Campbell Scientific SDM-AO4 4-Channel Continuous Analog Output Module - Manual (Page 5)

SDM-AO4 Four Channel Analog Output
1. Function
The SDM-AO4 is designed to output four continuous voltages at levels set by
a Campbell Scientific datalogger.
2. Specifications
Power Requirements
Operating voltage:
12 VDC Nominal (9.6 V - 16 V)
Typical current drain: 10.5 mA
Physical Specification
Size:
6.1" X 2.7" X 1.1"
Weight: 0.9 lbs.
Analog Output
Range: ±5000
mV
Resolution 2.5 mV
Maximum Current 1 mA
Accuracy ± (0.5% of |Vout| +5 mV)
Minimum load
(for above accuracy) 75, 000 ohms
Output Resistance
1 200 Ohms
Temperature Range
-25 to +55
o C
1 Output resistance can be viewed as a series resistance with the load the SDM-
AO4 is driving. A low resistance load will cause appreciable error due to the
voltage drop across the 200 ohm resistance. For example, the error (in addition
to the accuracy specification above) with a 4800 ohm load = 200 / (4800 +
200) * Vout = 4 % of Vout
3. Power Supply
It is often convenient to power the SDM-AO4 from the datalogger power
supply, but when doing so consideration must be given to the SDM-AO4's
10.5 mA continuous current drain. The alkaline supply available with the
datalogger has 7.5 Amp-hours and will power one SDM-AO4 for less than one
month. This supply is not recommended for continuous long-term operation.
The rechargeable lead acid option, float charged by an AC supply or solar
panel, may be used for long term operation.
The SDM-AO4 may also be powered from an external 12 Volt supply,
independent from the datalogger supply. The low side of an external 12 Volt
supply should be connected to datalogger ground and not directly earth
grounded. Slight alterations in ground potential across the 21X terminal strip
are created when the 21X 12 Volt supply is used to power peripherals.
Therefore, low level voltage measurements (e.g., thermocouples, thermopiles,
and radiometers) should be made differentially when powering the SDM-AO4
with the 21X 12 Volt output.
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