Laser Ta­chome­ter - Pre­cise Mea­sure­ment of Tor­sion­al Vi­bra­tions

Fiber optic sen­sor for non-con­tact mea­sure­ment

The new laser tachome­ter IfTA LMM2 (Laser Mea­sure­ment Mo­d­ule) is a fiber-optic sen­sor that can be used in com­bi­na­tion with an IfTA mea­sure­ment sys­tem, among other things, for non-con­tact mea­sure­ment of ro­ta­tion­al speed, an­gu­lar ve­loc­i­ty and vi­bra­tion angle on ro­tors and shafts.

The mea­sure­ment prin­ci­ple, which is based on op­ti­cal re­flec­tion, is car­ried out using a gear en­coder or zebra tape at­tached to the ro­tat­ing shaft. The high band­width and nar­row focus of the laser mean max­i­mum pre­ci­sion. The sen­sor head con­sists of a sin­gle fiber optic cable and can there­fore be placed even in lo­ca­tions that are dif­fi­cult to ac­cess.  We offer the sen­sor ei­ther as an input mod­ule for IfTA mea­sure­ment sys­tems or in its own hous­ing.

Ad­van­tages of the Laser Ta­chome­ter IfTA LMM2

Non-con­tact mea­sure­ment

Non-con­tact mea­sure­ment using laser tech­nol­o­gy en­sures high and re­li­able pre­ci­sion. Ex­ist­ing gears, slot­ted disks or even a zebra tape can be scanned.

Com­pact space-sav­ing Con­struc­tion

The sen­sor head con­sists of a sin­gle fiber optic cable and is there­fore very small and can be used well even when space is lim­it­ed. A com­plex sen­sor in­stal­la­tion is not nec­es­sary.

Wide Band­width

Thanks to the wide band­width, there are ver­sa­tile ap­pli­ca­tion pos­si­bil­i­ties. Mea­sure­ments of ro­ta­tion­al speed, tor­sion­al an­gu­lar vi­bra­tions, tor­sion­al vi­bra­tions up to torque are pos­si­ble.

Op­ti­cal Mea­sure­ment Method

The op­ti­cal mea­sure­ment method pre­vents the in­flu­ence of elec­tro­mag­net­ic in­ter­fer­ence and is in­de­pen­dent from the ma­te­ri­al's char­ac­ter­is­tics of, for ex­am­ple, gears.

Fast Setup

The LMM2 mod­ule, which gen­er­ates the laser beam and mea­sures the re­flec­tions, can be in­te­grat­ed di­rect­ly as an input mod­ule in the IfTA sys­tem. This re­sults in a sim­ple and fast mea­sure­ment setup that does not re­quire an ad­di­tion­al ex­ter­nal power sup­ply.

High Sen­si­tiv­i­ty

The high sen­si­tiv­i­ty and the very good sig­nal-to-noise ratio allow pre­cise time mea­sure­ment of slopes.

The LMM2 Mea­sure­ment Prin­ci­ple

How does the IfTA LMM2 sen­sor work?

The LMM2 sen­sor mea­sures mark­ings on a rotor based on re­flec­tion and out­puts a high band­width ana­log volt­age. Typ­i­cal mark­ing op­tions in­clude a gear, disk with holes/stripes, or a zebra tape. The small laser spot and high band­width allow sig­nals to be gen­er­at­ed with pre­cise and steep ris­ing and fall­ing edges.

In com­bi­na­tion with the input mod­ule IfTA AT2 High Speed Timer, the LMM2 acts as a tachome­ter for mea­sur­ing ro­ta­tion­al speed, an­gu­lar ve­loc­i­ty, vi­bra­tion angle and tor­sion­al vi­bra­tion on ro­tors and shafts. Si­mul­ta­ne­ous mea­sure­ments at dif­fer­ent axial po­si­tions en­able ap­pli­ca­tions such as shaft torque mea­sure­ment.

Laser Ta­chome­ter IfTA LMM2: Dual-Chan­nel Stan­dalone Mo­d­ule

  • Overview
  • Tech­ni­cal Spec­i­fi­ca­tion
  • Scope of De­liv­ery and Equip­ment
  • Ex­am­ples of Ap­pli­ca­tion
Tachometer IfTA LMM2 Standalone Version

The LMM2 is a 2-chan­nel mod­ule and com­bines one laser and one de­tec­tor unit per chan­nel for re­flec­tion mea­sure­ment. To­geth­er with the sig­nal input mod­ule IfTA AT2 High Speed Timer, it can be used as a high-pre­ci­sion en­coder.

The LMM2 mod­ule can be flex­i­bly in­te­grat­ed into mo­bile or sta­tion­ary IfTA sys­tems.

The IfTA LMM2 Stan­dalone ver­sion is par­tic­u­lar­ly rec­om­mend­ed

  • if the ap­pli­ca­tion re­quires sev­er­al mea­sur­ing points
  • if the dis­tance be­tween mea­sure­ment sys­tem and mea­sure­ment point is > 2m

High­lights

  • Laser class 2 (red) with power < 1 mW
  • In­clud­ing bi­fur­cat­ed op­ti­cal fiber with laser input, probe and de­tec­tor out­put (2 m)
  • Photo de­tec­tor with 120 kHz band­width
  • Ana­log volt­age sig­nal out­put in the range 0 ... -15 V
  • Ro­bust pro­tec­tive hous­ing made of alu­minum
Tachometer IfTA LMM2 Standalone Version

Gen­er­al

Num­ber of chan­nels:2
Sup­ply volt­age/power sup­ply unit:23 ... 25 VDC

Laser Spec­i­fi­ca­tion

Op­ti­cal per­for­mance:< 1 mW
Wave length:650 nm
Laser class:2

Photo de­tec­tor Spec­i­fi­ca­tion

Spec­tral range:400 ... 1100 nm
Band­width:0 ... 120 kHz (-3dB)
Sig­nal rise time:3 µs

Volt­age Out­put

Sen­si­tiv­i­ty:-0.43 V/µW (@650 nm)
Dark off­set volt­age:± 0.5 mV
Noise volt­age:0.2 mVrms
Sat­u­ra­tion:-14.8 V

Re­flec­tion Probe / Fiber Optic Spec­i­fi­ca­tion

Spec­tral range:400 ... 2400 nm
Numer­i­cal aper­ture:0.22
Fiber length:2 m
Mea­sur­ing dis­tance:1 mm (max. re­flec­tion)
Tachometer IfTA LMM2 Standalone Version

Scope of de­liv­ery

Sup­plied as stand­alone ver­sion in pro­tec­tive hous­ing. For full func­tion­al­i­ty a mea­sure­ment sys­tem is re­quired, but not in­clud­ed in the scope of de­liv­ery. Ideal­ly used in com­bi­na­tion with the IfTA mod­u­lar mea­sure­ment sys­tems.

The fol­low­ing op­tions are avail­able for the LMM2

  • Ex­ten­sion of the op­ti­cal fiber
  • SMA cable for the out­put sig­nal
  • An ideal com­ple­tion for pre­cise mea­sure­ment of the out­put sig­nal is the input mod­ule IfTA AT2 High Speed Timer
Tachometer IfTA LMM2 Standalone Version

Ap­pli­ca­tion ex­am­ples

  • Mea­sure­ment of tor­sion­al vi­bra­tions in drive trains, gas tur­bines, steam tur­bines, power gen­er­a­tors
  • A ro­tat­ing shaft is equipped with 100 stripes around the cir­cum­fer­ence by means of ze­brat­ape. The LMM2 de­ter­mines in a flash which stripe is in front of the sen­sor head. The ana­log out­put sig­nal is fur­ther pro­cessed by the IfTA AT2 High Speed Timers and the IfTA DSP. In this way, not only the ro­ta­tion­al speed and ro­ta­tion­al ve­loc­i­ty are de­ter­mined, but also the tor­sion­al vi­bra­tions up to the 50th order. In that way, for ex­am­ple, a tor­sion­al vi­bra­tion can be de­ter­mined with­out hav­ing to equip the rotor with a ro­tary en­coder.
Tachometer IfTA LMM2 Standalone Version

Laser Ta­chome­ter IfTA LMM2: Dual-Chan­nel Mo­d­ule for IfTA Sys­tems

  • Overview
  • Tech­ni­cal Spec­i­fi­ca­tion
  • Scope of de­liv­ery and equip­ment
  • Ex­am­ples of Ap­pli­ca­tion
Picture IfTA LMM2 input module

The LMM2 is a 2-chan­nel mod­ule and com­bines one laser and one de­tec­tor unit per chan­nel for re­flec­tion mea­sure­ment. To­geth­er with the sig­nal input mod­ule IfTA AT2 High Speed Timer, it can be used as a high-pre­ci­sion en­coder.

The LMM2 mod­ule can be flex­i­bly in­te­grat­ed into mo­bile or sta­tion­ary IfTA sys­tems.

High­lights:

  • Laser class 2 (red) with power < 1 mW
  • In­clud­ing bi­fur­cat­ed op­ti­cal fiber with laser input, probe and de­tec­tor out­put (2 m)
  • Photo de­tec­tor with 120 kHz band­width
  • Ana­log volt­age sig­nal out­put with 0 ... -15 V
Picture IfTA LMM2 input module

Gen­er­al

Num­ber of chan­nels:2
Sup­ply volt­age/power sup­ply unit:23 ... 25 VDC

Laser Spec­i­fi­ca­tion

Op­ti­cal per­for­mance:< 1 mW
Wave length:650 nm
Laser class:2

Photo de­tec­tor Spec­i­fi­ca­tion

Spec­tral range:400 ... 1100 nm
Band­width:0 ... 120 kHz(-3dB)
Sig­nal rise time:3 µs

Volt­age Out­put

Sen­si­tiv­i­ty:-0.43 V/µW (@650 nm)
Dark off­set volt­age:± 0.5 mV
Noise volt­age:0.2 mVrms
Sat­u­ra­tion:-14.8 V

Re­flec­tion Probe / Fiber Optic Spec­i­fi­ca­tion

Spec­tral range:400 ... 2400 nm
Numer­i­cal aper­ture:0.22
Fiber length:2 m
Mea­sur­ing dis­tance:1 mm (max. re­flec­tion)
Picture IfTA LMM2 input module

Scope of de­liv­ery

Sup­plied as an in­ter­change­able input mod­ule for IfTA mea­sure­ment sys­tems. For full func­tion­al­i­ty, a mod­u­lar IfTA mea­sure­ment sys­tem is re­quired.

The fol­low­ing op­tions are avail­able for the LMM2

  • Ex­ten­sion of the op­ti­cal fiber
  • SMA cable for the out­put sig­nal
  • An ideal com­ple­tion for pre­cise mea­sure­ment of the out­put sig­nal is the input mod­ule IfTA AT2 High Speed Timer
Picture IfTA LMM2 input module

Ap­pli­ca­tion ex­am­ples

  • Mea­sure­ment of tor­sion­al vi­bra­tions in drive trains, gas tur­bines, steam tur­bines, power gen­er­a­tors
  • A ro­tat­ing shaft is equipped with 100 stripes around the cir­cum­fer­ence by means of ze­brat­ape. The LMM2 de­ter­mines in a flash which stripe is in front of the sen­sor head. The ana­log out­put sig­nal is fur­ther pro­cessed by the IfTA AT2 High Speed Timers and the IfTA DSP. In this way, not only the ro­ta­tion­al speed and ro­ta­tion­al ve­loc­i­ty are de­ter­mined, but also the tor­sion­al vi­bra­tions up to the 50th order. In that way, for ex­am­ple, a tor­sion­al vi­bra­tion can be de­ter­mined with­out hav­ing to equip the rotor with a ro­tary en­coder.
  • If there are sev­er­al mea­sure­ment points, one or more IfTA LMM2 stand­alone ver­sions can be in­stalled ad­di­tion­al­ly
Picture IfTA LMM2 input module

1st Place for Laser Ta­chome­ter

Pre­sen­ta­tion of the messtec + sen­sor mas­ters award 2021

The Laser Ta­­cho­me­ter LMM2 won the 1st place of the messtec + sen­sor mas­ters award 2021 in the cat­e­go­ry mea­sure­ment. On Septem­ber 28, 2021 IfTA man­age­ment Dr. Her­­mann and Dr. Wid­hopf-Fenk, re­ceived the award at the show in Böblin­gen, Ger­many. The LMM2 is char­ac­ter­ized by high flex­i­bil­i­ty, pre­ci­sion and noise im­mu­ni­ty. It is also used for non-con­tact mea­sure­ment of tor­sion­al vi­bra­tions.

 

 

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