Delta CS2 Technical Information

CS2 Color Scanner
A Self-Contained, Easy-To-Use Scanning/Lighting System in a
Compact Package For Production Line Automation Applications
The CS2 Color Scanner analyzes reflected light captured by a silicon cell.
The CS2 then activates data outputs based on the relative magnitude of the Base color and the ratio of the Base color and the Sense color.
Primary features
Fast response rate: 500 microseconds, 50 uS optional.
100,000 hour life LED lighting system
Automatic adjustment to changing ambient
Optically isolated outputs for Base limit and Ratio limit. Analog outputs for Base and Sense colors
Easy set-up using integrated bar graph display
Compact size: 6 x 6.4 x 1.25"
Low power requirements: 24Vdc @ 250 mA maximum
Color range options: blue to near­infrared
Versatility: Other options include optimizing computer interface. Use with rotary pulse generator to check product or defect length, too.
Use the CS2 Color Scanner to:
Sort objects and compare
peeled vs. unpeeled organic vs. non-organic ripe vs. green over-ripe/ro tten vs. normal
Detect product defects such as
stains spills knots over or undercooked product
Align
materials labels packages
Read paint markings
where bar coding or inkjet printing is impractical or impossible
The CS2 detects deviations from normal or average color, based on the Sense/Base ratio.
It can be configured to detect either a high or low ratio. whether that's a feature needed to be recognized or a product defect.
Using the narrow-line scanning area option, a wide area up to 1.25" can be scanned for defects or features.
Detecting green areas on carrots, knots on wood, and burned cookies are applications that typically use the Low Ratio setting. Detecting white ends on asparagus is an example of a High Ratio setting.
Setup is a simple, three-step process
1. Mount scanner(s)
2. Wire power & outputs
3. Adjust gains & thresholds and you're your way to the benefits of improved product quality. Fast!
Where to find more information
Free Sample Testing 2 How The CS2 Works 2 Using the Displays 3
Bar Graph Display 3 Status Indicators 3
Inputs and Outputs 3
Scan Cycle 3 Base & Sense Limit Outputs 4 Data Ready Output 4 External Trigger Input 4 Threshold Analog Inputs 4
Analog Outputs 4 Mounting the CS2 5 Wiring 6 Configuration 8 Adjustments 9
Color Tolerances 10
Pencil Sorting Example 10 Putting It To Work 11
Comparing Colors 11 Application Guidelines 12
Power Supplies 12
Electrical noise 1 2
Data Skew 12
Color Errors 12
Background Errors 12
Reflections 12
Intensity Variations 12
Using Multiple CS2s 12 Technical Information 14 Ordering Information 14 Company Profile 14 General Application Information 15
:
11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 Fax (360)254-5435
email@deltacompsys.com http://www.deltacompsys.com
CS2 Color Scanner
Free Sample Testing
Delta will test your samples and tell you if your application is a candidate for the CS2 color scanner (or another Delta color scanning product).
This service is available to anyone with a potential application. Simply send the samples, along with a business card (se we can call and get a brief description of the application) to:
Delta Computer Systems, Inc. 11719 NE 95th Streed, Suite D Vancouver, WA 98682 Attn: Steve Nylund
If this brochure is more than a year old, please call and cornfirm our address before sending. Please call (360)254-
8688. After receiving your samples and discussing the application,
we will test your samples using a CS2 scanner and/or a spectrometer. Will will then recommend a praticular configuration for online testing.
Take advantage of the offer today. It's easy!
How The CS2 Works
The CS2 measures the difference in reflected light between two light sources. In its standard configuration, the reference color is 880-940nm (near-infrared) which is referred to as the Base color. The second light source is 660nm (red) which is referred to as the Sense color. The reflected color is measured by turning on the Base and Sense high intensity LEDs, one color at a time, and reading a silicon photocell. The amplified information is stored so that the measured color information will still be present when the LEDs are off. The LEDs are on for only about 20 microseconds out of the 500 microsecond cycle in order to reduce power and maximize life.
Once the reflected Base and Sense color amplitudes are stored, the current or real time-time values are subtracted from the running averages ( running averages are derived from the minimum color amplitudes) for each color. The running averages change ove r time, allowing the CS2 to automatically adjust to changes in temperature, ambient lighting, etc., and making periodic recalibration to compensate for these changes unnecessary.
By comparing the ratio of the Base and Sense colors, a determination can be made as to when and where a color deviation occurs. The CS2 can be configured to detect either a Low or High Ratio deviation. Example applications where the Low Ratio setting is used include detecting green areas on carrots, knots on wood and burned cookies, while the High Ratio setting would be used to detect white ends on asparagus, some paint applications, eand so on. The default setting is Low Ratio.
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When more sophisticated filtering, thresholds, or limit algorithms are needed, the CS2 provides an easy interface to an optimizing computer. In addition to analog inputs to permit control of the Base and Sense Thresholds, analog outputs are provided for Base and Sense colors. The outputs do not provide absolute color information, but provide relative values that can be processed by an optimizing computer.
, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 2
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Using the Displays
LED's
LED's
Bar Graph Display
In order to make adjustment easy, the CS2 contains its own voltmeter with a bar graph display which is visible through the top. This display uses a "moving dot" technique where the segment position represents the amplitude of the reflected light.
Output Bar Graph Displa
ht bar indicates Sense Color
Bri
Green
Yellow
Less intense bar indicates Base Color
Red
The lowest voltage segments are yellow, the center green, and the highest are red. Usually, once the Gains are adjusted, the background intensity will be no higher than the yellow segments and normal objects will be in the green range. The 10th (red) segment indicates an overrange condition; at this point the readings are invalid. The Gains need to be set such that the highest intensity is not higher than the 9th segment.
Both the Base color and the Sense color are simultaneously displayed using a different intensity for each color. The brighter LED represents the Sense color.
Status Indicators
Four indicators provide status of the digital inputs and outputs. Indicators are lit when the condition they represent is true (Output NPN transistor ON).
Bar Graph
TB2 TB1
Status Indicators
Trig In
Data Read
Trig In
Base Limit
Sense Limit
Inputs and Outputs
The CS2 provides two analog and three digital outputs and two analog inputs. The digital outputs are: Data Ready, Base Limit and Sense Limit. All three are optically isolated uncommitted NPN open-collector outputs.
The two analog outputs provide voltages proportional to the real time Base color and Sense color. Updated every scan cycle, the outputs range from 0-10V and will drive high impedance inputs (2 kohms or higher). These outp uts are not temperature compensated and must be used with the appropriate software algorithms.
Scan Cycle
RPG Phase
NPN output ON
Bus
Scan Cycle
Trigger Delay Time
Data Read
Outputs Stable
Limits NPN output ON when limits exceed setpoint
See
Note 1
Jumpers
Internal Trigger
OR
External Trigger Input
Measure Sense
Measure Base
Data Read Output
Limit & Analo Outputs
Trigger Delay Time
(Determines Scan
Cycle Time when
using internal Data B & S Auto Restart
trigger) Ready 2 4 8
(default) 500us 110us 22us
*Special order, must
be set by factory
Note 1. When using an external trigger, the Scan Cycle Tim e i s determined by the tim e between RPG transitions ( RPG NPN output changes from OFF to ON). I f the time between transitions i s less than the Trigger Delay Time, scan data will be lost.
S
B
NPN output ON
435us 110us 22us Yes 380us 110us 22us Yes 330us 110us 22us Yes Yes 275us 110us 22us Yes 220us 110us 22us Yes Yes 164us 110us 22us Yes Yes 110us 55us 22us Yes Yes Yes
*50us 25us 12us Yes Yes Yes
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, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 3
CS2 Color Scanner
Base & Sense Limit Outputs
Limit outputs provide the means to control an external device when the setpoints are exceeded. Each is an isolated open collector NPN output. When the limit setpoint is met (Base color above setpoint and Sense limit below setpoint), the NPN output is turned ON. ON current is 1.6 mA minimum, 8 mA typical. The maximum open collector voltage is 30VDC.
Note: If the limit outputs are connected to a high speed input, they may need to be qualified with the Data Ready output.
Data Ready Output
The Data Ready output should be used when the CS2 is connected to a fast Analog-to-Digital converter. Inaccurate readings can result if the A-D tries to read the analog color voltages at the same time that the CS2 is updating them. By synchronizing the external A-D converter to the CS2's scanning cycle, this problem is eliminated.
The Data Ready output varies with the scan time. When scanning with the internal trigger, Data is valid (Data Ready line OFF) for approximately 110 microseconds each scan. For high scan rates, the Data Ready NPN open collector load resistor may need to be lowered (below 2.7k). It is a good idea to allow 20-50% margin for gain degradation of the opto-coupler. The ON current is 1.6 mA minimum, 8 mA typical. The maximum open collector voltage is 30Vdc.
External Trigger Input
This input allows a scanning cycle to be started by an external signal. It is particularly useful when the scanner is connected up to an optimizing computer. When the scanning cycle is initiated by a signal from a rotary pulse generator (RPG) connected to a belt or other co nveying system, the length of objects and features detected can be determined by counting the number o f RPG counts that occur while the object or feature is within view of the scanner. In this way, dimensional information can be obtained.
To use this option, jumper the scanner for external triggered operation, and wire the output of the RPG (or other trigger source) to the Trig In terminals. The trigger input of the CS2 requires 5 mA and will work with signal sources between 3.5 and 24V, ensuring compatibility with most TTL and open-collector encoders.
Threshold Analog Inputs
The CS2 provides two analog inputs to control the Base and Sense limit setpoints. For applications using these inputs, please contact Delta for assistance.
Analog Outputs
The CS2 provides two analog outputs proportional to the real time Base color and Sense color. These outputs are updated every scan cycle. The outputs are 0-10V and will drive high impedance inputs ( 2 kohms or higher).
When using the analog outjputs with a PLC or other computer, the Sense reading is divided by the Base reading to get the Sense/Base ratio. This ratio is then compared with a threshold value as is done within the CS2.
However, using the analog outputs allows additional flexibility, such as multiple thresholds, thresholds that can be stored and set remotely.
Note that is is often advantageous to subtract the background readings before calculating ratios in cases where the object being viewed does not completely fill the viewing area.
Contact Delta for help with specific applications.
Delta Computer Systems, Inc.
email@deltacompsys.com http://www.deltacompsys.com
, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 4
Mounting the CS2
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The CS2 scanner is contained in a enclosure which has mounting tabs on the bottom. The lighting LEDs shine through the clear bottom and the optics pick up the reflected light through the bottom also. The bar graph display and status indicators can be viewed through the clear top.
Mount the CS2 so that the object to be scanned is within the scanning area. In the default configuration, the center of the scanning range is 1.75" from the bottom of the scanner. Although the CS2 can see to some extent from about 1" to about 4", best performance is from 1.5 to 2".
The CS2 will operate in any position. However, in dirty environments, it is best to have the CS2 lo oking straight down, and worst to be loo king straight up. If the scanner must be placed such that it is looking up, a stream of air may be adequate to keep the window clean.
CS2 Color Scanner
It is also advantageous to be able to see the indicators through the clear top of the unit when it is in operation.
CS2
Viewer
LEDs
Scanning Range
LEDs
Nominal Distance from Scanner to ob
ect
Object
Background
Scanning Area Line Orientation
P/N CS2-NR-A1X8-00
Bottom View of CS2
Object
Scanning Area
Various scanning areas and shapes are possible. Please contact Delta for further information.
Delta Computer Systems, Inc.
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Top View of Scanned Area
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Wiring
The CS2 is designed to be wired using watertight flexible plastic conduit. In applications where sealed operation is unnecessary, the wires can be run out through a strain relief connector. The conduit can also be used to pressurize the CS2 with low pressure, dry air for additional protection.
The number and type of wires required depend on the mode of operation. Only two wires, for 24Vdc power, are required to operate the device. In simple applications, two more wires are used for the output. A four wire cable with an overall shield is fine.
If analog threshold inputs or color outputs are used they need to be run through individually twisted, shielded pairs.
General Wiring Guidelines
1. The CS2 has sensitive circuitry which can be affected by electrical noise generated by loads. Its power supply should not be used to power other loads.
2. The output of the 24Vdc sensor power supply must be isolated from earth ground. The CS2's common is connected to earth ground through its case.
Application using Sense and Base Limits Outputs for Sorting or Rejecting Objects
CS2
Sense Threshold
Base Threshold
Common
Sense Color
Base Color
Common Data Read Data Read
Sense Limit ­Sense Limit +
Base Limit ­Base Limit +
Common
24V +
External Tri External Tri
er ­er +
Case
In this application, the CS2 is used in its default configuration (internal trigger, darker
+
SSR Load
-
-
+
areas to be sorted or rejected, object scanned every 500uS). In order to activate the solid­state-relay (SSR), the object in the scanning
- Output
+
Phoenix
- Sensor Power
+
24Vdc
Phoenix CM 90-PS-110 AC/24 Order No. 2943408
or equiv.
CM 90-PS-110 AC/24 Order No. 2943408 or equiv.
Power 24Vdc
area must cause the Base color to exceed the Base Threshold (object present)
and
the Sense color must be below the Sense Threshold (Low Ratio).
Delta Computer Systems, Inc.
email@deltacompsys.com http://www.deltacompsys.com
, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 6
CS2 Color Scanner
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Using the CS2 With a Rotary-Pulse-Encoder (RPG) for Counting Objects and Defects
Defect Counter
To synchronize CS2's scan with an external event, use the external trigger input. In this example, a new scan is started every time a pulse is received from the RPG. The Sense Limit output is used to count the number of dark areas (defects) seen, while the Base Limit output is used to count the number of objects.
CS2
Sense Threshold
Base Threshold
Common
Sense Color
Base Color
Common Data Read Data Read
Sense Limit -
Sense Limit +
Base Limit ­Base Limit +
Common
24V +
External Tri External Tri
er ­er +
Case
Object Counter
Phase A
­+
Open Collector NPN
RPG
+
-
-
+
Phoenix
- Sensor Power
+
24Vdc
Phoenix CM 90-PS-110 AC/24 Order No. 2943408 or equiv.
CM 90-PS-110 AC/24 Order No. 2943408 or equiv.
Output Power 24Vdc
Sense Threshold
CS2
External Tri External Tri
Base Threshold
Common
Sense Color
Base Color
Common Data Read Data Read
Sense Limit ­Sense Limit +
Base Limit ­Base Limit +
Common
24V +
er ­er +
Case
Example Using the CS2 with an Optimizing Computer
Optimizing Computer
+
-
Isolated Differential Analo
5V
2.7K
Phase A Open Collector
NPN
RPG
-
+
-
+
Phoenix CM 90-PS-110 AC/24 Order No. 2943408 or e
Inputs 0-10Vdc
A/D Trigger
TTL or CMOS
Output Power 24Vdc
uiv.
+
-
­+ +
-
-
­+
+
+
-
- Sensor Power
+
24Vdc
Phoenix CM 90-PS-110 AC/24 Order No. 2943408
uiv.
or e
In applications that require more sophisticated filtering, thresholds, or limit algorithms, CS2's analog outputs and inputs provide an easy interface to an optimizing computer. As shown, the analog outputs are read each time the Data Ready isolated NPN output goes from ON to OFF. The optimizing computer then processes the analog information. Remember, the analog data provided by the CS2 is not absolute color information, but relative values.
In this example the Base and Sense Threshold analog inputs are not used. If desired, these can be used to control of the Base and Sense Limits setpoints. By controlling the se tpoints, the optimizing computer can use the CS2's two isolated NPN outputs for control. Contact Delta for additional information.
Delta Computer Systems, Inc.
email@deltacompsys.com http://www.deltacompsys.com
, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 7
Configuration
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2 4
8 Internal Tri External Tri Hi
h Ratio
Low Ratio
er
er
LED's
LED's
Internal Tri External Tri Hi Low Ratio
Configuration
Jumpers
Default Jumper Configuration
2 4 8 er
er
h Ratio
Bar Graph
TB2
TB1
Status Indicators
CS2 Color Scanner
Sense Low/High Ratio
The Sense Limit is jumper configurable to respond to either Sense/Base ratios that are lower than normal (Low) or Sense/Base ratios that are higher than normal (High). Example applications where the Dark setting (default) is used including detecting green areas on carrots, knots on wood and burnt cookies, while the High setting would be used to detect white ends on asparagus, some paint applications, etc.
External and Internal Triggers
When using the Internal trigger (default), every 500 microseconds the CS2 automatically takes new Sense and Base color readings, calculates averages and Sense/Base ratio and updates the outputs and indicators.
If an external trigger is desired, move the jumper from the internal trigger position to the external trigger position and wire the output of the RPG (or other trigger source) to the Trig In terminals located on TB1.
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CS2 Color Scanner
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Adjustments
The CS2 has five potentiometers (pots): LED Time, Overall Gain, Sense Match, Base Threshold, and Sense Threshold. The LED time adjustment is not used for basic operation; contact Delta for more information
LED's
LED's
Trim Pots
Output Bar Graph
TB2
TB1
Status Indicators
Data Read
Trig In
Base Limit
Sense Limit
Status Indicators
Overall Gain
Led Time
Sense Match
Sense Limit Threshold
Base Limit Threshold
Yellow
Output Bar Graph
Red
Green
Displa
The procedure below is for applications where the background (with no object present) is dark compared to the objects to be viewed and the features to be identified are relatively dark (in the Sense color spectrum) compared to the object. Examples include green areas on carrots, knots on wood and burned cookies.
Gains and Thresholds
1. Mount and wire the unit and connect power. The lighting LEDs on the bottom of the CS2 and the Data Ready indicator
should come on when power is applied. The output bar graph display may or may not be lit.
2. Find a sample object with the greatest reflectance (biggest and lightest). Put it in the viewing area and adjust the Overall
Gain until the less intense bar graph indicator is in the 8th or 9th p osition (red).
Output Bar Graph Displa
Green
Less intense bar indicates Base Color
ht bar indicates Sense Color
Bri
Yellow
Red
3. Adjust the Sense Match pot until the bright bar graph indicator is on to p of the less intense bar graph indicator (8th or 9th
position).
4. Put an average object in the viewing area. Both base color and sense color bar graph indicators should be within the
center of the display (green).
5. Remove all objects. Reflected light from background should display no higher tha n the second bar graph indicator
(yellow).
6. Place an average size and color object in the viewing area for about ten seconds. Remove all objects and then
immediately put a minimum size, normal color object in the viewing area. Adjust the Base Threshold pot such that the Base Limit indicator is just activated.
7. Put a marginally nominal object in the viewing area (make sure the low/high ratio limit configuration jumper setting is
correct). Adjust the Sense Threshold pot such that the sense limit indicator is just activated.
8. Fine tune both threshold adjustments while observing on-line operations.
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CS2 Color Scanner
Color Tolerances
You want a bunch of paperweights in the shape of our logo. You sketch the thing, add dimensions, and send it off to a turn-key manufacturing shop with these instructions:
Dimensions: ±0.035" Weight 1 LB, ±1 oz. Color: Red; just like the sample.
To keep costs down, you've given generous to lerances on dimensions and weights, but what is your color tolerance? The manufacturer might think he's got an exc ellent match, and you might think it clashes terribly. It ge ts worse. If you are matching items that are not colored the same way, such as plastic and metal, you have to take into account the lighting as well.
Most colors are made up of a mixture of pigments and can look very different under varied lighting. Different pigments are used for paints, plastics, inks, dyes, etc. Perfect matches of diffe rent materials under varie d lighting conditions is virtually impossible.
So how do you express color tolerances? Color can be expressed in mathematical terms; intensity, hue, etc., and can have mathematical tolerances, but this will seldom produce optimum results.
Why is that? In order to keep manufacturing costs d own, tolerances should be as wide as possible. But color tolerances are based on perception, and are not evenly distributed. In most cases, larger variations in intensity are permissible than in hue.
The pencils travel lengthwise, erasers first, under the CS2 which is configured for a viewing area of 1/32" by 1/2". A rotary pulse generator (RPG) provides a pulse for every 1/32" of pencil travel so that the entire top side of pencil is examined. The CS2 is triggered from this RPG.
The optimizing computer reads the raw analog color information, subtracts the average background intensity, and determines when a pencil is in the viewing area -- Base color amplitude 15% or more than average Base amplitude, pencil length -- counts RPG pulses while Base amplitude is high, eraser present -- counts RPG pulses while Sense/Base ratio is 110% or more than average Sense/Base ratio at the beginning of the pencil, paint present -- checks that Sense/Base ratio does not go high again during remainder of the pencil length.
The system was set up, adjusted and it ran great. Except, after maintenance shutdowns. Sometimes it would just ignore the pencils.
A little troubleshooting pinpointed the prob lem. During maintenance, the machine was cleaned using air nozzles. The fine sawdust settled everywhere, including on the pencil conveying belt. The sawdust was light colored and highly reflective, making the background intensity readings as high as the pencils!
A simple continuous belt cleaning system took care of the problem.
Tolerances in hue are often not even. Butter, for example can be quite orange without cause for concern, but even slightly green butter is likely to be repulsive.
Creating a multidimensional tolerance color model is possible, but would take a lot of time. Even if you went to this expense, on line, high speed testing against this model would be very expensive.
In short, color is a perception issue, and is still more of an art than a science. Fortunately, in many real-world situations, a one dimension test for color is all that is required; green areas on carrots, white ends on asparagus, dark knots on wood, paint either there or not there, etc. These types of applications are suited to the CS2 scanner.
Pencil Sorting Example
In this hypothetical application, red pencils are being examined for missing erasers and missing paint. The CS2 is used with an optimizing computer in order to make length as well as color decisions on the product.
Delta Computer Systems, Inc.
, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 10
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CS2 Color Scanner
Putting It To Work
Comparing Colors
The CS2 is primarily intended for use in applications where objects are 100% scanned for a deviation in average or normal color, whether the deviation is a defect or a feature that needs to be recognized.
It is possible to compare against a sample and activate the limit outputs based on deviation from a sample.
Consider the hypothetical case where paper is being manufactured for manila envelopes.
Currently, samples are taken to the lab on a regular basis and tests are conducted to determine if the paper has the proper beige color. The problems with the current system is that the paper machines run continuously and at a rate that makes it unfeasible to take samples often. On the other hand, if the paper color goes out of spec., a tremendous amount of waste can be created before the problem is identified and corrected.
A CS2 was mounted above the flow of paper (web) inside of a special wheel. One-half of the area of the wheel was removed and the inside of the other half covered with a lab­tested sample of the paper. The wheel is mounted just above the web and rotated at the same speed as the web. The CS2 alternately looks at the web and the sample paper.
In this special case the concepts of Base color and Sense color do not apply. Instead the CS2 colors were chosen to correspond to the colors of the various dyes used in the paper, and the outputs analyzed for differences between the sample and the web.
Traversing Heads
In the case of slow moving lineflow (baked goods, for example), a 100% inspection can be done using a CS2 and a traversing mechanism.
The outputs of the CS2 are connected to a controlling computer which also reads the position of the CS2 as it is moved back and forth across the lineflow.
A traversing head can also extend beyond the lineflow to check against a reference color, as in the previous manila envelope example.
The paper is still lab tested, but now, with the on-line inspection, out-of-spec. color conditions can be found and corrected immediately.
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, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 11
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CS2 Color Scanner
Application Guidelines
Power Supplies
The silicon cell used in the CS2 is electrically connected to its metal package which is connected to the CS2's metal enclosure. Therefore the CS2 must be connected to a good ground, preferably the same ground as the machinery around it, and the signals from the CS2 isolated. The CS2 must be powered by a dedicated power supply, and the optional analog inputs and outputs must be isolated if they are used. The Limit outputs are isolated in the CS2.
Electrical noise
The signal level from the silicon cell is low and is amplified by high speed circuitry. This circuitry is sensitive to electrical noise from intense electrical fields. The CS2's metal enclosure is an adequate shield against most electrical interference. Use high quality shielded cable to reduce electrical noise. If analog inputs or outputs are used, they should be wired using individually shielded, twisted pairs.
Data Skew
The CS2 reads colors one at a time, in sequence. The Base color is captured 22 microseconds after the Sense color. If an object is moving while it is scanned, the information from the two colors will be skewed slightly. If an abrupt change in data occurs, the Sense/Base ratio will be momentarily incorrect. Usually this will not cause any problems. If it is a problem, it can be filtered out, either electronically in stand­alone applications or with a software filter when used with a computer. The data skew can also be reduced by decreasing the LED time (contact Delta for more information).
Color Errors
The CS2 uses an unfiltered silicon cell which captures all reflected light. It determines color by turning on only the desired color at a given time. The wavelength of the LED lighting is a function of the LEDs. This wavelength varies slightly with temperature.
Ambient light, or any other extraneous light, is an error source. The CS2's LEDs are very bright, so reasonable amounts of ambient light can be tolerated. (Don't be fooled by the apearance of the CS lighting. The LEDs are only on about 5% of the time. Your eyes average this light, making it appear 20 times less intense.)
Background Errors
In order to see o bjects, it is necessary to distinguish the m from the background. To maintain a good contrast, the background should be black in the color spectrum of
interest. If the background is paintable, a flat black paint such as Krylon 1602 can be used. Most black belting is also acceptable. Wet or otherwise reflective surfaces actually produce low backgr ound readings as long as light cannot reflect directly back into the viewer.
Because the light from the CS2 tends to dissipate in all directions, increasing the distance from the CS2 to the background will reduce the background readings. If this is done, be sure the increased distance does not allow ambient light to become a problem.
Usable results can sometimes be obtained even if the background cannot be made totally black. Ho wever, the object signal should be at least twice as strong as the background signal. The background will also contribute more errors if the Sense/Base ratio of the background is very different from the Sense/Base ratio of the objects. If this is the case the background signal must be reduced to an insignificant level.
Reflections
When either the CS2 lighting or ambient light is allowed to reflect directly into the scanner it will overdrive the circuitry and cause meaningless outputs. Usually this condition can be avoided by controlling the relative angle of the scanner to the objects and background.
In some applications it is impossible to avoid an occasional reflection. In these cases, an external optimizing computer can be used to "trap" the overdrive readings and ignore them. This technique avoids making decisions on bad data, but the overdriven data are still lost.
Intensity Variations
The CS2 lighting pattern is made up of multiple LEDs; some variation in intensity is to be expected. The larger the viewing area, (length, width, and depth), the more intensity variation will occur. The LEDs used in the CS2 are specially selected and the light pattern is optimized at the factory. The default configuration pattern is optimized for low ratio limit operation. The light pattern is adjusted such that objects outside the specified viewing area but still within the lighting area will not be read as having low Sense/Base ratios, thus eliminating false limits. If needed, other light pattern optimization techniques can be used.
Using Multiple CS2s
The scanning area of the CS2 is limited to about 1.25" by the lighting. However, multiple CS2s can be used to cover a wide area. Care must be taken to avoid interference between the units. This is easily accomplished by either physical
Delta Computer Systems, Inc.
email@deltacompsys.com http://www.deltacompsys.com
, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 12
spacing or controlling the scans. If CS2s are mounted such that the light from one does not extend into the other's viewing area, then they will not interfere with each other.
In multiple unit applications, it is often advantageous to have the units next to each other so that they take up as little space as possible. The light from each unit will extend into the adjoining unit's viewing area. In this case, interference can be avoided by using the External Trigger mode and triggering adjacent units at different times. A separation of 50 microseconds is sufficient. In applications which use a quadrature output rotary pulse generator, this can be done by connecting ajacent units to the other output phase, i.e. scanners 1, 3, 5, etc. to phase A and scanners 2, 4, 6, etc. to phase B.
If large numbers of units are requir e d, you may want to consider a custom scanner. Multiple units can be packaged into a single enclosure, resulting in a cleaner package. Units can also be packaged around a tube, etc. Contact Delta for details.
CS2 Color Scanner
Delta Computer Systems, Inc.
email@deltacompsys.com http://www.deltacompsys.com
, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 13
CS2 Color Scanner
Technical Information
Base and Sense Color
Light Source Options
Stand Off Distance
Scanning Range
Scanning Area
Response Time
Operating Modes
Two Analog Outputs
(Base and Sense)
Two Analog Inputs
(Base and Sense Threshold)
One Digital Input
(External Trigger)
Three Digital Outputs
(Data Ready, Sense
and Base Limit)
Supply Voltage
Blue, green, yellow, orange, red, and near-infrared (450nm to 950nm)
1.75 inches (44.5mm); configurable to six inches ±0.25 inches (6.4mm); configurable to ±2 inches
0.04 x 0.33 inches (1mm x 8mm); configurable to 2 inches. Various shapes and sizes available
50us Continuous or External Trigger
0-10 volts at 5 mA maximum
0-10 volts, input impedance minimum of 50k
Optically isolated, 3.5 - 24 volts, 5 mA minimum
Optically isolated, TTL/CMOS compatible;
1.6 mA minimum, 8 mA typical; 30 volt maxi mum
24 VDC (±5%)
Current Consumption
Enclosure
250 mA maximum Extruded aluminum, optional NEMA 4X
Ordering Information
License agreements provide Delta with the exclusive rights to use the CS2 technology in all applications outside of frozen potato processing. If you have any questions, please ask a Delta representative.
Company Profile
Delta Computer Systems, Inc. manufactures color scanners, motion controllers a nd other industrial controls providing high performance automation solutions to a wide range of industries.
Delta Computer Systems, Inc.
, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 14
email@deltacompsys.com http://deltacompsys.com
CS2 Color Scanner
General Application Information
The term "color" actually inplies visable light -­wavelengths from about 400 nm (violet) to about 750 nm (deep red), although in this document any color that can be seen by the CS2 is refered to as a color.
With high intensity LEDs available at 450nm (blue) and at a variety of wavelengths up to 700nm, the CS2 can see all of athese colors. But the CS2's capability does not stop there; the precision silicon photodiodes in the CS2 can see into the near-infrared (NIR) up to about 1,000nm, and LEDs are readily available in this region as well.
NIR LEDs are used in the CS2 and similar scanners for several different functions. One involves using the NIR reading to establish a baseline value that is constant (or nearly constant) regardless of the visible color of the product.
For example, to detect "browness" on cookies, any one of several visable colors can be used. But using one color (monochromatic) and looking for changes in amplitude will not produce good results, since other factors, such as dirty optics, temperature changes, etc., can produce signals that are indistinguishable from "browness" changes.
However, using the ratio of a visable color to an NIR color will give the desired result: the ratio will only change with product color, not with ambient conditions.
Here are some examples of items and applications that Delta has successfully tested:
Detecting the presence or absence of brown glue on brown wood
Detecting "browness" of crackers, etc.
Detecting green ends on carrots
Detecting white ends on asparagus
Detecting various defects on potatoes
Differentiating between tomatoes and MOT (material other than tomatoes)
Using a modified CS2, differentiating between several different colors of cloth
Using a modified CS2, ide ntifing several different colors on a cardboard box
Some of these applications are in use, and some remain in testing. More tests are done on a regular basis.
Other uses of the NIR spectrum include sorting items that can be differentiated in the NIR spectrum. Delta's CS­plus-T50 tomato sorters, for example, uses two different NIR colors to differentiate tomatoes and virtually any other item.
Delta's LGM length graders use monochromatic NIR light to detect product presence only. They function as reflective light curtains and detect products regardless of visable color. The viewing area is very long and narrow allowing the LGM to cover an area approximately two inches in diameter at about six inches from the scanner. The LGM measures product length at 1/32 inch resolution at speeds of 550 ft/min.
Delta Computer Systems, Inc.
, 11719 NE 95th Street, Vancouver, Washington 98682-2444 (360) 254-8688 15
email@deltacompsys.com http://deltacompsys.com
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