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Date Created: 7/24/2000   Date Modified: 5/6/2016

-DTP41 Strip definition - How to read a custom strip

The DTP41 is an accurate, powerful, fast  strip reading spectrophotometer. The only problem with such a powerful tool, is that users often find that they'd like to do more with it than can be done with the software they use with it every day. A frequent call to the applications desk is "how do I do X with my DTP41?" Below we will outline the basic steps to use to retrieve data from the DTP41 using the supplied ToolCrib software. To illustrate this we will use the calibration strip as the strip to read from. You can design your own strip if you want, following some simple guidelines also outlined below.

Designing the Strip

There are several elements in any successful strip design, all of which can be seen in the calibration reference supplied with the DTP41. The minimum recommended patch size is 7mm in the direction of travel and 13mm wide, this allows for easy positioning of the strip in the reader. Each patch is delineated by a gap, or divider which is .5D in shift from the patches on either side. The most common gap colors are thus white, 50% gray and black. While the minimum gap size is only .5mm it is strongly recommended that you use a larger gap, which allows for more variation in the printed output, here we use the standard recommended size of 2mm. The above elements seem relatively obvious, but their are two other pieces that are also important for a successful strip design: The leader and trailer. The leader is defined as the material before the first patch. The DTP41 requires a minimum of a 1.5 inch leader, with at least .5 inch of clean base before the first patch. The trailer length is defined as at least the width of two patches plus two separators. In the above design, the minimum trailer is then 7mm+2mm+7mm+2mm=18mm. This is very important almost every day we get a call from a distraught user who was a bit to tight with the scissors!

Defining the Strip

Just like you need a road map to know where you are, the DTP41 requires a "roadmap" of the strip you want it to read. This roadmap is the strip definition (the DS command) which consists of 5 distinct parts for a reflection strip and 6 parts for a transmission strip.

Number of placesDescriptionOptionsExample StripTrans-
parency Strip
3 number of patches 1-100 011 011
4 Patch size, expressed in millimeters with an implied decimal point in the middle Patches can be up to xx in size 1000 1000
4 Gap size, expressed in millimeters with an implied decimal point in the middle Gaps can be no more than 40% of the size of a patch. 0200 0200
1 Strip is normal (0) or step wedge (1). Step wedge is only for measuring dot area Step wedges must ascend or descend and include a solid and paper patch. 0 0
1 color mode, Choose a single color (for dot readings) or auto (8) for all others 8 8
4 trailer length This is only used for transparencies and is defined as the length of material after the last patch, subtracting 2 patch and gap widths N/A 0016 (40mm - 24mm)

Looking at the chart above one can then see that the strip definition for the Calibration reference above is 0111000020008DS. If this were a transmission strip we would use the same definition with the addition of the trailer length 01107000200080016DS. But what do you do with this definition? Lets look at ToolCrib:


ToolCrib is a utility program that ships with every DTP41. There is a version for the Windows platform and the Macintosh platform. This contains a simple setup tool, as well as a dedicated terminal (communications) window. When you first start ToolCrib you will be asked to select the instrument and serial port. After a successful connection you are presented with a blank window. Go to the menu bar and Select Tools>Setup. The Setup window is divided into two sections: The left window is dynamic and allows you to set certain parameters of your instrument. Most likely the only two things you will want to change here will be data type, and whether you are reading in reflective or transmission mode. The Right window reveals certain things about your instrument including the firmware installed and the boot version of firmware. After setting the data type you want, you will once again use the Tools menu to select the Terminal tool.

The Terminal tool is where we send commands to the instrument and it sends back data along with status codes that allow it to speak to you. This is the window where we will enter our strip definition. Before we do this, lets verify that the instrument is talking correctly, and contains no errors. Type: sv [return] This should return the instrument type and the firmware followed by a <00> "I'm okay" status code. Any other code should be cleared with the xe [return] command. This will list all errors and clear them. Now use the the strip definition from above: 0111000020008DS [return]. You might also want to set a configuration switch to auto-transmit the data after you read a strip. This can be done using the 0105cf [return] switch.

Let's Try it!

After selecting the data type you want in the Setup menu and entering your strip definition in the Terminal window you are ready to read the strip! With the terminal window insert the cal reference until it hits the back rollers, centering the patches under the two lines on the front of the DTP41. Push the black pushbutton. After a second or so the strip should be pulled through the instrument. Assuming that the light returned directly to green, you should see data in the terminal window if you used the 0105cf [return] switch. If you didn't turn auto-transmit on, use the ts [return] command to transmit the strip data. Now try it with your own strip, just make sure you follow the rules stated above and you can easily read any DTP41 compatible strip into ToolCrib.