SDM-AO4A 4-Channel Analog Output Module
Increases Available CAO Ports
Provides high resolution and high accuracy
weather applications water applications energy applications gas flux & turbulence applications infrastructure applications soil applications


The SDM-AO4A module increases the number of continuous analog outputs available to your datalogger. You can use these outputs for proportional control or driving strip charts. Measured or processed values in the datalogger are scaled to millivolts and transferred to the SDM-AO4A as digital values. The SDM-AO4A then performs a digital-to-analog conversion and outputs an analog voltage signal.

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Benefits and Features

  • Increases the number of CAO ports available to the datalogger
  • Supports both ±5 V and 0 to 10 V modes, allowing the module to be used in more applications
  • Includes a choice of synchronous and sequential operation
  • Provides high resolution and high accuracy


Detailed Description

The datalogger enables individual modules through an addressing scheme; multiple SDMs (in any combination) can be connected to one datalogger. After a module is enabled, it operates independently of the datalogger until additional commands are received or results are transmitted.


Operating Temperature -40° to +60°C
Voltage Range ±5 V or 0 to 10 V
Resolution 167 µV
Operating Voltage 12 Vdc nominal (9.6 to 16 Vdc)
Maximum Output Current
  • 50 mA (per channel)
  • 100 mA (total)
Overcurrent Shutdown Point 130 mA ± 15 mA
Dimensions 13.46 x 8.51 x 2.41 cm (5.3 x 3.35 x 0.95 in.)
Weight 175 g (6.2 oz)

Accuracy with 20 kΩ Load (maximum)

25°C ±(0.05% of |Vout(V)|+500µV)
-40° to +60°C ±(0.1% of |Vout(V)|+500µV)

Additional Full-Scale Error with 50 mA Load

±5 V Mode -1.3 mV (typical)
0 to 10 V Mode -1.5 mV (typical)

Typical Current Drain (±5 V Mode)

No load, Vout=0, Vsupply=12V 11 mA
No load, Vout=fullscale, Vsupply=12V 13 mA
With load, Vsupply=12V 13 mA + load
Power Down Mode, Vsupply=12V 1.1 mA

Typical Current Drain (0 to 10 V Mode)

No load, Vout=0, Vsupply=12V 21 mA
No load, Vout=fullscale, Vsupply=12V 28 mA
With load, Vsupply=12V 28 mA + (2.4)(load)
Power Down Mode, Vsupply=12V 1.1 mA


Datalogger Considerations

Up to 15 SDM devices can be connected to a single datalogger.

Compatible Contemporary Dataloggers

CR200X Series CR800/CR850 CR1000 CR3000 CR9000X CR6

Compatible Retired Dataloggers

CR200 Series CR500 CR510 CR10 CR10X 21X CR23X CR5000 CR7X CR9000
# # # # * ♣#

*For the CR3000 and CR5000, SDMs are connected to the ports labeled SDM-C1, SDM-C2, and SDM-C3.

#Edlog dataloggers only support the ±5 V mode and synchronous operation.

The CR700X module needs to have been ordered after 1 Sept 1996 or upgraded to include a CR700X CPU module.

Power Supply

It may be convenient to use the datalogger’s batteries to power the SDM-AO4A, but consideration must be given to the SDM-AO4A’s continuous current drain (11 mA in ±5 V mode or 21 mA in 10 V mode). The datalogger’s alkaline batteries can power one SDM-AO4A for less than a month, and therefore these batteries are not recommended for continuous long-term operation. The datalogger’s sealed rechargeable batteries, float charged by an ac supply or solar panel, typically can be used for long-term operation.

The SDM-AO4A may also be powered from an external 12 Vdc source, independent from the datalogger batteries. The low side of this external 12 Vdc source needs to be connected to datalogger ground and not directly to earth ground.

Enclosure Considerations

The SDM-AO4 requires a desiccated, non-condensing environment; a Campbell Scientific enclosure is recommended. The SDM-AO4A has built-in keyhole flanges for mounting to the backplates of Campbell Scientific enclosures. Grommets and screws are provided to attach the flanges/bracket to the backplate of our enclosures.

Frequently Asked Questions

Number of FAQs related to SDM-AO4A: 4

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  1. For the CR1000, to get continuous analog outputs, an SDM-AO4A (4-channels, non-isolated, voltage only) or an SDM-CVO4 (4-channels, isolated, voltage or current) is needed. Multiples of these devices can be used to get more outputs.  For single channels of output, some third-party devices can be used.

  2. To get continuous analog outputs, either the SDM-AO4A (four channels, non-isolated, voltage only) or the SDM-CVO4 (four channels, isolated, voltage or current) is needed. Multiples of those devices can be used to acquire more outputs.
  3. Yes. The CR3000 and CR5000 have two native Continuous Analog Output channels. The SDM-AO4A (voltage) or SDM-CVO4 (voltage or current) can also be used.
  4. The CR1000 does not have any continuous analog outputs. It has three excitation channels that are momentarily turned on during measurements. Use the SDM-AO4A for proportional control or driving strip charts.