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3. When the Data Log Interval count has reached his count, the data logger will awake from the sleep
mode, and will take a sample and stores the data on the SD-card. When the sample is taken, the data
logger goes into sleep-mode again. This is repeated, until the time has matched the Send interval.
So, in this example, this is 3 hours.
4. When Data Send interval is reached, the data logger will wake-up, and starts to send the previously
collected data (stored on the SD-card) to the server. So, in this example, every 10 minutes a sample
is taken, and every 3 hours, 18 samples are send.
Note: So, the data logger does not perform any averaging. Even if the sample interval is much faster than
the data log interval, only one sample is stored.
The use of the sample interval is for evaluating proper behavior of the system, while the USB is
connected. Because in that case, the sample interval is valid, and the user can observe the value's
obtained from the sensor in real time. In this case, the user can evaluate these values every 5 seconds.
4.2 SDI-12
The ML-2012/13 is provided with an SDI-12 port. This port is connected to port 2 and is shared with the
normal RS232 operation. This means that the user has to select whether he wants to use RS232 or SDI-
12. When SDI-12 is selected, it acts like a SDI-12 recorder and its specific SDI-12 commands are
embedded in the driver of the input-sensor. So the user can easily select his sensor and specify its SDI-
12-adress. For more information see the description of you SDI-12 sensor.
4.2.1
SDI-12 Hardware
The SDI-12 standard is a very commonly used interface-standard in the USA. In Europe, it is rarely used.
The signal levels are quite different from those of RS232 and RS485. So, you cannot connect a SDI-12
sensor to a RS232 or RS485 port, it won't work. The use of convertors between RS232/485 and SDI-12 is
discouraged, because of the high pricing of the convertors and the bad performance (see note).
4.2.2
SDI-12 Wiring
The SDI-12 electrical interface uses the SDI-12 bus to transmit serial data between SDI-12
data recorders and sensors. The SDI-12 bus is the cable that connects multiple SDI-12 devices.
This is a cable with three conductors:
1) a serial data line, 2) a ground line and 3) a 12VDC line
Manufacturers of low power instruments
USER MANUAL
TYPE ML-2012/13
page 17
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