Setting up a Titration Test

A titration test is one where you measure the quantity of reagent required to cause a color change in the sample.

These tests can be quite difficult to run consistently, so the AutoTester helps.  If the test calls for counting the number of drops until the sample turns from blue to yellow, this can be quite subjective as there are a lot of intermediate shades.

The first step is to define the starting and target color.  This is done by defining a ColorSheet.

From the AutoTester webpage navigate (using the purple buttons on top) to the ColorSheet page.  From here you can view, edit, delete, create, and rename colorsheets.

At this point, the AutoTester is generating a live stream of what is in front of the camera. You need to place the colors to be learned in front of the camera.  There are various ways this can be done.  If the test calls for changing from red to blue, you can go to the hardware store and get paint swatches that are similar to the starting or ending color.  The AutoTester measures colors using the CIE-lab color scale which is designed to mimic human perception, so colors that seem similar to you will seem similar to AutoTester (unless you are colorblind.)  Alternatively, you can just mix the solution in the mixer tube itself.  One of the 3D printed objects is an easel that you can attach swatches to. One way or another, get the sample to be learned in front of the camera lens.  Look at the image being streamed to the webpage and make sure all the swatches are visible without a lot of glares or anything else that would prevent accurate rendering of the color.  You will capture each color swatch one at a time.  If you need to change samples between captures, you can do that.

Before capturing the colors on the colorcard, put the cover back on the AutoTester.  It is important that the lighting conditions used for capture be the same as the one used for evaluating the test.  Those are LED provided lighting with the cover on.

Now we want to create a new colorsheet (or edit one if you previously created one for this test).  To define a new colorsheet, give it a name (I usually give it a name based on what it measures (like ‘Hardness’) and the test manufacturer (like ‘API’) and click on CREATE NEW.

You have now created a new color sheet, but it is empty.  You will see it appear in the list of radio buttons above the VIEW/EDIT/DELETE/… buttons.  Click on EDIT to start adding color swatches.  This will take you to a static display screen for capturing the colors.

For titration tests you will capture 2 colors.  One is the color before the desired transition and the second is the color after the desired transition.  For the before transition color, type in a value of 0 and right click on the spot in the image that bests represents the before color.  You will see that color appear in a colortable to the left of the image.  That is the color sheet that you are building.  If you want to change the swatch, enter the value of 0 and click on the screen again.  The new color captured from that location will replace the previous color in the color sheet.  If you want to delete the color swatch, then click on that swatch in the color table.  Repeat the process to capture the “after transition” color.  Assign this a value of 1.  It is important that the colors be distinct.  The AutoTester tries to mimic human perception of when the color is more like “after Transition” than “before Transition”.  If the before color is bright blue and the after color is bluish pink, then the halfway color will likely be more blue than red.  You can also select the before and after colors to be “just before the transition” and “just after the transition”.  The important point is that the midpoint between the colors not be biased.

When you are finished, click on Done.  It will save the ColorSheet under the name you assigned previously.

Now that you have set up the ColorSheet, you can define the test.  Using the purple button navigate to the Test Setup page.  You can create a new test or edit an existing test.  If you create a test click on CREATE NEW.  This leads you to a test setup page.

There are two types of reagents for titration tests.  The first are fixed reagents.  You will add a certain number of drops (or ml) to the sample of each of these reagents.  These are reagents 1-3.  The titration reagent is the 4th reagent and it is a variable number of drops.  For a titration test, reagents 1-3 can be zero, but the titration reagent must be supplied.

  • The name of the test
  • You can create, but disable the test if you like.  This means it won’t actually run until you enable it.
  • Amount of water needed in the mixer tube (in ml)
  • What is the first fixed reagent (carousel slot number)
  • How many drops to dispense (or ml)
  • How many seconds to agitate the reagent before dispensing drops (or 0 for no agitation)
  • If there are more fixed reagents, then insert the information for the additional reagents.  If the amount to dispense is 0, then that reagent is skipped.
  • Set up if the final mixture needs to be agitated before the titration step and for how long.
  • If there is a delay (to allow the solution to set up) before the titration step, indicate that.  This is the total time since the last fixed drop was dispensed in seconds.
  • The carousel slot number of the titration reagent
  • Seconds of mixing after each drop (0 if no agitation required).  10 seconds is useful just to make sure the reagent is mixed properly after each drop.
  • Transition level.  This is normally .5 which means halfway between color 0 and color 1, but you can set it to different levels.  For example, .2 means that the color is 20% of the way between color 0 and 1 (e.g., 80% match to color 0 and 20% match to color 1).
  • Max number of drops – The maximum drops that will be dispensed in the case that the color change is not detected.  Note: if no color change was detected, then you can go to the  history page and click on the See Color link next to the test.  This will display a color table showing the detected color after each drop.  This can be useful in diagnosing if perhaps the colorsheet is off or the transition level is wrong.
  • Finally, from the drop down list, select the colorsheet that you just set up in the previous sets.
  • The results from the test are the number of drops dispensed to get the color change.
  • If you want any alarms or warnings sent to you, then enter the appropriate thresholds there.  If the value is empty, then no alarm will be sent.

One these parameters are all set up, click on Save.  The test is ready to go.

If you want to schedule the test to run automatically, then set that up from the Schedule screen.