Hubner AMP 41, Operating And Assembly Instructions Manual

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32 AMP(H)41_MANUAL-en_R11 - 2019-03-28
Absolute Encoder AMP(H) 41
5.6.2 Option HTL-Level, 13...27 V DC
Optionally the incremental interface is available also with HTL levels. For technical reasons, the
user must consider the following boundary conditions at this variant: Ambient temperature,
cable length, cable capacitance, supply voltage and output frequency.
In this case the maximum reachable output frequencies about the incremental interface are a
function of the cable capacitance, the supply voltage and the ambient temperature. Therefore,
the use of this interface is reasonable only if the interface characteristics meet the technical
requirements.
From the view of the measuring system, the transmission cable represents a capacitive load
which must be reloaded with each impulse. In dependence of the cable capacitance, the load
quantity necessary for it varies very strongly. Exactly this reloading of the cable capacitances is
responsible for the high dissipation and heat, which result thereby in the measuring system.
Example: Cable with 75 pF/m, cable length = 100 m, half limiting frequency related to the rated
voltage of 24 V DC: It results a twice as high current consumption of the measuring system.
By the arising heat the measuring system may be only operated with approx. 80% of
the given working temperature.
The following diagram shows the different dependences with respect to three different
supply voltages.
Fixed items are

Capacity of the cable: 75 pF/m

Ambient temperature: 25 °C
Fig. 7: Cable length / Limiting frequencies
Other cable parameters, frequencies and ambient temperatures as well as bearing heat and
temperature increase over the shaft and flange, can produce a considerably worse result in the
practice.
Therefore, the fault-free function of the incremental interface with the application-dependent
parameters has to be checked prior to the productive operation.