Campbell Scientific CR6 CR6 Measurement and Control System - Page 311

Input Limits / Common-Mode Range

Page 311 highlights

Section 8. Operation NAN (not a number) for the measurement. Automatic Range Finding For signals that do not fluctuate too rapidly, range argument AutoRange allows the CR6 to automatically choose the voltage range. AutoRange makes two measurements. The first measurement determines the range to use. It is made with a first notch frequency (fN1) of 50 kHz on the ±5000 mV range. The second measurement is made using the range determined from the first and the same fN1. Both measurements use the settling time entered in the SettlingTime parameter. Auto-ranging optimizes resolution but takes longer than a measurement on a fixed range because of the two-measurement sequences. An auto-ranged measurement will return NAN ("not a number") if the voltage exceeds the range picked by the first measurement. To avoid problems with a signal on the edge of a range, AutoRange selects the next larger range when the signal exceeds 90% of a range. Use auto-ranging for a signal that occasionally exceeds a particular range. AutoRange should not be used for rapidly fluctuating signals, particularly signals traversing multiple voltage ranges rapidly. The possibility exists that the signal can change ranges between the internal range check and the actual measurement. Table 62. Analog Voltage Input Ranges and Options Range Code Description mV50001 measures voltages between ±5000 mV mV10001 measures voltages between ±1000 mV mV2001 measures voltages between ±200 mV AutoRange1 datalogger determines the most suitable range 1 Append with C to enable common-mode null / open-input detect (p. 321) (Example: mV5000C) Input Limits / Common-Mode Range Note Much of the information in the following section is highly technical and is not necessary for the routine operation of the CR6. The information is included to foster a deeper understanding of the CR6 Input Limits specification. Summary: • Input Limits is a fixed number (±5 Vdc). It is a specification listed for the CR6 in the Specifications (p. 91) section. • Common-mode range is not a fixed number. It varies with respect to the magnitude of the input voltage. • The CR6 has features that help mitigate some of the effects of signals that exceed the Input Limits specification or the common-mode range. 311

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Section 8.
Operation
NAN
(not a number) for the measurement.
Automatic Range Finding
For signals that do not fluctuate too rapidly, range argument
AutoRange
allows the
CR6 to automatically choose the voltage range.
AutoRange
makes two
measurements.
The first measurement determines the range to use.
It is made
with a first notch frequency (
fN1
) of 50 kHz on the ±5000 mV range.
The second
measurement is made using the range determined from the first and the same
fN1
.
Both measurements use the settling time entered in the
SettlingTime
parameter.
Auto-ranging optimizes resolution but takes longer than a measurement on a fixed
range because of the two-measurement sequences.
An auto-ranged measurement will return
NAN
("not a number") if the voltage
exceeds the range picked by the first measurement.
To avoid problems with a
signal on the edge of a range,
AutoRange
selects the next larger range when the
signal exceeds 90% of a range.
Use auto-ranging for a signal that occasionally exceeds a particular range.
AutoRange
should not be used for rapidly fluctuating signals, particularly signals
traversing multiple voltage ranges rapidly.
The possibility exists that the signal
can change ranges between the internal range check and the actual measurement.
Table 62.
Analog Voltage Input Ranges and Options
Range Code
Description
mV5000
1
measures voltages between ±5000 mV
mV1000
1
measures voltages between ±1000 mV
mV200
1
measures voltages between ±200 mV
AutoRange
1
datalogger determines the most suitable range
1
Append with
C
to enable common-mode null /
open-input detect
(p. 321)
(Example:
mV5000C
)
Input Limits / Common-Mode Range
Note
Much of the information in the following section is highly technical and is
not necessary for the routine operation of the CR6.
The information is included to
foster a deeper understanding of the CR6 Input Limits specification.
Summary:
Input Limits is a fixed number (±5 Vdc).
It is a specification listed for the
CR6 in the
Specifications
(p. 91)
section.
Common-mode range is not a fixed number.
It varies with respect to the
magnitude of the input voltage.
The CR6 has features that help mitigate some of the effects of signals that
exceed the Input Limits specification or the common-mode range.
311