of fixed electrodes arranged at predetermined intervals on both sides of the movable electrode. Capacitances _CH and _CL are formed by the fixed electrodes.

[0012] Then, the capacitance C _H and C _L only by the movement by applied differential pressure or pressure in the moving electrode corresponding to this movement is changed in a complementary manner. Changes in the capacitance C _H and C _L in the detection unit 10 is output to the converter 11. Capacity / voltage converting unit C / V in the converter unit 11 converts the change in the electrostatic capacitance C _H and C _L into a voltage signal V.

The voltage signal V is input to an A / D converter ADC, converted into a digital signal, and output to a one-chip microcomputer MCP. The microcomputer MCP includes a microprocessor CPU, a read only memory ROM, a random access memory RAM1, an address decoder ADR1, input / output ports I / O1, I / O.
2, control bus CNB1, data bus DAB1,
It is composed of an address bus ADB1 and the like.

The microprocessor CPU controls these components via a control bus CNB1, and the address decoder ADR1 specifies an address of data to be stored in the random access memory RAM1 by a control signal obtained via the control bus CNB1. I do. The random access memory RAM1 is used as a memory for temporarily storing data required for calculation.

In the read-only memory ROM, a program used by the microprocessor CPU for calculation or an initial value is stored at a predetermined address. The microprocessor CPU transfers the program stored here to the data bus as necessary. The data is read out via the DAB 1 and a predetermined operation is executed.

The microprocessor CPU is supplied with a clock signal from an oscillator OSC. The microprocessor CPU controls the input / output port I / O1 to calculate and output the result as a pulse width signal PWM as a duty / current converter. Output to DIC.

A state signal of a switch SW for giving a command to start automatic zero adjustment executed by the microcomputer MCP is read into the microcomputer MCP via the input / output port I / O1.

The input / output port I / O1 outputs parallel data for communication with the outside to the communication modulator / demodulator MDM under the control of the microprocessor CPU, or a communication input from the communication modem MDM. Capture parallel data for

The communication modulator / demodulator MDM receives a clock signal from the oscillator OSC. The communication modem MDM uses the clock signal to modulate a communication digital signal output from the input / output port I / O1, and to perform duty / demodulation. Output to the current converter DIC.

Further, the input / output port I / O2 forms an interface with the control bus CNB2, the data bus DAB2, and the address bus ADB2, and an electrically rewritable memory EEPROM via these buses.
1, EEPROM 2, random access memory RAM
2. The liquid crystal display driver LRV and the liquid crystal display element LCD are controlled.

The address of the random access memory RAM2 is specified by an address decoder ADR2 controlled by a control signal obtained via a control bus CNB2. Various data are stored in the random access memory RAM2 and used as a memory area.

Electrically rewritable memory EEPRO
M1 includes, for example, a setting parameter, calibration data, a low level range value (LRV), and a high level range value (HR).
V) are stored.

Also, an electrically rewritable memory EE
The PROM 2, data corresponding to the current signal I ₀ to be transmitted to the load are stored in chronological order in response to the time at predetermined time intervals, the memory EEPROM2 functions as a storage area for historical data. Microcomputer MC
The calculation result at P is transmitted as a pulse width signal PWM to the duty / current converter DIC via the input / output port I / O1.

From the external power source E, electric power is transmitted to the converter 11 as a current through the receiving resistor R, the two transmission lines L1 and L2, and the terminals + and-. A diode D, an output transistor Q, and a feedback resistor _Rf are connected to these terminals + and-, and the output impedance of the output transistor Q is controlled by the output of the duty / current conversion unit DIC, thereby changing the internal impedance of the output transistor Q. The signal is transmitted to the receiving resistor R as a current signal I ₀ corresponding to PWM.

The current signal I ₀ is accurately converted into a current signal I ₀ corresponding to the pulse width signal PWM by feeding back the feedback voltage generated in the feedback resistor R _f to the duty / current converter DIC. The current supplied from the transmission lines L1 and L2 is converted into a voltage signal by the power supply circuit PC to cover the internal power of the converter 11.

Further, the communication device H is provided at both ends of the reception resistor R.
An HT is connected as necessary, and communication data in a burst waveform output from the communication device HHT is transmitted through transmission lines L1 and L1.
2, and is given as a voltage change between terminals + and-.
The duty / current converter DIC detects this and outputs it as serial data to the communication modem MDM.

Next, the operation of the signal converter configured as described above will be described. The moving electrode moves correspondingly from the detection unit 10 due to a pressure or a differential pressure, and the capacitances _CH and _CL change.

The change in capacitance C _H and C _L, under the control of the microprocessor CPU via is converted into a voltage signal V A / D converter ADC in a volume / voltage converter C / V The data is sequentially stored in the random access memory RAM1 at a predetermined sampling cycle.

The microprocessor CPU reads out an operation program stored in the read-only memory ROM for performing linearity correction or the like and converting the output signal into an output signal, and converts it into an output signal using the data stored in the random access memory RAM1. The calculation result is output to the duty / current converter DIC as a pulse width signal PWM via the I / O1.

The output of the duty / current converter DIC controls the base current of the transistor Q to output the terminals + and-.
Via, for example, differential pressure receiving resistor R as a current signal I ₀ of the 4 to 20 mA, or transmitted as a signal corresponding to the pressure.

In this case, if necessary, the conversion unit 11
If the zero point is checked for normality and is different from the reference value, it is necessary to adjust it to match this reference value, but this operation is started by rotating the switch SW, The zero point is automatically adjusted by the microprocessor CPU.

By the way, the microprocessor CPU has:
As the scheduled processing according to the processing program stored in the read only memory ROM, and data corresponding to the current signal I ₀ to be transmitted to the load side, a certain time interval, for example Toka every hour, at a rate of Toka per day, The processing of storing the data in the electrically rewritable memory EEPROM 2 is executed. Therefore, the current signal I is stored in the memory EEPROM 2.
_This means that history data of ₀ is sequentially stored.

When accessing the stored history data, first, a request command for the history data is transmitted from the communication device HHT as burst wave serial data (digital signals) via the transmission lines L1 and L2 to the terminal of the conversion unit 11. Output to + and-.

As a result, the voltage between the terminals + and-changes digitally.
The communication modulator / demodulator MDM takes in the data via the IC. The serial request command received by the communication modem MDM is converted into parallel data and received by the microprocessor CPU via the input / output port I / O1.

The microprocessor CPU decodes the contents of the request command and stores it in the memory E according to the contents.
The history data stored in the EPROM 2 is read out in a range according to the request and output to the communication modem MDM via the output port I / O1.

The communication modulator / demodulator MDM modulates the history data by using the clock signal from the oscillator OSC and outputs it to the duty / current converter DIC as serial data. The modulated signal is controlled by controlling the base current of the transistor Q and superimposed on a current signal of 4 to 20 mA as a burst wave via terminals + and-to be transmitted.

The communication device HHT receives and decodes the modulated history data via the receiving resistor R, and decodes the data.
It is displayed on the display of T. The above is a case where a request command for displaying the history data on the display of the communication device HHT is issued.
D may be output as a request command to be displayed. The request command may be configured to sequentially update and output, for example, history data including the current time and the previous data as a locus of a graph.

[0038]

As described above, according to the present invention, the past output history of the current signal can be stored and taken out as needed.
Even if an abnormal situation occurs, this abnormal accident can be reliably grasped, and there is a great effect that contributes to the investigation of the cause of the accident.

[Brief description of the drawings]

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

[Explanation of symbols]

 Reference Signs List 10 detection unit 11 conversion unit CPU microprocessor MDM communication modem MCP microcomputer EEPROM1, EEPROM2 Memory HHT communication device

Claims (1)

(57) [Claims] 1. A signal transmitter which converts a physical quantity to be measured into an electric signal by a sensor, processes the electric signal by a signal processing circuit, and transmits the electric signal to a load side via a transmission line as a current signal. A memory means in which data is stored in a predetermined format as a trend at predetermined time intervals under the control of a microprocessor, and transmitted from an external power supply
Needed on both sides of the receiving resistor that transmits power along with wires and terminals
Connected according to the history data request command.
Sent out under control of the microprocessor
A communication device for displaying the history data on a display .