Campbell CR3000 Micrologger, Руководство оператора

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Section 8. Operation
343
FIGURE 80: Input voltage rise and transient decay
CRBasic Measurement Settling Times
SettlingTime
Argument
Integ
Argument
Resultant
Settling Time
1
0 250 200 µs
0 _50Hz 3 ms
0 _60Hz 3 ms
integer ≥
100 integer
μs entered in
SettlingTime
argument
1
200 µs is the minimum settling time required to meet CR3000 resolution
specifications.
Settling Errors
When sensors require long lead lengths, use the following general practices to
minimize settling errors:
•
Do not use wire with PVC-insulated conductors. PVC has a high
dielectric constant, which extends input settling time.
•
Where possible, run excitation leads and signal leads in separate shields
to minimize transients.
When measurement speed is not a prime consideration, additional time can be
used to ensure ample settling time. The settling time required can be measured
with the CR3000.
•
When relatively large resistances are measured (> 1000 ohms), or
relatively long cable lengths are used (> 50 feet) with sensors requiring
current excitation, a 0.1 µf feed-forward capacitor should be placed
between the IX and IXR to prevent excessive ringing
(p. 553).
With this
capacitor present, a minimum of 3 ms is recommended for the
SettlingTime parameter in the measurement instruction. The capacitor