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.Lesen Sie mehr
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).
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
|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.|
The SDMCVO4 instruction controls the SDM-CVO4 operation in CRBasic; Instruction 103 controls the SDM-CVO4 operation in Edlog.
*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).
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.
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.
Number of FAQs related to SDM-CVO4: 5
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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.
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.
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.