JPH0326443Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention mainly relates to a portable refractometer that uses a digital display method to measure the sugar content, soluble solid content concentration, etc. in a solution.

(Prior technology) Most of the conventional refractometers used for measuring sugar content are based on the light transmission method, and most of the hand-held refractometers used for measuring sugar content use an analog method, such as a pointer meter. Therefore, the error associated with the measurement was large, making it impossible to quickly and easily measure the sugar content or concentration of the sample, and the entire device became bulky, making it unsuitable for outdoor use.

(Technical Issues) The present invention was developed in view of the shortcomings of the prior art, and it is possible to quickly and easily measure samples using a digital display method, and to perform temperature correction at the same time as sugar content or concentration measurement. In addition, an appropriate power supply circuit is installed so that it can be used outdoors.
Another technical challenge is to eliminate the effects of light source deterioration and circuit drift.

(Technical means) In order to solve the above technical problems, this invention adopts a total reflection measurement method instead of the conventional light transmission method, and uses an image sensor to completely replace the conventional visual measurement method. The system has been improved to digital display measurement, and a peak hold circuit has been built in to remove the negative effects of light source deterioration and the effects of drift on the circuit, as shown in Figures 1 to 4. As shown in the embodiment, the configuration is as follows.

Reference numeral 1 denotes a refractometer main body for measuring sugar content or concentration which employs a digital display, and in this embodiment, a total light reflection method is employed as will be described later.

2 is the shape attached to the sample dropping window 3
The prism is shaped like a prism, and is configured so that the light emitted from the light source P is incident on the prism interface 2A (the interface between the prism 2 and the sample solution), which is the base surface of the prism 2.

3A is a tapered portion of the sample dropping window 3, which is configured to suitably set the depth of the rise of the sample solution. Reference numeral Q designates a start switch, which is configured to energize a constant voltage circuit 15 and an electric circuit section R, which will be described later, to turn on the light source P.

Reference numeral 4 denotes an objective lens installed on the light reflection side with respect to the prism interface 2A, and is configured to image the reflected light beam r _B on a reflection mirror 5 placed behind the objective lens 4.

Reference numeral 6 denotes an image sensor, which forms an image of the light reflected by the reflecting mirror 5 on the image sensor 6, and converts this optical signal into an electrical signal.

Therefore, the incident light ray _r0 from the light source P travels through the sample solution at the prism interface 2A due to the critical angle of total reflection determined by the refractive index of the sample solution and the prism 2, and the refracted light _rA and the prism The reflected light r B is divided into two parts, and only the reflected light r _B is imaged on the image sensor 6 .

7 is a comparison circuit which connects the image sensor 6
The electrical signal SA converted by the amplifier circuit 8 is once amplified into an electrical signal SA' of a constant level by the amplifier circuit 8 and then inputted to the comparison circuit 7.

Reference numeral 9 denotes a peak hold circuit in which the same signal SA input to the amplifier circuit 8 is attenuated to a predetermined level value and input to the peak hold circuit 9 for peak holding.

Further, the peak-held signal PH is inputted to the comparison circuit 7, where it is amplified to a constant level by the amplifier circuit 8, and then the original electrical signal is amplified to a constant level.
SA' and the peak hold signal PH attenuated by the peak hold circuit 9 are compared, and when the original electrical signal SA' exceeds the level of the peak hold signal PH, that signal S is set as the total reflection point, that is, the critical point. The information is transmitted to the CPU circuit 10.

In other words, by employing the peak hold circuit 9,
Hold the first signal during cycle measurement, and then
By comparing the signal with the second signal, the boundary position of the amount of light of each bit generated on the image sensor 6 can be specified.

As shown in Figure 3, points a, b, and c correspond to changes in the refractive index of the sample solution (refractive index a<b<
c) and the movement of the total reflection point on the image sensor 6 are displayed, and for example, point d indicates that the light does not reach the image sensor 6 because the light is refracted into the sample solution. Become.

10A is a temperature sensor that essentially measures the temperature of the prism 2, and the temperature change ΔT is first converted by the resistance voltage conversion circuit 11 from the resistance change ΔRT to the voltage change ΔVT, and then by the voltage frequency conversion circuit 12. The CPU circuit 10 is configured to convert the digital signal DS into a digital signal DS.
I am trying to convey this to you.

In this CPU circuit 10, a program for converting the number of bits of the image sensor 6 into sugar content, and a program for converting the digital signal DS from the voltage frequency conversion circuit 12 into temperature correction of sugar content are set, and the results are The weight percent of sugar, ie Brix%, is also transmitted to the display 13. 14 indicates the bit position of the water when it is dropped into the sample dropping window 3 in the CPU circuit 1.
This is a zero switch for holding the bit within 0, and the device is calibrated by continuing to hold that bit position until the next time the zero switch 14 is pressed.

15 is a constant voltage circuit that supplies voltage to each circuit section. Further, when the measurement is completed, the constant voltage circuit 15 supplies voltage only to the display 13 and the CPU circuit 10, and after a certain period of time, the voltage is supplied to the CPU circuit 10.
Only the circuit 10 is supplied with that voltage.

Since the CPU circuit 10 is configured to be driven by a minute current, the water bit position (set value) will be held until the dry battery 16 is exhausted unless the zero switch 14 is pressed during the calibration as described above. becomes. 17 is an AC adapter terminal.

(effect) The above technical means works as follows.

First, drop a sample solution, which is a sample, onto the sample dropping window 3, press the start switch Q, and turn on the light source P.
lights up.

At this time, the incident light ray _r0 emitted from the light source P passes through the prism 2, and at the prism interface 2A, refracted light enters the sample due to the critical angle of total reflection determined by the refractive index of the sample solution and the prism 2. The light is separated into r _A and reflected light r _B.

Next, the reflected light r _B reflected at the prism interface 2A
passes through the objective lens 4 and is reflected by the reflecting mirror 5, and then is imaged on the image sensor 6, where the reflected light r, which is an optical signal, is converted into an electrical signal SA.

The electric signal SA is amplified by the amplifier circuit 8 to an electric signal SA' of a constant level and then enters the comparator circuit 7.

Further, the same electric signal SA from the amplifier circuit 8 is amplified to a certain level value and inputted to the peak hold circuit 9, where the peak hold signal PH is peak held and input to the comparison circuit 7 together with the electric signal SA'.

At this time, the original amplified electrical signal SA' and the attenuated peak hold signal SH are compared, and the point when the original electrical signal SA' exceeds the threshold level of the peak hold signal PH is determined as the total reflection point, that is, the critical point. It is transmitted to the CPU circuit 10 as a point.

The movement of the total reflection point on the image sensor 6, that is, the change in the refractive index of the sample solution, is as shown in FIG. Further, the temperature sensor 10A measures the temperature of the prism 2, and the temperature change ΔT is converted into a resistance change ΔRT, which is converted into a voltage change ΔVT by the resistance voltage conversion circuit 11, and further converted into a digital signal DS by the voltage frequency conversion circuit 12. After that, it is transmitted to the CPU circuit 10. This CPU circuit 10 is set with a program for converting the number of bits of the image sensor 6 into sugar content and a program for temperature-correcting the digital signal DS from the voltage-frequency conversion circuit 12.
The sugar content value indicating the weight of sugar in 100 g is transmitted to the display 13 in weight percent, ie, Brix%.

Note that this device can also be used to measure the specific gravity of battery liquid and the concentration or viscosity of ink.

Next, a method for calibrating this device will be explained.

First, fresh water is dropped onto the sample dropping window 3, and then the zero switch 14 is pressed to hold the bit position of the water in the CPU circuit 10. From then on, the bit position of the water can be held until the next time the zero switch 14 is pressed. I can do it. In this case, the constant voltage circuit 15 supplies voltage only to the display 13 and the CPU circuit 10 after the measurement is completed, and further supplies voltage only to the CPU circuit after a certain period of time has elapsed.

Therefore, since the CPU circuit 10 itself is driven by a minute current, the zero switch 14 must be turned off during calibration.
As long as the button is not pressed, the water bit position (set value) can be maintained until the dry battery 16 is exhausted.

Furthermore, the structure and operation described above provide the following general features.

It is compact and can be used outdoors as it is powered by 16 dry batteries, and the light emitting diode as the light source P and electric circuits are energized for about 3 seconds during measurement by pressing the start switch Q, and are automatically turned off from the internal power supply after the measurement is completed. The display is set so that it automatically disappears if the switch is not operated for about 5 minutes after the measurement is completed, resulting in the optimum effect for energy saving.

(Effects) The present invention has the following unique effects.

In particular, since a peak hold circuit is employed, it is possible to eliminate the adverse effects and drift effects associated with deterioration of the light source, and to completely compensate for the effects.

In addition, by appropriately changing the prism and CPU circuit programs, the concentration of soluble solids can be directly observed.

[Brief explanation of drawings]

1 to 4 show an embodiment of the present invention. FIG. 1 is a longitudinal sectional side view showing the arrangement of each component of the refractometer body, FIG. 2 is a block diagram of the device, and FIG. Figure 3 is a graph showing the movement of the total reflection point on the image sensor, with the vertical axis representing the amount of light for each bit and the horizontal axis representing the number of bits of the image sensor. Figure 4 also shows the critical point when transmitting light to the CPU circuit. This is a graph showing the following. 2...prism, 2A...prism interface, 3...
...Sample dropping window, 6...Image sensor,
9...Peak hold circuit, 10...CPU circuit,
10A... Temperature sensor, 13... Display, 15
... Constant voltage circuit, 17 ... AC adapter terminal.

Claims (1)

[Scope of utility model registration request] The light emitted from the light source P is totally reflected from the prism interface 2A of the prism 2 installed in the sample dropping window 3 toward the objective lens 4, and the totally reflected light is imaged on the image sensor 6 and converted into an electrical signal. In the refractometer main body 1, which digitally displays the sugar content, etc. of the sample solution by a CPU circuit 10 with an appropriately programmed setting, a peak hold circuit is connected between the CPU circuit 10, the comparator circuit 7, and the amplifier circuit 8. The circuits 9 are connected in parallel to form the amplifier circuit 8.
The original electrical signal SA' amplified to a certain level by the peak hold circuit 9 is compared with the peak hold signal PH attenuated by the peak hold circuit 9. A digital refractometer for measuring sugar content, etc., characterized in that the signal S is transmitted to the CPU circuit 10 by using the point at which the signal S exceeds the level as a total reflection point.