Ther
mocouples
: The analog input circuit for
LogBox 3G
ensures the specified accuracy in the thermocouple sensor reading with a maximum
cable impedance of 100 Ω. Thermocouple sensors with impedance above 100 Ω are read by
LogBox 3G
. Accuracy, however, is not guaranteed.
For reading thermoc
ouple sensors,
LogBox 3G
uses th
e internal temperature sensor for Cold Joint compensation. Just like the internal
temperature sensor,
thermocouples may present a greater error than specified when there are sudden variations in ambient temperature. The
specified accuracy is only guaranteed when the device is installed in an environment with stable temperature for longer than one hour.
Pt100
: The
LogBox
3G
analog input circuit guarantees the accuracy specified in reading PT100 type sensors with a maximum cable resis
tance of
up t
o 25 Ω. The device can read sensors with cables that have resistance above 25 Ω, but in these cases, the accuracy and measurement range
are not guaranteed.
LogBox 3G
performs the cable resist
ance compensation internally, as long as it’s equal in the three wires connecting the
device to the sensor.
Linear 0 to 50
mV:
The analog input circuit for
LogBox 3G
ensures the specified accuracy when reading electrical voltage magnitudes fro
m 0 to
50 V
and with a maximum cable impedance of up to 100 Ω. Voltage sources with series impedance above 100 Ω can be read by
LogBox 3G
.
A
ccuracy, however, is not guaranteed.
Linear 0 to 5 V and
0 to 10 V:
The analog input circuit for
LogBox 3G
ensures the specified accuracy when reading electrical voltage ma
gnitudes
from 0 to 5 V and 0 to 10 V with a maximum cable impedance of up to 200 Ω. Voltage sources with series impedance above 200 Ω can be read by
LogBox 3
G
. Accuracy, however, is not guaranteed.
Linear 0 to 20
mA and 4 to 20 mA:
All
LogBox 3G
input channels have common grounding between each other and with the power supply.
Hence, for
LogBox 3G
to be able to correctly measure current transmitters, they need to be powered by isolated sources or by using al
l current
transmitters with the
grounding interconnected.
Digital Input
: All
LogBox 3G
input channels have common
grounding between each other and with the power supply. For
LogBox 3G
to
correctly
measure the digital input sensor, this characteristic must be considered. For correct detection of the logical levels of the sensor connected to the
di
gital input, the maximum series impedance with the sensor should be less than 10 kΩ.
Internal Te
mperature Sensor
:
LogBox 3G
has an NTC-type internal temperature sensor that can be used for monitoring ambient temperature.
This sensor is used for the Cold Joint compensation of thermocouples. Because it is located inside the device’s casing, it may present
a greater
error than specified when there are abrupt variations in ambient temperature. The specified accuracy is only guaranteed when the
device is
installed in an enviro
nment with stable temperature for longer than one hour. The sensor allows for readings in a range from -40 °C to 125 °C. The
temperature, however, is limited to the device’s operating range.
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