This product is no longer available and has been replaced by: SDM-IO16A.
SDM-SW8A 8-Channel Switch Closure Input Module
Services Available
Repair Yes
Free Support Yes


Your data logger can measure more switch closures or voltage pulses with an SDM-SW8A. Sensors that output a switch closure or voltage pulse signal include tipping bucket rain gages, flow meters, and anemometers.

Read More

Benefits and Features

  • Well suited for use in energy management studies
  • Provides eight individually configured channels
  • Measures a variety of signals: reed switches, dry contacts, or slow voltage pulses
  • Allows up to four SDM-SW8As to be connected to a single data logger


Detailed Description

The SDM-SW8A provides eight channels for connecting the sensors. Each channel is individually configured for single-pole double-throw (SPDT), single-pole single-throw (SPST), or voltage pulse measurements. Output options include counts, duty cycle, and state.

SDM Operation

The data logger enables individual modules through an addressing scheme; multiple SDMs (in any combination) can be connected to one data logger. We recommend a maximum of four SDM-SW8As be connected to a single data logger. After a module is enabled, it operates independently of the data logger until additional commands are received or results are transmitted.


Function Increases the number of switch closures or voltage pulses a data logger can measure.
Number of Channels 8
Measurement Types Switch closure (SPDT, SPST), dc voltage pulse
Input Voltage Threshold From below 0.9 to above 4.0 Vdc (±20 Vdc maximum)
Maximum Input Frequency 100 Hz (50% duty cycle)
Minimum Input Pulse Width 5 ms high, 5 ms low
Maximum Bounce Time 3 ms open without counting
Output Options State, duty cycle, counts
Maximum Count/Port 65535
Internal Sampling Frequency 500 Hz
Watchdog Reset Yes
Operating Temperature -25° to +55°C
Operating Voltage 9.6 to 16 V
Typical Current Drain
  • 3 mA quiescent
  • 6 mA active (maximum)
Relative Humidity 0 to 90% RH (non-condensing)
Maximum Cable Length 6 m (20 ft) total to all SDM devices
Consult Campbell Scientific if longer lengths are necessary.
Dimensions 15.7 x 6.9 x 2.3 cm (6.2 x 2.7 x 0.9 in.)
Weight 0.23 kg (0.5 lb)


Note: The following shows notable compatibility information. It is not a comprehensive list of all compatible or incompatible products.

Data Loggers

Product Compatible Note
21X (retired)
CR10 (retired)
CR1000 (retired)
CR10X (retired)
CR200X (retired)
CR206X (retired)
CR211X (retired)
CR216X (retired)
CR23X (retired)
CR295X (retired)
CR3000 (retired) For the CR3000, SDMs are connected to the ports labeled SDM-C1, SDM-C2, and SDM-C3.
CR500 (retired)
CR5000 (retired) For the CR5000, SDMs are connected to the ports labeled SDM-C1, SDM-C2, and SDM-C3.
CR510 (retired)
CR800 (retired)
CR850 (retired)
CR9000 (retired)
CR9000X (retired)

Mounting Equipment

Product Compatible Note

Distributed Data Acquisition

Product Compatible Note
Granite 10
Granite 6
Granite 9

Additional Compatibility Information

Data Logger Considerations


In the CRBasic data loggers, the SDM-SW8A operation is controlled by the SDMSW8A instruction. Instruction 102 controls the SDM-SW8A operation for Edlog data loggers that were shipped after October 1988 (consult Campbell Scientific for equipment shipped prior to this date).

Power Supply

Due to the 3 mA continuous and 6 mA active current drain, an auxiliary 12 Vdc power supply is recommended for powering the SDM-SW8A in remote, long-term applications.

For some applications, it may be convenient to use the data logger power supply. You can do this where ac power is available, or where a solar panel can be used for recharging the data logger's sealed rechargeable battery.

Enclosure Considerations

The SDM-SW8A requires a desiccated, non-condensing environment; a Campbell Scientific enclosure is recommended. Grommets and screws are provided to attach the SDM-SW8A to the backplate of our enclosures.

Case Studies

Flemish Coast: Pile Monitoring
Cofely Fabricom NV/SA (GDFSuez) has utilized Campbell Scientific equipment on numerous projects in both more
This Product Replaced

Privacy Policy Update

We've updated our privacy policy.  Learn More

Cookie Consent

Update your cookie preferences.  Update Cookie Preferences