JPH01200499A - Signal conditioner - Google Patents

Abstract

PURPOSE:To flexibly cope with the change of engineering by setting the output condition of a pulse corresponding to a signal from a sensor. CONSTITUTION:A signal from a sensor 1 is supplied to an arithmetic means 3 through an A/D converter 2. To the means 3, data related to the kind and the range of the sensor 1 are set from a setting means 6, and the means 3 executes a digital operation based on a prescribed operational expression by using these data. The result of its operation is converted to a pulse signal in accordance with data of a range and a span set from the setting means 6, by a pulse output means 4, and outputted as a standard signal through a smoothing means 5.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a signal conditioner for converting signals from sensors such as temperature, pressure, and flow rate into unified standard signals. It relates to a signal conditioner that has functions such as linearization, various correction calculations, and averaging calculations.

(Prior Art) Receiving instruments such as recorders and controllers that are currently in practical use are configured to input standard signals such as 1 to 5 V and 4 to 20 mA. This requires a converter to convert the signal from the thermocouple, resistance temperature detector, or other sensor into a standard signal that can be input to the receiving instrument.

Conventionally, several types of converters of this kind have been prepared depending on the type of sensor, input signal range and span, calculation function, etc.

(Problem to be solved by the invention) However, there are many types of sensors, signal ranges, and spans, and it is not easy to install and adjust hardware converters according to these types. .

The present invention has been made in view of these points, and its purpose is to realize a signal conditioner that can easily change sensor types, ranges, and spans, and can flexibly respond to engineering changes. There is a particular thing.

(Means for Solving the Problems) FIG. 1 is an R function block diagram showing the basic configuration of the present invention.

In the figure, 1 is a sensor, 2 is an A/D converter that converts the signal from the sensor 1 into a digital signal, and 3 is a calculation means that performs a predetermined digital calculation on the digital signal corresponding to the signal from the sensor 1. 4 is a pulse output means for outputting a pulse signal with a duty ratio corresponding to the calculation result; 5 is a smoothing means for smoothing the pulse signal from the pulse output means 4 and outputting it as a predetermined single signal a; 6 is the calculation Means 3
This is a setting means for receiving an external signal and setting data used for digital calculation in the pulse output means and output conditions for the pulse output means.

(Operation) A signal from the sensor is converted into a digital signal by the A/D converter 2 and applied to the calculation means 3. Data regarding the type and range of the sensor 1 are set in the calculation means 3 from the setting means 6, and the calculation means 3 uses these data to perform digital calculation according to a predetermined calculation formula. The calculation result is converted into a pulse signal by the pulse output means 4 according to the range and span data set from the setting means 6, and is output as a standard signal via the smoothing means 5.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment of the present invention. In FIG. 0, parts corresponding to those in FIG. 1 are denoted by the same reference numerals.

In this example, a thermal pair for detecting temperature is used as the sensor 1.

Reference numeral 11 denotes a temperature sensor for detecting the temperature of the reference junction, for example, a thermistor is used. 12 is a constant current source that supplies a constant current via a resistor Rref; 13 is a reference voltage V r e
f, thermoelectromotive force signal Ex from thermocouple 1, resistance Rre
Voltage across f ■S, temperature signal Es from thermistor 11
a first multiplexer that sequentially selects and inputs 14.
A preamplifier 15 amplifies the signal selected by the multiplexer 13, and here the signal system from the thermocouple 1 and the signal system from the thermistor 11 are made to be separate systems.

16 selects the signal from the preamplifier 14.15 and outputs the A/
This is a second multiplexer that supplies data to the D converter 2.

The D/A converter 2 has a dynamic range of 20 mV to 80 mV, assuming that it handles the seven types of thermocouples specified by JIS: T, E, J, R, S, and B. A combination of preamplifiers 14 is used.

7 is a microprocessor to which the digital signal from the A/D converter 2 is input.

In this microprocessor 7, 71 is an arithmetic control unit (CPU), 72 is a ROM that stores various programs, tables composed of data for performing arithmetic operations, and other necessary data, and 73 is a ROM that stores arithmetic formula data and external RA that stores various data given from
M, 74 is an input port, 75 is an output port, 76 is a communication interface, and 77 is an EEPROM, which are interconnected via a bus 78.

By executing the program stored in the ROM 72, the CPU 71 operates the calculation means 3 and the pulse output means 4.
, and setting means 6 together with data input means 8 which will be described later.
It is designed to function as a

17 is a photo-isolator that isolates and outputs the pulse signal output from the microprocessor 7; 18 is an output amplifier that amplifies the signal from the smoothing means 5; and 19 is a DC/DC that supplies isolated power for operation to each part. It is a converter.

Reference numeral 8 denotes a data input means through which data such as the type of thermocouple, temperature measuring range, etc. are inputted and provided to the microprocessor 7.

This data input means 8 is a microprocessor (CPU).
) 81, a keyboard 82 for inputting data, a display 83, a communication interface 84, a memory 85, etc. When inputting data, a communication line 9 is connected and the microprocessor is connected via this communication line. 7
The data entered using the keyboard 82 is transmitted to the side. Furthermore, the microprocessor 71Fl is accessed as necessary to display data stored in the RAM 73, input signals from sensors, or output signals on the display 83.

FIG. 3 is a conceptual diagram of the external appearance of the device.

The whole circuit is housed in a small case, and on one side terminal TM1 receives the signal from thermocouple 1.
, a terminal TM2 to which a power supply line is connected, a terminal TM3 to which an output signal is taken out, and a connector CC to which a communication line 9 is connected.

The CB is a cover that can be opened as shown in the figure when connecting signal lines and power lines to each terminal, or when connecting the communication line 9 and inputting data, and can be closed at other times. It becomes.

The operation of the device configured in this way will be described next.

Initially, the communication line 9 of the data input means 8 is coupled to the microprocessor 7 by a connector CC. Then, by operating the keyboard 82 of the data input means 8, data such as the type of thermocouple 1 to be connected and the temperature measuring range are input. These data are transmitted to the microprocessor 7 via the communication line 9. After the necessary data is input to the microprocessor 7 side by this data input means 8, the data input means 8 is removed from the connector CC portion and covered with a cover CB to protect the terminal portion.

When the microprocessor 7 receives these data,
This data is stored in predetermined areas in the RAM 73 and EEPROM 77.

As mentioned above, the thermoelectromotive force Ex from the thermocouple 1 is -20
It is in the range of mV to +80mV. This thermoelectromotive force Ex is
The first multiplexer 13 selects the preamplifier 14.
, are converted into digital values by the A/D converter 2. Further, the first multiplexer 13 selects the reference voltage Vref, the voltage generated at the resistor Rref, and the voltage generated at the thermistor 11, converts them into digital values using the A/D converter 2, and supplies the digital values to the microprocessor 7.

The microprocessor 7 receives these digital values and first stores the data indicating the type of thermocouple 1 set by the data input means 8 into the RAM 73 and the EBPROM 77.
Based on the data, calculations for temperature conversion are performed using a corresponding conversion table or calculation formula.

This calculation includes a linearization calculation to make the relationship between temperature and output signal linear, and a reference voltage V
It includes gain correction calculations, zero correction calculations, reference contact correction calculations, etc. performed using r e f, OV, and the voltage across the thermistor 11.

The dynamic range of the temperature signal obtained by calculation at this time needs to be about -273°C to +2000°C.

Next, the microprocessor 7 uses the function as the pulse output means 4 to first read data regarding the temperature measurement range specified by the data input means 8 from the RAM 73, and determines whether the temperature measurement range is, for example, 0 to 300°C. If so, 0% duty ratio for temperature data of 0℃,
A periodic pulse with a duty ratio of 100% is output for temperature data of 300°C, and a periodic pulse of a duty ratio of 50% is output for temperature data of 150°C.

The pulse signal output from the microprocessor 7 is isolated by a photo-isolator 17 and applied to the smoothing means 5. The smoothing means 5 is composed of, for example, a low-pass filter, and outputs an analog signal proportional to pulse width modulation. The amplifier 18 outputs this analog signal as a standard signal, for example, a voltage signal of 1 to 5 square meters.

In the above embodiment, a thermocouple is used as a sensor and a signal from the thermocouple is input. RAM and EEPR can also be used as rewritable memory means for inputting signals.
Although OM and OM are provided, either one may be used. - (Effects of the Invention) As described in detail above, according to the present invention, the type, range, and span of the connected sensor can be easily changed, and it is flexible in response to engineering changes. We can provide a signal conditioner that can handle this.

[Brief explanation of the drawing]

FIG. 1 is a basic functional block diagram of the present invention, FIG. 2 is a configuration block diagram showing an embodiment of the present invention, and FIG. 3 is a conceptual diagram showing the external appearance of the device. 1...Sensor 2...A/D converter 3...Calculating means 4...Pulse output means 5...Smoothing means 6...Setting means 7...Microprocessor 8...Data Input means Fig. 1 Fig. 3

Claims (3)

[Claims] (1) A/ that converts the signal from the sensor into a digital signal
A D converter, a calculation means for performing a predetermined digital calculation on a digital signal corresponding to the signal from the sensor, a pulse output means for outputting a pulse signal with a duty ratio corresponding to the calculation result, and from this pulse output means smoothing means for smoothing the pulse signal and outputting it as a predetermined standard signal;
A signal conditioner comprising a setting means for receiving an external signal and setting data used for digital calculation by the calculation means and output conditions for the pulse output means. (2) The setting means includes a removable data input means,
The signal conditioner according to claim 1, which is configured to receive data input from the data input means. (3) The signal conditioner according to claim 1, wherein the sensor detects temperature, and the type of temperature sensor and data regarding the temperature measuring range are input from the data input means.