JPS641838B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a battery-powered signal detection circuit that samples and measures a detection signal from a sensor unit that detects a quantity to be measured, and particularly relates to a battery-driven signal detection circuit that samples and measures a detection signal from a sensor unit that detects a quantity to be measured, and in particular, it generates a sampling pulse according to the rate of change of the quantity to be measured. In other words, when the rate of change of the measured quantity is slow, the sampling pulse period is lengthened to reduce battery power consumption without reducing measurement accuracy.

In general, signal detection circuits in which the sensor that detects the measured quantity is battery-powered are required to have low power consumption due to battery life, etc. Therefore, conventionally, the sensor detection signal is sampled to calculate the average power consumption. efforts are being made to make it smaller. However, in conventional sampling detection circuits, the sampling rate is constant, and the sampling rate must be faster than the rate of change of the measured quantity, so it is set to a fairly high speed. When the current value is changing or changing slowly, more sampling is being performed than necessary, increasing power consumption.

The present invention was made in view of the above-mentioned circumstances, and the period of the sampling pulse is shortened when the measured quantity becomes fast, and when
When the change in the measured quantity is zero or slowly changing, the period of the sampling pulse is lengthened to reduce power consumption.

FIG. 1 is an electric circuit diagram for explaining one embodiment of a signal detection circuit according to the present invention, in which 10 is a sensor section, 20 is a sampling pulse transmitter, and 3
0 is the amplifier section, 40 is the sample and hold section,
50 is a waveform shaping circuit, 60 is a retriggerable monomulti, 70 is a counting circuit, and the sensor unit 10 has sensors S ₁ and S ₂ , and is, for example, a water meter, a gas meter, etc. It is detected as a measured quantity.

The transmitter 20 includes C-MOS inverters IC ₁ to _{IC 3}
It consists of a general three-stage CR oscillation circuit using an inverter IC ₃ in the oscillation state.
Since inverter IC ₄ becomes low level when is high level, transistor Tr is turned off, capacitor C is charged through resistor R ₁ or R ₂ ,
When the charging potential exceeds the threshold, the gate is inverted, inverter IC ₃ becomes low level and IC ₄ becomes high level, transistor Tr is turned on, and the charge stored in capacitor C is transferred to resistor R ₁ or R ₂ and resistor r
The battery is discharged through the battery, and the above charging and discharging operation is repeated. Here, if the resistance r is selected as r≪R ₁ or R ₂ , then
During discharge, most of the charge flows through the resistor r, so its time constant becomes small, and as a result, it is possible to obtain oscillation signals with different duty ratios, and the resistors R ₁ and R ₂ as well as the analog switch that selects them SW ₁ and SW ₂ constitute a control means for changing the period of the sampling pulse. Furthermore, the monomulti 60 is used as a means for detecting the rate of change of the measured quantity, and when the output of the monomulti 60 is at a low level, the analog switch SW ₁ is turned on and off.
Since SW ₂ is non-conductive, capacitor C is charged through resistor R _1. Conversely, when it is at a high level, analog switch SW ₁ is non-conductive and SW ₂ is conductive, and charging is performed through resistor R ₂ . I will do it.
Therefore, if the resistors R ₁ and R ₂ are selected so that R ₁ > R ₂ ,
The charging time constant changes and the oscillation period changes depending on the output state of the monomulti 60, and the electric signal waveform at point a in FIG. 1 becomes as shown in FIG. 2 A or A'.

The amplifier 30 is supplied with the sampling pulse obtained as described above (see FIG. 3a), and only when the sampling pulse is at a high level, a voltage is applied to the sensor section 10 and the amplifier section 30, and the sensor detects the sensor. The signal is amplified and output. This amplifier section 30 operates like a comparator, and when the potential of the inverting input section (see FIG. 3 c) becomes higher than the reference potential of the non-inverting input section (see FIG. 3 b), the amplifier output becomes low level. , conversely, when the potential of the inverting input section becomes low, it becomes high level (see FIG. 3d).

In the sample and hold section 40, when the input section (amplifier output) has a low impedance and the output section (waveform shaping circuit) has a high impedance, the gate of the analog switch _SW3 becomes high level and the analog switch is switched off. When SW ₃ is turned on, the impedance becomes low and its output follows the amplifier section output in a short time. However, when the gate of the analog switch SW ₃ becomes low level and the analog switch SW ₃ is turned off, the impedance becomes high, and the charge accumulated in the capacitor C ₀ has nowhere to go and maintains its potential (Fig. 3). (see e).

In FIG. 1, normally the sensor level is lower than the reference level and the amplifier output is at a high level. In this state, the output of the mono multi 60 is at a low level, so the analog switch SW ₁ is conducting and the oscillator is resistor
Capacitor C is charged through _R1 , and relatively long-period sampling pulses are generated. Therefore, the sensor section 10 and the amplifier section 30 are also sampled at long cycles. Now, when the measured quantity starts to change and the sensor level fluctuates in a certain period as shown in FIG. At the same time, the signal is input to the monomulti 60 and the output of the monomulti 60 is set to high level, analog switch SW ₁ is turned off, SW ₂ is turned on, the charging time constant of the oscillator is changed, and a short period sampling pulse is generated. . If the change in the measured quantity is slower than the predetermined monomulti time constant, the monomulti 60
The output becomes low level again and the oscillation period becomes longer, but if the change in the measured quantity becomes faster and becomes shorter than the time constant of the monomulti 60, the output remains high level and the oscillation period is shortened. Perform fast sampling operation.

As is clear from the above explanation, according to the present invention, the sampling rate is increased only when the change in the measured quantity becomes rapid, and is slowed down when the change is zero or slow.
Power consumption can be reduced without impairing measurement accuracy, and it is particularly effective when applied to meters that are not used for a long time, such as water meters and gas meters.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram for explaining one embodiment of the signal detection circuit according to the present invention, and FIG.
The output signal waveform diagram of the transmitter 20 shown in FIG. 3 is a signal waveform diagram for explaining the operation of the electric circuit shown in FIG. 1. 10...sensor section, 20...oscillator section, 30...
Amplifier section, 40...Sample and hold section, 5
0... Waveform shaping circuit, 60... Retriggerable mono multi, 70... Counting circuit.

Claims (1)

[Claims] 1. A signal detection circuit of the type that has a sensor section for sampling and detecting a measured quantity by a sampling circuit, and a transmitter section that generates a sampling pulse, and in which the sensor section and the transmitter section are driven by a battery. A signal detection circuit comprising: control means for changing the period of the sampling pulse according to the output of the detection means for detecting the rate of change of the measured quantity.