Process evaluation using a tolerance window Process evaluation using a tolerance window | HBM

PMX Tolerance window

These instructions describe how to create a tolerance window in the PMX that can be used for a component or performance test for example. Several of those tolerance window analyses can be used at the same time. In principle, the limits of the tolerance window as well as the start and stop condition can be defined statically or using variable signals, a PLC or PC software. Those parameters can be changed at runtime resulting in a “dynamic” measurement window.

In this particular example a tolerance window is triggered by a rotary encoder during a force measurement. When the rotary angle reaches a value of 90° the window is started. When rotating 180° back to a value of -90° (or 270°) the measurement is stopped.

The upper and lower limit of the window each is defined by a constant; however a variable value is possible, too. If the upper or lower limit is exceeded during a run, a flag for signalization is set. Furthermore it is possible to display various measurement values within a window.

All those values and flags can be further processed through the analog/digital interfaces as well as through Ethernet and field bus. This allows automation of testing tasks.



For creating a tolerance-window go to “Settings” -> “Calculated channels”.

Click the  symbol and choose “Tolerance window” in the “Analysis” category.

A short description opens.
Confirm by clicking “Select”.

The generated tolerance window has to be filled with parameters now.

Define sources

Input: Declare your measuring signal here. In this particular example it is the output signal of the force sensor.

Start Input: This is the trigger for starting the window. Assign a flag for starting. Create a trigger signal for this purpose.
Generate a new calculated channel: “Trigger (pulses)”.

Assign a flag for the output of the trigger signal. Make sure that it is identical to the flag of the start input of your tolerance window. Afterwards assign a meaningful name for your trigger signal. The threshold must be exceeded for starting a measurement. Specify this as a condition.

Set the signal for angle of rotation as input. Then assign a threshold value for triggering the impulse. We want to define a constant threshold. Generate another calculated channel: “Constant signal”.

Assign a clearly relatable name and define the value to be used as the threshold for starting the window later. In this example the value is set to 90 for a quarter rotation of the rotary encoder.

The last step is to select the newly generated constant signal as the threshold for the trigger from the dropdown menu.

Stop Input: This is the trigger for stopping the window. Perform the same steps as for Start Input and make sure to choose the right trigger signal and trigger condition.

In this example a trigger signal with a constant threshold of 270 that is triggered when dropping below the threshold is used.

Threshold high: The upper threshold is the upper limit of the tolerance window. This threshold can be chosen as a variable or constant. In this example a constant with the value of 10 related to 10 N of the force signal is used.
Generate this constant as described above.

Threshold low: The lower threshold is the lower limit of the tolerance window. The same applies as for the upper threshold. Here the constant has a value of 4.

Manage outputs

Different values of a measurement can be displayed and processed in the window:
Maximum, minimum, peak to peak value, mean value, period, upper and lower limit exceeded.

Those can be assigned to a new calculated channel in each case. Exceeding of thresholds can be assigned to a flag each.

The example shows how to assign the maximum value in a window:

Select a result channel. The value is transferred to a new calculated channel here. Make sure to assign a name to be able to retrieve your value. Afterwards make user-defined settings for decimal places, physical unit and update rate according to your needs.

Exceeding of limit value

Map on digital output

To evaluate a process as effectively as possible (OK or NOK), a digital signal is generated once a limit within the window is exceeded. This digital signal can be further processed on one of the digital outputs of the PMX.

At first a flag is assigned to this signal in the settings for the tolerance window.

Then the flag can be mapped to one of the digital outputs.

For this purpose click digital outputs in the channel overview and assign the flag of the calculated channel to any output you want.

Note: Of course it is also possible to use a ProfiBus, ProfiNet or Ethercat interface for further processing.


These examples are for illustrative purposes only. They cannot be used as the basis for any warranty or liability claims.