SDM-CVO4 4-Channel Current and Voltage Output Module
Lets Datalogger Control Voltage
Expands datalogger's current/voltage output capability
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The SDM-CVO4 is attached to a datalogger and outputs variable voltage or current signals under datalogger program control. Typical applications include driving remote current-loop display units, retransmitting measured values to industrial control systems, sending control signals to valve controllers, and providing excitation voltages or currents to external sensors.

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Funktionen und Vorteile

  • Erweitert die Möglichkeit zur Ausgabe von Spannung und Strom
  • Vier unabhängige Strom- oder Spannungsausgänge
  • Drives remote current-loop display units
  • Gemessene Werte werden an industrielle Kontrollsysteme, die Strom oder Hochspannungseingänge haben, weitergeleitet
  • Sendet Signale an das Kontrollsystem der Ventile
  • Liefert Anregungsspannung oder -strom für externe Sensoren


Technische Beschreibung

The SDM-CVO4 includes four output channels for connecting the external devices. It outputs variable voltage or current signals under datalogger program control. The outputs are isolated both from the datalogger and the other channels on the SDM-CVO4, thereby avoiding ground loop problems. Each output can be set to 0 to 10 Vdc or 0 to 20 mA by the datalogger program (current outputs can also be scaled and limited to 4 to 20 mA).

In the current mode, the output either acts as a two-wire current controller, where the loop is powered from a remote voltage source, or generates a 0 to 20 mA current source using a voltage output derived from its own power supply.


The SDM-CVO4 includes an internal isolation barrier and components rated to provide signal isolation for transients up to 1500 Vac (rms), 2500 Vdc nominal. The isolation is between any output and the SDM-CVO4 ground connection and between individual output channels.

Protection components are built-in, which will break down in a controlled fashion at voltages close to this limit (see Operator’s Manual Section 4.5, Safety Issues, for details).


  • Weight: 363 g (13 oz)
  • Dimensions w/o mounts:
    17.8 x 10.2 x 2.3 cm
    (7.0" x 4.0" x 0.9")
  • Dimensions w/ mounts:
    23.4 x 11.2 x 2.3 cm
    (9.2" x 4.4" x 0.9")
  • Operating Temperature: -25 to +50°C 
  • Operating Voltage: 12 Vdc nominal
    (8 to 16 V)
  • Minimum voltage drop across the internal current regulating circuit: 2.5 V @ 20 mA current flow
  • Maximum input voltage relative to channel ground: 20 Vdc
  • EMC Status: Complies with EN55022-1:1998 and EN50082-1:1998


  • Tested Isolation: Each channel of each unit is tested for isolation resistance at 500 Vdc. Pass level > 10 MΩ
  • Maximum Recommended Continuous Operating Voltage: 240 Vac rms differential between an output and datalogger ground, providing all issues relating to local regulations for safe installation and operation are followed (see Operator’s Manual Section 4.5, Safety Issues)

Current mode

  • Range: 0 to 20,000 µA
  • Resolution: 5 µA
  • Minimum output current (leakage): 5 µA at +50°C
  • Accuracy at +23°C:
    ±0.02% of set current + (±5 µA)
  • Typical Accuracy at -25° to +50°C:
    ±0.1% of set current + (±5 µA)
  • Worst Case Accuracy at -25° to +50°C:
    ±0.15% of full scale range + (±5 µA)

Voltage Mode

  • Range: 0 to 10,000 mV
  • Resolution: 2.5 mV
  • Maximum output current: 30 mA per channel
  • Minimum load current:
    5 µA if output < 200 mV
  • Accuracy at +23°C:
    ±0.02% of set voltage + (±2.5 mV)
  • Accuracy at -25° to +50°C:
    ±0.13% of set voltage + (±2.5 mV)

Current drain @ 12 Vdc

  • Typical active current: 27 or 54 mA, depending on operating mode (no load on output ports). To estimate the total current, add the active current to the sum of all output currents multiplied by 1.5.
    For example, if each port is at 10 mA output, the total = 54 + (1.5•4•10) = 114 mA.
  • With all outputs off: < 0.5 mA

Kompatibel mit

Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.


Product Compatible Note
CR200X (retired)
CR216X (retired)
CR3000 For the CR3000, SDMs are connected to the ports labeled SDM-C1, SDM-C2, and SDM-C3.
CR5000 (retired) For the CR5000, SDMs are connected to the ports labeled SDM-C1, SDM-C2, and SDM-C3.
CR9000X Although the CR9000X is compatible, the SDM-CVO4 does not support its fastest communication rates and therefore may not be practical for CR9000X applications.

Halterungen und Masten

Product Compatible Note

Additional Compatibility Information


The SDMCVO4 instruction controls the SDM-CVO4 operation in CRBasic; Instruction 103 controls the SDM-CVO4 operation in Edlog.

Datalogger Considerations

Compatible Contemporary Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR9000X CR6

Compatible Retired Dataloggers

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.

†Although the CR9000X and CR9000 are compatible, the SDM-CVO4 does not support their fastest communication rates and therefore may not be practical for CR9000(X) applications.

#On the CR7X, SDMs connect to the C1, C2, and C3 terminals provided on the CR700X control module (after Sept 1996).

Power Considerations

The SDM-CVO4 power requirements are large compared to most Campbell Scientific products—especially when driving significant loads. Care must be taken to ensure the power supply can deliver this higher demand. Alkaline batteries are not recommended for long-term applications.

The SDM-CVO4 has two internal power supplies—one for channels 1 and 2 and one for channels 3 and 4. The power supply for channels 3 and 4 is only turned on if the datalogger sends an instruction that sets the output of those channels. If channels 3 and 4 are not used, the power consumption is approximately 20 mA lower than when all outputs are used.

Where supported by the datalogger, and when the application allows it, the SDM-CVO4 can be shut down to reduce its power consumption to less than 0.5 mA. In this state, all outputs are switched off.

Enclosure Considerations

The SDM-CVO4 requires a desiccated, non-condensing environment; a Campbell Scientific enclosure is recommended. A mounting bracket, grommets, and screws attach the SDM-CVO4 to the backplates of a Campbell Scientific enclosure.

Compatible Enclosures

ENC10/12 ENC10/12R ENC12/14 ENC14/16 ENC16/18 ENC24/30 ENC24/30S

FAQs für

Number of FAQs related to SDM-CVO4: 5

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  1. The SDM-CVO4 allows most Campbell Scientific dataloggers to produce a value by whatever means measured or derived as a scaled 0 to 20 or 4 to 20 mA signal (four terminals).

    The datalogger sends an instruction to the SDM-CVO4 with the voltage or current to be transmitted to the other device. The SDM-CVO4 does not itself convert a voltage to a current. A datalogger is needed to make a measurement and instruct the SDM-CVO4 as to what the output should be. 

  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. Up to 15 SDM devices can be attached to a datalogger because they are addressable with a hex number of 0 to F.  Some of those devices may require more power, which would need to be considered when adding devices.

  4. 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.

  5. 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.