JPS63285430A - Temperature measuring apparatus - Google Patents

Abstract

PURPOSE:To achieve a smaller size and a lower cost without temperature sensors and complicated light transmitting and receiving circuits, by providing a light emitting diode (LED) at a remote point to detect variations in light output power of the LED with temperature on the light receiving side. CONSTITUTION:An LED 3 always emits light with a constant current source 10. Light output power of the LED 3 varies with temperature, supplied to a low pass filter 14 through an optical fiber 4 to be turned to a certain wave band range and transmitted to a light receiver 5 to vary a light input power thereof 5. Thus, an output V0 level of a light power level detector 11 varies with changes in the light input power to the light receiver 5 and is transmitted to a temperature display device 7 to display temperature.

Description

[Detailed Description of the Invention] [Summary] The present invention solves the conventional problem that a temperature measuring device requires a forward transmitting circuit and a receiving circuit in addition to a temperature sensor, which makes the device large and cannot be constructed at a low cost. In order to solve this problem, the device can be made smaller and less expensive by adopting a configuration in which the optical receiving side detects temperature-related fluctuations in the optical output power of a light emitting diode (hereinafter referred to as LED) installed in a remote location. This is how it was done.

[Industrial application field]

The present invention uses a thermometer 811 that measures the temperature of a remote location, such as a warehouse or a freezer, and displays it on the receiving side using optical transmission.
Regarding equipment. Although such a temperature measuring device is required to be small like other measuring devices, since optical transmission is performed, the devices tend to be large-scale on the optical transmitting side and the optical receiving side. Therefore, small devices are required on both the optical transmitting side and the optical receiving side.

[Conventional technology]

FIG. 6 shows a block diagram of an example of a conventional device.

In the figure, 1 is a temperature sensor, 12 is an electric wire, and 13 is a signal processing section. In the figure, a temperature information signal detected by a leakage sensor 1 is supplied to a signal processing section 13 via an electric wire 12, where the signal is processed and displayed on a temperature display (not shown) or the like.

In this case, the temperature sensor 1 and the signal processing section 13 are connected to the electric current fQ1.
2, the influence of external noise was large, and the transmission loss was also large, making it unsuitable for long-distance transmission.

Therefore, conventionally, the temperature information from the temperature sensor 1 is transmitted via an optical fiber to reduce the influence of external noise.
A temperature measuring device using an optical transmission method that can reduce transmission loss has been proposed.

FIG. 7 shows a block diagram of an example of a conventional device using the above optical transmission system. In the figure, 1 is a temperature sensor, 2 is a light transmitting circuit, 3 is an LED, 4 is an optical fiber, 5 is a light receiver such as a photodiode, 6 is a light receiving circuit, and 7 is a temperature display.

In the figure, a temperature information signal detected by a temperature sensor 1 is converted into an optical signal by an optical transmission circuit 2 and an LED 3, that is, an optical signal having different binary values (emission, non-emission) depending on the temperature information. and sent out via optical fiber 4. When the optical signal is received by the light receiver 5, it is converted into an electric signal by the optical receiving circuit 6 with a level corresponding to the above two parameters, and the temperature is displayed on the temperature display 7.

[Problem that the invention seeks to solve]

The conventional device described above requires a temperature sensor 1 and an optical communication system including an optical transmitting circuit 2 and an optical receiving circuit 6, which makes the device large and has problems that cannot be constructed at low cost. . Further, each of the optical transmitting circuit 2 and the optical receiving circuit 6 has a problem that the circuits are complicated and expensive.

(Means for Solving the Problems) Fig. 1 shows a principle block diagram of the temperature measuring device according to the present invention. The explanation will be omitted. In the figure, 10 is a constant current source;
11 is an optical power level detector. The device of the present invention is configured such that an LED 3 is installed at a remote location, and fluctuations in the optical output power of the LED 3 due to temperature are detected on the optical receiving side.

[Effect]

L E D 3 also serves as a temperature sensor, and L E D
The temperature-related fluctuations in the optical output power of step 3 are detected on the optical receiving side. Therefore, there is no need for a temperature sensor, optical transmitter circuit, and optical receiver circuit as in conventional devices. In this case, the sending side
The ED3 may be driven with a constant current, while the receiving side only needs to detect the optical power level sent from the transmitting side.

〔Example〕

FIG. 2 shows a block diagram of an embodiment of the device of the present invention;
In the figure, the same components as those in FIG. 7 and FIG. 1 are given the same numbers and their explanations will be omitted. In the same figure, constant current source 1
0G, tDrive LED3 with constant current. This allows L.E.
D3 is always emitting light.

The optical low-pass filter 14 has the characteristics shown in FIG. 3, and is connected between the optical fiber 4 and the light receiver 5.

The optical power level detector 11 detects the electric power (f, i) corresponding to the amount of light received by the light receiver 5.

Generally, LEDs have temperature characteristics (light output power fluctuates depending on temperature) as shown in FIG. 4, and the present invention actively utilizes this characteristic. In the same figure, the optical output power of the LED 3 varies depending on the temperature, and this is supplied to the optical low-pass filter 14 via the optical fiber 4, where it is made into a certain wavelength bandwidth, and transmitted to the optical receiver 5. The initial cover power of 5 will fluctuate. As a result, the output vo level of the optical power level detector 11 changes in accordance with the fluctuation of the optical input power to the light receiver 5, and is transmitted to the temperature display 7 to display the temperature.

In the optical power level detector 11, 1. The output current I of the photoreceiver 5 is current-voltage converted by an amplifier 8 and is supplied to a non-inverting amplifier A2. In this case, if the Φλ voltage vS1 resistance of the amplifier A2 is R3°R7 and the output voltage is V, then vo-v, ((R,:+-R3)/R)) is obtained. Note that the Φλ power voltage (2) of the amplifier A2 is set to the human power voltage (voltage obtained from the light receiver 5) at 0°C.

As shown in FIG. 5, among LEDs, edge-emitting type LEDs exhibit significant fluctuations in optical output power due to temperature even at low temperatures. Therefore, when an edge-emitting type LED is used as the LED 3, especially when detecting a low temperature such as a freezer, temperature changes can be detected accurately on the receiving side.

〔Effect of the invention〕

According to the present invention, in addition to eliminating the need for a temperature sensor, there is no need for complicated forwarding and receiving circuits as in conventional devices, and as a result, the device can be made smaller and therefore less expensive than conventional devices. Furthermore, by using an edge-emitting type LED as the LED, low temperatures such as freezing temperatures can be detected with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a principle block diagram of the device of the present invention, FIG. 2 is a circuit diagram of an embodiment of the device of the present invention, FIG. 3 is a characteristic diagram of an optical low-pass filter, FIG. 4 is a temperature characteristic diagram of an LED, and FIG. The figure is a temperature versus optical output power characteristic diagram of an edge-emitting type LED, and FIGS. 6 and 7 are block diagrams of a conventional device. In the figure, 3 is a light emitting diode (LED), 4 is an optical fiber, 5 is a light receiver, 7 is a temperature display, 10 is a constant current source, and 11 is an optical power level detector. N! J#, Quantity Fake U! Professional report Figure 1 Figure 2 Wavelength - Medium light low/tsu 741 Riri M 1st page Figure 3 Figure 5

Claims (2)

[Claims] (1) In a temperature measurement device that optically transmits temperature information at a remote location and detects it on the optical receiving side, a light emitting diode (3) is installed at the remote location, and the temperature of the optical output power of the light emitting diode (3) is What is claimed is: 1. A temperature measuring device characterized in that the temperature measuring device is configured to detect fluctuations due to the change of temperature on an optical receiving side (5, 11). (2) The temperature measuring device according to claim 1, wherein the light emitting diode (3) is an edge-emitting type light emitting diode.