Campbell Scientific CS11-L Current Transformer - Manual (Page 32)

Appendix A. Theory of Operation
The CS11-L contains a 10-ohm burden (shunt) resistor (R=10 ohm).
Therefore, E is:
E = 0.01 amps • 10 ohms = 0.1 volts (or 100 mV)
From these calculations, it can be determined if a better resolution on the
measurement is needed. The Range Code can be lowered to 250 mV for some
dataloggers.
A.4 Multiplier
Use Equation D to calculate the multiplier.
m=C•n
2
/n
1
•(1/R)•(1 V/1000 mV) Equation D
Where, C = a correction constant
If a correction constant of 1 is assumed, then the equation can be solved from
the above information.
m = 1 • 2000/1 • (1/10) • (1/1000) = 0.2 multiplier
A.5 CS11-L Details
The CS11-L consists of a CR Magnectic’s CR8459 Current Transducer with a
10-ohm burden resistor incorporated into its cable (see FIGURE A-7). The
resistor allows most of our dataloggers to measure it.
CS11-L
WHITE
RED
BLACK
CLEAR
Wire Color
WHITE
RED
BLACK
CLEAR
All Other
Dataloggers
SE
CR200X
Datalogger
SE
VX (EX)
1250 mV offset
Cable
FIGURE A-7. CS11-L schematic
CR200X-series dataloggers require special treatment because they cannot
measure negative values; range is only 0 to 2500 mV (see FIGURE A-8). To
create positive reference, the CS11-L uses Voltage Excitation to shift the
measurement range (see FIGURE A-8 and FIGURE A-9).
A-4