Pulse Detection

Pulse Detection

Use this dialog box to evaluate analog tachometer signals. The tachometer signals contain signals measured with sensors at a shaft. The threshold and hysteresis settings prevent that noisy tachometer signals lead to incorrect pulses.

Settings

Channels to be analyzed
	Time channel	Specifies the data channel containing the time values of the tachometer channel. The data channel must not contain NoValues and must start from zero. The values of the data channel must be monotonic increasing.
	Tachometer channels	Displays the data channels with the tachometer signals.
	Select Channels	Opens the channel selection list.
Calculation parameters
	Threshold	Specifies the threshold which the signal must exceed or undershoot in order to be detected as a pulse.
	Threshold reference	Specifies whether DIAdem interprets the threshold value as an absolute numeric value or as a percentage. If you select Percentage, the threshold refers to the range between the global minimum and maximum of the current tachometer channel.
	Pulses per revolution	Specifies the number of pulses for one revolution.
	Hysteresis	Specifies the hysteresis, which prevents noisy signals from resulting in incorrect pulses. If you search for increasing pulses, the tachometer signal must fall below the threshold value minus the hysteresis before the next pulse is possible. If you search for decreasing pulses, the tachometer signal must rise above the threshold value plus the hysteresis before the next pulse is possible.
	Hysteres reference	Specifies whether DIAdem interprets the hysteresis as an absolute numeric value or as a percentage. If you select Percentage, the hysteresis refers to the range between the global minimum and maximum of the current tachometer channel.
	Pulse detection	Specifies whether the pulse must increase or decrease.
	Minimum pulse width	Specifies the minimum width of a pulse. The default value is 2, which means that two consecutive tachometer values must reach the threshold for a pulse to be detected.
Tachometer signal evaluation
	Pulse start times	Calculates the time range until the next pulse occurs in seconds. The first time measures the time of the first pulse from the start of the measurement, and the subsequent times specify the intervals between the pulses.
	RPM	Calculates the RPM values between the subsequent pulses per minute.
	Index pulse start times	Calculates the indexes of the start position of the individual pulses.
	Pulse start status channel	In order to redisplay the tachometer, DIAdem sets the value 1 at the start position of every recognized pulse and fills the channel with zeros.
	Interpolate missing pulses	Specifies whether DIAdem uses linear interpolation to add missing pulses.

If you want to use waveform channels in this dialog box, follow Rule 2.3 for Calculating with Waveform Channels. If you specify a time channel although the tachometer channels are waveform channels, the sampling rate is specified from the time channel.

Note  If you do not calculate quantity-based, the pulse detection expects the numeric values to be in seconds. This means that the rpm is calculated correctly in revolutions per minute only if the time channel or the time base of the waveform channel has the unit seconds.

Result

DIAdem uses the tachometer channel length to generate the result channel PulseStartTime for the calculated pulse start times.

DIAdem generates the result channel PulseDetectedRevolution for the calculated rpm and in addition an appropriate time channel PulseDetectedRevolutionTime. DIAdem calculates the rpm only for completed revolutions. For example, if a revolution returns two pulses but 50 pulses are detected, DIAdem calculates only 25 rpm values. For every rpm value, the time channel contains the point in time of the first pulse of the respective revolution. Unlike the Pulse detection, the Order analysis for Bode display only calculates an average speed over the selected interval.

DIAdem uses the length of the tachometer channel to generate the result channel PulseStartChnLine for the calculated indexes of the start times. If the linear interpolation of the pulse positions produces values with decimal places, DIAdem rounds the values to an integer, for example, 144.55 to 145 or 144.01 to 144.

DIAdem generates the pulse start status channel PulseStartDetected with the length of the tachometer channel.

All result channels contain the channel properties Result~PulseDetection~UsedPulses, Result~PulseDetection~MissingPulses, Result~PulseDetection~MeanPulsePeriod, and Result~PulseDetection~MeanSpeed. The Result~PulseDetection~UsedPulses property contains the number of pulses used for the calculation. This value also contains the added pulses if you select the setting Interpolate missing pulses. The Result~PulseDetection~MissingPulses channel property contains the number of detected and added pulses. The Result~PulseDetection~MeanPulsePeriod property specifies the average duration of a period in seconds. The Result~PulseDetection~MeanSpeed property specifies the average rotating speed per second.

To calculate quantity-based in DIAdem, click the Calculate Quantity-Based button on the DIAdem ANALYSIS toolbar. When executing quantity-based calculations, DIAdem checks whether the program can also execute calculations on physical quantities in the same calculation. If DIAdem cannot execute the calculation because the physical quantities are unsuitable, the program displays an error message. Refer to the Help page Calculating Quantity-Based and Non-Quantity-Based in DIAdem for the conditions and rules for quantity-based calculations.

Script Call

Call SUDDlgShow("Main", ResourceDrv & "AnaChnPulseDetection")

ChnPulseDetection

Procedures

Examining Measurement Signals in the Frequency Domain

Examples

AC/DC Coupling | Adapted DIAdem Functions | Calculate Characteristics of an Oscillation | Communicating with MATLAB | Frequency Weighting (A-, B-, C-Filtering) | Hysteresis Analysis | Optimized Heating Control