Patent Publication Number: US-11660876-B2

Title: Detection method for liquid level of storage tank

Description:
BACKGROUND OF THE DISCLOSURE 
     Technical Field 
     The technical field relates to a detection method, and more particularly related to a detection method for a liquid level of a storage tank. 
     Description of Related Art 
     In the related art, monitoring an ink level of a material tank of a printer (namely, detecting a remaining volume of the printing materials in the material tank) is very important to avoid printing failures or printer malfunctions. 
     For example, when the remaining capacity of the printing material is insufficient (namely, the ink level is too low), the printing may be interrupted by an exhaustion of the printing material. When the remaining capacity of the printing material is excessive (namely, the ink level is too high), the printer may be malfunction due to a backflow of the printing material. 
     A float level switch is arranged in the material tank of the printer in the related art to effectively detect whether the ink level is higher/lower than a default level. However, the float level switch is too expensive. Moreover, the float level switch is easily damaged and difficult to be repaired because the float level switch soaks in the printing materials. 
     If the level float switch is replaced with an optical level switch, there are problems about excluding defect products and configuring a trigger threshold of the optical level switch. More specifically, when a photoelectric sensor of the optical level switch has any defect, the whole optical level switch must be replaced, thereby increasing the product cost. Moreover, the photoelectric sensors manufactured by the consistency manufacturing process may have different sensitivity. Thus, it&#39;s an important problem to configure a correct trigger threshold to make sure that the photoelectric sensor may precisely detect the ink level (namely, how to recognize “a status of having-print material” and “a status of non-print-material” effectively). 
     Thus, the existing level detection method has the above-mentioned problem, and there is a need for a more effective solution. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure is directed to a detection method for a liquid level of a storage tank. The detection method uses a sensor capable of sensing different types of print material to execute a liquid level detection and a liquid level control. 
     In one of the embodiments, a detection method for a liquid level of a storage tank includes: a) executing a first sensing process on a tank object through an optical sensor to acquire a first sensing value, wherein a transmittance of the tank object is corresponding to a transmittance of a storage tank; b) determining the optical sensor as a liquid level detection purpose when the first sensing value is consistent with a first threshold condition; c) executing a second sensing process on the storage tank through the optical sensor determined as the liquid level detection purpose to acquire a second sensing value corresponding to a status of non-print-material and a third sensing value corresponding to a status of having-print-material, and determining the optical sensor determined as the liquid level detection purpose to be valid on a liquid level detection when the second sensing value is consistent with a second threshold condition and the third sensing value is consistent with a third threshold condition; d) executing a third sensing process on the storage tank through the optical sensor determined as valid on the liquid level detection to acquire a fourth sensing value in a printing procedure; and, e) staring or stopping pouring print materials into the storage tank when the fourth sensing value is consistent with a fourth threshold condition, wherein the fourth threshold condition is corresponding to the second sensing value or the third sensing value. 
     The present disclosure may eliminate a sensing error generated by an unsuitable optical sensor, and keep a liquid level of the storage tank to be normal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the present disclosure are believed to be novel are set forth with particularity in the appended claims. The present disclosure itself, however, may be best understood by reference to the following detailed description of the present disclosure which describes an exemplary embodiment of the present disclosure, taken in conjunction with the accompanying drawings, in which: 
         FIG.  1    is an architecture diagram of an inspection fixture of one embodiment of the present disclosure; 
         FIG.  2    is an inspection schematic view of an automatic pouring apparatus of one embodiment of the present disclosure; 
         FIG.  3    is a cleaning schematic view of an automatic pouring apparatus of one embodiment of the present disclosure; 
         FIG.  4    is a drying schematic view of an automatic pouring apparatus of one embodiment of the present disclosure; 
         FIG.  5    is an application schematic view of an automatic pouring apparatus of one embodiment of the present disclosure; 
         FIG.  6    is a first sensing schematic view of an optical sensor of one embodiment of the present disclosure; 
         FIG.  7    is a second sensing schematic view of an optical sensor of one embodiment of the present disclosure; 
         FIG.  8    is a circuit architecture diagram of an optical sensor of one embodiment of the present disclosure; 
         FIG.  9    is a flowchart of a detection method of one embodiment of the present disclosure; 
         FIG.  10    is a flowchart of a first sensing process of one embodiment of the present disclosure; 
         FIG.  11    is a flowchart of a sensing process on an empty tank of one embodiment of the present disclosure; 
         FIG.  12    is a flowchart of a sensing process for a light-transmissive print material of one embodiment of the present disclosure; 
         FIG.  13    is a flowchart of a sensing process for a particle print material of one embodiment of the present disclosure; and  FIG.  14    is a flowchart of an application pre-process of one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The technical contents of this disclosure will become apparent with the detailed description of embodiments accompanied with the illustration of related drawings as follows. It is intended that the embodiments and drawings disclosed herein are to be considered illustrative rather than restrictive. 
     The present disclosure presents a detection method for a liquid level of a storage tank. In a sorting stage, the detection method may eliminate the optical sensors having hardware defects or other factors and being unsuitable for liquid level detection through a first sorting process. In an onboard stage, the detection method ensures that the optical sensor has an ability to correctly detect a status of non-print-material and a status of having-print material and configures a suitable threshold condition for the optical sensor through a second sorting process. Thus, in an application stage, the detection method may correctly execute the liquid level detection to adjust a liquid level of the print material. 
     Please refer to  FIG.  6   ,  FIG.  6    is a first sensing schematic view of an optical sensor of one embodiment of the present disclosure.  FIG.  6    is used to explain how an optical sensor is used in a liquid level detection of a print material in the present disclosure. 
     The present disclosure arranges a plurality of optical sensors  201 - 203  on a storage tank  21 . The optical sensors  201 - 203  respectively correspond to different liquid levels. A number of liquid levels (namely, a number of the optical sensors  201 - 203 ) may be changed arbitrarily based on requests. The present disclosure doesn&#39;t limit the number of optical sensors arranged on the storage tank. 
     For example, the optical sensor  201  may be arranged at a lower limit liquid level position having the lowest height. As a lower limit liquid level sensor, detecting no print material by the optical sensor  201  expresses that a remaining volume of the print material is too little, and an additional print material is necessary to be poured into the storage tank  21 . When the optical sensor  201  detects the print material, the remaining volume of the print material in the storage tank  21  is sufficient. 
     The optical sensor  202  may be arranged at an upper limit liquid level position having the second-highest height. As an upper limit liquid level sensor, detecting no print material expresses that the remaining volume of the print material is sufficient, and the additional print material may be stopped pouring. When the optical sensor  202  detects the print material, the remaining volume of the print material in the storage tank  21  is too much. 
     The optical sensor  203  may be arranged at a safety liquid level position having the highest height. As a safety liquid level sensor, detecting no print material expresses that the remaining volume of the print material in the storage tank  21  doesn&#39;t cause backflow. When the optical sensor  203  detects the print material, the remaining volume of the print material in the storage tank  21  is more than a safety limit, and there is a backflow risk of the print material. For example, the print material may flow back to an air pressure system through an upper pipe. In one of the embodiments, the optical sensor may be an infrared sensor and include an optical emitter (such as one or more infrared LEDs for emitting an infrared light signal), an optical receiver (such as one or more phototransistors for receiving light signal), and an amplifier drive circuit. The amplifier drive circuit is not a necessary component of the present disclosure. 
     Furthermore, each of the optical sensors  201 - 203  may execute a sensing process to acquire a sensing value. The above sensing process may include: emitting the infrared light through the optical emitter; and sensing a voltage triggered by a reflected infrared light as a sensing value, wherein the reflected infrared light is received by the optical receiver. 
     In one of the embodiments, the optical sensors  201 - 203  may be arranged inside the storage tank  21 . For example, the optical sensors  201 - 203  may be coated with a light-transparent waterproof protective shell (such as a light-transparent acrylic shell), and the coated optical sensors  201 - 203  are arranged on an inner wall of the storage tank  21 . 
     In one of the embodiments, the optical emitter may be arranged on the inner wall of the storage tank  21 , and the optical receiver may be arranged on an outer wall of the storage tank  21 . Thus, this arrangement may reduce a number of penetrating a wall  210  to reduce energy consumption. 
     In one of the embodiments, a part or the entire wall  210  of the storage tank  21  may be made with a light-transparent material, such that a sensing light (such as the infrared light) emitted by the optical sensors  201 - 203  may penetrate the wall  210  for sensing a liquid level status inside the wall  210 . For example, only the parts corresponding to the arrangement positions of the optical sensors  201 - 203  are made with the light-transparent material. The light-transparent material may be high light-transparent glass or high light-transparent acrylic, but this specific example is not intended to limit the scope of the present disclosure. 
     Taking the optical sensor  202  in  FIG.  6    for an example, when the storage tank  21  contains no print material, the sensing light of the optical sensor  202  penetrates the solid wall  201  and contacts with air. This situation causes a total internal reflection (an incident angle is greater than a threshold angle of the total internal reflection), and the sensing light will trigger a higher photovoltage (such as 2.8V). 
     Taking the optical sensor  201  in  FIG.  6    for another example, when the storage tank  21  contains the print material (such as a light-transmissive print material  60 ), the sensing light of the optical sensor  201  penetrates the solid wall  201  and contacts with the liquid print material  60 . This situation causes a refraction of the sensing light in the light-transmissive print material  60  because the wall  201  and the print material  60  have densities close to each other, and only less of the sensing light will be reflected to trigger a lower photovoltage (such as less than 1V). The light-transmissive print material  60  may include at least one of a transmissive ink, a high light-transmissive ink, or other high light-transmissive print materials (having a transmittance higher than 70%), etc. 
     The present disclosure may realize through the above variation characteristics of the photovoltages whether each of the optical sensors  201 - 203  detects the print material or not. 
     Please refer to  FIG.  8   ,  FIG.  8    is a circuit architecture diagram of an optical sensor of one embodiment of the present disclosure. One or more optical sensors  80  may be arranged on a liquid level control panel in the present disclosure. 
     The liquid level control panel may be arranged on the storage tank and include a voltage follower circuit  81  and a Schmitt trigger  82 . An output of each optical sensor  80  is connected to the voltage follower circuit  81 , and an output of the voltage follower circuit  81  is connected to the Schmitt trigger  82 . 
     In one of the embodiments, each optical sensor  80  may be connected to a variable resistance or an electronic impedance device (electronic impedance component). 
     In one of the embodiments, a sensing process of the optical sensor  80  includes: outputting a voltage signal triggered by a reflected infrared light at the optical sensor  80 ; executing an analog noise filtering process on the voltage signal at the voltage follower circuit  81  to filter out an analog noise from the voltage signal to generate a filtered voltage signal; and executing a compensating process on the filtered voltage signal at the Schmitt trigger  82  to compensate an error in the filtered voltage signal caused by the print material remaining on a wall of the storage tank. 
     The voltage follower circuit  81  and the Schmitt trigger  82  are existing circuit components, the relevant description of specific principles and architectures of the voltage follower circuit  81  and the Schmitt trigger  82  are omitted for brevity. One improvement of the present disclosure is that the voltage follower circuit  81  and the Schmitt trigger  82  are applied to the liquid level detection. 
     Please refer to  FIG.  9   ,  FIG.  9    is a flowchart of a detection method of one embodiment of the present disclosure. The detection method of the present disclosure includes a sorting stage S 1 , an onboard stage S 2 , and an application stage S 3 . 
     First, the sorting stage S 1  will be explained. Please refer to  FIG.  1    at the same time, wherein  FIG.  1    is an architecture diagram of an inspection fixture of one embodiment of the present disclosure. The sorting stage S 1  is mainly to apply the inspection fixture  1  to fast eliminate unsuitable optical sensors  101 . 
     In one of the embodiments, the inspection fixture  1  may include a stage  10 , a liquid level control panel  11 , a measurement device  13 , and a power supply device  12 . 
     The stage  10  may include a removable connection module  100  and a fixing structure  102 . The removable connection module  100 , such as a solderless breadboard, is used to connect the liquid level control panel  11  to one or more optical sensors  101 . 
     In this embodiment of the present disclosure, to make the optical sensor  101  fast connecting to/disconnecting from the liquid level control panel  11 , the user only needs to plug/unplug the optical sensor  101  in/out the removable connection module  100 . Thus, the user may effectively inspect the optical sensors  101 . 
     The fixing structure  102 , such as a latch, a fixture, or other fixable structures, is used to fix the stage  10  on a tank object  14 . The tank object  14  is used to simulate a light-transmissive condition of the storage tank. For example, the tank object  14  may have a transmittance, a thickness, or a material, etc. being the same as or similar to the storage tank, but have a less volume than the storage tank. Thus, the tank object  14  is easily used in an inspection. 
     In one of the embodiments, the tank object  14  may be the practical storage tank, but this specific example is not intended to limit the scope of the present disclosure. 
     In this embodiment of the present disclosure, the arrangement positions of the removable connection module  100  and the fixing structure  102  are adjusted to make all of the optical sensors  101  connected to the removable connection module  100  to be faced to the tank object  14  for sensing the tank object  14  when the fixing structure  102  is fixed on the tank object  14 . The liquid level control panel  11  is used to provide electricity to each of the optical sensors  101  for each optical sensor  101  to emit the infrared light, and the liquid level control panel  11  is used to receive a voltage signal corresponding to the photovoltage of each of the optical sensors  101 . 
     The measurement device  13  is connected to the liquid level control panel  11 , and used to measure the voltage value of the photovoltage of each of the optical sensors  101  as a sensing value. 
     In one of the embodiments, the measurement device  13 , such as a multimeter, may be changed to connect to the removable connection module  100  to directly measure the sensing value on the removable connection module  100 . 
     The power supply device  12  is connected to the liquid level control panel  11 , and used to provide the electricity, such as 3.3 V of DC power. 
     Please refer to  FIG.  9   , the sorting stage may include steps S 10 -S 13 . 
     In the step S 10 , the optical sensor  101  is connected to the removable connection module  100 , and the inspection fixture  1  is operated to execute a first sensing process. More specifically, the optical sensor  101  senses toward the tank object  14 , and the measurement device  13  measures the sensing value (a first sensing value) of the optical sensor  101 . 
     The step S 11  is to determine whether the first sensing value is consistent with a default threshold condition (a first threshold condition) or not. 
     In one of the embodiments, the first threshold condition may include: the first sensing value being greater than a first threshold (such as 2.3V) or within a first threshold range (such as 2V-3V). 
     When the first sensing value is consistent with the first threshold condition, step S 12  is performed. In the step S 12 , the optical sensor  101  is determined to be capable of a liquid level detection purpose. Namely, the optical sensor  101  passes the first sorting process. 
     When the first sensing value is inconsistent with the first threshold condition, step S 13  is performed. In the step S 13 , the optical sensor  101  is determined to be capable of other purpose, such as a human detection purpose or other non-liquid level detection purpose, etc. 
     Please be noted that, in addition to hardware defects, one optical sensor  101  may be eliminated in the first sorting process because its sensitivity does not meet a strict condition of the liquid level detection. In this situation, the eliminated optical sensor  101  may be suitable and used for other purposes having a lower sensitivity request to avoid wasting of the optical sensor  101 . 
     Then, a next optical sensor  101  is selected to perform the steps S 10 -S 13  to execute the first sorting process on the next optical sensor  101 , and so on. The first sorting process is repeatedly performed until all the optical sensors  101  are inspected. 
     Then, the onboard stage S 2  will be explained. Please refer to  FIG.  2    at the same time, wherein  FIG.  2    is an inspection schematic view of an automatic pouring apparatus of one embodiment of the present disclosure. In the onboard stage S 2 , an automatic pouring apparatus  2  is used to inspect a detection ability of a status of non-print-material and a status of having-print-material of the optical sensors  201 - 203  determined as the liquid level detection purpose. An automatic pouring apparatus  2  may include a liquid level control panel  20 , a storage tank  21 , a regulating apparatus  22 , and a material tank  23  for storing the print material. 
     The optical sensors  201 - 203  determined as the liquid level detection purpose in the sorting stage S 1  are welded/adhered on the liquid level control panel  20 . The liquid level control panel  20  may be arranged on the wall of the storage tank  21  to monitor different liquid levels, and control the regulating apparatus  22  to execute a regulating corresponding to the current liquid level. 
     The regulating apparatus  22 , such as a pump, is electrically connected to the liquid level control panel  20  to be controlled. The regulating apparatus  22  is connected to the material tank  23  through a pipe  25 , and connected to the storage tank  21  through a pipe  26 . 
     When the regulating apparatus  22  operates forward, the regulating apparatus  22  may pour the print material along a flowing direction D 1  from the material tank  23  to the storage tank  21 . 
     When the regulating apparatus  22  operates backward, the regulating apparatus  22  may pump the print material along a flowing direction D 2  from the storage tank  21  to the material tank  23 . Thus, the liquid level of the print material in the storage tank  21  may be regulated. 
     In one of the embodiments, the storage tank  21  is further connected to the material tank  23  through a pipe  24 . Thus, the excess print material in the storage tank  21  may flow along a flowing direction D 3  to the material tank  23  through the pipe  24 . 
     Please refer to  FIG.  9   , the onboard stage S 2  may include steps S 20 -S 23 . 
     In step S 20 , a second sensing process is executed through the liquid level control panel  20 . In one of the embodiments, the second sensing process is to control the regulating apparatus  22  to extract the print material from the storage tank  21  to make the storage tank  21  to be in a status of non-print-material, to sense the storage tank  21  to acquire a sensing value (a second sensing value) corresponding to the status of non-print-material through each of the optical sensors  201 - 203 . Also, the second sensing process is to control the regulating apparatus  23  to pour the print material to the storage tank  21  to make the storage tank  21  be in a status of having-print-material, and sense the storage tank  21  to acquire a sensing value (a third sensing value) corresponding to the status of having-print-material through each of the optical sensors  201 - 203 . 
     The step S 21  is to determine whether each of the sensing values is consistent with a default threshold condition or not. More specifically, the detection method is to determine whether the second sensing value is consistent with a default second threshold condition corresponding to the status of non-print-material, and determine whether the third sensing value is consistent with a default third threshold condition corresponding to the status of having-print-material. 
     In one of the embodiments, the second threshold condition may include: the second sensing value being greater than a second threshold (such as 2.4V) or within a second threshold range (such as 2.4V-2.8V). 
     In one of the embodiments, the first threshold may be less than the second threshold. In one of the embodiments, the third threshold condition may include: the third sensing value being less than a third threshold (such as 1.5V) or within a third threshold range (such as 1.2V-1.5V). 
     In one of the embodiments, the third threshold may be less than the first threshold. 
     When the second sensing value is consistent with the second threshold condition and the third sensing value is consistent with the third threshold condition, step S 22  is performed: determining the optical sensors  201 - 203  on the liquid level control panel  20  as valid on a liquid level detection. 
     When the second sensing value is inconsistent with the second threshold condition and/or the third sensing value is inconsistent with the third threshold condition, step S 23  is performed: adjusting a parameter or replacing the optical sensors  201 - 203 . 
     In one of the embodiments, the liquid level control panel  20  may include a variable resistance or an electronic impedance device. The user may adjust a sensitivity of each of the optical sensors  201 - 203  through the variable resistance or the electronic impedance device, so as to try to make an adjusted sensing value of the optical sensors  201 - 203  to be inconsistent with the threshold condition. 
     When the user is unable to make the sensing value to be consistent with the threshold condition through adjustment, the user may remove (such as desoldering or removing glue) the optical sensors  201 - 203  from the liquid level control panel  20 , and replace the removed optical sensors  201 - 203  with other optical sensors that have passed the first sorting process. 
     Thus, the present disclosure may use the first sorting process and the second sorting process to ensure that the optical sensors  201 - 203  have the good ability of liquid level detection. 
     Then, the application stage S 3  will be explained. Please refer to  FIG.  5    at the same time, wherein  FIG.  5    is an application schematic view of an automatic pouring apparatus of one embodiment of the present disclosure. In the application stage S 3 , the automatic pouring apparatus may instantly adjust a remaining volume of the print material in the storage tank based on a current liquid level. 
     The optical sensors  201 - 203  passing the first sorting process and the second sorting process are arranged on the liquid level control panel  20 . The liquid level control panel  20  is arranged on a sub storage tank  51  (such as the storage tank  21  with a small volume) to monitor different liquid levels through the optical sensors  201 - 203 , and to control a regulating apparatus  50  to execute a regulating action corresponding to the current liquid level. 
     The regulating apparatus  50  is used to pour the print material from a main storage tank  53  (such as the material tank  23  with a large volume) to the sub storage tank  51  (along a flowing direction D 10 ), or extract the print material from the sub storage tank  51  to the main storage tank  53  (along a flowing direction D 11 ). 
     In one of the embodiments, the liquid level control panel  20  further includes a storage module  205 , a communication module  206 , a printing apparatus  52 , and a processing module  204  electrically connected to the above modules and the optical sensors  201 - 203 . The storage module  205 , such as a flash memory, an EEPMOM, or other non-volatile memory, is used to store data (such as the threshold conditions). 
     The communication module  206 , such as a networking module or a signal transceiver, is used to transmit signals to the regulating apparatus  50 . 
     The printing apparatus  52 , such as a printing head, is configured to use the print material in the sub storage tank  51  to execute a printing procedure. 
     The processing module  204 , such as a signal processing circuit, a microcontroller, a CPU, or other processors, is used to compare the sensing values with the threshold conditions correspondingly and generate a control signal to the regulating apparatus  50  based on a comparison result. 
     Please refer to  FIG.  9   , the application stage S 3  may include steps S 30 -S 33 . 
     In step S 30 , the detection method is to execute a sensing process (a third sensing process) on the storage tank (the sub storage tank  51 ) to acquire a sensing value (a fourth sensing value) of each of the optical sensors  201 - 203  through the liquid level control panel  20 . The optical sensors  201 - 203  of the liquid level control panel  20  had passed the first sorting process and the second sorting process and is valid on the liquid level detection. 
     In the step S 31 , the method is to determine whether the fourth sensing value of each of the optical sensors  201 - 203  is consistent with a default fourth threshold condition. 
     In one of the embodiments, each threshold condition corresponding to each of the optical sensors  201 - 203  is determined based on an inspection result of each of the optical sensors  201 - 203  in the onboard stage S 2 . 
     For example, as a lower limit liquid level sensor, the optical sensor  201  may be configured with the fourth threshold condition based on the second sensing value corresponding to the status of non-print-material, such that the optical sensor  201  may detect that the storage tank changes from the status of having-print-material to the status of non-print-material. As the upper limit liquid level sensor and the safety liquid level sensor, the optical sensors  202  and  203  may be configured with the fourth threshold condition based on the third sensing value corresponding to the status of having-print-material, such that the optical sensors  201  and  203  may detect that the storage tank changes from the status of non-print-material to the status of having-print-material. 
     When the fourth sensing value is consistent with the fourth threshold condition, step S 32  is performed: controlling the regulating apparatus  50  to start or stop pouring the print material into the sub storage tank  51 . 
     In one of the embodiments, the present disclosure may start pouring the print material into the sub storage tank  51  when the sensing value of the lower limit liquid level sensor is consistent with the fourth threshold condition, and stop pouring the print material into the sub storage tank  51  when the sensing value of the upper limit liquid level sensor is consistent with the fourth threshold condition. Moreover, the present disclosure may extract the print material from the sub storage tank  51  to the main storage tank  53  when the sensing value of the safety liquid level sensor is consistent with the fourth threshold condition. 
     When either the fourth sensing value is inconsistent with the fourth threshold condition, or the step S 32  is performed completely, step S 33  is performed: determining whether a printing procedure is terminated, such as all of the printing works are finished, or the user interrupts the printing. 
     When the printing procedure is terminated, the detection method is terminated. Otherwise, the printing procedure continues to be executed, and the step S 30  is performed again. 
     Thus, the present disclosure may effectively detect and regulate the liquid level to prevent the printing from failure. 
     Please refer to  FIG.  1   ,  FIG.  9   , and  FIG.  10   ,  FIG.  10    is a flowchart of a first sensing process of one embodiment of the present disclosure. The first sensing process of the step S 10  may include steps S 40 -S 42 . 
     In step S 40 , the optical sensor  101  is removably arranged on the inspection fixture  1  to perform optical sensing toward the tank object  14 . 
     In step S 41 , the measurement device  13  is connected to the optical sensor  101  for arrangement. 
     In step S 42 , a voltage of the optical sensor  101  is acquired through the measurement device  13  to be the first sensing value. 
     Please refer to  FIG.  9    and  FIG.  11    at the same time, wherein  FIG.  11    is a flowchart of a sensing process on an empty tank of one embodiment of the present disclosure. 
     In this embodiment, the sensing process of the step S 20  may include an empty sensing process of steps S 50 -S 54 . The empty sensing process is used to inspect an ability of the optical sensors  201 - 203  in detecting the storage tank  21  of the status of non-print-material. The second sensing value may include a first empty sensing value, and the second threshold condition may include a first empty threshold condition. 
     The empty sensing process of this embodiment may include following steps S 50 -S 53 . 
     In step S 50 , each of the optical sensors  201 - 203  is adjusted to increase the sensitivity, thereby increasing a variation range of the sensing value of each of the optical sensors  201 - 203 . 
     In one of the embodiments, the sensitivity may be adjusted through a variable resistance or an electronic impedance device shown in  FIG.  8   . For example, the user may adjust the resistance value of the variable resistance to the maximum. 
     In step S 51 , the detection method is to execute a sensing process through the optical sensors  201 - 203  on the storage tank  21  without the print material to acquire a first empty sensing value. The above storage tank  21  without print material (i.e., in the status of non-print material) may be empty or have the print material with the liquid level not entering a sensing zone of each the optical sensors  201 - 203 . 
     In step S 52 , the detection method is to determine whether the first empty sensing value is consistent with a default first empty threshold condition. 
     In one of the embodiments, the first empty threshold condition may include: the first empty sensing value being greater than a first empty threshold (such as 2.4V) or within a first threshold range (such as 2.4V-2.8V). 
     When the first empty is consistent with the first empty threshold condition, step S 53  is performed: executing a material sensing process, such as a sensing process for light-transmissive print material shown in  FIG.  11    or a sensing process for particle print material shown in  FIG.  12   . 
     When the first empty is inconsistent with the first empty threshold condition, step S 54  is performed: eliminating an unqualified one of the optical sensors  201 - 203  and replacing the eliminated one of the optical sensors  201 - 203  with other optical sensor, and performing step S 50  on the replaced optical sensor. 
     Thus, the optical sensors  201 - 203  passing the above empty sensing process may effectively detect the status of non-print-material. 
     Please refer to  FIG.  9   ,  FIG.  11   , and  FIG.  12   , wherein  FIG.  12    is a flowchart of a sensing process for a light-transmissive print material of one embodiment of the present disclosure. 
     In this embodiment, the second sensing process of step S 20  may include a sensing process for the light-transmissive print material of steps S 60 -S 66 . The sensing process for the light-transmissive print material is used to inspect an ability of the optical sensors  201 - 203  in detecting the storage tank  21  with the light-transmissive print material. The third sensing value may include a light-transmissive sensing value, and the third threshold condition may include a light-transmissive threshold condition. Moreover, the second sensing value may include a second empty sensing value, and the second threshold condition may include a second empty threshold condition. 
     The sensing process for the light-transmissive print material of the embodiment may include following steps S 60 -S 66 . 
     In step S 60 , the detection method is to execute the sensing process through each of the optical sensors  201 - 203  on the storage tank  21  with light-transmissive print material to acquire the light-transmissive sensing value. 
     In steps S 61 , the detection method is to determine whether the light-transmissive sensing value is consistent with the default light-transmissive threshold condition. 
     In one of the embodiments, the light-transmissive threshold condition may include: the light-transmissive sensing value being less than a light-transmissive threshold (such as 1.5V) or within a light-transmissive threshold range (such as 1.2V-1.5V). 
     When the light-transmissive sensing value is consistent with the light-transmissive threshold condition, step S 62  is performed: determining the optical sensors  201 - 203  as valid on the particle print material. 
     When the light-transmissive sensing value is inconsistent with the light-transmissive threshold condition, step S 63  is performed: determining whether an adjusted light-transmissive sensing value is consistent with the light-transmissive threshold condition. 
     More specifically, the user may adjust the resistance value (such as lowering the resistance value) of the variable resistance or the electronic impedance device to adjust the sensed light-transmissive sensing value, thereby making the adjusted light-transmissive sensing value to be consistent with the light-transmissive threshold condition. 
     When the light-transmissive sensing value may be consistent with the light-transmissive threshold condition after the adjustment, step S 64  is performed: executing the sensing process on the storage tank  21  without print material to acquire the second empty sensing value based on an adjusted resistance value of the variable resistance or the electronic impedance device. In step S 65 , the detection method is to determine whether the second empty sensing value is consistent with the second empty threshold condition. 
     In one of the embodiments, the second empty threshold condition may be the same as or similar to the above first empty threshold condition. 
     When the second empty sensing value acquired after adjusting the resistance value is consistent with the second empty threshold condition, step S 62  is performed to determine the optical sensors  201 - 203  as valid on the light-transmissive print material. 
     When the user is unable to make the adjusted light-transmissive sensing value to be consistent with the light-transmissive threshold condition through adjustment or the second empty sensing value acquired after adjusting the resistance value is inconsistent with the second empty threshold condition, step S 66  is performed: determine the optical sensors  201 - 203  as invalid on the light-transmissive print material. 
     Thus, the optical sensors  201 - 203  passing the above sensing process for the light-transmissive print material may effectively detect a liquid level of the light-transmissive print material. 
     Please refer to  FIG.  6    and  FIG.  7   , wherein  FIG.  7    is a second sensing schematic view of an optical sensor of one embodiment of the present disclosure.  FIG.  7    is used to explain another problem solved by the present disclosure. The print material may usually be classified into two types, including the light-transmissive print material  60  shown in  FIG.  6    and a particle print material  70  shown in  FIG.  7   . 
     When the particle print material  60  is stored in the storage tank  21 , most of the sensing light (such as the sensing light emitted by the optical sensor  201 ) is reflected, and the reflected sensing light triggers a higher photovoltage (for example, the photovoltage may be greater than 2.8V). The particle print material may include at least one of white ink, low light-transmissive color ink, and other low light-transmissive print materials (having a transmittance less than 30%), etc. 
     Moreover, when the storage tank  21  doesn&#39;t store the print material, most of the sensing light (such as the sensing light emitted by the optical sensor  202 ) is reflected, and the reflected sensing light triggers a higher photovoltage (for example, the photovoltage may be greater than 2.4V). 
     Because a difference between the photovoltages of the above two statuses (the status of non-print-material and the status of having-particle-print-material) is very small, the current liquid level detection method for the optical sensors may be unable to effectively recognize the two statuses. 
     Please refer to  FIG.  9    and  FIG.  13   , wherein  FIG.  13    is a flowchart of a sensing process for a particle print material of one embodiment of the present disclosure. 
     To solve the above problem, in this embodiment, the second sensing process of the step S 20  may include a sensing process for the particle print material of steps S 70 -S 75 . The sensing process for the particle print material is used to inspect an ability of the optical sensors  201 - 203  in detecting the storage tank  21  with the particle print material. The third sensing value may include a particle sensing value, and the third threshold condition may include a particle threshold condition. 
     The sensing process for the particle print material of the embodiment may include following steps S 70 -S 75 . 
     In step S 70 , the detection method is to sense the storage tank  21  with the particle print material through each of the optical sensors  201 - 203  to acquire the particle sensing value. In step S 71 : the detection method is to adjust the resistance value of the variable resistance or the electronic impedance device so that an adjusted particle sensing value (the first particle sensing value) of each of the optical sensors  201 - 203  may be consistent with a particle threshold condition (such as a range of 1.2V-1.8V), and to record the particle sensing value (being within 1.2V-1.8V) acquired after adjust the resistance value and the resistance value being adjusted. In step S 72 , the detection method is to executing the sensing process on the storage tank  21  without the print material through each of the adjusted optical sensors  201 - 203  to acquire an empty sensing value. When the empty sensing value of any of the adjusted optical sensors  201 - 203  is inconsistent with the second threshold condition, the corresponding one of optical sensors  201 - 203  is determined as invalid on the particle print material. 
     In step S 73 , the detection method is to determine whether each of the optical sensors  201 - 203  passes a stability test. 
     In one of the embodiments, the stability test may include: sensing the storage tank without the print material to acquire an empty sensing value (the third empty sensing value); sensing the storage tank with the particle print material to acquire a particle sensing value (the second particle sensing value); determining that the optical sensor passes the stability test when the third empty sensing value is consistent with the second threshold condition and the second particle sensing value is consistent with the particle threshold condition; and determining that the optical sensor fails to pass the stability test when the third empty sensing value is inconsistent with the second threshold condition and/or the second particle sensing value is inconsistent with the particle threshold condition. 
     In one of the embodiments, the particle threshold condition may be the particle sensing value being within the particle threshold range (such as 1.2V-1.8V). 
     In one of the embodiments, when a first particle sensing value that is consistent with the particle threshold range is acquired, the particle threshold condition used in the following stability test may be modified to the acquired first particle sensing value. In other words, the stability test is used to test whether the sensing values (such as the third empty sensing value and the first particle sensing value) of each of optical sensors  201 - 203  may be stable in either detecting non-print material or the particle print material. 
     When the optical sensors  201 - 203  pass the stability test, step S 74  is performed: determining the optical sensors  201 - 203  as valid on the particle print material. When any of the optical sensors  201 - 203  fails to pass the stability test, step S 75  is performed: determining the failed one of the optical sensors  201 - 203  as invalid on the particle print material. 
     Thus, the optical sensors  201 - 203  passing the above sensing process for the particle print material may effectively detect a liquid level of the particle print material. 
     Please be noted that the stability test is not a necessary process in the present disclosure. For example, when there is a request of shortening an inspection time, the stability test may be omitted. 
     Please refer to  FIG.  14   ,  FIG.  14    is a flowchart of an application pre-process of one embodiment of the present disclosure. When the onboard stage is finished, the present disclosure may perform steps S 80 -S 83  to clean the storage tank and the pipes, and to process and configure each optical sensor. 
     In step S 80 , the detection method is to execute a cleaning process on the storage tank  21  and the pipes to clear the remaining print material in the storage tank  21 . 
     Please refer to  FIG.  3    at the same time, wherein  FIG.  3    is a cleaning schematic view of an automatic pouring apparatus of one embodiment of the present disclosure. An automatic pouring apparatus  3  may include a cleaning solvent tank  30  for storing unused cleaning solvents and a waste solvent tank  31  for storing used cleaning solvents. The above clearing solvents may be 75%-100% alcohol, or other highly volatile solvents, but this specific example is not intended to limit the scope of the present disclosure. 
     In one of the embodiments, the clearing process may include following steps: connecting the storage tank  21  to the cleaning solvent tank  30  through a pipe  26 , an regulating apparatus  22 , a pipe  37 , an electromagnetic valve  35 , and a pipe  34 , connecting the storage tank  21  to the waste solvent tank  31  through the pipe  26 , the regulating apparatus  22 , the pipe  37 , an electromagnetic valve  36 , and a pipe  33 , and connecting the storage tank  21  to the waste solvent tank  31  through a pipe  32 ; opening the electromagnetic valve  36 , closing the electromagnetic valve  35 , and pumping all of the print material from the storage tank  21  to the waste solvent tank  31  through the regulating apparatus  22  (the flowing directions D 5  and D 6 ); pouring the cleaning solvent into the storage tank  21  from the cleaning solvent tank  30  through the regulating apparatus  22  (the flowing directions D 4 ); waiting for a default time (such as 5 minutes but may be omitted); opening the electromagnetic valve  35 , closing the electromagnetic valve  36 , and pumping the cleaning solvents from the storage tank  21  to the waste solvent tank  31  through the regulating apparatus  22 ; repeatedly performing the above steps for a default clearing times (such as three times); removing the cleaning solvent tank  30  and the waste solvent tank  31 . 
     In step S 81 , the detection method is to execute a drying process on the storage tank  21  and the pipes to clear the remaining print material in the storage tank  21 . 
     Please refer to  FIG.  4   ,  FIG.  4    is a drying schematic view of an automatic pouring apparatus of one embodiment of the present disclosure. An automatic pouring apparatus  4  may include a pumping apparatus  40 , such as an air compressor. 
     In one of the embodiments, the drying process may include following steps: connecting the storage tank  21  to the pumping apparatus  40  through a pipe  41 ; transmitting a pressurized gas to the storage tank  21  through the pumping apparatus  40  and the pipe  41  for a first default air supply time (such as 2 minutes) to dry the storage tank  21 , wherein the pressurized gas flows out of the storage tank  21  through a pipe  42  and a pipe  43  (along the flowing directions D 9  and D 8 ); transmitting the pressurized gas to the storage tank  21  again for a second default air supply time (such as 1 minute) to dry the storage tank  21  through the pumping apparatus  40  and the pipe  41  after the first default air supply time had elapsed and a provision of the pressurized gas is stopped; and, removing the pumping apparatus  40 . In the embodiment, the second default air supply time may be shorter than the first default air supply time, but this specific example is not intended to limit the scope of the present disclosed example. 
     In step S 82 , the detection method is to execute an assembling process. 
     Please refer to  FIG.  5   , the assembling process is to assemble a liquid level control panel  20 , a sub storage tank  51 , a regulating apparatus  50 , a main storage tank  53  and a printing apparatus  52 . 
     In one of the embodiments, the liquid level control panel  20  may include a lower limit liquid level sensor and an upper limit liquid level sensor, such as the optical sensors  201 - 203  arranged at the different positions. 
     In step S 83 , the detection method is to set a fourth threshold condition for the application stage S 3 . 
     In one of the embodiments, the detection method may determine the fourth threshold condition of the lower limit liquid level sensor based on the second sensing value for the lower limit liquid level sensor to detect whether the liquid level of the print material is lower than the sensing position of the lower limit liquid level sensor. Moreover, the detection method may determine the fourth threshold condition of the upper limit liquid level sensor based on the third sensing value for the upper limit liquid level sensor to detect whether the liquid level of the print material is higher than the sensing position of the upper limit liquid level sensor. 
     While this disclosure has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of this disclosure set forth in the claims.