JPS61275622A - Level meter - Google Patents

Abstract

PURPOSE:To perform maintenance of the titled meter efficiently by detecting a deviation of an optical axis in a vertical direction to a liquid level to be measured of a light irradiating and photodetecting optical system from the quantity of light of the output light outputted from an edge of an a photodetecting fiber and enabling to give a notice to urge to correct the deviation of the optical axis. CONSTITUTION:A signal corresponding to each selective light outputted after being converted into an electrical signal by a photodetection part 26 is detected by a detection part 219 of a level of the quantity of light as the level of the quantity of light and further, digitized by an A/D conversion part 220 and sent to a CPU 217. As to each light selected with a light selection part 24, when the optical axis of a detection head part 30 is located in the vertical direction to the liquid level 50 to be measured, almost the same level of the quantity of light is detected with the detection part 219 and further, when the optical axis is deviated, the level of the quantity of light is inclined to the specific photodetecting fiber 42 and becomes larger or smaller. Accordingly, the CPU 217 stores the level of the quantity of light in accordance with each selective light in a memory table or the like and decides the deviation of the optical axis from a distribution state of the level of the quantity of light and can urge to correct the optical axis.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a level meter used for measuring the liquid level in an oil tank, etc., and in particular, the present invention relates to a level meter used for measuring the liquid level in an oil tank, etc. Related to level meters that detect deviations.

[Technical background of the invention]

Conventionally, as a measurement technique using light waves, there is a light wave distance meter as shown in FIG. This distance meter is a technology mainly used for surveying, etc., and includes a signal processing section 1 that transmits and receives optical signals, and an incident light set at a measurement target position and input from the signal processing section 1. It is composed of a reflector 2 such as a corner cube that reflects the light in the same direction and in the opposite direction regardless of the angle. Then, the optical signal from the light N4 having the light emitting element 3 built into the signal processing section 1 is transmitted to the reflector 2 via the light emitting fiber 5 and the lens 6 installed at the other end of the fiber 5. The reflected light that is sent out, reflected by the reflector 2, and sent through the lens 2 and the light-receiving fiber 7 is received by the light-receiving section 9 having a light-receiving element 8, and is converted into an electrical signal. The distance to the reflector 2 is measured by detecting the phase difference between the emitted light and the received light by an arithmetic and control unit 10 built into the reflector.

Note that each end of the light emitting fiber 5 and the light receiving fiber 7 is set at the focal position of the lens 6 in order to efficiently emit and receive optical signals.

[Problems with background technology]

By the way, in such a light wave distance meter, in order to accurately direct the direction of the optical signal onto the reflector 2 during distance measurement, the measurement operator adjusts the optical axis of the signal processing unit 1 using a reference telescope or the like. has been done.

However, even if the optical axis adjustment described above is possible for distance measurement, it is impossible to constantly align the optical axis using the above method when measuring levels such as in oil tanks. That's true. Furthermore, even if an optical axis misalignment occurs, it may not have much of an effect on measurement accuracy depending on the degree of the misalignment, and it is also necessary to understand the optical axis misalignment from the standpoint of maintenance.

[Purpose of the invention]

The present invention was made based on the above demands.
We provide a level meter that makes it easy to adjust the optical axis alignment during installation, etc., allows you to determine whether or not to continue measurement work by understanding the optical axis deviation, and is also effective in terms of maintenance. It's about doing.

[Summary of the invention]

The present invention comprises at least a plurality of light-receiving fibers, and is capable of detecting an optical axis deviation of a light emitting/receiving optical system in a direction perpendicular to the measurement liquid surface from the amount of output light outputted from the ends of these light-receiving fibers. It is something to do.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the overall configuration of the level meter, which includes a signal processing section 20 that emits and receives an optical signal and calculates the phase difference between the emitted and received light signals to measure the level, and a detection head section 30 as a light emitting/receiving optical system that is installed in the liquid surface and emits and receives optical signals in a direction perpendicular to the liquid surface; and an optical fiber that is interposed between the signal processing section 20 and the detection head section 30 and guides the optical signals. 40 etc.

The optical fiber 40 is, for example, one light emitting fiber 41.
and six light-receiving fibers 42..., and as shown in FIG. It is something that has been done.

The signal processing section 20 includes an arithmetic control section 21, and this arithmetic control 'I! A light source 2-3 serves as a light-emitting element drive source that causes the light-emitting element 22 to emit light in response to a command signal from S21 and enters the light into the light-emitting fiber 41, and the light is reflected by the measuring liquid surface 50 and passes through each light-receiving fiber 42... - a light selection unit 24 that selectively takes in reflected light sent through it in a predetermined order;
A light receiving element 2 that receives the light selected by the light selection section 24
It consists of a light receiving section 26 having a 5-inch diameter.

Further, the detection head section 30 has a head main body 31 having, for example, a concave cross section, and a lens 32 is supported at a predetermined position of the concave section 31a.

Note that in this detection head section 30, the optical fiber 4
The end face of 0 and the lens 32 are set in the following relationship. For example, if the lens 32 is an ideal lens with no aberrations and the end faces of each optical fiber 41, 42, etc. are at the focal position of the lens 32, then the light projected from the projection fiber 41 will be: Lens 32 → Measured liquid level 50 →
The light passes through the path of the lens 32 and enters the light emitting fiber 41 again, but does not enter the light receiving fibers 42 .

Therefore, in order to prevent such problems from occurring, the optical fiber 40
The end face of the lens 32 is set at a position slightly shifted from the focal position of the lens 32, so that the light from the light emitting fiber 41 reaches the liquid level 5.
The diameter of the spot that is reflected at
2. The positional relationship is such that the light is uniformly incident on the light beams.

FIG. 3 is a configuration diagram showing an example of an integrated unit of the arithmetic and control section 21. As shown in FIG. That is, this arithmetic control section 21 has a reference signal generation section 211 that receives a start signal and generates a reference frequency signal, and the reference signal output from this section is given to the light source 23 as a drive control signal. In addition, the reference signal generation section 211
The output terminal of the local oscillator 212 and the output terminal of the local oscillator 212 are respectively connected to a mixer 213, where a certain frequency signal sufficiently lower than the reference signal frequency is obtained and input to the phase difference detection section 214. 215 is a mixer that mixes a signal corresponding to the reference signal received by the light receiving section 26 and converted into an electric signal with the signal of a certain frequency from the local oscillator 212 and inputs the mixed signal to the phase difference detection section 214; be. This phase difference detection section 2
Reference numeral 14 detects the phase difference between both outputs of both mixers 213 and 215, and the phase difference detected here is introduced into the subsequent signal conversion means 216, where the level is determined. Reference numeral 217 denotes an arithmetic and control processing unit (hereinafter referred to as CPU), which includes the function of the signal conversion means 216, controls necessary components, and sends desired pulses to a remote process control room 51, etc. It has a function of transmitting a signal, and has a function of displaying necessary information on the display section 218.

219 is a light amount level detection section, and 220 is an A/D conversion section.

Next, the operation of the level meter configured as above will be explained. When a predetermined reference frequency signal is generated from the reference signal generator 211 in response to a start signal, the light source 23 receives the reference signal and drives the light emitting element 22 at a predetermined frequency to emit light. The optical signal outputted from the light emitting element 22 passes through the light projection fiber 41 and is projected onto the measurement liquid surface 50 as parallel light by the lens 32 of the detection head section 30 installed at the other end of the fiber 41. Then, the detection head section 30
The light projected is reflected by the measurement liquid surface 50, passes through the lens 32 again, enters the light receiving fiber 42, is guided by these light receiving fibers 42, and is supplied to the signal processing section 20.

In this signal processing section 20, the light receiving fiber 42...
The light outputted from the optical fibers 42 and 42 is introduced into the light selection section 24, where a rotary chopper device, for example, is rotated upon receiving a selection command from the CPU 217, and sequentially selects and outputs the light from each of the light receiving fibers 42 and 42. It is something. This selection light is then received by the light receiving section 26, converted into an electrical signal, and sent to the arithmetic control section 21. In this arithmetic control section 21, the signal output from the light receiving section 26 and the reference signal are respectively attenuated by mixers 213 and 215 and supplied as low frequency signals to the phase difference detection section 214. A comparison is made to determine the phase difference, and the signal conversion means 2
16, the level is measured by the CPU 217.

Further, the signal corresponding to each selected light that is converted into an electric signal and outputted by the light receiving section 26 is detected as a light amount level by a light amount level detection section 219, and roughly the A/D converter 2
20 and sent to the CPU 217.

By the way, if the optical axis of the detection head section 30 is perpendicular to the measurement liquid level 50, the multiple lights selected by the light selection section 24 will be detected by the detection section 219 at almost the same light intensity level. Moreover, if the optical axis is deviated, the light intensity level will be biased towards a particular light receiving fiber 42 and will become larger or smaller. Furthermore, if the measurement liquid surface 50 is undulating, the light intensity level of the selected light from each light receiving fiber 42 will fluctuate discontinuously. Therefore, C
The PU 217 stores the light intensity level associated with each selected light in a memory table, for example, and determines the optical axis deviation from the distribution state of the light intensity level. When the PU 217 determines that the amount of deviation exceeds a certain value, the lamp, display unit 218 or This notification is made by means of a sound generating means, etc., and prompts correction of the optical axis.

Therefore, the configuration of the embodiment as described above has the following various effects.

(1) First, the optical axis alignment is easy and the level can be reliably measured even if some optical axis deviation occurs.

In conventional light wave distance meters, the transmitting and receiving fibers each have one
The fiber end faces of the fibers were set at the focal point of the lens 6. Therefore, it was necessary for a measurement operator who requires skill to carefully align the optical axis. On the other hand, in the level meter of the present invention, a plurality of light receiving fibers 42 are arranged around the light emitting fiber 41, and the measuring liquid level 5
The spot of the reflected light from 0 is all the receiving fiber 42.
..., so even if the optical axis is slightly shifted or the amount of light coupled to the receiving fiber 42 in one direction decreases, the light receiving fiber 42 in the opposite direction will Since the amount of light coupled into the fiber 42 is increasing,
There is no problem with measurement, and the level of the object to be measured can be reliably measured.

(2) Optical axis misalignment can be detected.

Since the light receiving section 26 independently measures the amount of light coupled to each light receiving fiber 42, it is possible to easily determine the optical axis deviation from the light amount distribution, and for example, the optical axis shift can be determined by the detection head section 30. If an adjustment mechanism is provided, the optical axis can be relatively easily corrected based on the above judgment result, which is very effective for maintenance.

(3) It is possible to align the optical axis during installation.

For example, when it is necessary to align the optical axis of the detection head section 30 when installing it in an oil tank or the like, each light receiving fiber 42...
The optical axis can be easily oriented vertically based on the distribution of the amount of received light output from the optical system.

In the above embodiment, the light receiving section 26 receives light for each amount of light received by each light receiving fiber 42 via the light selecting section 24.
6 may be provided to receive light. In this case, the light selection section 24 becomes unnecessary. Furthermore, the arrangement example of the optical fibers 40 is not limited to that shown in FIG.
1... and the light receiving fibers 42... may be arranged alternately. In addition, although the light selection section 24 selects the output light of each light receiving fiber 42..., for example, the output light of all the light receiving fibers 42 is normally sent to the light receiving section 24.
6, and only when it is desired to check a predetermined time interval or optical axis deviation, a drive control signal may be given to the light selection section 24 to separate and capture the output light for each light receiving fiber. In addition, the present invention can be implemented with various modifications without departing from the gist thereof.

〔Effect of the invention〕

As described in detail above, according to the present invention, optical axis alignment can be performed relatively easily, the level can be accurately measured even if the optical axis is slightly shifted, and the amount of light received by all optical receiving fibers can be adjusted to a certain value. It is possible to provide a level meter that is very effective in terms of maintenance because it is possible to issue a notification to prompt correction of the optical axis deviation when the optical axis exceeds the level or when the distribution becomes uneven.

[Brief explanation of drawings]

Figures 1 to 3 are for explaining one embodiment of the level meter according to the present invention. Figure 1 is a schematic configuration diagram of the entire level meter, Figure 2 is a side view of the arrangement of optical fibers, and Figure 2 is a side view of the arrangement of optical fibers. FIG. 3 is a diagram showing a specific configuration of the arithmetic and control unit shown in FIG. 1, FIG. 4 is a diagram showing another example of the arrangement of optical fibers, and FIG. 5 is a schematic configuration diagram of a conventional optical distance meter. 20... Signal processing section, 21... Arithmetic control section, 23.
...Light source, 24... Light selection section, 26... Light receiving section, 3
0...Detection head section, 32...Lens, 40...
Optical fiber, 41... Light emitting fiber, 42... Light receiving fiber. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 4 Figure 5

Claims (1)

[Claims] A signal processing unit that transmits the light output from the light source using a light-emitting fiber and projects it onto the measurement liquid surface, receives the reflected light from the measurement liquid surface with a light-receiving fiber, and is installed at the other end of the light-receiving fiber. In a level meter that measures the level of the measured liquid by detecting it with a light receiving section, the light receiving fiber is composed of a plurality of light receiving fibers, and the light emitting/receiving optical system determines the level of the light emitting and receiving optical system based on the amount of output light outputted from the other end of these light receiving fibers. A level meter that detects optical axis deviation in the vertical direction of the measured liquid level.