Campbell Scientific CR3000 CR3000 Micrologger - Page 329

RS-232 and TTL, 1.9 Field Calibration, 1.10 Cabling Effects

Page 329 highlights

Section 8. Operation 8.1.8 RS-232 and TTL Read More! Serial Input / Output Instructions (p. 512) and Serial I/O (p. 205). The CR3000 can usually receive and record RS-232 and 0 - 5 Vdc logic data from sensors designed to transmit via these protocols. Data are received through the CS I/O port with the proper interface (see the appendix CS I/O Serial Interfaces (p. 569) ), the RS-232 port, or the digital I/O communication ports (C1 & C2, C3 & C4, C5 & C6, C7 & C8). If additional serial inputs are required, serial input expansion modules (see the appendix Serial Input Expansion Modules ) can be connected to increase the number of serial ports. Serial data are usually captured as text strings, which are then parsed (split up) as defined in the user entered program. Note Digital I/O communication ports (control ports) only transmit 0 - 5 Vdc logic. However, they read most true RS-232 input signals. When connecting serial sensors to an Rx control port, the sensor power consumption may increase by a few milliamps due to voltage clamps. An external resistor may need to be added in series to the Rx line to limit the current drain, although this is not advisable at very high baud rates. Figure Circuit to Limit Control Port Input to 5 Volts (p. 329) shows a circuit that limits voltage input on a control port to 5 Vdc. Figure 106: Circuit to limit control port input to 5 Vdc 8.1.9 Field Calibration Read More! Field Calibration of Linear Sensors (FieldCal) (p. 156) has complete information. Calibration increases accuracy of a measurement device by adjusting its output, or the measurement of its output, to match independently verified quantities. Adjusting a sensor output directly is preferred, but not always possible or practical. By adding FieldCal() or FieldCalStrain() instructions to the CR3000 program, a user can easily adjust the measured output of a linear sensors by modifying multipliers and offsets. 8.1.10 Cabling Effects Sensor cabling can have significant effects on sensor response and accuracy. This is usually only a concern with sensors acquired from manufacturers other than Campbell Scientific. Campbell Scientific sensors are engineered for optimal performance with factory-installed cables. 329

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Section 8.
Operation
329
8.1.8 RS-232 and TTL
Read More!
Serial Input / Output Instructions
(p. 512)
and
Serial I/O
(p. 205).
The CR3000 can usually receive and record RS-232 and 0 – 5 Vdc logic data
from sensors designed to transmit via these protocols. Data are received through
the
CS I/O
port with the proper interface (see the appendix
CS I/O Serial
Interfaces
(p. 569)
), the
RS-232
port, or the digital I/O communication ports (
C1 &
C2, C3 & C4, C5 & C6, C7 & C8
). If additional serial inputs are required, serial
input expansion modules (see the appendix Serial Input Expansion Modules
) can
be connected to increase the number of serial ports. Serial data are usually
captured as text strings, which are then parsed (split up) as defined in the user
entered program.
Note
Digital I/O communication ports (control ports) only transmit 0 – 5 Vdc
logic. However, they read most true RS-232 input signals. When connecting serial
sensors to an
Rx
control port, the sensor power consumption may increase by a
few milliamps due to voltage clamps. An external resistor may need to be added
in series to the
Rx
line to limit the current drain, although this is not advisable at
very high baud rates.
Figure
Circuit to Limit Control Port Input to 5 Volts
(p.
329) shows a circuit that limits voltage input on a control port to 5 Vdc.
Figure 106: Circuit to limit control port input to 5 Vdc
8.1.9 Field Calibration
Read More!
Field Calibration of Linear Sensors (FieldCal)
(p. 156)
has complete
information.
Calibration increases accuracy of a measurement device by adjusting its output, or
the measurement of its output, to match independently verified quantities.
Adjusting a sensor output directly is preferred, but not always possible or
practical. By adding
FieldCal()
or
FieldCalStrain()
instructions to the CR3000
program, a user can easily adjust the measured output of a linear sensors by
modifying multipliers and offsets.
8.1.10 Cabling Effects
Sensor cabling can have significant effects on sensor response and accuracy. This
is usually only a concern with sensors acquired from manufacturers other than
Campbell Scientific. Campbell Scientific sensors are engineered for optimal
performance with factory-installed cables.