NVGate CBT principle and settings - Revision history

Lmagimel at 08:58, 26 November 2024

2024-11-26T08:58:45Z

← Older revision		Revision as of 10:58, 26 November 2024
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			[[category:WikiOros]]
	Constant Band Tracking (CBT) feature consists of Order analysis calculations based on energy summation from FFT data. Summation bands (in Hz) defined by a user will be fixed over time, through run up or down condition of the measurement. The provided tach signal is connected to FFT and energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.		Constant Band Tracking (CBT) feature consists of Order analysis calculations based on energy summation from FFT data. Summation bands (in Hz) defined by a user will be fixed over time, through run up or down condition of the measurement. The provided tach signal is connected to FFT and energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.

LDesmet: English edits

2020-06-10T21:27:29Z

English edits

Lmagimel at 12:41, 29 April 2020

2020-04-29T12:41:29Z

← Older revision		Revision as of 14:41, 29 April 2020
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	Picture 6: Trigger delay setting in CBT		Picture 6: Trigger delay setting in CBT


			=== Difference beetween CBT and SOA ===

			[[NVGate_SOA_and_CBT_techniques#Principles\|Read this page.]]

Lmagimel at 12:24, 29 April 2020

2020-04-29T12:24:13Z

← Older revision		Revision as of 14:24, 29 April 2020
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	Constant Band Tracking feature consists in Order analysis calculation based on energy summation from FFT data. Summation band (in Hz) defined by user will be fixed over time, through run up or down condition of measurement. Provided tach signal is connected to FFT, energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.		Constant Band Tracking (CBT) feature consists in Order analysis calculation based on energy summation from FFT data. Summation band (in Hz) defined by user will be fixed over time, through run up or down condition of measurement. Provided tach signal is connected to FFT, energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.

	FFT Spectrum giving discrete frequency lines, energy summation will be bases on summation of spectral lines values. Minimum number of lines to be taken into account is related to windowing function used for time block filtering. Up to 8 different orders may be extracted per channels. Order selection may be different from one channel to another.		FFT Spectrum giving discrete frequency lines, energy summation will be bases on summation of spectral lines values. Minimum number of lines to be taken into account is related to windowing function used for time block filtering. Up to 8 different orders may be extracted per channels. Order selection may be different from one channel to another.

Lmagimel: Lmagimel moved page NVGate CBT principle adn settings to NVGate CBT principle and settings

2020-04-29T12:23:48Z

Lmagimel moved page NVGate CBT principle adn settings to NVGate CBT principle and settings

← Older revision	Revision as of 14:23, 29 April 2020
(No difference)

Lmagimel: /* c/ Phase calculation in Constant Band Tracking */

2020-04-29T12:23:24Z

c/ Phase calculation in Constant Band Tracking

← Older revision		Revision as of 14:23, 29 April 2020
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	Picture 5: Time domain averaging setting		Picture 5: Time domain averaging setting

	Similarly, to guaranty that core information of Trigger Block (and therefore phase information) is not filtered out by weighting window, it is recommended to center time Trigger Bock by shifting it half a block. This is made possible through feature Start Delay by adjusting it to a negative value of half the size of a trigger block (equivalent to 1/<nowiki>[</nowiki>2*f<nowiki>]</nowiki>, where f is the spectral resolution). (see picture 6)		Similarly, to guaranty that core information of Trigger Block (and therefore phase information) is not filtered out by weighting window, it is recommended to center time Trigger Bock by shifting it half a block. This is made possible through feature Start Delay by adjusting it to a negative value of half the size of a trigger block (equivalent to 1/<nowiki>[</nowiki>2*"delta"f<nowiki>]</nowiki>, where "delat"f is the spectral resolution). (see picture 6)

	[[Image:CBT_06.png\|framed\|none]]		[[Image:CBT_06.png\|framed\|none]]

	Picture 6: Trigger delay setting in CBT		Picture 6: Trigger delay setting in CBT

Lmagimel: /* b/ Frequency bandwidth definition */

2020-04-29T12:21:52Z

b/ Frequency bandwidth definition

← Older revision		Revision as of 14:21, 29 April 2020
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	From the curve shown in Picture 3, it is to be seen that applying Hanning weighting window on a pure tone sine wave will result in energy spread between the 2 side spectral lines (-1 and <nowiki>+</nowiki>1 on Picture 3) of sine frequency. Energy on the next spectral lines (-2 and <nowiki>+</nowiki>2 on Picture 3) will be reduced to 0 amplitude.		From the curve shown in Picture 3, it is to be seen that applying Hanning weighting window on a pure tone sine wave will result in energy spread between the 2 side spectral lines (-1 and <nowiki>+</nowiki>1 on Picture 3) of sine frequency. Energy on the next spectral lines (-2 and <nowiki>+</nowiki>2 on Picture 3) will be reduced to 0 amplitude.

	~~[[Image:CBT_03.gif\|framed\|none]]~~

	Picture 3: Hanning weighting window		Picture 3: Hanning weighting window

	~~In this case, if f is the spectral resolution of FFT, f<sub>0</sub> the frequency of a vibration phenomenon, minimum energy calculation for Constant Band tracking should be done at spectral lines~~:		[[Image:cbt formula.png\|framed\|none]]

	~~<nowiki>[</nowiki>(f<sub>0</sub>-f) <nowiki>+</nowiki> f<sub>0</sub> <nowiki>+</nowiki> (f<sub>0</sub><nowiki>+</nowiki>f)<nowiki>]</nowiki>~~

	~~that is to say a frequency bandwidth of~~

	~~{\|border="0" cellspacing="2" width="100%"~~
	~~\|colspan = "3"\|CBT min band~~
	~~\|= (f<sub>0</sub><nowiki>+</nowiki>f)-(f<sub>0</sub>-f)~~

	\|-
	~~\| ~~
	\|~~ ~~
	\|~~ ~~
	~~\|= 2*f~~

	\|}

	NOTE: when f<sub>0</sub> is not matching exactly one spectral line (f<sub>0</sub> is not a multiple of f) leakage phenomenon may happen. In this case energy of vibration will be spread on next closest spectral lines (on the left and right). Energy picked up at spectral lines (f<sub>0</sub><nowiki>+</nowiki>f) or (f<sub>0</sub>-f) corresponds itself to the energy component measured on a frequency band of <nowiki>[</nowiki>f<sub>0</sub><nowiki>+</nowiki>f-; f<sub>0</sub><nowiki>+</nowiki>f<nowiki>+</nowiki><nowiki>]~~</nowiki> or <nowiki>[</nowiki>f<sub>0</sub>-f-; f<sub>0</sub>-f<nowiki>+</nowiki><nowiki>~~]~~</nowiki>, where  correspond to leakage bandwidth. In OROS OR2x,  was considered to be equivalent to f/2.~~

	=====c/ Phase calculation in Constant Band Tracking=====		=====c/ Phase calculation in Constant Band Tracking=====

Lmagimel at 12:16, 29 April 2020

2020-04-29T12:16:09Z

← Older revision		Revision as of 14:16, 29 April 2020
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	~~'''Hardware type:''' OR3x~~

	~~'''Software Release:''' V2.1 and higher~~

	Constant Band Tracking feature consists in Order analysis calculation based on energy summation from FFT data. Summation band (in Hz) defined by user will be fixed over time, through run up or down condition of measurement. Provided tach signal is connected to FFT, energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.		Constant Band Tracking feature consists in Order analysis calculation based on energy summation from FFT data. Summation band (in Hz) defined by user will be fixed over time, through run up or down condition of measurement. Provided tach signal is connected to FFT, energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.

Lmagimel: /* SUBJECT: CBT Principle and Settings */

2020-04-29T12:15:53Z

SUBJECT: CBT Principle and Settings

← Older revision		Revision as of 14:15, 29 April 2020
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	~~==SUBJECT: CBT Principle and Settings<br>==~~

	'''Hardware type:''' OR3x		'''Hardware type:''' OR3x

	'''Software Release:''' V2.1 and higher		'''Software Release:''' V2.1 and higher

	~~=====/ Introduction=====~~

	Constant Band Tracking feature consists in Order analysis calculation based on energy summation from FFT data. Summation band (in Hz) defined by user will be fixed over time, through run up or down condition of measurement. Provided tach signal is connected to FFT, energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.		Constant Band Tracking feature consists in Order analysis calculation based on energy summation from FFT data. Summation band (in Hz) defined by user will be fixed over time, through run up or down condition of measurement. Provided tach signal is connected to FFT, energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.
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	FFT Spectrum giving discrete frequency lines, energy summation will be bases on summation of spectral lines values. Minimum number of lines to be taken into account is related to windowing function used for time block filtering. Up to 8 different orders may be extracted per channels. Order selection may be different from one channel to another.		FFT Spectrum giving discrete frequency lines, energy summation will be bases on summation of spectral lines values. Minimum number of lines to be taken into account is related to windowing function used for time block filtering. Up to 8 different orders may be extracted per channels. Order selection may be different from one channel to another.

	===~~==/~~ Setting Constant Band Tacking Parameters=====		=== Setting Constant Band Tacking Parameters===

	=====a/ Order amplitude extraction=====		=====a/ Order amplitude extraction=====

Lmagimel: Created page with "==SUBJECT: CBT Principle and Settings
== '''Hardware type:''' OR3x '''Software Release:''' V2.1 and higher =====/ Introduction===== Constant Band Tracking feature consi..."

2020-04-29T12:15:22Z

Created page with "==SUBJECT: CBT Principle and Settings == '''Hardware type:''' OR3x '''Software Release:''' V2.1 and higher =====/ Introduction===== Constant Band Tracking feature consi..."

New page

==SUBJECT: CBT Principle and Settings ==

'''Hardware type:''' OR3x

'''Software Release:''' V2.1 and higher

=====/ Introduction=====

Constant Band Tracking feature consists in Order analysis calculation based on energy summation from FFT data. Summation band (in Hz) defined by user will be fixed over time, through run up or down condition of measurement. Provided tach signal is connected to FFT, energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.

FFT Spectrum giving discrete frequency lines, energy summation will be bases on summation of spectral lines values. Minimum number of lines to be taken into account is related to windowing function used for time block filtering. Up to 8 different orders may be extracted per channels. Order selection may be different from one channel to another.

=====/ Setting Constant Band Tacking Parameters=====

=====a/ Order amplitude extraction=====
Order amplitude extraction from FFT spectra is highly dependant on FFT speed itself. High resolution in FFT setting (delta f very small) will result in long trigger block and consequently slow FFT refresh. Fast run or run down conditions (quickly changing vibration signature) may therefore be incompatible with slow FFT calculation. Several ways to go round this problem may be to reduce Spectrum resolution to an acceptable value and add Overlap (see picture 1) in FFT calculation.

Number of averages is also a parameter to look after as too many averages may smooth run up/down vibration signature. Contrarily too few averages may result in a noisy looking order amplitude curve.

[[Image:CBT_01.png|framed|none]]

Picture 1: Overlap setting

=====b/ Frequency bandwidth definition=====
Frequency band on which order amplitude may be extracted is to be defined by user for each channel (see picture 2). Too wide frequency band definition may lead to measurement error, as harmonics from rotation speed may be very close at low speed. For instance at 1000 RPM, Order 1 will be at 16.6Hz, Order 2 at 33.2Hz, defining a frequency band for energy summation of 50Hz for instance for order 1 will result in integrating Order 1 and Order 2 in this case. More generally speaking the amplitude value of Order 1 calculated with Constant Band Tracking technique may often be overestimated during low speed analysis process.

[[Image:CBT_02.png|framed|none]]

Picture 2: frequency bandwidth definition

Minimum frequency bandwidth available

Minimum band available is directly related to weighting window type used in FFT calculation.

Due to window shape, energy of a pure tone sine wave for instance may be split on 3 to more spectral line. Consequently a minimum frequency band will be proposed in the setting window.

Example of Hanning window:

From the curve shown in Picture 3, it is to be seen that applying Hanning weighting window on a pure tone sine wave will result in energy spread between the 2 side spectral lines (-1 and <nowiki>+</nowiki>1 on Picture 3) of sine frequency. Energy on the next spectral lines (-2 and <nowiki>+</nowiki>2 on Picture 3) will be reduced to 0 amplitude.

[[Image:CBT_03.gif|framed|none]]

Picture 3: Hanning weighting window

In this case, if f is the spectral resolution of FFT, f0 the frequency of a vibration phenomenon, minimum energy calculation for Constant Band tracking should be done at spectral lines:

<nowiki>[</nowiki>(f0-f) <nowiki>+</nowiki> f0 <nowiki>+</nowiki> (f0<nowiki>+</nowiki>f)<nowiki>]</nowiki>

that is to say a frequency bandwidth of

{|border="0" cellspacing="2" width="100%"
|colspan = "3"|CBT min band
|= (f0<nowiki>+</nowiki>f)-(f0-f)

|-
| 
| 
| 
|= 2*f

|}

NOTE: when f0 is not matching exactly one spectral line (f0 is not a multiple of f) leakage phenomenon may happen. In this case energy of vibration will be spread on next closest spectral lines (on the left and right). Energy picked up at spectral lines (f0<nowiki>+</nowiki>f) or (f0-f) corresponds itself to the energy component measured on a frequency band of <nowiki>[</nowiki>f0<nowiki>+</nowiki>f-; f0<nowiki>+</nowiki>f<nowiki>+</nowiki><nowiki>]</nowiki> or <nowiki>[</nowiki>f0-f-; f0-f<nowiki>+</nowiki><nowiki>]</nowiki>, where  correspond to leakage bandwidth. In OROS OR2x,  was considered to be equivalent to f/2.

=====c/ Phase calculation in Constant Band Tracking=====
In order to extract precise phase information from Constant Band Tracking, measurement has to be synchronised with rotational speed. Acquisitions of FFT blocks (trigger block) will need to be synchronised with Tach pulse in order to guaranty exact start condition in time (see Picture 4)

[[Image:CBT_04.png|framed|none]]

Picture 4: Trigger setup for CBT phase

''Increase of phase precision with averaging domain.''

Provided the FFT trigger condition is set to Tach pulses, averaging domain be can be set to Time. This will have for consequence to activate Time Shift Resampling (see User Note: S015-081-1 Time shift resampling) in time domain and therefore increase phase accuracy of trigger block by a factor of 16.(see Picture 5)

[[Image:CBT_05.png|framed|none]]

Picture 5: Time domain averaging setting

Similarly, to guaranty that core information of Trigger Block (and therefore phase information) is not filtered out by weighting window, it is recommended to center time Trigger Bock by shifting it half a block. This is made possible through feature Start Delay by adjusting it to a negative value of half the size of a trigger block (equivalent to 1/<nowiki>[</nowiki>2*f<nowiki>]</nowiki>, where f is the spectral resolution). (see picture 6)

[[Image:CBT_06.png|framed|none]]

Picture 6: Trigger delay setting in CBT

← Older revision		Revision as of 23:27, 10 June 2020
Line 1:		Line 1:
	Constant Band Tracking (CBT) feature consists in Order analysis ~~calculation~~ based on energy summation from FFT data. Summation ~~band~~ (in Hz) defined by user will be fixed over time, through run up or down condition of measurement. ~~Provided~~ tach signal is connected to FFT, energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.		Constant Band Tracking (CBT) feature consists of Order analysis calculations based on energy summation from FFT data. Summation bands (in Hz) defined by a user will be fixed over time, through run up or down condition of the measurement. The provided tach signal is connected to FFT and energy summation around multiple (integer or not) of rotating frequency will be calculated in real-time.

	FFT ~~Spectrum~~ giving discrete frequency lines, energy summation will be ~~bases~~ on summation of spectral lines values. ~~Minimum~~ number of lines to be taken into account is related to windowing function used for time block filtering. Up to 8 different orders may be extracted per channels. Order selection may be different from one channel to another.		For FFT Spectrums giving discrete frequency lines, energy summation will be based on the summation of spectral lines values. The minimum number of lines to be taken into account is related to windowing function used for time block filtering. Up to 8 different orders may be extracted per channels. Order selection may be different from one channel to another.

	=== Setting Constant Band ~~Tacking~~ Parameters===		=== Setting Constant Band Tracking Parameters===

	=====a/ Order ~~amplitude extraction~~=====		=====a/ Order Amplitude Extraction=====
	Order amplitude extraction from FFT spectra is highly ~~dependant~~ on FFT speed itself. High resolution in FFT setting (delta f ~~very small~~) will result in long trigger ~~block~~ and consequently slow FFT ~~refresh~~. Fast run or run down conditions (quickly changing vibration signature) may therefore be incompatible with slow FFT ~~calculation~~. ~~Several ways~~ to ~~go round~~ this problem may be to reduce Spectrum resolution to an acceptable value and add Overlap (see picture 1) in FFT calculation.		Order amplitude extraction from FFT spectra is highly dependent on FFT speed itself. High resolution in FFT setting (very small delta f) will result in long trigger blocks and consequently slow FFT refreshes. Fast run or run down conditions (quickly changing vibration signature) may therefore be incompatible with slow FFT calculations. One way to avoid this problem may be to reduce Spectrum resolution to an acceptable value and add an Overlap (see picture 1) in FFT calculation.

	~~Number~~ of averages is also a parameter to look after as too many averages may smooth run up/down vibration signature. Contrarily too few averages may result in a noisy looking order amplitude curve.		The number of averages is also a parameter to look after as too many averages may smooth run up/down vibration signature. Contrarily too few averages may result in a noisy looking order amplitude curve.

	[[Image:CBT_01.png\|framed\|none]]		[[Image:CBT_01.png\|framed\|none]]
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	=====b/ Frequency bandwidth definition=====		=====b/ Frequency bandwidth definition=====
	Frequency band on which order amplitude may be extracted is to be defined by user for each channel (see picture 2). Too wide frequency band definition may lead to measurement ~~error~~, as harmonics from rotation speed may be very close at low speed. For instance at 1000 RPM, Order 1 will be at 16.6Hz, Order 2 at 33.2Hz, defining a frequency band for energy summation of 50Hz for instance for order 1 will result in integrating Order 1 and Order 2 in this case. More generally speaking the amplitude value of Order 1 calculated with Constant Band Tracking technique may often be overestimated during low speed analysis process.		Frequency band on which order amplitude may be extracted is to be defined by user for each channel (see picture 2). Too wide of a frequency band definition may lead to measurement errors, as harmonics from rotation speed may be very close at low speed. For instance at 1000 RPM, Order 1 will be at 16.6Hz, Order 2 at 33.2Hz, defining a frequency band for energy summation of 50Hz for instance for order 1 will result in integrating Order 1 and Order 2 in this case. More generally speaking the amplitude value of Order 1 calculated with Constant Band Tracking technique may often be overestimated during low speed analysis process.

	[[Image:CBT_02.png\|framed\|none]]		[[Image:CBT_02.png\|framed\|none]]
Line 25:		Line 25:
	Minimum band available is directly related to weighting window type used in FFT calculation.		Minimum band available is directly related to weighting window type used in FFT calculation.

	Due to window shape, energy of a pure tone sine wave for instance may be split on 3 to more spectral ~~line~~. Consequently a minimum frequency band will be proposed in the setting window.		Due to window shape, energy of a pure tone sine wave for instance may be split on 3 or more spectral lines. Consequently, a minimum frequency band will be proposed in the setting window.

	Example of Hanning window:		Example of Hanning window:

	From the curve shown in Picture 3, ~~it is to be seen~~ that applying Hanning weighting window on a pure tone sine wave will result in energy spread between the 2 side spectral lines (-1 and <nowiki>+</nowiki>1 on Picture 3) of sine frequency. Energy on the next spectral lines (-2 and <nowiki>+</nowiki>2 on Picture 3) will be reduced to 0 amplitude.		From the curve shown in Picture 3, you can see that applying Hanning weighting window on a pure tone sine wave will result in energy spread between the 2 side spectral lines (-1 and <nowiki>+</nowiki>1 on Picture 3) of sine frequency. Energy on the next spectral lines (-2 and <nowiki>+</nowiki>2 on Picture 3) will be reduced to 0 amplitude.


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	=====c/ Phase calculation in Constant Band Tracking=====		=====c/ Phase calculation in Constant Band Tracking=====
	In order to extract precise phase information from Constant Band Tracking, measurement ~~has~~ to be ~~synchronised~~ with rotational speed. Acquisitions of FFT blocks (trigger block) will need to be ~~synchronised~~ with Tach ~~pulse~~ in order to guaranty exact start condition in time (see Picture 4)		In order to extract precise phase information from Constant Band Tracking, measurement have to be synchronized with rotational speed. Acquisitions of FFT blocks (trigger block) will need to be synchronized with Tach pulses in order to guaranty exact start condition in time (see Picture 4).

	[[Image:CBT_04.png\|framed\|none]]		[[Image:CBT_04.png\|framed\|none]]
Line 46:		Line 46:
	''Increase of phase precision with averaging domain.''		''Increase of phase precision with averaging domain.''

	Provided the FFT trigger condition is set to Tach pulses, averaging domain be can be set to Time. This will ~~have for consequence to~~ activate Time Shift Resampling (see User Note: S015-081-1 Time shift resampling) in time domain and therefore ~~increase~~ phase accuracy of trigger block by a factor of 16.(see Picture 5)		Provided the FFT trigger condition is set to Tach pulses, averaging domain be can be set to Time. This will activate Time Shift Resampling (see User Note: S015-081-1 Time shift resampling) in time domain and therefore increasing phase accuracy of trigger block by a factor of 16.(see Picture 5)

	[[Image:CBT_05.png\|framed\|none]]		[[Image:CBT_05.png\|framed\|none]]
Line 52:		Line 52:
	Picture 5: Time domain averaging setting		Picture 5: Time domain averaging setting

	Similarly, to guaranty that core information of Trigger ~~Block~~ (and therefore phase information) is not filtered out by weighting window, it is recommended to center time Trigger ~~Bock~~ by shifting it half a block. This is made possible through ~~feature~~ Start Delay by adjusting it to a negative value of half the size of a trigger block (equivalent to 1/<nowiki>[</nowiki>2*"delta"f<nowiki>]</nowiki>, where "delat"f is the spectral resolution). (see picture 6)		Similarly, to guaranty that core information of Trigger Blocks (and therefore phase information) are not filtered out by weighting window, it is recommended to center time Trigger Blocks by shifting them half a block. This is made possible through the 'Start Delay' feature by adjusting it to a negative value of half the size of a trigger block (equivalent to 1/<nowiki>[</nowiki>2*"delta"f<nowiki>]</nowiki>, where "delat"f is the spectral resolution). (see picture 6)

	[[Image:CBT_06.png\|framed\|none]]		[[Image:CBT_06.png\|framed\|none]]