SW12V 12 V Power Switch Assembly


The SW12V is a power switch that enables your datalogger datalogger to determine whether 12 Vdc power is passed onto an external device.

Read More

Benefits and Features

  • Allows an older datalogger to supply power to an HMP45C or HMP155A temperature and RH sensor only during measurement, thereby reducing current drain


Detailed Description

The SW12 provides similar functionality as a datalogger's switched 12 V terminal. Therefore, this power switch is typically used with older dataloggers (e.g., CR510, 21X, CR7) that do not have a switched 12 V terminal.

The SW12V consists of a cable that connects to the datalogger, and a terminal block for connecting the external device.

The SW12V has a shrink wrap that lists the function of each wire by color. Wiring to the power source should be red to positive (12 V), black to ground, and green to control (on a Campbell Scientific datalogger this is a control port labeled with a “C” or a universal port labeled with a "U."). Power out (to the device being powered) requires a 12 V connection and a ground connection.

Power is distributed to the remote device when the control wire is activated. Wire the power (+ lead) from the device being powered to a connection labeled “SW12V” on the SW12V green connector. Wire the ground (─  lead) to the G terminal on the SW12V green connector.


Current Ratings
  • 0.9 A (@ 20°C)
  • 0.65 A (@ 50°C)
  • 0.36 A (@ 85°C)
Control Line Voltage Range 4 to 16 Vdc
Cable Length 17.7 cm (18 in.)



The SW12V is primarily used with the redesigned HMP45C relative humidity probe (effective May, 2004) and the HMP155A relative humidity probe.

Datalogger Considerations

Compatible Contemporary Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR9000X

Compatible Retired Dataloggers

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X

Frequently Asked Questions

Number of FAQs related to SW12V: 4

Expand AllCollapse All

  1. Yes, this is possible. Keep in mind, however, that a common ground between related devices is essential for obtaining a good measurement.

  2. The maximum voltage sourced through the SW12V is 16 Vdc.

  3. The maximum current is dependent on temperature:

    • 0.9 A @ 20° C
    • 0.65 A @ 50° C
    • 0.36 A @ 85° C

    These limits are set by the polyfuse incorporated in the device.

  4. The control line voltage range is 4 to 16 Vdc. A drive current of < 0.5 mA is required.

Listed Under

Common Accessory for the following products: