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Product overview

EL10xx, EL11xx 33Version: 4.5

2.7 Application notes

General note

To ensure proper function of the input circuit, the power voltage is required for the following series:

Power voltage 24V

• EL100x

• EL101x

• EL1104, EL1114

• EL18xx

Power voltage 5V

• EL1124

Notes for EL1x1x series (10µs typ.)

Application for frequency measurement

Due to their fast input filters (typ. 10µs, 10..50µs), terminals from the EL1x1x series can be used for

frequency measurement. The filter time refers to the time over which an external signal with rated voltage or

zero signal level must be present at the terminal point until it reaches the evaluation unit via the input circuit.

The maximum limit frequency depends on the following factors:

• EtherCAT cycle time

• Filter time in the input circuit

• Asymmetry of the filter time for rising and falling edge

• Duty factor for input signal

• Edge steepness of the input signal

Due to the production-related fluctuation range of the filter time the maximum limit frequency may be lower

than the upper limit defined by the cycle when the EL1x1x is used for frequency measurement.

Example:

• Task cycle: 100µs

• Actual filter time for rising edge: 10µs

• Actual filter time for falling edge: 50µs

• Duty factor 1:1

Derivation:

• Limit frequency from cycle time: 5000Hz; depending on the cycle a half-period must be detected

• Asymmetry of the filter time: 40µs

• Therefore minimum detectable half-period: 100 + 40 = 140µs

• Therefore maximum detectable limit frequency: 3500Hz

If detection of higher frequencies is required, it is advisable to either use an adequately fast input circuit (e.g.

EL1202), or the input signal must compensate the actual asymmetry in the terminal through a duty factor not

equal to 1:1.

Beckhoff EL10 Series User Manual

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