USER MANUAL
TYPE ML-2012/13
Manufacturers of low power instruments
page 31
4.14.2 Digital Pulse Sensor
Digital Pulse sensors like for instance rain gauges are based upon the “reed contact” principle. The rain
gauge has an internal bucket with a very precise volume. It is constructed to tip over when it reaches a
specified amount of water. The water is drained and while the bucked was turning, a magnet triggered a
magnetic switch, a so called “reed contact” So, the rain gauge itself works like a passive switch. The data
logger has a special input to trigger on these events. Even when the data logger is sleeping, the event of
a tipping bucked is never missed. The data logger uses a so called “interrupt-input” to make this possible.
To connect a rain-gauge, use this interrupt input and connect the other site
of the rain gauge to the 3V6
output.
Note:
The digital input offers the most energy-friendly measurements available. This is because the data logger
is allowed to sleep most of the time, and only capture the events of the digital interrupt (e.g. the tipping
bucket of a rain gauge). In the situation where only one digital sensor is used, the battery is probably
going to last much longer than any other measurement. For safety-reasons a user can include some
internal measurements in the configuration, to allow monitoring of the performance of the system.
Example configuration Rain Measurement
Here an example is shown for a tipping Bucket Rain Gauge, and how to set it up in the data logger.
The Rain-gauge should be connected to the “Digital input”
Underneath the menu for this input is shown.
First, change the name “Digital Pulse” into a more comprehensive one. We use “Rain” here.
The menu-item “pulses per unit” is very important and converts the input pulses into a physical value.
It is advised to test the hardware first, before proceeding to selecting the right settings for bucket-size etc.
Therefore leave this value (1) and test your sensor first.
To test , just connect it, and apply a known amount of pulses tot the data logger. You can verify this count
with the command
<Ctrl>A<Shift>V<Ctrl>D
When this is correct you can proceed to set up your
rain-gauge.
Now you have to enter the physical details of your rain-gauge.
Digital Pulse Sensor
[0] Exit
[1] Name >> Digital Pulse
[2] Sample interval >> Normal 00:00:10; Alarm Not used
[3] Port mode >> Internal Pull Down
[4] Pulses per unit >> 5
[5] Register mode >> Pulse (low frequency)
[6] Register value >> 1 Pulses
[7] Register reset >> Disabled
[8] Counter (unit) >> Counter
[9] Quantity (unit) >> Not used
[A] Mean Rate (unit/h) >> Not used
[B] Max Rate (unit/h) >> Not used
[C] Min Rate (unit/h) >> Not used
[R] Remove
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