Difference between revisions of "NVGate Torsional"

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NVGate Torsional (view source)

Revision as of 14:23, 1 October 2026

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Add quick guide for the operator: what to enter in NVGate (Pulse / rev, Missing teeth), 8-pulse example, measured typical mistakes
(Add quick guide for the operator: what to enter in NVGate (Pulse / rev, Missing teeth), 8-pulse example, measured typical mistakes)
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<font color="#0070C0"><u>''''' Piano tape junction for fractional missing pulse management'''''</u></font>
<font color="#0070C0"><u>''''' Piano tape junction for fractional missing pulse management'''''</u></font>


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 '''integer part''' of the gap length: in this example (gap of 2.x teeth): 2. See [[#Setting Pulse/rev and Missing teeth for a fractional gap|Setting Pulse/rev and Missing teeth for a fractional gap]] below.
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 '''integer part''' of the gap length: in this example (gap of 2.x teeth): 2. See the [[#Quick guide for the operator: what to enter in NVGate|quick guide for the operator]] below.


Note: the total number of teeth includes the missing teeth. By example, an encoder with '''24 pulse/rev''' and '''1 missing teeth''' must be set as :  
Note: the total number of teeth includes the missing teeth. By example, an encoder with '''24 pulse/rev''' and '''1 missing teeth''' must be set as :  
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'''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 3s for the missing pulse provide correct measurements.
'''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 3s for the missing pulse provide correct measurements.
====Quick guide for the operator: what to enter in NVGate====
You only need to enter '''two numbers''' in the Ext. sync. settings: '''Pulse / rev''' and '''Missing teeth'''.
{|class="wikitable" style="width:100%;"
!Word!!What it means
|-
|'''Pulses on the shaft'''||The stripes (or teeth) that you can actually '''count''' on the shaft. The gap is not counted.
|-
|NVGate setting '''Missing teeth'''||How many pulses would fit in the gap. Keep only the '''whole number'''.
|-
|NVGate setting '''Pulse / rev'''||'''Pulses on the shaft + Missing teeth'''. It is '''not''' the number of stripes you count.
|}
[[File:Torsional_operator_8_pulses.png|900px|none]]
=====Three steps=====
# '''Count the pulses on the shaft.''' Example: '''8'''.
# '''Look at the gap: how many pulses would fit in it?''' Keep the whole number. Example: 2.4 → '''2''' (2.1 → 2, 2.9 → 2, 1.3 → 1).
# '''Enter in NVGate''': Missing teeth = '''2''' and Pulse / rev = 8 + 2 = '''10'''.
'''How to estimate the gap with a ruler''': measure the normal spacing between two stripes (from the start of one black stripe to the start of the next one), then the distance from the start of the last stripe before the gap to the start of the first stripe after it.
Pulses that fit in the gap = (that distance ÷ normal spacing) − 1. Example: 34 mm ÷ 10 mm − 1 = 2.4 → Missing teeth = 2.
=====Examples=====
{|class="wikitable" style="width:100%;"
!On the shaft!!Pulses counted!!Pulses that fit in the gap!!NVGate Missing teeth!!NVGate Pulse / rev
|-
|Piano tape (picture above)||8||2.4||'''2'''||'''10'''
|-
|Encoder 60-2 (60 teeth, 2 removed)||58||2||'''2'''||'''60'''
|-
|Encoder 24-1||23||1||'''1'''||'''24'''
|-
|Piano tape||37||1.7||'''1'''||'''38'''
|-
|Piano tape||45||2.9||'''2'''||'''47'''
|}
=====Check after setting=====
Run the shaft at a constant speed and look at the Tors signal: it must be '''flat''', with '''no spike once per revolution''', and its mean value must match the speed given by another sensor. If not, see the typical mistakes below.
=====Typical mistakes (example: 8 pulses, gap of 2.4)=====
{|class="wikitable" style="width:100%;"
!Mistake!!What is entered!!What you see
|-
|'''Pulse / rev = only the pulses counted''' (Missing teeth not added)||Pulse / rev 8, Missing teeth 2||Speed '''wrong by +39 %'''
|-
|'''Missing teeth too small''' by one||Pulse / rev 9, Missing teeth 1||Speed '''too high by +16 %''', but the signal looks flat — easy to miss
|-
|'''Missing teeth = 0''' although there is a gap||Pulse / rev 8, Missing teeth 0||A '''big spike once per revolution''' (up to 62 %), mean speed +10 %
|-
|'''Missing teeth rounded up'''||Pulse / rev 11, Missing teeth 3||Correct here, but not always (a gap of 1.3 set to 2 is wrong). Always keep the whole number.
|}
With only a few pulses per revolution these mistakes are obvious. With many pulses (for example 58) the same mistakes give only a few percent and can go unnoticed: always do the check above.
The gap must be at least 1 pulse long and at most 3 pulses (see above). The detailed test results are given in [[#Annexe : Setting Pulse/rev and Missing teeth|the annex at the end of this page]].


===Tutorial ===
===Tutorial ===
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