JPS61159144A - Measuring instrument for humidity - Google Patents

Abstract

PURPOSE:To obtain a means of simple constitution which provides power source capacity for refreshing operation without requiring any separately provided power source by charging a capacitor with a small current by utilizing a measurement time and discharging the capacitor in the short time of the refreshing operation. CONSTITUTION:The detected value of humidity from a humidity sensor 1 is amplified by an amplifier 3 and this is displayed 6 after an arithmetic circuit 5 performs temperature compensation. A power source part for refreshing operation, on the other hand, connects a changeover switch 12 to the side of a contact b1 in the measurement state of humidity and the capacitor 9 is charged with the charging current from a power source 10 through a current limiting circuit 11. The charging current in this charging period is controlled by the current limiting circuit 11 to the small current and the capacitor 9 is charged to a sufficient value by utilizing the long time of this period. When the refreshing operation is carried out, a control circuit 13 switches the changeover switch 12 from the contact b1 to a side a1 to discharge the capacitor 9 to a heater 7, which operates with this discharging energy to heat up. This operation is performed repeatedly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a humidity measuring device, and particularly to a humidity measuring device that uses electric charge stored in a capacitor as a power source for refreshing a humidity sensor.

[Technical Preface of the Invention II] A humidity measuring device using a heat-refresh type humidity sensor needs to refresh the humidity sensor portion in order to ensure its detection accuracy. A heater is used as a means for refreshing, and a changeover switch is inserted between the power supply circuit and the heater, and a separate timer turns the changeover switch on and off to energize the heater at predetermined intervals. However, it has been common practice to refresh the humidity sensor using heating energy.

[Problems in the background art] In the humidity measuring device according to the conventional method described above, in addition to the power supply capacity required for normal humidity measurement, it is necessary to secure the power supply capacity necessary for refreshing, and for this purpose, the device is This results in an increase in size and weight. Also, the battery is M
In the case of '11, it is necessary to obtain a sufficient discharge current at the time of refreshing, so a small battery cannot be used, which is a factor that impairs portability. Furthermore, in order to obtain constant heating conditions, it is necessary to control the time when electricity is applied to the heater, which requires a timer.

[Object of the Invention] The present invention has been made to solve the above-mentioned problems, and provides a humidity measurement device that does not particularly require a separate power source and has a means that can cover the power supply capacity for refreshing with a simple configuration. The purpose is to provide equipment.

[Summary of the Invention] The present invention focuses on the fact that the time when the heater is energized is short compared to the time when the device is in the measurement state, and uses this long measurement time to measure the capacitor in the small II flow. The idea is to secure sufficient heating energy by charging the battery and discharging it for a short time during refresh.

[Embodiments of the Invention] Examples will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a humidity measuring device according to the present invention.

In FIG. 1, 1 is a humidity sensor, 2 is a power supply, and 3 is an amplifier, which amplifies the amount detected by the humidity sensor 1. 4 is a temperature detection section, for example, a thermistor is used. 5
is an arithmetic circuit in which the detection output from the amplifier 3 and the detection output from the temperature detection unit 4 are respectively input, temperature compensation is performed, and these outputs are linearly converted. 6 is a display device.

Reference numeral 7 denotes a refresh heater, which is provided close to the humidity sensor 1, and a power supply unit is attached to this heater. The power supply section includes a capacitor 9 (for example, electric double layer type), a power supply 10, a current limiting circuit 11, a changeover switch 12, and a control circuit 13.

Next, a series of operations will be explained. First, the humidity is detected by a known operation in which the amount detected by the humidity sensor 1 is amplified by the amplifier 3, temperature compensated by the arithmetic circuit 5, and displayed on the display device 6.

On the other hand, in the power supply unit for refreshing, when the humidity is being measured, the changeover switch 12 is connected to the contact b1 side, and the charging current from the power supply 10 charges the capacitor 9 via the current limiting circuit 11. .

The charging current during this charging period is controlled to a small current by the current limiting circuit 11, and the capacitor 9 accumulates a sufficient amount of charge over a long period of time during this period. At refresh time, the control circuit 13 switches the changeover switch 12 from the contact b1 to the a1 side, discharges the electric charge accumulated in the capacitor 9 to the heater 7, and heats the heater 7 with this discharge energy. Note that the above operations are repeated.

FIG. 2 shows another embodiment of the humidity measuring device according to the present invention.

This embodiment attempts to obtain the high voltage required by the heater using a low power supply voltage. In Figure 2,
Components that are the same as those in FIG. 1 are designated by the same reference numerals and their description will be omitted.

In Figure 2, 9a and 9b are capacitors arranged in parallel, and in the measurement state each changeover switch (interlocking) 12.12a
, 12b are switched to the charging side (bl, bl, b3), and therefore the capacitor 9a19b is connected in parallel to the power supply 10 and charged to a specified voltage. In this case as well, the charging current is limited by the current limiting circuit 11, similar to the embodiment described above. Then, when it is time to refresh, the control circuit 13 switches each changeover switch 12.12a, 1
2b are switched to the discharging side (al, a2, a:+) in conjunction with each other, and each capacitor 9a, '9b is discharged in series. Therefore, the discharge voltage becomes twice the terminal voltage, allowing rapid heating and sufficient refreshing.

In the above embodiment, the case where two capacitors are provided in parallel has been described, but the present invention is not limited to this, and it is clear that any number of capacitors may be used as required.

In the above embodiment, the case of charging the capacitor was explained, but instead of the capacitor, for example, a nickel
It is also possible to use a secondary battery that is small and has low internal resistance, such as a cadmium battery, and it goes without saying that repeated charging and discharging is possible in this case as well.

[Effects of the Invention] As explained above, according to the present invention, a capacitor is used as a refresh power source and is charged at the time of measurement and discharged at the time of refresh. By simply keeping the terminal voltage constant at the end of charging, the refresh conditions can be kept constant.
Moreover, it is possible to provide a humidity measuring device that does not require a timer to control the energization time.

[Brief explanation of drawings]

FIG. 1 is a block diagram of one embodiment of a humidity measuring device according to the present invention, and FIG. 2 is a diagram of another embodiment. 1... Humidity sensor 2.10... Power supply 3.
...Amplifier 4...Temperature detection section 5...
Arithmetic circuit 6...Display device 7...Heater 8.8a...NI for refresh! Part 1 9.9a, 9
b...Capacitor 11...Current limiting circuit 12.1
2a, 12b ... Selector switch 13 ... Control circuit tail 1 section

Claims (3)

[Claims] (1) In a humidity measuring device that refreshes a humidity sensor by intermittently heating a refresh heater, a capacitor is provided in parallel with the refresh heater power supply, and the capacitor is charged when the humidity sensor is in a measurement state. Additionally, a humidity measuring device is characterized in that switching control is performed so that the discharge occurs during refreshing. (2) The humidity measuring device according to claim 1, characterized in that a plurality of capacitors are provided in parallel to the refresh heater power source. (3) The humidity measuring device according to claim 1, characterized in that a secondary battery is used in place of the capacitor.