SDM-IO16 16 Channel Input/Output Expansion Module
4
Accuracy:
internal clock accuracy
0.01% (worst case) over
the standard temperature range of -25 to +50
C.
See also Appendix B for a discussion on
frequency resolution.
Duty cycle resolution:
this depends on frequency and measurement
interval - See Appendix B. The average duty cycle
can be measured for signals up to 4 kHz.
Max measurement interval:
for frequency or duty cycle measurements the
datalogger must request a measurement at an
interval no longer than 15.9375 seconds. Each
channel can be measured at different intervals,
both for frequency and duty cycle.
1
If more detailed input/output characteristics are required, experienced users
should consult the equivalent circuit diagrams shown in Figure 2.
2
See Appendix B for a more detailed discussion of switch debounce, resolution
and accuracy.
OV
.From sensor
0.510
0.33
5 V
100 K
5.6 V
0 V
To internal logic
a) Input biasing and protection
0.6 V Drop
.Output
.Output
.550
b) Output set ON
c) Output set OFF
0.510
V
5 V, 0
33
Figure 2. Simplified Equivalent Port Circuits
3. Power Considerations
For most applications, especially for pulse counting or status inputs, it is more
normal to use the datalogger supply to power the SDM-IO16, as shown in Figure
3(a).
When being used for control and outputting current the SDM-IO16 power
requirements can be large compared to most Campbell Scientific products when
driving significant loads. For this type of application an external power supply, as
shown in Figure 3(b), is recommended to power the SDM-IO16.