JPH06221882A - Environment measuring apparatus - Google Patents

Abstract

PURPOSE:To provide an environment measuring apparatus wherein its cost is low and its high accuracy can be maintained. CONSTITUTION:A thermistor 6 is connected in series with a capacitor 201 by an analog switch 7, and temperature data is detected on the basis of the charging time of the capacitor 201. Then, instead of the thermistor 6, a humidity sensor 3 is connected in series with the capacitor 201 by the analog switch 7, and humidity data which is changed by a temperature is detected on the basis of the charging time of the capacitor 201. Humidity as a desired variate is retrieved from the humidity data and the temperature data. Since the thermistor 6 and the humidity sensor 3 are used by being changed over by the same circuit, the cost of the title apparatus is lowered. Since the humidity data is compensated by the temperature data as described above, the humidity can be measured with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an environment measuring apparatus for measuring variables such as temperature, humidity and wind speed in an environment where the apparatus is used, and more particularly to an image forming apparatus such as a copying machine or a printer using an electrophotographic method. The present invention relates to an environment measuring device suitable for use.

[0002]

[Prior art]

(Conventional example 1) FIG. 5 is a schematic circuit diagram of a conventional environment measuring apparatus.
Shown in. FIG. 6 is a waveform diagram of the voltage applied to the humidity sensor. In FIG. 5, 1 is a pulse counter and 2 is a CP
U (central processing unit), 3 is a humidity sensor, 4 is a pulse generator, 5 is an oscillator for generating a clock signal of the pulse counter 1, 201 is a capacitor, and 301 is a comparator. When a pulse generation command is output from the CPU 2 to the pulse generator 4, the transistors 101,
The AC voltage shown in FIG. 6 is applied to the point b via 102. At the same time, the AC voltage is also applied to the humidity sensor 3 and the capacitor 201 (if the DC voltage is continuously applied to the humidity sensor 3 for several hundreds ms or more, the humidity sensor 3 is rapidly deteriorated. AC voltage is applied to.

After the point b is switched to 0V, the CPU 2 outputs a signal for stopping pulse generation and a start signal to the counter 1. Then, both the transistors 101 and 102 are turned off, and +1 V is applied to the series circuit of the humidity sensor 3 and the capacitor 201, and the capacitor 201
Starts charging and becomes the same potential as Vref shown in FIG. 6,
The "H" signal is output from the comparator 301 (a voltage corresponding to Vref is generated at the point c by resistance voltage division), and the operation of the counter 1 is stopped. Then, the counter value is sent to the CPU 2 and the time t until the charging voltage of the capacitor 201 reaches Vref inside the CPU 2.
To measure.

Here, the resistance value of the humidity sensor 3 and the actual humidity value have a certain linear function R (t) = αt + β (R is the resistance value of the humidity sensor, α,
β can be obtained by a constant). Also, the actual humidity is a function F (R (t)) with R (t) as a variable.
Required by. These calculations are processed inside the CPU 2 to measure the actual humidity.

(Conventional Example 2) Humidity is one of the variables in the environment. As elements for measuring the humidity, there are a variable capacity humidity sensor whose capacity changes according to environmental humidity and the like, and a resistance value variable humidity sensor whose resistance value changes.

First, the humidity measurement by the variable capacity humidity sensor will be described. An oscillation circuit is configured by using the variable capacitance humidity sensor as a component, and the capacitance value of the humidity sensor is calculated and the humidity is measured because the oscillation frequency changes depending on the humidity.

Next, the humidity measurement by the variable resistance value type humidity sensor will be described. AC voltage is applied to the humidity sensor with the load connected in series. By detecting the voltage drop in the humidity sensor and detecting the DC voltage, the resistance value of the humidity sensor is calculated to measure the humidity.

[0008]

[Problems to be Solved by the Invention]

(Regarding Conventional Example 1) In the above-mentioned Conventional Example 1, the resistance value of the humidity sensor is obtained from a certain function from the charging time, the resistance value is converted into the actual humidity, and the humidity is measured. High CPU is required. Further, the resistance value of the humidity sensor changes depending on the temperature even under a constant humidity, but there is no means for correcting the measured humidity depending on the ambient temperature. Therefore, it is difficult to realize low cost and high measurement accuracy.

(Regarding Conventional Example 2) In the humidity measuring apparatus using the variable capacity humidity sensor in Conventional Example 2, the cost of the variable capacity humidity sensor is high. Further, in the humidity measuring device using the variable resistance type humidity sensor, the resistance value of this sensor element is GΩ in a specific use environment, for example, a low humidity region.
Therefore, the measurement accuracy is not improved or the measurement becomes impossible, and the measurable environmental range is limited.

The present invention has been made under such circumstances, and an object of the present invention is to provide an environment measuring apparatus which can maintain high accuracy at low cost.

[0011]

In order to achieve the above-mentioned object, in the present invention, the environment measuring device is constructed as in the following (1) to (6).

(1) An element and a capacitor whose resistance value changes according to environmental variables are connected in series, and a constant DC voltage is applied to the series-connected circuit to determine the time until the voltage of the capacitor reaches a predetermined value. An environment measuring apparatus for detecting and determining the variable based on this time, comprising first detecting means for detecting the time by using a first element whose resistance value changes only by the first variable in the environment. Second detection means for detecting the time using a second element whose resistance value changes according to the first and second variables in the environment, the detection data of the first detection means, and the second Environment measuring device, comprising: a search unit that searches the second variable based on the detection data of the detection unit.

(2) The environment measuring device according to (1), wherein the first variable is temperature, the first element is a thermistor, the second variable is humidity, and the second element is a humidity sensor.

(3) The environment measuring device according to (2), wherein an AC voltage is applied to the humidity sensor during non-measurement.

(4) The environment measuring device according to any one of (1), (2), and (3), wherein the search means uses a lookup table.

(5) An element and a capacitor whose resistance value changes depending on environmental variables are connected in series, and a constant DC voltage is applied to the series-connected circuit to determine the time until the voltage of the capacitor reaches a predetermined value. An environment measuring apparatus which detects and obtains the variable based on this time, comprising a capacitor switching means for switching a plurality of capacitors having different capacities.

(6) The environment measuring device according to (5), wherein the capacitor switching means switches the plurality of capacitors in such an order that the characteristic deterioration of the element whose resistance value changes due to the environmental variable decreases.

[0018]

With the configurations (1) to (4) described above, the data of the first variable is obtained from the first detecting means, and the data of the second variable is changed from the second detecting means by the first variable. Is obtained, and the second variate is searched by the searching means.

In the configurations (5) and (6), the measurement range is expanded by switching the capacitors.

[0020]

EXAMPLES The present invention will be described in detail below with reference to examples.
It should be noted that Examples 1 and 2 correspond to Conventional Example 1, and Examples 3 and 4 correspond to Conventional Example 2.

(Embodiment 1) FIG. 1 is a schematic circuit diagram of an "environment measuring device" which is Embodiment 1, FIG. 2 is a diagram showing a lookup table used in this embodiment, and FIG. 3 is an operation of this embodiment. 2 is a flowchart (of CPU internal processing) showing the above.

In FIG. 1, 1 is a pulse counter, 2 is a CPU, 3 is a humidity sensor, 4 is a pulse generator, 5 is an oscillator for generating a clock signal of the pulse counter 1, 6 is a thermistor, and 7 is an analog switch. IC, 8
Is a ROM, 201 is a capacitor, and 301 is a comparator.

First, the CPU 2 outputs a 1-bit signal to the analog switch 7 to determine the object to be measured as the thermistor 6 (see S1 in FIG. 3) (if "0", the humidity sensor 3,
If it is “1”, the thermistor 6). After that, a start signal is output from the CPU 2 to the counter 1 and the pulse generator 4,
An alternating voltage of +2 V is applied to point b (humidity sensor 3
Will be destroyed if a DC voltage is excessively applied, so the target to be measured is determined to be the humidity sensor 3 when not measuring,
AC voltage of + 1V is applied). Since the thermistor 6 has a certain resistance value depending on the temperature, the capacitor 20
The electric charge is charged to 1.

At the moment when the charging voltage value of the capacitor 201 becomes equal to a certain voltage (Vref) given to the negative input side of the comparator 301, the comparator 301 outputs an "H" signal to the counter 1,
Stop the operation of counter 1 and set the binary counter value to C
PU2 fetches and inputs to the register (S2). Thereafter, the CPU 2 takes in the data (address 0 ° C.) of the address “1645” in the binary data in the look-up table stored in advance in the ROM shown in FIG. Compare with the actual measured value by. If they are equal to each other, the temperature is determined to be 0 ° C. If not, the address is incremented by 1 and the temperature is similarly determined to determine the temperature (S4). Here, there is a case where the measured value and the data in the table do not match, but since the thermistor 6 has a negative temperature characteristic, when compared sequentially with the measured value, the comparison value (measured value-specified value) There is always a case where "-" changes from "+". Therefore, the data is compared again with the two data of the addresses before and after, and the temperature is determined by the predetermined value closer to the measured value.

By this temperature determination, the default value start address when determining the humidity is (humidity default value start address) = (address of the determined temperature default value-1645) × 64H (hexadecimal or decimal 100) ) (S5). Then, the calculated humidity default value start address is stored in a register.

After that, the CPU 2 to the analog switch 7
A signal of "0" is output to the humidity sensor 3 as the object to be measured (S6). The same measurement as above is performed and the capacitor 201
Measures the charging time until Vref reaches Vref. Part 2
Take the decimal data into a register with CPU2 (S
7) and compare with the data of the previously determined humidity default value start address (S8). After that, the humidity is calculated by the same process as when the above temperature is determined. Humidity (%) Hex = (address of the determined humidity default value)
-(Humidity default value start address) calculates the humidity (S9). Note that the resistance value of the humidity sensor increases as the humidity decreases, and the counter value also increases, so the process when the measured value and the humidity default value are compared and they do not match is the same as the process when the temperature is determined. Use the method.

As described above, in this embodiment, the measurement error is ± 1 with respect to the default value by the method of comparing the counter value of the charging time and the preset default value to determine the humidity.
Within the%, it is easy to make the final correction when measuring humidity. Also, a CPU that does not have high processing capability
In addition to being able to use, the same circuit and processing means are used for the means for detecting the ambient temperature, so that high measurement accuracy can be maintained and cost can be reduced.

(Second Embodiment) FIG. 4 shows a schematic circuit diagram of the second embodiment.

In the figure, 1 is a pulse counter, 2 is C
PU, 3 is a humidity sensor, 4 is a pulse generator, 5 is an oscillator for generating the clock signal of the pulse counter 1, 6, 9 and 10 are thermistors, 7 is an analog switch IC, 8 is a ROM, 201 is a capacitor, 301 is a comparator. Further, in the thermistors 6, 9 and 10, one is installed near the humidity sensor 3 and the other is installed in a location in the apparatus where temperature control is performed (eg, a fixing device of a copying machine).

First, the CPU 2 outputs a 2-bit signal to the analog switch 7 to determine the object to be measured as a thermistor (for example, if "00", the humidity sensor 3, "01",
If "10" and "11" are 6, 9 and 10 thermistors respectively. Then, the same measurement as in Example 1 is performed to detect the temperature near the thermistor installed at each location and the humidity near the humidity sensor.

Therefore, it is possible to measure the temperature and humidity at each location of the device with the same circuit. Further, as in the case of the first embodiment, the humidity sensor 3 is destroyed when a DC voltage is excessively applied, so that the object to be measured is the humidity sensor 3 during non-measurement.
Then, the AC voltage of +1 V is applied.

(Embodiment 3) FIG. 7 is a schematic circuit diagram of Embodiment 3, FIG. 8 is a waveform diagram of a voltage applied to a humidity sensor, and FIG. 9 is a flow chart showing the operation of this embodiment.

In FIG. 7, 1 is a pulse counter, 2 is a CPU, 3 is a humidity sensor, 4 is a pulse generator, 5a,
Reference numeral 5b is an oscillator for generating a clock signal for the pulse counter 1, 6a and 6b are analog switch ICs, 2
Reference numerals 02, 203, and 204 are capacitors, and 301 is a comparator.

First, from the CPU 2 to the analog switch 6a
Output a 2-bit signal to the capacitor to be measured as the capacitor 202 (if "00", the capacitor 202, "0"
If it is “1”, the capacitor 203, if it is “10”, the capacitor 2
04, capacitors 202, 203, and 204 are 9100 PF, 22 PF, and 0.91 μF, respectively. ), A 1-bit signal is output to the analog switch 6b, and the counter clock is determined to be the output of the oscillator 5a ("0" is the standard clock oscillator 5a, and "1" is the high-frequency oscillator 5b) (see S21 in FIG. 9).

When the CPU 2 outputs a pulse generation command to the pulse generator 4, the AC voltage shown in FIG. 8 is applied to the point b via the transistors 101 and 102 (S2).
2). At the same time, it is also applied to the humidity sensor 3 and the capacitor 202 (If the DC voltage is continuously applied to the humidity sensor for several hundred ms or more, the humidity sensor will be rapidly deteriorated. ing.).

After the point b is switched to 0V, the CPU 2 outputs a signal for stopping pulse generation and a start signal to the counter 1 (S23). Then transistor 10
Both 1, 102 are turned off, the humidity sensor 3 and the capacitor 2
When + 1V is applied to the series circuit of 02, the capacitor 202 starts charging, and when the potential becomes the same as Vref shown in FIG. 8, the comparator 301 outputs a signal of “H” to the counter 1 (Vref at point c). Is generated by the resistance voltage division), the operation of the counter 1 is stopped. Simultaneously with the above operation, the time after the start signal is output to the counter 1 is counted by the counter inside the CPU 2. Then, the count value is sent to the CPU 2 so that the charging voltage of the capacitor 202 is Vre.
The time t to reach f is measured.

Here, this charging time t is from 10 mS to 1
Within the range of 00 μS (S24, NO, S26N
O), the resistance value of the humidity sensor 3 and the actual humidity value are shown in FIG.
A linear function R (t) = α with the time t shown in
It can be calculated by t + β (R is the resistance value of the humidity sensor, and α and β are constants) (S27).

Further, the actual humidity is obtained by a certain function F (R (t)) having R (t) as a variable (S28). This processing is performed inside the CPU 2.

The above-mentioned measuring method is completed when the humidity in the environmental conditions is in the medium humidity range (about 20% to 60%), but when the humidity is about 20% or more, the resistance value of the humidity sensor 3 is several tens of MΩ, The charging time is 10 ms since it is on the order of GΩ.
As described above, when the DC voltage is continuously applied to the humidity sensor 3 for several hundred mS or more, rapid deterioration occurs.
At the moment when the charging time measured by the counter in U2 becomes 10 mS or more (S24, YES), the CPU 2 outputs the pulse generation signal to the pulse generator 4, the counter 1 outputs the count stop signal, and the capacitor selection signal "01" indicates the analog switch 6a. And the capacitor 203 (22PF) is selected (S29, S30). After that, the charging time of the capacitor 203 is obtained in the same manner as described above, and the resistance value of the humidity sensor 3 and the actual humidity are obtained. If the humidity is about 60% or less, the resistance value of the humidity sensor 3 is on the order of several KΩ and several tens of KΩ, and the charging time is 100 μS or less (S26, Y
ES) and the accuracy of the count value of the counter 1 are affected, the pulse generation signal is sent from the CPU 2 to the pulse generator 4 to the analog switch IC 6a, and the capacitance selection signal "10" is sent to the capacitance 204 (0. 91 μF) is selected (S31, S34). After that, the charging time of the capacitor 204 is obtained, and the resistance value of the humidity sensor 3 and the actual humidity are obtained. If the charging time of the capacitor 204 (0.91 μF) is 100 μS or less, in order to improve the measurement accuracy, the 1-bit counter clock selection signal “1” is output to the analog switch 6b to raise the clock frequency (S32). , S33), the charging time of the capacitor 204 is calculated again, and the resistance value of the humidity sensor 3 and the actual humidity are calculated.

As described above, according to the present embodiment, the humidity range to be measured is divided into at least three kinds of ranges, and the combination of the humidity sensor and the capacity is provided according to the number of divisions, and the humidity range is adjusted according to the humidity range. The measurable humidity range is expanded by switching the combination.

Further, since the capacitor is switched from the medium capacity to the small capacity to the large capacity, generally, the measurement can be completed in a short time, the element deterioration of the humidity sensor can be avoided, and the measurement accuracy can be maintained.

(Fourth Embodiment) FIG. 10 shows a schematic flowchart of the fourth embodiment up to the completion of humidity measurement. The hardware configuration of this embodiment is the same as that of the third embodiment.

First, the CPU 2 to the analog switch 6a
Output a 2-bit signal to the capacitor to be measured to the capacitor 203 (if "00", the capacitor 202,
The capacitor 203 is "01", the capacitor 204 is "10", and the capacitors 202, 203, and 204 are 9100 PF, 22 PF, and 0.91 μF, respectively. ), A 1-bit signal is output to the analog switch, and the counter clock is determined to be the oscillator 5a (see S40 of FIG. 10) (if "0", the standard clock oscillator 5 is used).
a, high frequency oscillator 5b if "1").

After that, if the same processing as that of the first embodiment (the charging time to reach a certain potential of the capacitor is 100 μS or less (S45, YES), a capacitor having a larger capacitance value is selected to optimize the capacitance for each humidity range. In this case, when the charging time of the capacitors 203 and 22PF becomes 10 mS or more (S43, YES), the resistance value of the humidity sensor 3 and the actual humidity are determined by stopping the measurement).

Here, the humidity sensor 3 supplies a DC voltage of several hundred meters.
If applied continuously for more than s, the element will be rapidly deteriorated.
In order to finish the charging time of the capacitor as short as possible, the measurement is performed from the capacitor having the smallest capacitance value as in the above process.

Therefore, the accuracy and the measured humidity range are the same as those of the third embodiment, and the element deterioration of the humidity sensor 3 can be suppressed as much as possible.

Although each of the above embodiments measures humidity and temperature, the present invention is not limited to this, and can be applied to measurement of air volume and other variables.

[0048]

As described above, according to the present invention,
It is possible to provide an environment measuring device that can maintain high accuracy at low cost. Further, in the inventions according to claims 3 and 6, the performance deterioration of the element is reduced, and high accuracy can be maintained.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a first embodiment.

FIG. 2 is a diagram showing a lookup table used in the first embodiment.

FIG. 3 is a flowchart showing the operation of the first embodiment.

FIG. 4 is a schematic circuit diagram of a second embodiment.

FIG. 5 is a schematic circuit diagram of Conventional Example 1.

FIG. 6 is a waveform diagram of a voltage applied to the humidity sensor in Conventional Example 1.

FIG. 7 is a schematic circuit diagram of a third embodiment.

FIG. 8 is a waveform diagram of a voltage applied to the humidity sensor according to the third embodiment.

FIG. 9 is a flowchart showing the operation of the third embodiment.

FIG. 10 is a flowchart showing the operation of the fourth embodiment.

[Explanation of symbols]

 1 pulse counter 2 CPU 3 humidity sensor 6 thermistor 7 analog switch 8 ROM 201 capacitor 301 comparator

Claims (6)

[Claims] 1. An element and a capacitor whose resistance value changes according to environmental variables are connected in series, and a constant DC voltage is applied to the circuit connected in series to detect the time until the voltage of the capacitor reaches a predetermined value. An environment measuring apparatus for obtaining the variable based on this time, the first detecting means for detecting the time using a first element whose resistance value changes only by the first variable in the environment, A second element for detecting the time using a second element whose resistance value changes according to the first variable and the second variable in the environment.
Environment detecting apparatus, and a searching means for searching the second variable based on the detection data of the first detecting means and the detection data of the second detecting means. 2. The environment measuring apparatus according to claim 1, wherein the first variable is a temperature, the first element is a thermistor, the second variable is a humidity, and the second element is a humidity sensor. 3. The environment measuring device according to claim 2, wherein an AC voltage is applied to the humidity sensor during non-measurement. 4. The retrieval means uses a lookup table, wherein the retrieval means uses a lookup table.
The environment measuring device according to claim 3. 5. An element and a capacitor whose resistance value changes depending on environmental variables are connected in series, and a constant DC voltage is applied to the circuit connected in series to detect the time until the voltage of the capacitor reaches a predetermined value. An environment measuring apparatus for obtaining the variable based on this time, comprising a capacitor switching means for switching a plurality of capacitors having different capacities as the capacitors. 6. The environment according to claim 5, wherein the capacitor switching means switches the plurality of capacitors in such an order that the characteristic deterioration of the element whose resistance value changes depending on the environmental variables decreases. measuring device.