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Connector for main battery – the user can connect any type of battery (ZnMn,
alkaline, NiCd, NiMH, lithium, Pb accu, solar panel, mains adapter) with output
voltage in the range of 4Vdc – 20Vdc.
LED jumper – when jumper is closed, LED diode will indicate the operation. For
maximum power saving open the jumper. The LED indicates also when
communication with SD card can be performed. So, if LED is on, do not manipulate
(remove or insert) SD card. Otherwise, data could be either lost or partially
damaged.
If the SD card is not used it should be removed to extend battery life.
Relay output RE+ and RE- – this is optically isolated polarized solid relay output,
primary used for switching external devices. These contacts can be used for
switching power supplies for external sensors that do not share a common ground
with the LOGBOX SD.
The relay contacts are normally open and close during measurement interval. The
LOGBOX SD then takes after the programmed delay a measurement. After that the
relay opens again to switch off the sensor and limit the power consumption.
The relay can handle 60 VDC @ 300 mA.
PWR OUT output – switched battery output for powering local sensors or
instruments.
VREF output – switched reference voltage of 2.5V for bridge or similar instruments.
The whole instrument is in a plastic box (IP65 protection class) with possibility to
install outdoor directly. For smaller measuring systems it is possible to use 4 pieces
of AA battery (mignon) inside the battery compartment. It is then attached to the
cover. This solution allows the compact size of the LOGBOX SD.
The electronic design of the LOGBOX SD allows precision measurements with high
resolution. For this purpose it is equipped with two types of analog to digital
converters. They differ in resolution (12 bits or 24 bits), configuration options, speed
of conversion and applications for which they are used. Inputs for both converters
are physically the same and are configured by the software. It is possible to setup 8
unipolar inputs or 3 differential inputs and 2 unipolar inputs or combinations.
For unipolar inputs AIN6 is used as ground.
Data logger has one ground potential (referenced to power supply GND. There are
three connectors with GND potential – all are internally connected and allow
comfortable connection of battery, RS232 serial line and analog and digital inputs.
For setting up configuration of analog inputs there are few basic rules.
The highest priority is for 24 bits differential measurements, then 12 bit single
ended measurements. Depending on priority it is necessary to configure analog
inputs from AIN1 to AIN8. Practically it means that if the user wants to measure
differential signal with 24 bits resolution, this input must be located on AIN1, AIN2
(pair). If the user wants to measure two differential inputs, they must be located on
AIN1, AIN2 and AIN3, AIN4 (pairs). Only after the differential inputs there can be
single ended 12 bit resolution inputs (if any). Examples of few simple
configurations are shown in chapter 8.
Digital inputs can be configured for measuring frequency, time (when digital input is
in high logical state) or as a counter. After defining polynomial coefficients of the 3-
rd order it is converted to engineering units. The advantage is that measuring of
digital inputs is active also during sleep time (during whole period of logging). That
means if logging is configured every minute, frequency represents mean value over
one minute. If it is configured as counter, it will measure number of counts per one
minute and if it is configured for time measurement, it represents number of
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