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

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)

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

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.

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

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)

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

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

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