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Required Transmitter Configuration
•
At frequencies below the crossover frequency, the duty cycle is determined by the pulse width
and the frequency.
•
At frequencies above the crossover frequency, the output changes to a 50% duty cycle.
You can change the setting for Maximum Pulse Width so that the transmitter will output a pulse width
appropriate to your receiving device:
•
High-frequency counters such as frequency-to-voltage converters, frequency-to-current
converters, and Micro Motion peripherals usually require approximately a 50% duty cycle.
•
Electromechanical counters and PLCs that have low-scan cycle rates generally use an input
with a fixed nonzero state duration and a varying zero state duration. Most low-frequency
counters have a specified requirement for Maximum Pulse Width.
Note: For typical applications, the default pulse width is used.
Example
6.6.4
Configuring the frequency output polarity
The frequency output polarity controls how the output indicates the active (ON) state. See Table 6-14.
The default value, Active High, is appropriate for most applications. Active Low may be required by
applications that use low-frequency signals.
Table 6-14
Polarity settings and frequency output levels
Polarity
Active high
Active low
Configuration and Use Manual
Crossover frequency
=
--------------------------------------------------- -
×
2
max pulse width
The frequency output is wired to a PLC with a specified pulse width
requirement of 50 ms. The crossover frequency is 10 Hz.
Solution:
•
Set Max Pulse Width to 50 ms.
•
For frequencies less than 10 Hz, the frequency output will have a
50 msec ON state, and the OFF state will be adjusted as required.
For frequencies higher than 10 Hz, the frequency output will be a
square wave with a 50% duty cycle.
Reference voltage (OFF)
0
As determined by power supply,
pull-up resistor, and load (see the
installation manual for your
transmitter)
1
Pulse voltage (ON)
As determined by power supply,
pull-up resistor, and load (see the
installation manual for your
transmitter)
0
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