JPH01272941A - Concentration monitor device - Google Patents

Abstract

PURPOSE:To improve the monitoring accuracy without any troublesome adjustment by deciding concentration according to a detected value which is amplified and quantized and feeding the output value of an AD converter back to a DA converter digitally. CONSTITUTION:The output of an optical sensor 3B for concentration measurement which detects light from a light source 1 through a sample 2 is amplified by a subtracting amplifier 8. Its output is quantized by the AD converter 9. A digital control part 11 decides the concentration according to the quantization output. Further, the output of the converter 9 is passed through the control part 11. A subtraction value is supplied to an amplifier 8 with the analog output of the DA converter 10 and thus fed back digitally. Then the analog output range of the converter 10 is set wider in conformity with the amplifier 8.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a concentration monitoring device used for controlling the concentration of a developer in, for example, wet-type copying machines and printers.

BACKGROUND TECHNOLOGY A conventional device of this type has three
-7 A concentration measuring optical sensor 3 that detects the light from the light source 1 through the liquid sample 2, an amplifier 4 that amplifies the detection output of this sensor 3 at a predetermined amplification factor, and the amplified detection output Vrn
and a comparator 5 for comparing Vt with a predetermined reference value Vt, and based on the output Vout of the comparator 5, it is determined whether the concentration of the liquid sample 2 is higher than the predetermined reference concentration. was.

In this case, the liquid sample 2 is placed in the transparent cell 2A and its concentration is monitored. The transparent cell 2A is provided in the middle of the pipe 2B through which the sample is circulated.

FIG. 8 shows the relationship between sample concentration and detection output, where the horizontal axis shows the sample concentration and the vertical axis shows the amplified detection output V. The sample in this case is a developer used in a wet type copying machine, etc., where Dh is the concentration of the developer when it has not deteriorated, that is, the standard concentration, vh is the detection output at the standard concentration, and Dt is the detection output when there is no deterioration. If the concentration of the developer that needs to be replenished, that is, the standard concentration, is Vt, then the standard concentration D is
The reference values corresponding to t are shown respectively.

In this case, the density decreases as the developer deteriorates, and the detection output (2) increases as the density decreases. Therefore, by monitoring the detection output V and replenishing new developer when the output value exceeds the reference value Vt, the capacity of the developer can always be maintained above a certain level.

Problems to be Solved by the Invention However, with this configuration, there are problems in that it is difficult to improve the accuracy of concentration monitoring and adjustment is troublesome.

The above problem arises for the following reasons.

That is, in order to improve the accuracy of concentration monitoring, the amplification factor of the amplifier 4 should be increased, and the amplification output vh when detecting the standard concentration and the amplification output Vt when detecting the reference concentration should be
The output range of the amplifier 4 must be within the so-called dynamic range. The detection output must be within the dynamic range of the transmission system formed by the amplifier 4, etc., and detection output exceeding this range will not be transmitted. Detection output must be transmitted5
Otherwise, concentration cannot be monitored. The output range, that is, the dynamic range of the amplifier 4 is limited by the power supply voltage of the amplifier 4, and is usually within a range of about 90% of the power supply voltage.

However, as shown in FIG. 8, for example, the output of the sensor 3 never reaches a completely zero value even when detecting the standard concentration, and always has some kind of offset (biased value) Vof. Moreover, this off-sensitivity Vof is generated due to many factors such as variations in the light source 1 and the type of sample, and its magnitude is not necessarily constant. Therefore, the magnitude of the offset Vof cannot be determined in advance.

Therefore, in an attempt to improve the accuracy of monitoring, amplifier 4
When the amplification factor is increased, the change in detection output is also magnified, but at the same time, the offset Vof mentioned above is also magnified, and the amplified output vh at the standard concentration or the amplified output Vt at the reference concentration is within the output range of the amplifier 4. In other words, it deviates from the dynamic range of the transmission system and normal concentration monitoring becomes impossible.

In order to avoid such a situation, the amplification factor of the amplifier 4 must be kept low. However, if the amplification factor of the amplifier 4 is kept low, a trade-off occurs in that the rate of change in the detection output with respect to concentration changes, that is, the detection sensitivity decreases, and the accuracy of concentration monitoring deteriorates.

Therefore, in the conventional device shown in FIG. 7, the amplifier 4 and the comparator 5 are provided with variable resistors VR1 and VR2 for gain adjustment and offset compensation, respectively.

However, since the magnitude of the offset Vof changes depending on variations in the amount of light from the light source and the type of sample, it is necessary to adjust the variable resistor Vof for each device in order to properly monitor the concentration.
A problem arises in that troublesome calibration work must be performed to manually adjust RI and VR2.

The present invention has been made in view of the above-mentioned problems, and aims to provide a concentration monitoring device that can improve the accuracy of concentration monitoring without requiring troublesome adjustments. do.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention amplifies the detection output of a concentration measuring optical sensor that detects light from a light source through a sample using a subtraction amplifier, and converts the amplified detection output into an AD. It is quantized by a changer, and the concentration is determined based on this quantized detection value, and the subtracted value of the subtracting amplifier is
The A converter is used to provide the A converter, and the above A
The subtraction value is configured to digitally feed back the output value of the D converter to the DA converter to determine a subtraction value that level-shifts the output of the subtraction amplifier within a predetermined range.

Effect of the Invention The present invention improves the accuracy of concentration monitoring without the need for troublesome adjustments because the above-described configuration allows concentration detection to be performed appropriately within the dynamic range of the transmission system. It becomes possible to do so.

Embodiment FIG. 1 shows a schematic configuration of a concentration monitoring device according to an embodiment of the present invention.

The concentration monitoring device shown in the figure is built into a developer concentration control device in a copying machine, etc., in which 1 is a light source, 2 is a developer sample that is circulated in a sample cell 2A, and 3A is a light amount. 3B is a concentration measurement optical sensor, 6A and 6B are preamplifiers, 7 is a switching selection circuit,
8 is a subtraction amplifier, 9 is an AD converter (analog/digital converter), 10 is a DA converter (digital/analog converter), 11 is a digital control section, 12 is a storage means, and 13 is an electromagnetic device for replenishing developer. It is a valve.

Here, the light quantity measuring optical sensor 3A detects the light quantity of the light source 1 by directly detecting the light of the light source 1. The concentration measuring optical sensor 3B detects the sample 2 from the light source 1.
The concentration of the sample is detected by detecting the light that passes through it. Both sensors 3A and 3B are used which have the same characteristics.

The preamplifiers 6A and 6B are the optical sensor 3A.

to 9-7 Each of the 3B outputs is pre-amplified with a constant amplification gain.

The selection circuit 7 operates according to a command from the control unit 11, and selects the light amount detection output vL obtained from the light amount detection sensor 3A and the concentration detection output Vd obtained from the concentration detection sensor 3B.
Switch and select.

The subtraction amplifier 8 amplifies the detection output selected by the selection circuit 7. This subtracting amplifier 8 is a variable gain type subtracting amplifier whose amplification multiple K is digitally set.

The AD converter 9 quantizes (digitizes) the detection output amplified by the subtraction amplifier 8. The quantized detection value is input to the control section 11. In this case, the analog input range of the AD converter 9, the so-called input dynamic range, consists of two high and low reference potentials V r e f and GN given from the outside.
limited by D. Even if the analog input exceeds the high-side reference potential Vref, the digital output value will not exceed the predetermined maximum value Vmax. Further, even if the analog input falls below the low-side reference potential GND, the digital output value will not become less than the predetermined minimum value Vmin. In the device of the embodiment, the dynamic range of the transmission system including the amplifier 8 is determined by the dynamic range of the AD converter 9.

The DA converter 10 provides a subtraction value to the subtraction amplifier 8 using its analog output. A digital input of this DA converter 10 is given from a control section 11.

The output dynamic range, that is, the analog output range of this DA converter 10 is set to be wide enough to correspond to the output range of the subtracting amplifier 8.

The control unit 11 is configured using a microcircuit-based general-purpose information processing device, a so-called microcomputer, and in addition to the function of controlling the operation of the entire device, first to fourth digital control means as described below are implemented using software. It is structured as follows.

That is, the first digital control means determines the concentration based on the detected concentration value quantized by the AD converter 9.

The second digital control means converts the output value of the AD converter 9 into
For digital feedback to the A converter 10, a subtraction value is determined so as to shift the level of the output of the subtraction amplifier 8 within a predetermined range. Specifically, the output of the subtracting amplifier 8 is converted to the input voltage frequency (V
A subtraction value is determined to shift the level within (ref-GND). This operation of determining the subtraction value is performed separately for both the light amount detection and density detection operations. The subtraction value determined here and the detected value at that time are each stored in the storage means 12 in the form of digital data.

The third digital control means stores the light amount detection value obtained through the light amount measurement optical sensor 3A at the time of initial adjustment into the storage means 1.
2, and use the optical sensor for measuring the amount of light when monitoring the concentration.
The light intensity correction of the density detection value is performed based on the light intensity detection value obtained through the sensor 3B and the light intensity detection value stored in the storage means 12.

The fourth digital control means includes a light amount detection value obtained via the light amount detection optical sensor 3A and a concentration detection value obtained via the concentration measurement optical sensor 3B during initial adjustment when a sample of standard concentration is supplied. Based on this, the amplification multiple Ks of the subtraction amplifier 8 during concentration monitoring is determined.

The storage means 12 is non-volatile. This nonvolatile storage means 12 is constituted by, for example, EEP-ROM (electrically erasable and writable read-only memory) or S-RAM (static random access memory) whose power supply is back-amplified by a battery. Ru.

The solenoid valve 13 is controlled to open and close by the control section 11,
When the concentration detected by the control section 11 is determined to be lower than a predetermined reference concentration, the developer is temporarily driven open to replenish a developer having a new standard concentration.

FIG. 2 shows an example of the configuration of the variable gain subtraction amplifier 8.

The subtraction amplifier 8 shown in the figure includes a differential operational amplifier 81,
A plurality of resistances R1°R2, each weighted
, Rn, and a multiplexer 83 that switches the parallel connection state of the resistors R1, R2, . . . Feedback resistor Rf ko 3 h/
It is doing ゛. Thereby, by providing digital data for controlling the switching state of the multi-preverter 83 from the control section 11, it is possible to variably set an arbitrary amplification multiple.

The operation of the concentration monitoring device configured as described above will be explained below.

FIG. 3 is a flowchart showing an example of the operation when initially adjusting the concentration monitoring device shown in FIG.

Further, FIG. 4 is a graph showing the relationship between the sample concentration and its detected value at the time of initial adjustment.

At the time of initial adjustment, a standard concentration developer that has not yet deteriorated is supplied as a sample.

In FIG. 1, FIG. 3, and FIG. 4, first, the initial light amount is detected. This initial light amount detection is performed by setting the amplification factor K of the subtraction amplifier 8 to 1, selecting the light amount detection output vL, and further initializing the subtraction value Ct of the subtraction amplifier 8 to the minimum input value of the DA converter 10. done (Sl, S2. S3)
.

Under such settings, the amount J71-
The subtraction value Ct is increased stepwise until the initial light amount detection value VL8 converted into a digit becomes smaller than the maximum output value Vmax (Vmax=Vref) of the AD converter 9 (S4, S5). This allows the output of the subtraction amplifier 8 to be adjusted to the input range (Vref) of the AD converter 9 when detecting the amount of light.
-GND), that is, a subtraction value CL is determined such that the level is shifted within the dynamic range of the transmission system.

The subtraction value CL determined in this way and this subtraction value C
Initial light amount detection value VLS (Vt, 3=
Vt, -CL) is stored in the nonvolatile storage means 12 (S6).

Next, the standard concentration is detected. In this standard concentration detection, the amplification factor K of the subtraction amplifier 8 is set to 1, the concentration detection output vh is selected, and the subtraction value ch of the subtraction amplifier 8 is set to D.
This is done by initializing the maximum input value of the A converter 10 (S
7. S8).

Under such settings, the detected concentration value Vhs quantized by the AD converter 9 is the minimum output value V of the AD converter 9.
The subtraction value ch is decreased step by step until it becomes larger than min (Vmin to GND) (-7 Sin to S9°15). With this, the output of the subtraction amplifier 8 at the time of concentration detection can be adjusted to the input range of the AD converter 9 (Vref to GND).
) That is, a subtraction value ch is determined such that the level is softened within the dynamic range of the transmission system. The subtraction value ch determined in this way and the standard density detection value Vhs (Vhs −Vh −
Ch ) is stored in the nonvolatile storage means 12 (Sl
l).

After this, the initial light amount detection value vL8 and the standard density detection value Vhs
Based on this, the amplification factor Ks for concentration detection during concentration monitoring is determined (S12). This density detection amplification factor Ks is determined by the fact that the output of the subtraction amplifier 8 obtained at the initial light amount detection and the standard density detection is within the maximum input range of the AD converter 9 (
The size is set so that it does not protrude from V ref "G N D ). Specifically, the detected light amount value (Vs + Vhs) and the detected density value (Vhs + Ct, ) which have not been subtracted by the subtraction value are determined respectively. , the difference between both values 1 (V
It is obtained by dividing the maximum input Vref (Vref=Vmax) of the AD converter 9 by s+Vhs)+(Vhs+Ct)).

Amplification factor Ks for concentration detection obtained as above
[Ka2Vref/ ((Vs +Vhs) + (
Vhs +CL))] is stored in the nonvolatile storage means 12 (S13).

Next, the operation during concentration monitoring will be explained.

FIG. 5 is a flowchart showing an example of concentration monitoring operation performed by the concentration monitoring device shown in FIG.

Further, FIG. 6 is a graph showing the relationship between sample concentration and its detected value during concentration monitoring.

Concentration monitoring is performed using the subtraction value CL+c stored in the storage means 12.
h, the detection value VLSI Vhs and the amplification multiple Ks are used.

In FIG. 1, FIG. 5, and FIG. 6, first, the amount of light is detected. This light amount detection is performed by increasing the amplification factor K of the subtraction amplifier 8 by 1.
, selects the light amount detection output vLm, and further sets the light amount detection subtraction value CL stored in the storage means 12 in the subtraction amplifier 8 (Sl.

S2. S3).

Under such settings, the quantized light amount detection value ■Lm is read from the AD converter 9 (S4). Then, a light amount correction value Vr (Vr = VL3 - VLm) is calculated using the read light amount detection value VLm and the initial light amount detection value vL8 stored in the storage means 12 (S5).
.

The calculated light amount correction value Vr is temporarily stored.

After this, concentration detection is performed. Concentration detection is performed by setting the concentration detection subtraction value CL and concentration detection amplification factor Ks stored in the storage means 12 in the subtraction amplifier 8, and selecting the concentration detection output Vd (S6.S7.S8). )
.

The detected density value Vdm thus read is corrected using the light amount correction value Vr (Vr=Vt4-VLm) (SIO). This light amount correction is performed by adding a value obtained by multiplying the light amount correction value Vr by the amplification factor Ks to the density detection value Vdm. The detected density value Vdm, which has become lower (higher) in appearance due to a decrease in light intensity (increase in light intensity), is
Detected value Vd c (Vd c
−=Vdm 10Ks −Vr).

Corrected concentration detection value Vd c (Vd c −Vdm
+ K s ·Vr) is compared with a predetermined comparison reference value Vt (Sll).

The control unit 11 determines that the detected concentration value Vdc after correction is the reference value Vt.
If it is less than 18 h/, it is determined that the sample concentration is greater than or equal to the reference concentration Dt (Sll-NO). In addition, the detected concentration value Vd after correction
If c exceeds the reference value Vt, it is determined that the sample concentration has decreased below the reference concentration Dt (511-YES).
At this time, a command is issued to open the solenoid valve 13 to replenish new developer (812).

As described above, in the concentration monitoring of the embodiment described above, the light source 1
Concentration measurement optical sensor 3 that detects the light of through the sample 2
The detection output of B is amplified by the subtraction amplifier 8, the amplified detection output is quantized by the AD changer 9, and the concentration is determined based on the quantized concentration detection value.
The subtraction value of the subtraction amplifier 80 is given through the DA converter 10, and the output value of the AD converter 9 is digitally fed back to the DA converter 10 during initial adjustment, so that the output of the subtraction amplifier 8 is controlled within a predetermined range. By setting a subtraction value that shifts the level within the range, concentration detection can be performed appropriately within the dynamic range of the transmission system, allowing concentration monitoring to be performed without the need for troublesome adjustments. Accuracy can be improved by 19 bases 7'. Furthermore, since the detected values are processed as digital data, there are also advantages of good operational stability and reproducibility.

In addition, the light amount detection value vL3 obtained through the light amount measurement optical sensor 3A during initial adjustment is stored in the storage means 12, and the light amount detection value obtained through the light amount measurement optical sensor 3B during concentration monitoring. Based on vLm and the light amount detection value ■L8 stored in the storage means 12, the density detection value Vd is determined.
By performing the light amount correction of m, it is possible to compensate for errors over time caused by changes in light amount after initial adjustment, so that the accuracy of concentration monitoring can be further improved.

Furthermore, at the time of initial adjustment when a sample of standard concentration is supplied, a light amount detection value obtained via the light amount detection optical sensor 3A is added.
By determining the amplification multiple of the subtraction amplifier 8 during concentration monitoring based on the concentration detection value Vhs obtained via L8 and the concentration measurement optical sensor 3B, the amplification multiple of the subtraction amplifier 8 during concentration monitoring is transmitted. Optimization is now possible within the dynamic range of the system, and as a result, the amplification function of the amplifier 8 and the quantization resolution ability of the AD converter 9 can be utilized to the maximum, further increasing the accuracy of concentration monitoring. You will be able to do it.

Effects of the Invention As is clear from the above explanation, the present invention amplifies the detection output of a concentration measuring optical sensor that detects light from a light source through a sample using a subtraction amplifier, and converts the amplified detection output into an AD converter. Concentration determination is performed based on the concentration detection output quantized by , and the subtracted value of the subtracting amplifier is provided via a DA converter, and the output value of the AD converter is sent to the DA converter during initial adjustment. By determining a subtraction value that shifts the level of the output of the subtraction amplifier within a predetermined range by performing digital feedback, concentration detection can be performed appropriately within the dynamic range of the transmission system. The accuracy of concentration monitoring can be improved without the need for troublesome adjustments.
This has the effect of

Ichino to 21

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a concentration monitoring device showing an embodiment of the present invention, Fig. 2 is a circuit diagram showing an example of the configuration of a subtracting amplifier used in the device, and Fig. 3 is an initial adjustment of the device. 4 is a graph showing the relationship between sample concentration and detection output at the initial adjustment stage. FIG. 5 is a flow chart showing an example of the operation of the same device when monitoring concentration. FIG. 7 is a graph showing the relationship between sample concentration and detection output at the monitoring stage, FIG. 7 is a schematic diagram of a conventional concentration monitoring device, and FIG. 8 is a diagram showing the relationship between sample concentration and detection output. 1. Light source, 2. Sample, 3A. Optical sensor for detecting light amount.
, VL... light amount detection output, 3B... optical sensor for density detection, Vd... density detection output, 6A, 6B... preamplifier, 7... selection circuit, 8... subtraction amplifier , 9・
...AD converter, ]O...DA converter, 11...digital control unit, 12...nonvolatile storage means, 13...electromagnetic valve for replenishing developer, Vmax-AD converter 9 Maximum output value, Vref - To the high side reference potential 22 that determines the maximum input value of the AD converter 9 -7 Vmin... Minimum output value of the AD converter 9, GND
...Low side reference potential that determines the minimum input value of the AD converter 9,
K...Amplification factor, Ks...Amplification factor during concentration monitoring,
CL...Subtraction value when detecting light intensity, vL8...Light intensity detection value during initial adjustment, Vhs...Standard density detection value during initial adjustment, ch...Subtraction value when detecting standard density, VLm・・
-Density detection value during density monitoring, Vr...Light amount correction value, Vt
... Comparison standard value, Dh ... Standard concentration, 1) t ...
Reference concentration.

Claims (3)

[Claims] (1) A concentration measuring optical sensor that detects light from a light source through a sample, a subtracting amplifier that transmits the detection output of this concentration measuring optical sensor, and an AD converter that quantizes the output of this subtracting amplifier. a DA converter that provides a subtraction value to the subtraction amplifier; a first digital control means that performs concentration determination based on the detected concentration value quantized by the AD converter; and second digital control means for determining a subtraction value that level-shifts the output of the subtraction amplifier within a predetermined range by digital feedback to the converter. (2) A light sensor for measuring light amount that directly detects the light from a light source, a storage means for storing a detected light amount value obtained through the light sensor for measuring light amount during initial adjustment, and a light sensor for measuring light amount when monitoring concentration. 2. The density monitoring device according to claim 1, further comprising third digital control means for correcting the light amount of the density detection value based on the light amount detection value obtained through the storage means and the light amount detection value stored in the storage means. (3) An optical sensor for measuring the amount of light that directly detects the light from the light source, a subtracting amplifier with variable gain whose amplification factor is digitally set, and an optical sensor for detecting the amount of light that is used during initial adjustment when measuring a sample with a standard concentration. 2. The subtracting amplifier according to claim 1, further comprising a fourth digital control means for determining an amplification factor of the subtracting amplifier during concentration monitoring based on a detected light amount value obtained through the optical sensor and a detected concentration value obtained via the optical sensor for concentration measurement. The concentration monitoring device according to claim 2.