Campbell Scientific CR6 CR6 Measurement and Control System - Page 108
Installation
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Section 7. Installation 108 protection against accidental short circuits. Voltage on the 12V and SW12 terminals can vary widely and will fluctuate with the dc supply used to power the CR6, so be careful to match the datalogger power supply to the requirements of the sensors. U terminals configured for 5 Vdc output are internally regulated to within ±4%, which is good regulation as a power source, but typically not adequate for bridge sensor excitation. Table Current Sourcing Limits (p. 108) lists the current limits of 12V and U terminals configured for continuous five-volt output. Greatly reduced output voltages on these terminals may occur due to current limiting if the current limits given in the table are exceeded. See Terminals Configured for Control (p. 371) for more information. Table 13. Current Source and Sink Limits Terminal Limit1 U terminal configured for voltage excitation2 ±2500 mV @ ±25 mA U terminal configured for current excitation ±2 mA SW12 switched 12 Vdc terminal3 1600 mA @ -40 °C 1100 mA @ 20 °C 640 mA @ 70 °C 500 mA @ 85 °C 12V continuous 12 Vdc termianl + SW12 terminals (combined)4 3800 mA @ -40 °C 2500 mA @ 20 °C 1350 mA @ 70 °C 1000 mA @ 85 °C U odd terminal configured for continuous 5 Vdc5 Drops to 3.5 V @ 20 mA U even terminal configured for continuous 5 Vdc5 Drops to 3.5 V @ 10 mA C terminal configured as continuous 5 Vdc5 U odd terminal configured as continuous 3.3 Vdc5 U even terminal configured as continuous 3.3 Vdc5 C terminal configured as continuous 3.3 Vdc5 5 Vdc on CS I/O Drops to 3.5 V @ 11 mA Drops to 1.85 V @ 20 mA Drops to 1.85 V @ 10 mA Drops to 1.85 V @ 11 mA TBD TBD 1 "Source" is positive amperage; "sink" is negative amperage (-). 2 Exceeding current limits will cause voltage output to become unstable. Voltage should stabilize once current is again reduced to within stated limits. 3 A thermal fuse is used to limit power. Result of overload is a voltage drop. To reset, disconnect and allow circuit to cool. Operating at the current limit is OK so long some fluctuation can be tolerated. 4 Thermal fuse protected. See footnote 3. 5 Current is limited by a current limiting circuit that holds the current at the maximum by dropping the voltage when the load is too great.