JP3272509B2 - Sensor output correction circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor output correction circuit, and more particularly to a voltage sensor output correction circuit.

[0002]

2. Description of the Related Art There are two types of sensors for temperature, distortion, magnetic field, etc., of a voltage output type and a current output type, and a circuit for extracting the output of the sensor has the sensor installed almost at the installation position of the sensor. The power supply is supplied from a processing device via a power supply line, and a sensor output is put on a signal line and sent to the processing device.

Here, the number of wirings interposed between the circuit for extracting the output of the sensor and the processing device is two (two-wire type) when the current output type sensor is used, but the voltage output type sensor is used. In this case, there are three power supply lines, signal lines, and ground (GND) lines (three-wire type).

[0004]

Incidentally, in actual measurement, there are cases where it is desired to observe the output of the sensor as a change from a certain initial value. In such a case, it is very convenient if an initial value can be set in a circuit for extracting the output of the sensor and a corrected signal can be obtained.

In this case, a circuit for extracting the output of the sensor is compared with, for example, a serial-parallel conversion circuit, a circuit for converting the parallel output data of the serial-parallel conversion circuit into an analog voltage, and the magnitude relationship between the converted analog voltage and the sensor output. A circuit for transmitting the result to a signal line may be provided, and the initial value data may be externally supplied to the serial-parallel conversion circuit via an initial value setting line.

However, since the number of sensors used is considerably large, the method of newly providing an initial value setting line in addition to the signal lines increases the number of wirings by the number of sensors, which is not appropriate.

Therefore, a circuit for extracting the output of the sensor in order to maintain the three-wire system is provided with a circuit for comparing the magnitude relationship between the reference voltage and the sensor output and transmitting the result to a signal line.
It is conceivable to form the reference voltage with a manual variable resistor.

However, since the sensor is arranged in the vicinity of the object to be measured, as can be understood from the case of temperature measurement, for example, the setting operation of the reference voltage may be difficult or impossible, and the generality is lacking. There is.

The present invention has been made in view of such a conventional problem, and has as its object to provide a sensor output correction circuit which can maintain a three-wire system and can easily set an initial value from the outside. Is to do.

[0010]

In order to achieve the above object, a sensor output correction circuit according to the present invention has the following configuration. That is, the sensor output correction circuit of the present invention includes a first circuit that extracts a pulse train superimposed on a power supply voltage applied to a power supply line; a second circuit that counts or parallelizes the extracted pulse trains and outputs the pulse train; A third circuit for converting the output of the second circuit to an analog voltage; comparing the magnitude relationship between the sensor output voltage and the converted analog voltage, and adding both .
A fourth circuit for transmitting the calculated result to the signal line as a corrected sensor output; and a fifth circuit for forming operating power supply voltages of the second to fourth circuits from a power supply voltage applied to the power supply line. It is characterized by having.

[0011]

Next, the operation of the sensor output correction circuit according to the present invention will be described. A pulse train as initial value data is superimposed on the power supply voltage applied to the power supply line, the superimposed pulse train is taken out, an analog voltage giving an initial value is formed, and the sensor output is corrected.

Therefore, it is possible to provide a sensor output correction circuit that can maintain the three-wire system and can easily set the initial value from the outside.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a sensor output correction circuit according to one embodiment of the present invention. In FIG. 1, 1 is a connection terminal of a power supply line, 2 is a connection terminal of a signal line (SIG OUT), 3
Is a connection terminal of a ground (GND) line.

A power supply voltage of + V is applied to the power supply terminal 1. For example, as shown in FIG. 2, external control is performed so that + V = + 10 V before the start of measurement and + V = + 5 V during the subsequent measurement.
A pulse train of V _pp (for example, a data pulse train giving an initial value) is superimposed. As a result, before the start of the measurement, the power supply voltage is +15 V.

The power supply voltage is set to +10 V during measurement.
It is a measure to prevent malfunction and is not an essential matter.

The first circuit 4 includes a +
The pulse train superimposed on the V power supply voltage is extracted. Specifically, the first circuit 4 is, for example, a level shift circuit composed of a Zener diode ZD2 and a resistor R2 as shown in FIG. 3, and reduces + 10V to 0V to 5V _pp
Is taken out (initial value data).

The second circuit 5 comprises one of a counter and a serial / parallel converter. That is, the pulse train to be superimposed on the + V power supply voltage only needs to be able to give an initial value.
There are two cases: a so-called simple pulse sequence and a data pulse train giving a predetermined code pattern.

Therefore, when the second circuit 5 is constituted by a counter, the second circuit 5 counts the number of pulses of the pulse train extracted by the first circuit.
Counted and holding outputs parallel data indicating the count value.
Alternatively, when the second circuit 5 is constituted by a serial / parallel converter, the second circuit 5 converts the pulse train extracted by the first circuit into parallel data as it is, and outputs the parallel data.

As described above, since the second circuit 5 holds and outputs the parallel data, the power supply voltage is reduced from +10 V to +5 V at the time of measurement in order to prevent the held contents from being changed by noise or the like at the time of measurement. .

The third circuit 6 converts the parallel output data of the second circuit 5 into an analog voltage and converts it into a reference voltage (REF).
V) to one input of the fourth circuit 7. The other input of the fourth circuit 7 is a sensor output voltage.

The fourth circuit 7 comprises a comparator, an adder, etc., and compares the magnitude relationship between the reference voltage and the sensor output voltage,
Output terminal 2 as a sensor output in which the result of adding
To the signal line.

The fifth circuit 8 forms operating power supply voltages for the second circuit 5, the third circuit 6, and the fourth circuit 7 from the power supply voltage applied to the power supply terminal 1. Specifically, the fifth circuit 8
Is, for example, a Zener diode ZD1 as shown in FIG.
And a resistor R1.

In FIG. 3, R1 = 10 kΩ, R2 = 1
The simulation was performed as follows: 00 kΩ, ZD1 ≒ 7 V, ZD2 ≒ 5 V. As a result, a 5 V _pp data pulse (10 V → 10 V) was applied to the power supply voltage 10 V applied to point A (power supply terminal 1).
15V), the first circuit (level shift circuit)
A data pulse of 0 V to 5 V could be taken out at point C after 4 passes, and it was confirmed that point B at the output end of the fifth circuit 8 was stable at about 7 V.

[0024]

As described above, the sensor output correction circuit of the present invention takes out a pulse train superimposed on the power supply voltage applied to the power supply line, so that the three-wire system is maintained and simplified. This has the effect of providing a sensor output correction circuit capable of externally setting an initial value.

[Brief description of the drawings]

FIG. 1 is a configuration block diagram of a sensor output correction circuit according to one embodiment of the present invention.

FIG. 2 is a time chart showing a relationship between a power supply voltage and a pulse train superimposed thereon.

FIG. 3 is a circuit diagram showing a specific configuration of a first circuit and a fifth circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 power supply line connection terminal 2 signal line connection terminal 3 ground (GND) line connection terminal 4 first circuit 5 second circuit 6 third circuit 7 fourth circuit 8 fifth circuit

Claims (1)

(57) [Claims] A first circuit for extracting a pulse train superimposed on a power supply voltage applied to a power supply line; a second circuit for counting or parallelizing the extracted pulse train for output; and an analog output of the second circuit. A third circuit for converting the voltage into a voltage; a fourth circuit for comparing the magnitude relationship between the sensor output voltage and the converted analog voltage, and transmitting the result of adding both to the signal line as a corrected sensor output; And a fifth circuit for forming operating power supply voltages of the second to fourth circuits from the supplied power supply voltage.