L18T Photoelectric Linear Encoder

by Precizika Metrology

The sealed linear encoder L18T is used to convert linear displacements of key machine components into electrical signals containing information about the value and direction of the displacement.  The difference from encoder L18 series is that it has the other housing fixation and more stable thermal behaviour. 

The encoder consists of a glass scale installed into a rigid hollow housing and a ball-bearing-guided reading head. To be able to work in harsh environments (lubricants and chips), the encoder has sealing lips.  Filtered air can be supplied into the housing of the encoder for extra protection.

The photoelectric unit of the reading head generates sinusoidal micro-current or TTL square-wave (standard RS422) output signals.

Three versions of output signals are available:

  • L18T-A - Sinusoidal signals, with amplitude approx. 11 µApp, require external subdividing electronics.
  • L18T-AV - Sinusoidal signals, with amplitude approx. 1 Vpp, require external subdividing electronics.
  • L18T-F - Square-wave, with integrated subdividing electronics for interpolation x1, x2, x5, x10, x25x, x50.

MECHANICAL DATA

Measuring lengths (ML), mm

70; 120; 170; 220; 270; 320; 370; 420; 470; 520; 620; 720; 820; 920; 1020; 1140; 1240; 1340; 1440; 1540; 1640; 1740; 1840; 1940; 2040; 2140; 2240; 2340; 2440; 2540; 2640; 2740; 2840; 2940; 3040; 3140; 3240

(other intermediate lengths on request)

Accuracy grades to any metre within the ML (at 20°C): ±10; ±5; ±3 µm (optional)
Grating period 20 µm; 40 µm (optional)

Reference marks (RI):

-standard for ML ≤ 1020 mm

-standard for ML >1140 mm 

-optional

35mm from both ends of ML

45mm from both ends of ML

on Rl at any location, or two or more Rl's separated by distances of m x 50 mm or distance-coded

Max. traversing speed:

-when interpolation factor is 1, 2, 5, 10

-when interpolation factor is 25

-when interpolation factor is 50

1 m/s

 

0.5 m/s

0.4 m/s

Required moving force with sealing lips < 3 N

Protection (IEC 529)

-without compressed air

-with compressed air (optional)

IP53

IP64

Weight 0.4 kg + 0.8 kg/m
Operating temperature 0...+50°C
Storage temperature  -20...+70°C             
Permissible vibration (40 to 2000 Hz) ≤ 30 m/s²               
Permissible shock (11 ms) ≤ 100 m/s²

ELECTRICAL DATA

VERSION L18C-A ∼ 11 µApp L18C-AV ∼ 1 Vpp L18C-F TTL
Power supply  +5 V ± 5% / < 90 mA +5 V ± 5% < 120 mA
Light source  LED  LED  LED 
Resolution  Depends on external subdividing electronics  Depends on external subdividing electronics  5; 2.5; 1; 0.5; 0.2; 0.1 µm (after 4-fold dividing in subsequent electronics) 
Incremental signals 

Two sinusoidal l¹ and l² Amplitude at 1 k Ohm load:  

-l¹ = 7-16 µA

-l² = 7-16 µA

differential sine +AV-A and +B/-B Amplitude at 120 Ohm load:

-A=0.6-1.2 V

-B=0.6-1.2 V

Differential square-wave U1/¯U1 and U2/¯U2.

Signal level at 20 mA load current:

-low (logic "0") ≤0.5V

-high (logic "1") ≥2.4V

Reference signal 

One quasi-triangular l° peak per revolution. Signal magnitude at 1k Ohm load:

-lº - 2-8 µZ (usable component)

 One quasi-triangular +R and its complementary -R per revolution.  Signals magnitude at 120 Ohm load.

-R = 0.2-0.8 V (usable component)

 One differential square-wave U0/U0 per revolution.  Signal levels at 20 mA load current:

-low (logic "0")<0.5 V

-high (logic "1")>2.4 V

Maximum operating frequency   50 kHz  50 kHz

 50xk kHz, when interpolation factor is 1, 2, 5, 10

1000 kHz when interpolation factor is 25, 50

Direction of signals   l² lags l¹, at reading head displacement from left to right  B+ lags A+at reading head displacement from left to right  U2 lags U1 at reading head displacement from left to right
Standard cable length   3 m, without connector  3 m, without connector  3 m, without connector
Maximum cable length   5 m  25 m  25 m

Note:  if cable extension is used the power supply conductor section should not be smaller than 0.5 mm².