JPH0435013B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a sensing device that detects and discharges ultraviolet rays generated from a flame, and particularly relates to a sensing device that continuously detects the size of a flame, etc.

[Conventional technology]

In a conventional sensing device of this kind, as shown in FIG. 3, a voltage from a high voltage generating circuit 2 consisting of a booster circuit is applied to an ultraviolet discharge tube ₁ via a resistor R1 and a charging capacitor _C1 . When the discharge tube 1 is irradiated with ultraviolet rays emitted from a flame or the like, local ionization occurs, and then an avalanche phenomenon occurs to discharge the charge accumulated in the capacitor _C1 . However, since the impedance of the high voltage generation circuit 2 is high, the voltage applied to the discharge tube 1 immediately drops below the discharge sustaining voltage due to the discharge of the capacitor _C1 , the discharge is stopped, and the ultraviolet rays continue to exist. When this happens, an output waveform as shown in FIG. 4 appears at the resistor _R2 .

This output is passed through a waveform shaping circuit 6 such as a monostable circuit, an integrating circuit 7, and a level detecting circuit 8, respectively, and then connected to a switch circuit 10 to generate an alarm signal.

[Problem that the invention seeks to solve]

When extracting the output of such a conventional sensing device as an analog output corresponding to the intensity of ultraviolet rays, the output signal of the integrating circuit 7 shown in Fig. 3 can be used, but as the intensity of ultraviolet rays increases, discharge occurs frequently. Then, as shown in FIG. 4, the discharge pulse becomes different from a pulse that occurs rarely. In other words, the capacitor _C1 is not sufficiently charged, resulting in different peak values, and the third
If the waveform shaping circuit 6 is used to adjust the peak value and pulse width as shown in the figure, the discharge pulses generated within this pulse width will be lost, and the intensity of the ultraviolet rays will be converted into linear analog output. I couldn't take it out.

[Means for solving problems]

This invention adds a discharge tube that detects ultraviolet rays etc. from a flame and discharges it, and a pulse output generated by the discharge, and when the added value is greater than zero, the added value is added one step at a constant cycle. The above problem is solved by providing a counter that performs subtraction and a converter that outputs a digital or analog value according to the added value of the counter.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the apparatus of the present invention, and FIG. 2 is a time chart for explaining the circuit diagram of FIG. In FIG. 1, reference numeral 1 denotes a discharge tube such as an ultraviolet discharge tube, and a high voltage is applied between its anode and cathode via a high voltage generation circuit 2 and a charging capacitor _C1, respectively. The pulse during discharge is a resistor connected to the cathode.
Taken from R ₂ .

3 is an n-bit up-down counter,
The count terminal C is connected to the cathode electrode K of the discharge tube 1 via an inverter IC ₁ and a NAND gate IC ₂ , respectively. The output of the pulse generation circuit 4 is connected to the other input gate of the NAND gate IC ₂ via the NAND gate IC ₃ , and is also connected to the up/down setting input terminal U/D. The other input gate of NAND gate IC ₃ is connected to each output terminal of up-down counter 3.
Outputs are applied from Qo to Qn via OR gate _IC4 . This OR gate IC ₄ is used to prevent further subtraction when the output of the up-down counter 3 is zero.

The output of the up-down counter 3 is a binary digital signal, and when digitally transmitting it to a receiving device (not shown), it may be serially transmitted via a parallel-to-serial converter circuit 5, etc., and when obtaining an analog output value, , the output of counter 3 is D-A
Just apply it to the converter 6.

The operation of such a sensing device will be described below.

When there is no ultraviolet light or very little ultraviolet light, the discharge tube 1 to which a high voltage is applied will not discharge, and therefore the pulse output of the pulse generating circuit 4 will be applied to the count terminal C of the counter 3. There isn't. Note that this pulse generation circuit 4
The pulse is a pulse with a small duty ratio as shown in FIG. 2P, and oscillates at a predetermined period T.

When a pulse as shown in FIG. 2K is generated at the cathode K of the discharge tube 1 due to the occurrence of a flame or the like, the pulse shown in FIG.
A pulse as shown in FIG. 2 is applied, and binary digital signals as shown in FIG. Note that the up/down setting input terminal U/D of counter 3 has an OR
When the gate IC ₄ and the NAND output of the pulse generator 4 are applied, and this potential is negative as shown in FIG. 2 U/D, and a positive potential is applied to the count terminal C, 1 The steps are subtracted and therefore the output terminals Qo to Qn of the counter 3 are
When OR gate IC ₄ has no output, no further subtraction is performed. The number of output bits of the counter 3 is determined according to the number of discharge pulses of the discharge tube 1 generated within the output pulse period T of the pulse generating circuit 4.

The digital value of the counter 3 obtained in this way is converted into an analog value and is shown in FIG. 2A.

Although the n-bit up-down counter 3 is used in this embodiment, similar operations can be performed using other forward counters.

Although this embodiment specifically describes an ultraviolet flame detection device, it goes without saying that any device that can obtain discharge pulses according to the detection parameters, such as a Geiger-Muller tube for radiation detection, will operate in the same way. .

〔Effect of the invention〕

As mentioned above, the sensing device of the present invention can sequentially extract the intensity of ultraviolet rays caused by a flame as a relatively linear analog output, and since the processing circuit is digitalized, temperature drift of components, etc. It has characteristics such as not being easily affected by changes over time.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the sensing device of the present invention, FIG. 2 is a time chart for explaining FIG. 1, FIG. 3 is a circuit diagram of a conventional sensing device, and FIG.
The figures are diagrams each showing a time chart of the waveforms of the main parts of FIG. 3. 1...Discharge tube, 2...High voltage generation circuit, 3...
Up-down counter, 4...Pulse generation circuit,
IC ₁ ~ IC ₄ ...Gate circuit.

Claims (1)

[Claims] 1 A discharge tube that detects and discharges ultraviolet rays from a flame, and a counter that adds up the pulse output generated by the discharge and subtracts the added value one step at a time when the added value is greater than zero. and a converter that outputs a digital or analog value according to the added value of the counter.