Threshold Tab

The Threshold Unit tab allows the user to define discrimination conditions and logical operations on a selection of input signals and output the result as TTL signals in real time. This functionality and tab is available on all MF instruments.

Features

  • 4 threshold units for state detection

  • analog input signals: demodulator data (X, Y, R, Θ), PID data (error, output, shift; requires MF-PID Quad PID/PLL Controller option option)

  • digital input signals: 32 DIO channels, input and output overflows, etc.

  • threshold detection: above, below, inside, outside, rising edge, falling edge

  • absolute value and low-pass filtering can be applied prior to threshold detection

  • configurable activation and deactivation times

  • combination of up to 3 logical signals on one output with NOT, AND, OR, and XOR operation

  • minimum length, hold, and invert functionality

Description

The Threshold tab enables real-time logical analysis of measurement data in order to detect special conditions or failures, and trigger a reaction via a TTL output. Typical applications are AFM tip protection or microfluidics cell sorting. Whenever the tab is closed or an additional one of the same type is needed, clicking the following icon will open a new instance of the tab.

Table 1. App icon and short description
Control/Tool Option/Range Description

Threshold

btn mnu threshold um

Configure the threshold unit and the logical combinations to generate digital output signals.

The Threshold tab (see Figure 1) is divided in a Thresholds section on the left, and a Logic units section on the right. The rows in the Thresholds section represent the input signals of the unit and the discretization action that converts them into logical signals. The rows in the Logic units section represent the output signals of the unit and the logical operations performed to generate these signals.

functional threshold
Figure 1. LabOne UI: Threshold tab

The available input signals include analog signals such as demodulator R, but also digital inputs or error flags of the instrument such as Signal Input overload. An analog input signal can be low-pass filtered which helps to avoid false alarms when short glitches occur. After filtering the signal is discretized by comparing it to a user-defined threshold or range. Configurable minimum activation times after crossing a threshold allow further tuning of the time-domain behavior. The filtered threshold signal can be displayed in the Scope Tab which helps in defining meaningful threshold conditions. When digital signals are selected as inputs, the activation and deactivation times can be set the same way as for the analog signals. The figures below illustrate and detail the signal processing in the Threshold Unit using flow diagrams and signal graphs.

In order to output these signals on the Trigger outputs, the DIO Tab Mode setting needs to be set to Threshold units, and the Trigger output Drive needs to be enabled. By default, the four logical signals are routed as is to the four Trigger outputs. To set up more complex state detection, up to three input signals can be combined on one output using logical operations. The configuration of the logical operations in the Logic units section is collapsed by default. Base logical operators (AND, OR, XOR) as well as logical inversion (NOT) are available and grouping of the operations is indicated by brackets in the user interface.

functional tu thresholds
Figure 2. Flow diagram representing the Thresholds section of the Threshold tab.
functional tu guard
Figure 3. Signal graph showing an example of the signal processing that occurs in the Guard Timer. The Guard Timer block corresponds to the Enable/Disable settings in the Thresholds section of the Threshold tab and is represented in Figure 2.
functional tu logic units
Figure 4. Flow diagram for the Logic Units section of the Threshold tab.
functional tu hold width
Figure 5. Signal graph showing an example of the signal processing by the Hold and Width functionality of the Threshold Unit. The represented signals 1 to 5 are indicated in Figure 4.

Functional Elements

Table 2. Threshold tab
Control/Tool Option/Range Description

Signal

Select the signal source to be used in the threshold unit.

X

Select the demodulator X component as input.

Y

Select the demodulator Y component as input.

R

Select the demodulator magnitude component as input.

Θ

Select the demodulator phase component as input.

PID Out

Use the PID controller’s output signal as input. PID option needs to be installed.

PID Shift

Use the PID controller’s shift signal. PID option needs to be installed.

PID Error

Use the PID controller’s error as input. PID option needs to be installed.

DIO

Select one of the DIO channels as input.

Trigger In

Select a trigger input as input.

Trigger Out

Select a trigger output as input.

Input Overload (V)

Use voltaget input overload as input.

Input Overload (I)

Use current input overload as input.

Output Overload

Use signal output overload as input.

Aux Input Overload

Use aux input overload as input.

Aux Output Overload

Use aux output overload as input.

PID Output Overload

Use PID output overload as input.

TU Output Value

Use TU output value as input.

Channel

index

Select the channel according to the selected signal source.

Abs

ON / OFF

Takes the absolute value of an analog input signal.

TC/BW Value

numeric value

Defines the characteristic time constant of a low-pass filter applied to an analog input signal.

Value

numeric value

Shows the value after the low-pass filter.

Mode

Selects the analysis mode defining the output signal.

Above

Enable if the Signal is above Upper Threshold.

Below

Enable if the Signal is below Lower Threshold.

Outside

Enable if the Signal is outside the range [Lower Threshold, Upper Threshold].

Rising Edge

Enable if the Signal crosses Upper Threshold from below Lower Threshold. The difference between Upper an Lower Threshold defines the threshold hysteresis.

Falling Edge

Enable if the Signal crosses Lower Threshold from above Upper Threshold. The difference between Upper an Lower Threshold defines the threshold hysteresis.

Lower

numeric value

Lower threshold used to generate the output. In Rising Edge mode, this parameter defines the hysteretic behavior as the output state is reset only when the signal crosses Lower Threshold from above.

Upper

numeric value

Upper threshold used to generate the output. In Falling Edge mode, this parameter defines the hysteretic behavior as the output state is reset only when the signal crosses Upper Threshold from below.

State

low / high / toggling

Indicates the current output of the threshold unit before the Minimum Time analysis.

Enable

numeric value

Minimum duration of threshold violation needed before the output is activated. This can be used as a glitch filter.

Disable

numeric value

Minimum duration of threshold compliance needed before the output is deactivated.

State

low / high / toggling

Indicates the current output of the threshold after the Minimum Time analysis.

Not

ON / OFF

Inverts the input signal.

In

index

Selects threshold channel to be used as input.

Op

Logical operation applied to the signals to the left and right of the control.

none

No logical operation selected. No additional signals will be used to generate the output.

AND

Use a logical AND operation.

OR

Use a logical OR operation.

XOR

Use a logical XOR operation.

State

low / high / toggling

Indicates the current output of the threshold after the logical combination.

Width

numeric value

Select a minimum pulse width for the generated output signal. The width of pulses shorter than this time will be extended.

Hold

ON / OFF

Hold the output state indefinitely once it has changed to the activated state.

Inv

ON / OFF

Changes the output signal to low-active.

State

low / high / toggling

Final output state.