Power Considerations; Sdm-Cd16D; Connection Block Diagrams - Campbell SDM-CD16D Instruction Manual

3. Power Considerations

NOTE
SDM-CD16D 16 Channel Digital Control Port Expansion Module
The SDM-CD16D power requirements are large compared to most Campbell
Scientific products when driving significant loads. For many applications an
external power supply, as shown in Figure 3, is recommended to power the

SDM-CD16D.

For some applications it may be convenient to use the datalogger supply to
power the SDM-CD16D, as shown in Figure 3. For long-term applications, the
lead-acid power supply available with Campbell Scientific dataloggers should
be used, allowing the batteries to be float charged. Alkaline batteries are not
recommended for long term applications.
SDM-CD16D
Connection with External Supply
SDM-CD16D
Connection with Datalogger Supply
FIGURE 3. Connection Block Diagrams
If the 21X power supply is used to power the SDM-CD16D, all
low level analog measurements (thermocouples, pyranometers,
thermopiles, etc.) must be made differentially. This is a result of
slight ground potentials created along the 21X analog terminal
strip when the 12 V supply is used to power peripherals. This
limitation reduces the number of available analog input channels
and may make an external supply for the SDM-CD16D essential.
EXTERNAL
9 TO 18V DC
+ –
GND
DATALOGGER
C1
12V 12V
SDM-C1 or C1
SDM-C2 or C2
C2
SDM-C3 or C3 C3
GND
12V
DATALOGGER
SDM-C1 or C1
C1
SDM-C2 or C2
C2
SDM-C3 or C3
C3
3