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Found 3 results

  1. A common industrial use case is to select the highest or lowest signal value among several similar measurements. One example is identifying the highest temperature in a reactor or distillation column containing many temperature signals. One of many situations where this is useful is in identifying the current "hot spot" location to analyze catalyst deactivation/performance degradation. When selecting the highest value over time among many signals, Seeq's max() Formula function makes this easy. Likewise, if selecting the lowest value, the min() Formula function can be used. A more challenging use case is to select the 2nd highest, 3rd highest, etc., among a set of signals. There are several approaches to do this using Seeq Formula and there may be caveats with each one. I will demonstrate one approach below. For our example, we will use a set of 4 temperature signals (T100, T200, T300, T400). Viewing the raw temperature data: 1. We first convert each of the raw temperature signals to step interpolated signals, and then resample the signals based on the sample values of a chosen reference signal that has representative, regular data samples (in this case, T100). This makes the later formulas a little simpler overall and provides slightly cleaner results when signal values cross each other. For the T100 step signal Formula: Note that the T200 step signal Formula includes a resample based on using 'T100 Step' as a reference signal: The 'T300 Step' and 'T400 Step' formulas are identical to that for T200 Step, with the raw T signals substituted. 2. We now create the "Highest T Value" signal using the max() function and the step version T signals: 3. To create the '2nd Highest T Value' signal, we use the splice() function to insert 0 values where a given T signal is equal to the 'Highest T Value'. Following this, the max() function can again be used but this time will select the 2nd highest value: 4. The process is repeated to find the '3rd Highest T Value', with a very similar formula, but substituting in values of 0 where a given T signal is >= the '2nd Highest Value': The result is now checked for a time period where there are several transitions of the T signal ordering: 5. The user may also want to create a signal which identifies the highest value temperature signal NAME at any given point in time, for trending, display in tables, etc. We again make use of the splice() function, to insert the corresponding signal name when that signal is equal to the 'Highest T Value': Similarly, the '2nd Highest T Sensor' is created, but using the '2nd Highest T Value': (The '3rd Highest T Sensor' is created similarly.) We now have correctly identified values and sensor names... highest, 2nd highest, 3rd highest: This approach (again, one possible approach of several) can be extended to as many signals as needed, can be adapted for finding low values instead of high values, can be used for additional calculations, etc.
  2. There are various methods to do this. The easiest method is by using the max() or min() functions in the Formula Tool, which are available beginning in Seeq release R21.0.40.05. Here is an example for creating a new signal which is the maximum of 4 other signals: $a.max($b).max($c).max($d) You can also see additional information in this related forum post. Content Verified DEC2023
  3. As a user, I would like to be able to display the name of the maximum signal in an organizer this will help simplify troubleshooting. Is there anyway to do this? This is relatively simple using Formula and the splice() function. The main trick is getting the string value into the scorecard metric. This can be done by creating a scorecard metric with no statistics to create a scorecard that just displays the value of this string. I have shown an example of this below. This functionality is very useful if you want to create a string signal that has more than one value. For example, say that I have three signals. I want to create a scorecard metric that tells me which of these three signals is the largest at any point in time. I will start by creating a signal who's value at any given time is the corresponding name of the signal with the max value. This can be done relatively easy with formula using the max() and splice() functions. Example Formula: $maxValue = $s1.max($s2).max($s3) 'No Max'.splice('Signal1 is Max', $s1 == $maxValue) .splice('Signal2 is Max', $s2 == $maxValue) .splice('Signal3 is Max', $s3 == $maxValue) The following shows the result of the formula. Finally, I'll use Simple Scorecard again to create a metric that displays this Max Signal for use in Organizer Topics. Content Verified DEC2023
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