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5.2
DIGITAL INPUT
LogBox Wi-Fi
has a Digital Input channel that can be configured for "Pulse Count", "Event Log", or even for "Logs Control" modes. This Digital
Input can be disabled.
Regardless of the function for which it will be used, you must configure the type of sensor output that will be connected to the input: PNP, NPN, or
to see how the sensors should be connected). In addition to that, it is necessary to select the edge of
interest of the digital signal to generate the count, event, or start/end of logs: rising edge, falling edge, or both edges.
Relationship between Sensor Type, Sensor Status, and Logical Level obtained in LogBox Wi-Fi
Sensor Type
Sensor State
Logical Level
PNP
Open
0
Closed
1
NPN
Open
1
Closed
0
Dry Contact
Open
1
Closed
0
Table 3 –
Digital Input
For Dry Contact sensors, it is necessary to set a
debounce
time of at least 50 ms (sensor stabilization time / time in which the sensor must remain
in the state of interest for it to be considered valid). For PNP or NPN type sensors, if configured in "Pulse Count" mode, it is not necessary to set a
debounce
time. However, if the digital input is configured for the "Event Log" or "Logs Control" modes, a minimum
debounce
of 50 ms is required to
prevent any noise from generating a false event. In the "Event Log" and "Logs Control" modes, events will be generated after the end of the
debounce
time.
5.2.1
PULSE COUNT
When setting the digital input in "Pulse Count" mode, you can select an application mode: "Flow Rate" or "Count".
The "Flow Rate" mode allows, if "Average Flow by Acquisition Interval" is selected, to log the average flow rate or, if "Volume Since Last Reset" is
selected, to count the total volume within a previously configured period until the count is reset.
The "Count" mode, in turn, allows, if the "Acquisition Interval Counting" option is selected, to count the number of pulses that occurred within the
Log Interval or, if the "Accumulated Count Since Last Reset", to count the total number of pulses logged within a preset period until the count is
reset.
LogBox Wi-Fi
has a 32-bit register, responsible for accumulating the volume or number of pulses within a certain configurable reset interval. For
example, you can set the device to reset monthly or on a specific day and time (See
section of the
chapter).
LogBox Wi-Fi
also has a 16-bit register, responsible for measuring the average flow rate per acquisition interval or for performing the count per
acquisition interval. At each log interval,
LogBox Wi-Fi
counts the number of pulses that have occurred and registers it in memory, resetting the
register so that it can accumulate the pulses of the next interval.
If the sensor is a Dry Contact type, the
LogBox Wi-Fi
count registers (16 bits and 32 bits) will be able to count up to 10 pulses per second. For
PNP and NPN sensors, 2000 pulses per second. However, in the case of the 16-bit register, it is important to note that these pulses will accumulate
within each logging interval. Thus, if the "Average Flow Through Acquisition Interval" or "Acquisition Interval Count" modes are selected, it is
necessary to evaluate the maximum sensor frequency so that it does not exceed 65535 counts (16 bits) within the logging interval, causing an
overflow in the logger that accumulates them.
If the maximum sensor frequency is 2 kHz,
LogBox Wi-Fi
will accumulate 2000 pulses per second for up to 32 seconds. Upon exceeding this
interval, the number of accumulated pulses will exceed 65535 counts, resulting in overflow in the 16-bit register. For a sensor that can reach 2000
pulses per second, the recommended log frequency should be less than 32 seconds.
When the option "Volume since last reset" or the option "Accumulated count since last reset" is selected, the number of counts is, in turn, limited by
the 32-bit accumulator register and, thus, enables the counting of a limit number of 4294967295 pulses. Thus, the periodicity of the reset must also
be adjusted according to the frequency of the sensor pulses. By keeping the same example of sensor use at maximum frequency, i.e. 2 kHz, it is
recommended that the periodicity be less than 24 days, otherwise an overflow will be generated in the register.
In typical applications, such as flow and volume measurement, simple pulse counting is not enough, being necessary to convert these pulses into a
flow unit. For this, one can select the desired flow unit and a conversion factor which will transform the number of pulses generated by the
connected transmitter in flow information. The pulse conversion logged in the range for the flow unit configured by the user will occur every time the
logged data is displayed.
