Section 8. Operation
397
•
If the open circuit is at the end of a very long cable, the test pulse (7.6 V)
may not charge the cable (with its high capacitance) up to a voltage that
generates NAN or a distinct error voltage. The cable may even act as an
aerial and inject noise which also might not read as an error voltage.
•
The sensor may "object" to the test pulse being connected to its output,
even for 100 µs. There is little or no risk of damage, but the sensor
output may be caused to temporarily oscillate. Programming a longer
settling time in the CRBasic measurement instruction to allow
oscillations to decay before the A-to-D conversion may mitigate the
problem.
Range-Code Option
C
Over-Voltages
Input Range
Over-Voltage
±200 mV
±1000 mV
1250 mV
±5000 mV
8000 mV
Offset Voltage Compensation
Related Topics
•
Auto Self-Calibration — Overview
(p. 99)
•
Auto Self-Calibration — Details
(p. 412)
•
Auto Self-Calibration — Errors
(p. 565)
•
Offset Voltage Compensation
(p. 397)
•
Factory Calibration
(p. 96)
•
Factory Calibration or Repair Procedure
(p. 550)
Summary
Measurement offset voltages are unavoidable, but can be minimized.
Offset voltages originate with:
• Ground currents
• Seebeck effect
• Residual voltage from a previous measurement
Remedies include:
• Connect power grounds to power ground terminals (
G
)
• Use input reveral (
RevDiff
=
True
) with differential measurements
• Automatic offset compensation for differential measurements when
RevDiff
=
False
• Automatic offset compensation for single-ended measurements when
MeasOff
=
False
• Better offset compensation when
MeasOff
=
True
• Excitation reversal (
RevEx
=
True
)
• Longer settling times
Voltage offset can be the source of significant error. For example, an offset of 3
μV on a 2500 mV signal causes an error of only 0.00012%, but the same offset on
Summary of Contents for CR6 Series
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Page 76: ...Section 5 Overview 76 FIGURE 20 Half Bridge Wiring Example Wind Vane Potentiometer ...
Page 80: ...Section 5 Overview 80 FIGURE 23 Pulse Input Wiring Example Anemometer ...
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Page 454: ...Section 8 Operation 454 FIGURE 104 Narrow Sweep High Noise ...
Page 459: ...Section 8 Operation 459 FIGURE 106 Vibrating Wire Sensor Calibration Report ...
Page 535: ...Section 8 Operation 535 8 11 2 Data Display FIGURE 121 CR1000KD Displaying Data ...
Page 537: ...Section 8 Operation 537 FIGURE 123 CR1000KD Real Time Custom ...
Page 538: ...Section 8 Operation 538 8 11 2 3 Final Storage Data FIGURE 124 CR1000KD Final Storage Data ...
Page 539: ...Section 8 Operation 539 8 11 3 Run Stop Program FIGURE 125 CR1000KD Run Stop Program ...
Page 541: ...Section 8 Operation 541 FIGURE 127 CR1000KD File Edit ...
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Page 610: ...Section 11 Glossary 610 FIGURE 137 Relationships of Accuracy Precision and Resolution ...
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