Your datalogger 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
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.
The datalogger enables individual modules through an addressing scheme; multiple SDMs (in any combination) can be connected to one datalogger. We recommend a maximum of four SDM-SW8As be connected to a single datalogger. After a module is enabled, it operates independently of the datalogger until additional commands are received or results are transmitted.
|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|
|Internal Sampling Frequency||500 Hz|
|Operating Voltage||9.6 to 16 V|
|Typical Current Drain||
|Operating Temperature||-25° to +55°C|
|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)|
In the CRBasic dataloggers, the SDM-SW8A operation is controlled by the SDMSW8A instruction. Instruction 102 controls the SDM-SW8A operation for Edlog dataloggers that were shipped after October 1988 (consult Campbell Scientific for equipment shipped prior to this date).
*For the CR3000 and CR5000, SDMs are connected to the ports labeled SDM-C1, SDM-C2, and SDM-C3.
**For the CR7X, SDMs connect to the C1, C2, and C3 terminals provided on the CR700X control module (after Sept 1996).
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 datalogger power supply. You can do this where ac power is available, or where a solar panel can be used for recharging the datalogger's sealed rechargeable battery.
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.