7 facts you should know about double sheet sensors!
- Chapter 1: Introduction of the double sheet sensor
- Chapter 2: Choosing the ideal sensor system for your requirement
- Chapter 3: Installation and operation functions of Piezo Stack
- Chapter 4: Customized solutions: Double sheet sensor for specific industrial applications
- Chapter 5: Double sheet sensor AccessoriesPrinciple of Piezo Stack
- Chapter 6: Safety precautions for double sheet sensor
- Where to find the reliable double sheet sensor manufacturer?
Chapter 1: Introduction of the double sheet sensor
The double sheet sensor belongs to the class of Industrial ultrasonic sensors.
They are used to detect the presence of a double sheet during one process.
Double sheet sensors are commonly associated with paper, plastics, and metals.
They are also used to measure the thickness and density apart from detecting a splice in papers.
For perfect results in your paper printing industries, a double sheet sensor is the best choice to choose.
Double sheet sensors are quickly becoming good detectors in printing industries today.
They are also referred to as ultrasonic double sheet sensors, the key parts inside them are 300 kHz ultrasonic transducers.
Double sheet sensors are designed to detect, measure and record any double existence of material in most printing industries.
They are made of different sizes and shapes depending on the task to be done.
The different shapes and sizes of double sheet sensors include G, N and F flute. Double sheet sensors contribute to the increased quality and production rate through its reliable sheet detection.
The double sheet sensor is very simple to use and does not require skilled personnel or some calibrations.
It is flexible and can be used to multi-task, various paper types either thin thick or foils.
The double sheet sensor operates on the principle of detecting ultrasonic wave strength variety reflected from one or two materials. Generally, this is how the Double sheet sensor detects any double existence of materials.
General features of double sheet sensors
Basically, when feeding your sheets into a processing machine, it is an important aspect to prevent two or more sheets from entering into your machine inadvertently.
A double sheet sensor is designed to have the following features for proper functioning.
Double sheet sensors have ultrasonic systems for reliable detection of one, two or none overlapping sheets of papers.
Single side for contacting sensors
Double sheet sensors are designed to have a single side for contacting sensors. This single side is also responsible for the sheet thickness control up to 12mm.
As the name suggests, a double sheet sensor has two outputs basically for switching double and miss-fed sheets.
Automatic plug and play station
A double sheet sensor has a plug and operates the station for providing a flexible compacted area within limited space. This helps to detect any miss-fed sheets
Double sheet sensors have a very wide material spectrum for detecting finest papers including fine thin metal sheet and plastic foils.
Perpendicular or inclined sensor
This sensor is for mounting sheets relative to the sheet plane possible
A double sheet sensor system monitor
This monitor presents in the double sheet sensor is for double sheet detection from all situations to protect machines and also avoid wasting sheets.
Specification of double sheet sensors.
Double sheet sensors must satisfy the following requirements.
All double sheet sensors should have a minimum or a maximum value in which they operate best.
For this case, sheet sensors have some calibrations of the optimal distance of about 45mm. They also have a sensing range of about 20mm to 60mm. They should also have a transducer frequency of about 395 kHz.
Indicators/ operating means
Double sheet sensors must display the following colors to determine which type of sheet detection is observed.
LED green- once a double sheet sensor displays the LED green color, it’s an indicator that a single sheet has been detected.
LED yellow- a double sheet sensor displays the yellow color, to prove to the observer that no sheet has been detected.
The yellow color indicated the presence of air.
LED red- once a double sheet sensor displays the LED red color, it’s an indicator that a double sheet has been identified and it needs to be removed.
A double sheet sensor should have the following electrical specifications; Operating voltage- A double sheet sensor should have an operating voltage of about 18V to 30V of direct current.
The sheet should have a ripple of about 10%ss. Load supply current I0– A double sheet sensor should not have a load supply current which is less than 80Ma. The time-delay before availability tv–A double sheet sensor should not have a time delay which is less than 500ms before it is available.
A double sheet sensor should have the following input specification for proper functioning.
Input type- The inputs of the double sheet sensor should function well under the following conditions. The input should be of O level: -UB…-UB + 1V and 1-level: +UB-1V…+UB Pulse length- A double sheet sensor should have a pulse length which is not greater or equal to 100ms.
Impedance- a double sheet sensor should have an impedance which is not greater r equal to 4kΩ.
The output of a double sheet sensor should have the following specifications; Output type- The type of double sheet sensor output should be 3 switch outputs PNC, NC Related operating current- the operating current of the double sheet sensor should be 3×100 Ma. The current also should be short-circuited and overload protected.
Voltage drop- The voltage drop of a double sheet sensor should not be less than or equal to 2V. Switch-on delay- The switch on the delay of a double sheet sensor should be approximately 15ms.
This means that the switch delay should have a shorter response time on request.
Switch-off delay- The switch-off delay of the double sheet sensor should also be approximately 15ms.
It means that the switch-off delay should have a short response time on request.
Pulse extension- A double sheet sensor should possess a pulse extension that is less or equal to 120ms and the pulse possessed should be programmable.
- Ambient conditions
A double sheet sensor should have the following ambient specifications. Ambient temperature- the temperature should range between ˚0 to 60 ˚C, which is also equal to 32 ˚F to 140 ˚F. Storage temperature- The temperatures under which a double sheet sensor should be stored should range from 40 ˚C to 70 ˚C.
A double sheet sensor should have the following mechanical specification;
Connection type- A double sheet sensor should have a cable PVC connection of about 2m.
Core cross-section- The core cross-section of a double sheet sensor should be approximately 0.14mm2.
The degree of protection- a double sheet sensor should have an IP67 degree of protection.
Mass- The mass possessed by a double sheet sensor is 150g, which means it’s not heavy hence portable.
Material- double sheet sensors are made of nickel-plated brass, a plastic component, and a PBT material.
Transducer- The transducer of a double sheet sensor should be epoxy resin a hollow glass sphere mixture.
A double sheet sensor must pose a high degree of accuracy to determine how good the data is as compared with recognized data.
The accuracy is to compare the results of the outcome when using a double sheet sensor than when using manual methods to detect any double sheets.
A double sheet sensor keeps the same results consistently once different sheets are fed in. This proves that the double sheet sensor will give the correct result in different working conditions.
Operating Principle and Technology.
The technology of the double sheet sensor can be defined as the use of scientific knowledge to solve practical problems, which has been demonstrated by developing a high-quality double sheet sensor for various industrial applications.
Double sheet sensor detection is under the principle of detecting one or two materials by measuring the ultrasonic strength. Basically, a double sheet sensor detection is an important aspect in most printing industries for quality control and also to prevent two or more sheets from entering the processing machine at the same time. Failure to detect these sheets may result in damage to the machines resulting in high-cost repairs. While there are many solutions available in the market of detecting double sheets, none is easier to operate than double sheet detector sensor ultrasonic.
The double sheet sensor deploys high technology to effectively discriminate between one or two sheets of defined thickness. Basically, this is how the Double sheet sensors work. The ultrasonic double sheet sensor is fitted with a monitoring device for automatic double sheet detection. The monitor works under the principle of beam ultrasonic detection. Using this monitor the following feeding results can be detected:
- No sheet
- Single sheet
- Double sheet.
After using a monitor, the microprocessor available in the double sheet sensor evaluates the signal. The output switch on the sensor is set to evaluate the sheets. The double sheet sensor is equipped with 6 connecting switches which include, Blue, white, black, grey, pink and brown. They all function differently when the sensor is operating in normal conditions. The table below summarizes it all.
|For power input
|For single sheets
|The width corresponds to the event
|For double sheets
|The pulse width corresponds to the event
|Switch output for air
|The pulse width corresponds to the event
|This input is for parameters assignment and pulse propagation
|For power output
The entire sheet sensing process: The switches that are active under normal conditions are the white, black and grey switches only.
The other two switches function when the double sheet sensor power source is either switched on or off.
The double sheet sensor is mounted with the magnetic front for touching the sheet from one side.
There is no distance allowed between the sheet and the sensor.
In the case of air gaps or small distances occurrence, they may be tolerated if they are also present during single sheet programming.
The presence of these gaps or distances reduces the maximum distance and makes it for the sensor to monitor.
Double sheet sensors also have two outputs that are short-circuited.
These outputs allow no sheet, one sheet and also double sheet discrimination.
They also have an advantage in sensor checking. Each switch has a loading cycle for checking the presence and absence of the already monitored sheets.
After installation and writing, the sensors have to be programmed once in a single sheet.
After programming, they have to be connected to an input pin with low signal strength.
The programmed single sheet is permanently stored in a nonvolatile space and remains valid even after the power is cut off.
The nonvolatile storage is called an EEPROM which has a programming capacity of about 100,000 cycles per minute.
Programming with a single sheet can be made after installation if only one and the same sheet thickness is retained in the entire process.
The short-circuited protected switches one and two are PNP transistors.
If the machine is stopped from the double sheet sensor while detecting the presence of double sheets.
the double sheet sensor output will switch back into the state of no sheets and single sheet detection.
The double sheet sensors apart from detecting papers are designed in a way that they can detect thin sheet layers of steel and aluminum foils up to a high transportation speed.
The double sheet sensor consists of two sensors, as shown above, that is the transmitter sensor and the receiver sensor. Both the transmitter sensor and the receiver sensor are fitted to oppose each other in perfect alignment.
The sheet to be checked is passed between the sensors making sure it is not coming into contact with the sensors.
The recommended distance between the two sensors is supposed to be small to allow sheet thickness. Generally, double sheet sensors operate by connecting the sensors in the machine, followed by switching on the power supply and then driving a single sheet between both sensors.
The general classification of double sheet sensors
Double sheet sensors can be classified into different classes depending on the task they do.
- 0P3S, S 2.0P3S, S 3.0P3S, Double sheet sensor
These types of double sheet sensors are used for detecting overlapping sheet materials.
They are for monitoring multiple steel sheet as well as magnetic sheets overlapping.
They have magnetic sensors on the front side for touching the extra sheet from one side.
They have highly protected output one and two made of PNP transistors.
The sensors are polythene capsulated in a flat cylindrical stainless steel tube.
The tubes are fixed with clamps with locking screws.
Basically, the sensor can be fixed in any steel material.
The length of the sensor is approximately 20m and should not exceed 20 m depending on the input specifications.
To avoid risks or injuries or damage to your machine do not stop the machine while the sensor is still detecting the materials.
Receiver sensor SIZ 30P3SE SIZ 54P3SE SIZ 75P3SE and transmitter sensor SIZ 30PSS, SIZ 54PSS, and SIZ 75PSS double sheet
This type of double sheet is mainly used to detect layers of thin gauge steel and aluminum sheets.
Like the above sensor, it contains two sensors namely the transmitter sensor and the receiver sensor.
These two sensors are fitted in a manner that they tend to oppose each other in perfect alignment as you can see in the diagram below.
The distance recommended between each sensor is about 35mm. Monitoring sheets are possible both on moving and non-moving sheets.
Programming receiver sensors are important in every single sheet after installation and wiring.
For this to happen, a single sheet must be put between both sensors with a pulse of about 50msec.
After programming, the pin input must go low and low until a tech in calibration is observed.
After programming the sheet is stored permanently in a non-volatile EEPROM sensor until the power is cut off.
The alignment of the sensors facing each other is for allowing sheets to pass in the middle without coming into contact with the sensors.
You should also make sure that the sheets do not wave between the sensors during transportation hence a recommendation for one to use a guiding roller during the process.
Generally this type of double sheet sensors work like this;
first, connect the sensors to the machine with the sheet materials, switch on power supply then put sheets between the sensors for detection.
The observation in the changes of colors in the switch will tell what kind of sheets have been monitored.
For example, if the sensors display LED green color it’s an indication that you should reduce the distance between the sensors and try programming again.
Keep checking the difference in sheet thickness to ensure that your sensor is functioning g well.
Types SIE 1.50P3S, SIE 3.0P3S double sheet sensors
These types of double sheet sensors are modified for monitoring double or multiple non-magnetic steel sheets.
The measuring amplifier is inbuilt in the sensor hence no need for an external switch box.
Again the sensor is made in a way that the monitored sheets pass the active front of the sensor by touching the sheet from one side.
This sheet monitoring is possible both on moving and non-moving sheets.
As you can see in the diagram below this type of sensor does not allow any distance between sheets and the sensor.
Small distances may be allowed if they don’t alter the thickness of the sheet.
The sensors have two outputs protected for connecting to the input and output switch.
These two outputs allow the detection of a single sheet, double sheet, and no sheet.
The presence of the loading sheet cycle help to check the proximity of monitored sheets.
The sensors are Polyurethane capsulated in a cylindrical stainless steel tube.
It is an important aspect for the sheets to be fixed so that every sheet passing through the sensor is fully covered.
The sensor cable length should be approximately 20m.
Make sure you don’t stop the machine or switch off the power before the programming process is complete as the results will change to single sheet condition and this may end up damaging both the sensors and the machine.
Transmitter- Sensor: SIE 30RSS, Receiver- Sensor: SIZ 30P3SE Double sheets
This type of double sheet sensor is mainly for supplying sheet thickness of correlated output voltage of 1 to 10 VDC.
The measuring amplifier is inbuilt in the sensor hence no need for an external switch box. The output voltage is used for monitoring applications on non-magnetic steel sheets.
The two sensors are fixed opposite to each other to allow sheets between both sensors for detection.
This type of arrangement allows the formation of the current barrier between the sensors where one sensor transmits current and it’s received by the other one.
The sheet between the two sensors reduces the received field strength. It has two output voltage for connecting to the source of power.
These double sheet sensors are fitted into a 30m thread tube.
The sensors unlike the others discussed above are made of nickel-plated brass. Both the receiver and the transmitter sensors have the same dimensions.
Type S 0.5AS, S 1.0AS, S 2.0AS, and S 3.0AS Double sheet sensors
These double sheet sensors are used for monitoring the presence of multiple sheets on materials and also modifying their thickness to make sure it’s the perfect thickness of the material.
Like the other sheets, their measuring amplifier is inside the sensor so no need for an external one.
These sensors are built into rugged stainless steel tubes.
The magnet in the sensor is used to calculate sheet thickness and also attracts monitored sheets to the sensor active front page.
The sensors are still polyurethane which is capsulated into a stainless steel tube. The tube must be 10m long.
Reasons why we need double sheet sensors.
Printing of books, newspapers, magazines journals and any other reading material can be a complex process involving paper handling and electronic controls.
In order to print large volumes of these materials effectively and efficiently definitely you need a double sheet sensor connected to your printer.
You need a double sheet sensor that can detect any problem in the printing process fast and with a high degree of accuracy.
You won’t like to be surprised that after a whole printing process you find that you have printed double pages or blank pages or missing pages.
It’s also time-wasting to find that after the entire printing process, you have to reprint a whole 5000 pages or more because a single sheet made its way through the middle of the books.
In the printing process the double sheet sensor can detect three different states;
- No sheet
- Single sheet
- Double sheet
In order to detect the different states, a double sheet changes the LED color depending on the type of sheet detected. If the sensor detects a single sheet then the LED light turns green.
When the sensor again detects the presence of a double sheet the LED light turns red. When the sensor does not detect any sheet the LED light turns yellow.
Double sheet sensors originated in the printing industries to quickly detect the presence of a double sheet on splice of papers.
With the advancement in technology, it is not only used in paper detection but also in plastic, metal and shiny transparent materials.
It has found its way in the plastic and metal industry with the improvement in technology.
To install a double sheet to your printer you need the following;
- A mounting bracket for a double sheet monitor
- 1m length emitter-receiver extension cable
- 2m length emitter-receiver extension.
In general, we need double sheet sensors to avoid wastage of time, resources and money.
Double sheet sensor makes work easier and it’s not an expensive process as it doesn’t require any skilled personnel.
Chapter 2: Choosing the ideal sensor system for your requirement
In order to make sure you have the right double sheet sensor for your system, it must have the following requirements;
A double sheet sensor must operate under the principle of paper detection through the reduction of ultrasonic signal strength by one or two materials.
The double sheet sensors are positioned across from one another with one transmitter and one receiver.
The transmitter sends out pulses that meet the boundary of the first sheet to weaken its signal strength.
This weakening of the first sheet shows that the sensor has detected a single sheet condition.
In the case of the double sheet, the transmitter sends a pulse that meets the sheets weakening their signals even further to trigger out an output.
These changes in the amplitude help the sensor to distinguish between a single sheet, a double sheet, and no sheet detection. The diagram below shows the operating principle of the double sheet sensor.
The double sheet sensors have the following outputs;
- Output 1 and Output 2- these two outputs are used to discriminate double sheet, single sheet, and no sheet.
- Short circuit protected NPN transistor- for connecting to the switches
- A transmitter with 4 pins male connector- used for VDC supply voltage
- A receiver with 5 pin connectors
- Multiple calibrations remote
Generally, double sheet sensors require an external power supply in order to operate.
This power supply is called an excitation signal which is used by the sensor to produce output signals
Programming in a double sheet sensor is very simple, they are equipped with four programming modes for different applications.
The double sheet sensors are connected to PACT ware to detect any occurrence of a double sheet condition using steel sheets.
Once they are connected what is observed is that there will be a varying thickness which affects the amplitude signal strength.
Resolution measurement and accuracy
Resolution in double sheet sensor can be expressed in two ways;
The ability of a double sheet sensor to record the smallest signal strength that can be resolved.
And the ability of the same double sheet sensor to detect any theoretical change in sheet detection.
For most double sheet sensors it is desirable to choose a sensor that has absolute accuracy, can measure the smallest unit of the material and has good resolutions.
Absolute accuracy in double sheet sensors is the uncertainty error in the exact distance of sheets measured.
Relative accuracy, on the other hand, is the uncertainty error in the exact distance measured when the sheets move closer to the sensors.
The resolution, measurement, and accuracy of double sheet sensors are affected by factors such as;
- The wavelength of the transmitter and the receiver.
- The reflecting characteristics of the sheets
- The uncertainty assumed the value of the speed in which the sheets pass between the two sensors.
- The operation of the electronics in the sensor.
- The material used to make the sensors.
Chapter 3: Installation and operation of double sheet sensors.
This is how Double sheet sensors are installed for excellent operation;
The double sheet monitor is inbuilt in the double sheet sensors to monitor any double, single or no sheet passing between the two sensors.
We have the microprocessor also found inside the sensors it is used to evaluate the signals emitted during transmission of materials.
Outside the double sheet sensors, we have switches for detecting any change in ambient temperatures within the machine.
The evaluation electronics of double sheet sensors are installed in a cuboid like a plastic house that is separate from the sensor heads.
For a double sheet sensor to be complete it must have the following installations;
- Ultrasonic emitter
- Ultrasonic receiver
- Evaluation system.
They have a mutual relationship and failure of one of them may lead to the running down of the entire double sheet sensor.
To ensure the proper functioning of the double sheet sensor, the sensor heads must be aligned at an angle of 20˚ and 45˚ vertically on the paper surface.
Guide the sheet over the emitter for a distance of about 5mm to 15mm.
The emitter is installed below in order to prevent any dust deposits from going back to the receiver.
The sensor heads are installed using plastic nuts since plastic is a poor conductor of heat.
Make sure the sound cone is completely covered by the sheet of paper.
The sensor heads are installed above the sheet of paper at a distance of about 10mm away from the side edge of the paper.
The overlapping sheets must not exceed 20mm and the speed should be 5ms.
Once an operating voltage has been applied, a single sheet can now be fed in and automatically be programmed as a reference value by the system.
In cases where one is inserting a thin sheet of paper, one can disperse it with the use of tech in signal to program the system.
This is only possible if you place the single thin sheet of paper between the receiver and emitter for approximately 10 seconds.
For thicker types of sheets, they can be dispersed using a teach-in signal which will result in a double sheet of paper detection.
In order to detect the double sheet of paper, the thick sheet of paper must be placed between the emitter and receiver for approximately 10 seconds.
If you are inserting a new type of sheet to result in double sheet output or single sheet output the system must be reprogrammed.
To do this, the new sheet of paper must be placed between the emitter and receiver for approximately 10 seconds.
Apply the tech in signal to disperse the paper and the results of the observations are generally acceptable.
During the installation of double sheet sensors, one should take care of the ultrasonic signal to prevent them from passing around the paper that is being detected due to multiple reflections.
In cases where more than one double sheet sensor is needed per machine, isolation called acoustic should be provided to avoid cross-talk.
Chapter 4: Customized solutions: Double sheet sensors for specific industrial applications.
Apart from detecting the presence of double sheets on printing industries, double sheet sensors are also applied in other industries such as plastic industries, metal industries.
In these industries, they are used for determining the size of the material and also to make sure that only one plastic or metal sheet has been processed. Double sheet detection is an important aspect in these industries as it increases the life of the equipment and minimizes the chances of material getting wasted.
In the plastic industries, double sheet sensors operate by checking the presence of an extra plastic material before it reaches the blade. Once an extra item is detected by the double sheet sensor as a result of static electricity, an alarm present in the sensors signals.
This type of sensor is designed in a way that it can even check all materials including transparent film to plastics, steel sheets, and even aluminum sheets.
Double sheet sensors are constantly evolving with more functions and intelligence and in the coming years, they might find broad applications in almost every manufacturing industry.
With a double sheet sensor in your company, there are no chances of producing blank documents or multiple unwanted materials or finding some parts of your materials that are not printed. Sensors for sheet metal applications are quite different from the ones for detecting papers. Metal sheet sensors have the following characteristics;
- A sensitive range of about 3mm to 5mm
- The sensitivity of about 0.8mm to 1,2 mm per metal sheet
- A voltage of 10 to 30 VDC
- An output of about 200Ma
- A power-up delay of about 10msec
- A switching frequency of about 100Hz
- They are made of stainless steel material
- And a pressure resistance of about 40 bars
Unlike the sensors for detecting sheets of papers, this one’s for metal are exposed to strong magnetic fields, high heat, and sparks.
Chapter 5: Double sheet sensors Accessories
In order to make double sheet sensors more attractive and more functional the following accessories have been added to them;
- A shielded cable socket, the material used to shield the cable being plastic.
- Ultrasonic system for reliable detection of overlapping sheets, single sheets, and no sheet.
- Two sensors for enabling materials to pass between for detection
- An emitter and a receiver for sensing signals and emitting pulse
- Automatic adjustment plug and play operation
- Two outputs for switching double and miss-fed sheets
Chapter 6: Safety precautions
Precautions for safety use.
Despite the fact that double sheet sensors do not require a special handling process, it is always advisable to handle them with a lot of care to void breakages and also for a longer life span.
It is always advisable to make sure you don’t use your double sheet sensor in an environmental condition that exceeds the product rating.
For instance, a double sheet sensor for detecting an extra sheet of paper should not be used in an environmental condition the same as the one used to detect metal sheets.
When installing double sheet sensors a lot of care has to be taken to make sure that ultrasonic signals do not pass through the sheet material being detected.
Always make sure to use suitable mounting brackets. Some parts of the double sheet sensor should be covered with sound-absorbing material.
- Do not use a voltage which exceeds the operating voltage range.
- Applying a voltage that exceeds 100V AC may result in the explosion of the double sheet sensor.
- Do not short-circuit the sensor as also it may explode.
- Do not reverse the power supply terminal wires or else the double sheet sensor won’t operate.
- Do not connect or leave the double sheet sensor on a running current without a sheet inside it as it may explode.
- Make sure you mount the sensor to align with the reflection surface
- When installing the sensor make sure to use mounting nuts.
Precautions for correct use.
The following precautions are for the correct use of a Double sheet sensor;
As stated earlier, do not use double sheet sensors in temperatures that exceed the rated temperature of the material.
Do not use the sensors in a wet area or coming into contact with water as this may reduce the detection distance.
Do not use double sensor s near any kind of air nozzle.
Do not use double sheet sensors to detect materials such as cotton, wool, and powder.
Do not bend the cables used to connect the Double sheet sensor to the power source at low temperatures as it may break.
Where to find the reliable double sheet sensor manufacturer?
To conclude the above case of a double sheet sensor, you should try at least to boost your product quality and manufacturing efficiency by using double sheet sensors. They don’t have any disadvantage not unless you handle them with a lot of reckless.
Once you follow the above-given double sheet sensor guidelines of how to install the machine and safety precautions, you won’t be disappointed by the outcome of the results.
For the detection of double sheets, single sheets and no sheets in your papers, plastics and metal materials, a double sheet sensor is an ultimate choice.
In sheet feed printing and stamping, process doubles are definitely viewed as negative if you’ve ever been in an office environment and a paper jam occurs, then you open up a copy machine and look in the rollers and see two sheets of papers.
It gives you an idea of what can happen to a print process when a double occurs.
Maybe you can get a bigger idea if you expand that out and when somebody is making instead of just a copy of a single sheet, a magazine, newspaper or something like that.
Those jam ups can be catastrophic. A 300 kHz ultrasonic transducer is the perfect helper for keeping downtime, subsequent maintenance and damage to an absolute minimum.
The 300 kHz ultrasonic transducer is designed to instantly identify double sheet occurrences before the problems get too far downstream. Think about this, how would you react if ATM gives you wrong banknotes?
Definitely, you will get mad.