JPS6410766B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention detects the temperature difference between the supply water and return water of an air conditioner, and also detects the flow rate of the supply water or return water,
This invention relates to an improvement in a calorimeter used when measuring the amount of heat wasted due to an air conditioning load based on both detection outputs.

[Prior art]

Conventionally, individual thermometers are used to detect the temperature difference between two points, and a two-wire or three-wire line is connected between the temperature sensor installed at the measurement point and the thermometer body. Although it is supposed to be connected,
In the two-wire system, the resistance of the line affects the measured value, so the wiring length between each measurement point and the thermometer body must be set equal, which makes installation work cumbersome. On the other hand, in the case of 3-wire system,
Although the influence of the resistance value of the line is smaller than that of the two-wire system, the same effect appears when the resistance value of the line increases due to an increase in the wiring length, so this method has the drawback that the wiring length cannot be increased. It is occurring.

In addition, to display the amount of heat, the temperature difference obtained from the output of the thermometer is multiplied by the flow rate obtained from the flowmeter, the multiplied value is integrated, and this result drives an electromagnetic counter. There is also the drawback that it becomes complicated.

[Summary of the invention]

The present invention has the purpose of eliminating such drawbacks of the conventional technology at once, and the present invention aims to eliminate such drawbacks of the conventional technology.
The same constant current is passed through the current wires and the second heat-sensitive element, and the terminal voltage of each heat-sensitive element is derived from each individual voltage line, and the temperature difference detection circuit is connected to each heat-sensitive element. A signal indicating the temperature difference between the temperatures detected by each heat-sensitive element is obtained by a temperature difference detection circuit, and this output is pulsed by a voltage/frequency converter. Convert to signal frequency,
This pulse signal is counted by a counter, and a control pulse of a predetermined time width is generated according to the flow rate pulse generated for each unit flow rate from an electromagnetic flowmeter that detects the flow rate of the flow path in which the heat-sensitive element is arranged. This control pulse is generated by the circuit, and by putting the counter in the counting state,
The present invention provides an extremely effective calorimeter that obtains a signal indicating the amount of heat from the count output of a counter.

〔Example〕

Hereinafter, details of the present invention will be explained with reference to circuit diagrams showing embodiments.

FIG. 1 is a block diagram of the calorific value calculation section, showing first and second heat-sensitive elements TS ₁ and TS ₂ individually arranged in each flow path such as a water supply pipe and a water return pipe, and a terminal plate TB. and two current lines Li ₁ , Li ₂ and Li ₃ , Li ₄ and two voltage lines Lv ₁ , Lv ₂ and
These current lines Li ₁ to Li _{4 are connected by individual wiring of 4-wire lines consisting of Lv 3 and} Lv ₄ .
are connected in series by a short-circuit wire SL, and also connected to a constant current circuit Is, which allows the same current to be applied to each heat-sensitive element TS ₁ to TS ₂ via each current line Li ₁ to _{Li 4} . A constant current is passed through it.

Therefore, each terminal voltage of the heat-sensitive elements TS ₁ and TS ₂ corresponds to each detected temperature, and each terminal voltage is individually derived by the voltage lines Lv ₁ to Lv ₄ to be connected to the temperature difference detection circuit TDD. Here, a voltage indicating the temperature difference between the temperatures detected by each thermosensitive element TS ₁ and TS ₂ is determined and sent to the absolute value circuit VO.

Note that the output of the temperature difference detection circuit TDD is designed so that the polarity of the output is reversed accordingly, since the height relationship of the temperatures detected by the heat-sensitive elements TS ₁ and TS ₂ is reversed during cooling and heating. The output is always converted to the same polarity by the absolute value circuit VO, multiplied by a coefficient corresponding to cooling and heating, and then sent to a voltage/frequency converter (hereinafter referred to as VFC) V/F ₁ such as a voltage controlled oscillator. Given, here,
It is converted into a pulse signal with a frequency corresponding to the temperature difference, and then counted by a counter CNT.

However, the counter CNT is configured to be in a counting state only during a period when a control pulse having a predetermined time width t is applied from the control pulse generation circuit CPG, and the control pulse generation circuit CPG is
Depending on the flow rate pulse P _F given via the photocoupler PC ₄ and the waveform shaping circuit WS, the AC voltage
A control pulse is generated based on the frequency of Va, and a flow rate pulse P _F is generated at a constant unit flow rate from an electromagnetic flowmeter that detects the flow rate in the flow path in which the heat-sensitive element TS ₁ or TS ₂ is arranged. Therefore, the count value of counter CNT indicates the amount of heat due to the product of temperature difference and unit flow rate, and by repeating this according to the generation of flow rate pulse P _F ,
The count value of the counter CNT indicates the cumulative heat sensitivity.

Therefore, if the count value of the counter CNT is taken as it is, the cumulative amount of heat can be obtained, but in Fig. 1, the electromagnetic counter MGC is driven,
Since this indicates the cumulative amount of heat, the counter CNT is used as a frequency divider,
Frequency division is performed for each control pulse period, and reset is performed when the control pulse ends, thereby sending out a frequency division output corresponding to the product of temperature difference and unit flow rate as a pulse signal. The number of pulses indicates the amount of heat per unit flow rate.

The output of the counter CNT is the photo cutter PC ₂ ,
It is given to PC ₃ and sent out as a heat pulse Pc via the photocoupler PC ₃ and the terminal board TB, but the photocoupler PC ₂ is connected in series with the photocoupler PC 2.
PC ₁ is inserted, transistor Q is turned on via the photocoupler PC ₁ and resistor R, and the terminal board
It is designed to drive an electromagnetic counter MGC via TB, and photo cutter PC ₁ is an absolute value circuit.
Low level cut circuit connected to the output side of VO
Temperature difference is reduced because it is controlled by LLC,
When the output of the absolute value circuit VO drops to, for example, 0.5V or less, the low level cut circuit LLC responds and turns off the photo coupler _PC1 , thereby disabling the electromagnetic counter MGC.

This is because slight temperature differences may need to be ignored as errors due to the configuration of air conditioners, etc. Depending on the conditions, the response of the low level cut circuit LLC may be stopped as described below. It is also possible to keep the Photo Katsupura PC ₁ on at all times.

The time width t of the control pulse is set to 1 sec, for example, and the output frequency of VFC/V/F ₁ is several 100 Hz.
The generation period of the flow rate pulse P _F is set to be much longer than 1 sec.

Figure 2 is a block diagram of the flow rate measurement unit, and is based on an AC power supply with a stable frequency such as a commercial AC power supply.
AC is stepped down by power transformer PT, and power supply circuit PS
After rectifying and stabilizing the DC power supply +
In addition to supplying to each part as V, -V, AC voltage
While supplying the power supply Va to the control pulse generation circuit CPG shown in Fig. 1, a clock pulse is generated by the clock pulse generation circuit CKG in synchronization with the power supply Va.
It is given to the pulse generator PG.

A pulse generator PG using a frequency divider etc. generates drive pulses of a predetermined frequency and outputs a photocoupler PC ₅ .
The inverter INV generates a square wave alternating current based on this, and the inverter INV generates a square wave alternating current.
It is applied to the excitation coil L of the electromagnetic flowmeter detector via the terminal plate TB to excite it.

The magnetic flux generated by the excitation coil L is passed to the measuring tube MP of the detector, and the electromotive force generated according to this magnetic flux and the flux of supply water or return water flowing through the measuring tube MP is applied to the electrodes P ₁ , P ₂ Detected by terminal board TB
The voltage is applied to the amplifier AMP ₁ via the drive pulse, where it is amplified, and then sampled and held at its peak voltage by the sample-and-hold circuit S/H that operates according to the drive pulse, and then amplified again by the amplifier AMP ₂ . Moreover, it is given to VFC・V/F ₂ , where it is converted into a pulse signal with a frequency according to the flow velocity, and then divided by a frequency divider FD,
It is sent to the waveform shaping circuit WS in FIG. 1 as a flow rate pulse P _F via the photocoupler PC ₆ .

Note that the amplifier AMP ₂ is equipped with a regulator for zero adjustment and span adjustment of the output value, and is thereby configured to set the output frequency of VFC/V/F ₂ within a predetermined range.

FIG. 3 is a circuit diagram showing details of the temperature difference detection circuit TDD, in which first and second thermal elements using a thermistor or the like whose resistance value changes depending on the temperature are used.
TS ₁ and TS ₂ are housed in a probe, etc., and these and the terminal board TB are connected by first and second 4-core cables W ₁ and W ₂ , but the cable W ₁ are the first and second current lines
Li ₁ , Li ₂ , and first and second voltage lines
The cable W ₂ consists of third and fourth current lines Li ₃ , _{Li 4} and third and fourth voltage lines Lv 3 , Lv 4 , and the cable W ₂ consists of third and fourth current lines Li ₃ , Li 4 and third and fourth voltage lines Lv 3 , Lv ₄ . ₁
One end of the voltage line Lv ₁ is connected in a straight line to one terminal t ₁ of the thermal element TS ₁ , and one end of the current line Li ₂ and the voltage line Lv ₂ is connected to the other terminal t ₂ of the same element TS ₁ .
and one end of the current line Li ₃ and the voltage line Lv ₃ is connected to one terminal t ₃ of the heat sensitive element TS ₂ , and the current line Li ₄ and the voltage line Lv ₄ are connected directly to each other. One end is similarly connected to the other terminal _t4 of the same element _TS2 .

Further, the other ends of the current lines Li ₂ and Li ₃ are connected via the terminal plate TB by a shorting line SL, and a constant current circuit Is is connected to the other end of the current line Li ₄ .
A power source -V is applied through this, and
A series resistor Rs is connected to the other end of the current line Li ₁ to bring the shorting line SL to approximately zero volts, and a power supply +V having the same voltage as the power supply -V is applied through this resistor Rs.

For this reason, each heat-sensitive element passes through the current lines Li ₁ to _{Li 4}
The same constant current passes through TS ₁ and TS ₂ , and the current line Li ₁
~The value of constant current becomes irrelevant to the resistance value of Li ₄ ,
If heat-sensitive elements TS ₁ and TS ₂ having substantially the same characteristics are used, the voltages at these terminals will indicate the temperature at each measurement point.

In addition, since the power supplies +V and -V have the same voltage and opposite polarity, and a series resistor Rs is inserted, the short-circuit wire SL has almost zero V, and the leakage current to each amplifier circuit described below decreases significantly.

i.e. differential amplifier A ₁ and resistors R ₁ to _{R 4}
As a result, a first amplifier circuit having high input impedance is configured, and a differential amplifier A ₂
and resistors _R5 to _R8 constitute a similar second amplifier circuit, and a voltage line is connected to these inputs.
Since _the other ends of Lv ₁ , Lv ₂ and Lv ₃ , Lv ₄ are connected via the terminal plate TB, there is _a
The terminal voltages between t ₃ and t ₄ are each amplified by the same amplification degree.

Each output of each amplifier circuit is given as an input to a subtraction circuit constituted by a differential amplifier A ₃ , resistors R ₉ to R ₁₄ and potentiometers RV ₁ and RV ₂ ,
A voltage corresponding to the difference between each output is sent to the output OUT, which indicates the temperature difference between each measurement point detected by each heat-sensitive element TS ₁ , TS ₂ .

Therefore, the temperature difference between each measurement point can be detected with a simple configuration, and the negative feedback provided by the resistors R ₄ and R ₈ allows each DC amplification circuit made up of the differential amplifiers A ₁ and A ₂ to have a high input impedance. Therefore, no current flows through the voltage _lines Lv ₁ to _{Lv 4} , and their resistance values are completely unrelated to the measured value _. Accurate temperature difference can always be obtained regardless of the wiring length.

Note that a resistor is connected to the non-inverting input of differential amplifier _A3 .
Bias voltage is applied from potentiometer RV ₂ through R ₁₁ and R ₁₃ , and the potentiometer
The setting of RV ₂ is such that the zero point adjustment of the output OUT is performed, while the negative feedback to the movable element of the potentiometer RV ₁ inserted between the output of the differential amplifier A ₃ and the common circuit is performed. A resistor _R14 is connected, and the amplification degree is adjusted by setting the potentiometer _RV1 , and the span of the output OUT is adjusted.

Fig. 4 is a circuit diagram of the low level cut circuit LLC, in which the output of the absolute value circuit VO is applied from the input IN to the inverting input of the differential amplifier _A4 via the resistor _R21 , and the output of the absolute value circuit VO is applied to the inverting input of the differential amplifier A4. The non-inverting input of ₄ has
While the reference voltage obtained by dividing the power supply +V by resistors R ₂₂ and R ₂₃ is applied via resistor R ₂₄ ,
A positive feedback resistor is connected between the non-inverting input and the output.
If R ₂₅ is connected and the voltage from the input IN is above the reference voltage, the output of the differential amplifier A ₄ is of negative polarity, so the diode D is in the off state, and accordingly the transistor Q ₁ is turned off. off, forward bias is applied from the supply +V through the base resistor R ₂₇ of transistor Q ₂ , and transistor Q ₂
is turned on, the photo cutlet is turned on.
A current is passed to the light emitting diode of PC ₁ , and the photocoupler PC ₁ is maintained in an on state.

On the other hand, if the voltage from the input IN becomes lower than the reference voltage, the output of the differential amplifier _A4 becomes positive, the diode D turns on, and the resistor
A forward bias is applied to the base of the transistor Q ₁ through R ₂₆ , turning the transistor Q ₁ on, so that the transistor Q ₂ turns off, and the light-emitting diode of the photocoupler PC ₁ is no longer energized, and the photocoupler PC ₁ is turned off. is in the off state.

Furthermore, due to the positive feedback provided by the resistor _R25 , hysteresis characteristics are given to the output polarity reversal of the differential amplifier _A4 , which stabilizes the operation when the voltage from the input IN fluctuates around the reference voltage. On the other hand, if the jumper wire J inserted in series with the resistor R ₂₂ is cut, the output of the differential amplifier A ₄ will always maintain negative polarity, and the photo coupler PC ₁ will be connected to the voltage from the input IN. It can be kept on regardless of the situation.

Therefore, according to the configuration shown in FIG. 1, the wiring length for each heat-sensitive element TS ₁ and TS ₂ can be determined arbitrarily, and an accurate temperature difference can be detected.
A signal corresponding to the amount of heat can be obtained with a simple configuration, and in the configuration shown in Figure 2, the clock pulse is generated based on the AC power supply, so an expensive crystal oscillator etc. is not required, and the calorimeter can be installed at a low cost. It becomes easy to manufacture.

In addition, by providing the low-return circuit LLC, measurement errors are prevented, and the amount of heat measured is accurate.

However, in FIG. 1, the count value of the counter CNT may be sent out as is depending on the situation, and a gate circuit may be provided on the input side of the counter CNT.
The same effect can be obtained by controlling this with control pulses or by the output of the low-level cut circuit LLC, and even if VFC/V/F ₁ is controlled by the output of the low-level cut circuit LLC as shown by the dotted line. In addition, if it is only used for cooling or heating, the absolute value circuit VO may be omitted, and depending on the configuration of the air conditioner, etc., the low level cut circuit LLC may be used.
It is also optional to omit .

In addition, in FIG _. 2, the alternating current power supply AC may be directly converted into square wave alternating current and applied to the excitation coil L, _and in _{FIG .}
may be wired individually, and each amplification circuit and subtraction circuit may be wired in other configurations as long as they exhibit equivalent functions.In Figure 4, the threshold level Various modifications are possible, such as the use of other circuits having the following.

[Effects of the Invention] As is clear from the above explanation, according to the present invention, the wiring length to each heat-sensitive element is irrelevant to the measured value, and if a wire with characteristics similar to each heat-sensitive element is selected, the wiring length can be reduced. It eliminates the need for adjustment depending on the length, simplifies installation work, and simplifies the overall circuit configuration, making it easier to reduce manufacturing costs, and provides remarkable effects in calorific value measurement for various applications. It will be done.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, in which Fig. 1 is a block diagram of the calorific value calculation section, Fig. 2 is a block diagram of the flow rate measurement section, Fig. 3 is a circuit diagram showing details of the temperature difference detection circuit, and Fig. 4 is a circuit diagram of a low level cut circuit. TS ₁ , TS ₂ ... heat sensitive element, Li ₁ - _{Li 4} ... current line,
Lv ₁ to Lv ₄ ... Voltage line, Is... Constant current circuit, TDD
...Temperature difference detection circuit, V/F ₁ ...VFC (voltage/frequency converter), CNT...Counter, CPG...Control pulse generation circuit, P _F ...Flow rate pulse.

Claims (1)

[Claims] 1. A first and second heat sensitive element whose resistance value changes according to temperature, and each consisting of two current wires and two voltage wires individually wired to each of the heat sensitive elements. a wire line, a constant current circuit that passes the same constant current to each of the heat-sensitive elements via the current line of each of the four-wire lines, and each of the heat-sensitive elements guided by the voltage line of each of the four-wire lines; a temperature difference detection circuit that sends a signal indicating the temperature difference between the temperatures detected by the respective heat sensitive elements based on the terminal voltage of the temperature difference detection circuit; and a voltage/frequency converter that converts the output of the temperature difference detection circuit into the frequency of a pulse signal. , a counter that counts the output of the voltage/frequency converter, and a flow rate pulse generated for each unit flow rate from an electromagnetic flowmeter that detects the flow rate of the flow path in which the heat-sensitive element is disposed, and the counter is placed in a counting state. A calorimeter comprising: a control pulse generation circuit that generates a control pulse with a predetermined time width.