Campbell CR300 series, Operator'S Manual

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CR300-Series Datalogger
28
Options for filtering noise are:
•
4000 — for fast measurements, 0.5-ms analog-to-digital conversion
time
• 400 — 6.226-ms analog-to-digital conversion time
•
50/60 — filters 50 and 60 Hz noise, 49.812-ms analog-to-digital
conversion time
6.1.2 Resistance Measurements – Details
Bridge resistance is determined by measuring the difference between a known
voltage applied to the excitation (input) of a resistor bridge and the voltage
measured on the output arm. The CR300 supplies a precise voltage excitation
via VX terminals. Return voltage is measured on H/L terminals configured for
single-ended ( SE ) or differential ( DIFF ) input. The result of the measurement
is a ratio of measured voltages, as shown in TABLE 6-1 .
CRBasic instructions for measuring resistance include:
BrHalf() — half-bridge
BrHalf3W() — three-wire half-bridge
BrHalf4W()
— four-wire half-bridge
BrFull() — four-wire full-bridge
BrFull6W() — six-wire full-bridge
TABLE 6-1. Resistive-Bridge Circuits with Voltage Excitation
Resistive-Bridge Type and
Circuit Diagram
CRBasic Instruction and
Fundamental Relationship
Half-Bridge
1
CRBasic Instruction: BrHalf()
Fundamental Relationship 2 :
𝑋𝑋 =
𝑉𝑉
1
𝑉𝑉
𝑋𝑋
=
𝑅𝑅
𝑠𝑠
𝑅𝑅
𝑠𝑠
+ 𝑅𝑅
𝑓𝑓