Emotron CDU/CDX 48-026 [24/82] Ttl 4 channel

EMOTRON DSV 5445/5444

Page 24

 Emotron 21.04.09

5.3.2 TTL 4-channel

The TTL 4-channel encoder can be employed as an alternative to the 1Vpp encoder; however its properties

are poorer by a factor of 16, since the high analogue sampling is not activated. (JP3 flag at 255). The

relatively low number of increments per revolution still allow good travel properties with worm gears, whereby

drive noise is noticeably increased. The encoder system is only conditionally suitable or sometimes even

unsuitable for epicyclical gears or gearless drives.

The system offers perfect monitoring during cable breaks and encoder faults by evaluating the 4 tracks in the

DSV 544x system, whereby the motor needs only to move minimally to recognize this fault.

5.3.3 HTL 2-channel

The HTL encoder with two channels should be used only in emergency situations, e.g. during the conversion

of old systems where the encoder is already installed.

The system does not offer monitoring facilities by the DSV 544x during cable breaks and encoder faults, due

to the presence of only two channels.

5.3.4 Mounting of encoder and coupling

In addition to the choice of encoder, the positioning and type of coupling are, of course, highly significant for

the quality of the control characteristics of your drive. A "poor" actual speed value destroys the best

controller!

The encoder should be connected to the motor or worm gear shaft, with as little play as possible, at the

location with the highest moment of inertia. The coupling may not permit resonance, especially at the control

time constants. In this respect, couplings manufactured from sawn aluminium (Helical) and wound steel

springs (SEW) have shown themselves to be only of low suitability or even unsuitable. You can achieve good

results with periflex and bellow-type couplings; couplings with a hard rubber star must not be pressed

together under any circumstances during installation. Align the two shafts exactly and pay attention to the

instructions of the encoder manufacturer with regard to fastening the encoder to the drive unit. Secure the

connections against loosening (grub screws, locking rings, tensioning collet). Ensure that the encoder casing

is connected in an electrically conducting manner with the motor or worm gear casing.

5.3.5 Encoder cable screening

The correct and noise-free measurement of the actual speed value is very important for high-quality control

properties of your drive system. The actual speed value is part of the overall control loop. Its quality is

determined solely by the worst component, i.e. by a possibly defective actual value.

Therefore employ the cable specified by the encoder manufacturer with satisfactory cross-section, good

screening and "twisted pair" cable design.

The screen must be earthed at both ends (motor and frequency converter). Rotary encoder types without

earthed outer casings are therefore unsuitable for our application.