Difference between revisions of "NVGate Front End"

Jump to navigation Jump to search

NVGate Front End (view source)

Revision as of 12:25, 6 May 2020

10,916 bytes removed ,  12:25, 6 May 2020
→‎External Syncs
Line 565: Line 565:
Externals syncs are high speed levels comparator that provides accurate events date for the tachs and trigger. External sync is sampled at 64 tim the Front-end sampling frequency in order to achieve higher precision in delay or phase measurements.
Externals syncs are high speed levels comparator that provides accurate events date for the tachs and trigger. External sync is sampled at 64 tim the Front-end sampling frequency in order to achieve higher precision in delay or phase measurements.


For external sync or tach signals whose frequencies overload the inputs sampling rate, an internal hardware divider is available in order to lower signal frequency. The upper frequency of the external sync must be lower than 64 times the Front-end frequency range. At input frequencies greater than 300 kHz, sensitivity can be decreased due to the electronic circuitry.
[[NVGate_Tachometer#Ext._Tach|For more details : Read ext synch tach part.]]
 
In any case the maximum frequency of a signal on an Ext Sync (before any pre-divider has been applied) is 375 kHz.
 
[[Image:front_end_12_1024.png|framed|none]]
 
* '''Label''': the name of this External Sync. (by default Ext. sync. n, with 1 <nowiki><</nowiki>= n <nowiki><</nowiki>= 2). The label of each External Sync is used in the result name and in all connection tools.
* '''Threshold''': the detection level.
 
[[Image:front_end_13.png|framed|none]]
 
 
 
* '''Slope''': the slope associated with the threshold that defines the trigger detection.
 
{|border="2" cellspacing="0" cellpadding="4" width="82%" align="center"
| '''Slope'''
|'''Description'''
 
|-
|Rise
|The threshold is reached on rising edge of the External sync. signal
 
|-
|Fall
|The threshold is reached on falling edge of the External sync. signal
 
|}<br clear="all">
 
* '''Hold off''': defines the minimum time (expressed in seconds) between two pulses. If a pulse is detected before this time has expired since the last valid pulse then the new pulse is rejected. The user can enter any value between 0 and 36000s.
 
[[Image:front_end_14.png|framed|none]]
 
* '''Hystersis''': defines the hystersis around the threshold. The value can be adjusted between 0 and the full scale of the input signal (depending on the input range).
* If Slope is set to RISE, the input signal must go below Threshold - Hystersis before a new pulse can be detected.
* If Slope is set to FALL, the input signal must go above Threshold <nowiki>+</nowiki> Hystersis before a new pulse can be detected. This setting is used to reject false pulse detection following, for example, a transition of the input signal. This setting can be displayed in dB.
* '''Pre-''''''divider''': Hardware pre-divider is available after the edge detector and is used to reduce the frequency of the signal to be measured. When the tach is enabled, the measured speed take into account the pre-divider setting when displaying the true RPM value. The user can enter any integer value between 1 and 255. If tach is <nowiki>’</nowiki>On<nowiki>’</nowiki> this setting is linked to the <nowiki>’</nowiki>pulse/rev<nowiki>’</nowiki> setting.
* '''Post''''''-mutiplier:''' selection of the multiplier factor. It allows to generate an <nowiki>’</nowiki>ExtSync<nowiki>’</nowiki> signal which the pulse frequency is multiplied by the selected factor. The user can enter any integer value between 1 and 50. This is particularly used with slow time base as GPS or standard clock.
 
[[Image:front_end_15.png|framed|none]]
 
* '''Multiplier Hold off: '''defines the maximum time (expressed in percentage of the last period measured after multiplication) between a detected pulse and a simulated pulse. If a simulated pulse is detected before this time has expired since the detected pulse then this pulse is not added. By this way, the simulated signal is synchronize with the input signal. The user can enter any value between 1% and 99%.
 
[[Image:front_end_16.png|framed|none]]
 
* '''Physical qty'''.: the physical quantity applied to this External sync. It modifies the sensitivity and range peak units if necessary.
* '''Sensitivity''': the sensitivity of the transducer. Changing it updates the range peak.
* '''Range pk'''.: the maximum input level for this channel, from 300mV up to 40V. For a sensibility of 2 V/m/s<sup>2</sup> those values will be divided by 2 (0.015 m/s<sup>2</sup> and 20 m/s<sup>2</sup>) and for a gain of 0.1 those values will be multiplied by 10 (3 V and 400V). This setting can be displayed in dB.
* '''External ''''''gain''': this setting can be displayed in dB. This allows the analyzer to offset an external gain: for example if there is an external gain of 3dB, the value may be set to 3dB to retrieve the genuine amplitude of the signal.
* '''Offset comp'''.: the offset compensation in Volts.
 
[[Image:front_end_17.png|framed|none]]
 
* '''Coupling''': the coupling of this external sync.
[[NVGate_SOA_and_CBT_techniques#Tachometer_setup|This article compare the difference beetween coupling AC Vs DC for the tachometer phase.]]
 
{|border="2" cellspacing="0" cellpadding="4" width="92%" align="left"
|'''Coupling'''
|'''Description'''
 
|-
|AC
|AC coupling with signal ground connected to the analyzer hardware ground and a 0.35 Hz high pass filter.
 
|-
|DC
|DC coupling with signal ground connected to the analyzer hardware ground. It is advisable to use the DC coupling when analyzing very low frequency (<nowiki><</nowiki> 10 Hz frequency range).
 
|}<br clear="all">
 
* '''Mode: '''This setting allows selecting available signal generated by the Ext. synch input to be used by the NVGate analysis components.
 
{|border="2" cellspacing="0" cellpadding="4" width="92%"
|'''Mode'''
|'''Description'''
 
|-
|Trigger
|The Input generates events only. It can be used as trigger, start and stop of plug-in analyzers and be recorded. Recorded event occurs as 0/1 V signals. Note that the trigger event remains available on any mode.
 
|-
|Tach
|The input generates a tach signal (RPM and revolution phases) in addition to the events. See Tach § for details
 
|-
|Torsional
|The input generates the instantaneous velocity measured with the F. to V converter<ref> Optional.</ref> from a pulses train. The torsional signal is considered as a dynamic input. It appears as Tors # in the inputs list (# being the Ext sync number)
 
|-
|Torsional <nowiki>+</nowiki> Tach
|Same as above plus the tach signal is also available. The revolution phase correspond:
* to the missing teeth occurrence if missing teeth is <nowiki>></nowiki> 0
* to the ending of the pulse/rev counting at each revolution (no phase reference) if missing teeth setting is <nowiki>></nowiki> 0
 
|-
|Sampling
|The detected pulses on the inputs will be used to synchronize the SOA re-sampling algorithm. The number of pulse/rev is f free and may be different from the SAO resolution.
 
|-
|Sampling <nowiki>+</nowiki> Tors
|Combine the sampling and the Torsional modes. Both angular re-sampling and instantaneous velocity are provided by the input
 
|-
|Sampling <nowiki>+</nowiki> Tach
|Combine the sampling and the Tachometer modes. Both angular re-sampling and RPM measurement are provided by the input
 
|-
|Sampling <nowiki>+</nowiki> tach <nowiki>+</nowiki> tors
|Combine the sampling, the Tachometer and the Torsional modes. Angular re-sampling, Tachometer speed  and instantaneous velocity are provided by the input
 
|}
 
* '''Hold off (% period): '''defines the minimum time (expressed in % of the last valid tach period) between 2 tach pulses used to measure RPM.
If a pulse is detected before this time has expired since the last valid pulse then the new pulse is rejected. This is used to reject angular speed variations that are too large. This minimum time is in fact the maximum between the Hold off setting value and the value computed using the last tach period length and the Hold off (% period) setting value.
 
''Hidden/fixed: ''Hidden if Mode is Trigger or Torsional.
 
[[Image:front_end_18.png|framed|none]]
 
[[Image:front_end_19.png|framed|none]]
 
* '''Pulse / rev''': the number of pulses per revolution. The user can enter an integer value between 1 and 4092. For a non-integer number of pulses per revolution the user must use a virtual tach.
''Hidden/fixed: ''Hidden if Mode is Trigger.
 
* '''Rotation''': This setting defines the way the phase variation is counted: clockwise or counter-clockwise for each tachometer.
The rotation side is managed independently for each tachometer (Ext. sync, input, D, combined and fractional).
 
[[Image:front_end_20.png|framed|none]]
 
* '''Average size''': defines the average number used to compute the average speed. Revolution number n average speed is: avrg_speed<nowiki>[</nowiki>n-1<nowiki>]</nowiki> <nowiki>+</nowiki> (inst_speed<nowiki>[</nowiki>n-1<nowiki>]</nowiki> - avrg_speed<nowiki>[</nowiki>n-1<nowiki>]</nowiki>) / avrg_size.
''Hidden/fixed: ''Hidden if Mode is Trigger.
 
* '''Max speed''': defines the highest measured angular speed. All revolutions with a speed higher than Max speed are rejected. By default Max speed is expressed in RPM. The limit of Max speed depends on the sampling frequency of the input, on the pulse/rev and on the hold off. If the Max speed value is modified, the Min speed is automatically adjusted according to a speed ratio (''MinSpeed = MaxSpeed / SpeedRatio''). The Speed Ratio value is not able to be modified.
*
The Max speed setting is also used:
 
* to specify the limit of Y axis of the RPM profile result
* to compute the limit of the maximum order of the SOA plug-in analyzer.
''Hidden/fixed: ''Hidden if Mode is Trigger.
 
* '''Min speed''': defines the lowest measured angular speed. All revolutions with a speed lower than Min speed are forced to 0 RPM. By default Min speed is expressed in RPM. The user can enter any value between Max speed / 1000 and Max speed. The max Min speed and min Min speed are defined according to the Max speed and Speed ratio.
''Hidden/fixed: ''Hidden if Mode is Trigger.
 
* '''Missing teeth:''' This setting indicates the number of possible consecutive missing teeth (no pulses). In such case depending on the active mode:
* ''Torsional:'' the system interpolates the missing pulses intervals in order to maintain the instantaneous speed at a continuous level during the missing pulses.
OROS torsional function is able to manage fractional pulses. It offers to achieve torsional measurement on the field in a simple and easy way.
 
[[Image:front_end_21.png|framed|none]]
 
The empty area (missing teeth) length at the piano tape junction must be included between 1 and 3 teeth. The number of missing teeth must be set to the exact number of missing teeth: In this example: 2.
 
Note: the total number of teeth includes the missing teeth.
 
[[Image:front_end_22.png|framed|none]]
 
'''Attention''': The time lap of the first missing pulse must be longer than twice the time lap of the previous pulse interval
 
'''It is recommended to set the instrumentation in order to limit the number of missing pulse below 3s''': Indeed long interval without pulses will lead to a strong order 1 artefact in the instantaneous speed signal due to interpolation of sample. Remaining below 3 missing pulse provide correct measurements
 
* ''Tach:'' the system uses the missing teeth occurrence as the phase reference.
''Hidden/fixed: ''Hidden if Mode is Trigger
 
* '''Input filter:''' Select the filter to apply on the instantaneous angular velocity signal computed by the torsional converter. The applied bandwidth is the front-end one.
''Hidden/fixed: ''Hidden if Mode is Trigger or Tach


=====Aux. External Syncs=====
=====Aux. External Syncs=====
Retrieved from "https://wiki.oros.com/index.php?title=Special:MobileDiff/3755"

Navigation menu