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Campbell SDM-CVO4 Instruction Manual

4-channel current/voltage output module
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SDM-CVO4 4-Channel
Current/Voltage Output Module
Revision: 7/11
C o p y r i g h t
©
2 0 0 1 - 2 0 1 1
C a m p b e l l
S c i e n t i f i c ,
I n c .

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  • Page 1 SDM-CVO4 4-Channel Current/Voltage Output Module Revision: 7/11 C o p y r i g h t © 2 0 0 1 - 2 0 1 1 C a m p b e l l S c i e n t i f i c ,...
  • Page 2 435-750-9579. Campbell Scientific will not process any returns until we receive this form. If the form is not received within three days of product receipt or is incomplete, the product will be returned to the customer at the customer’s expense. Campbell Scientific reserves the right to refuse service on products that were exposed to contaminants that may cause health or safety concerns for our employees.

  • Page 3: Table Of Contents

    SDM-CVO4 Table of Contents PDF viewers note: These page numbers refer to the printed version of this document. Use the Adobe Acrobat® bookmarks tab for links to specific sections. 1. Introduction..............1 2. Specifications ..............2 2.1 General Specifications ................2 2.2 Output Specifications................3 2.3 Isolation Specifications................3...
  • Page 4 SDM-CVO4 Table of Contents Tables 4-1. Datalogger to SDM-CVO4 Connections ..........4 4-2. Switch Position and Addresses............. 10 6-1. Description of SDM Speed..............16 6-2. Description of Instruction 103.............. 17...

  • Page 5: Introduction

    SDM-CVO4 4-Channel Current/Voltage Output Module The SDM-CVO4 is a synchronously addressed datalogger peripheral designed to allow the datalogger to output variable voltage or current signals under program control. FIGURE 1. SDM-CVO4 (shown without mounting brackets) 1. Introduction The SDM-CVO4 expands the analog output capability of Campbell Scientific dataloggers.

  • Page 6: General Specifications

    SDM-CVO4 4-Channel Current/Voltage Output Module The SDM-CVO4 is a synchronously addressed datalogger peripheral. The datalogger’s SDM ports are used to address the SDM-CVO4 and send out data that defines the desired voltage/current output of each of the four channels. The output levels are set by four values stored in variables or successive input locations in the datalogger.

  • Page 7: Output Specifications

    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 section 4.5, Safety Issues).

  • Page 8: Power Considerations

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

  • Page 9: Use Of The Spring-Loaded Terminal Blocks (Top Position)

    An additional G terminal is provided which can be connected directly to the enclosure earth ground terminal to ensure this. Make sure the ground wire from the SDM-CVO4 to the datalogger goes to its G terminal and not the AG terminal.

  • Page 10: Output Device Connections

    SDM-CVO4 4-Channel Current/Voltage Output Module You cannot reliably insert more than one solid-core wire into one terminal connector unless the wires are soldered or clamped together. When inserting more than one stranded wire, twist the bare ends together before insertion.

  • Page 11: Shield And Ground Connections

    SDM-CVO4 4-Channel Current/Voltage Output Module CVO4 Remote Current Input b) The SDM-CVO4 provides the voltage source to drive the loop. In this case the only real option is: Remote Current CVO4 Input – In both cases you need to consider whether the voltage supply is high enough to allow the maximum current to flow (20 mA) through all of the series resistances in the current loop.

  • Page 12: Output Terminal Connectors

    SDM-CVO4 4-Channel Current/Voltage Output Module SDM-CVO4. Do not connect the screen at both ends of the cable as this may result in a ground loop being formed. The output circuitry of the SDM-CVO4 includes protective components to minimize the chances of damage that can be caused by transients which can be induced in the signal cable.

  • Page 13: Sdm Address Setting

    Please contact Campbell Scientific for details. 4.4 SDM Address Setting Each SDM-CVO4 can have 1 of 16 addresses. The factory-set address is 00. Table 4-2 shows switch position and the corresponding address. Figure 4-4 shows the position of the switch on the right-hand end of the casing. Note that you will have to remove the right-hand mounting bracket to gain access to this switch.

  • Page 14: Safety Considerations

    The SDM-CVO4 has two G terminals on the black connector which are used for connections to the datalogger. One of these can be used to connect the device directly to the earth ground point of the enclosure to ensure the lowest resistance path to ground.
  • Page 15 SDM-CVO4 4-Channel Current/Voltage Output Module Where the SDM-CVO4 is going to be used in applications where the potential difference between the datalogger and the output terminals exceeds 50 V RMS AC, 74 VDC then careful consideration has to be taken to ensure safe operation and compliance with local safety regulations.

  • Page 16: General Principles Of Use

    As the required output levels are held in a digital form in the SDM-CVO4, there is little advantage in sending data more frequently – the only benefit being that it would recover more quickly in the event of a loss of power.

  • Page 17: Datalogger Programming

    The reason for this is that direct datalogger excitation is a ratiometric measurement whereby any drift in the excitation output of the datalogger is compensated for. With the SDM-CVO4 as an excitation source, any drift in its output accuracy, or of the logger measurement accuracy, can result in a combination of those errors.

  • Page 18: Crbasic Sdmcvo4 Instruction

    SDMCVO4 ( CVO4Source, CVO4Reps, SDMAddress, CVO4Mode ) Remarks This instruction controls the SDM-CVO4, which outputs a voltage or a current. Internal jumpers are used to set the mode for the device, but the jumpers can be overridden with the Mode parameter in this instruction.

  • Page 19: Sdmcvo4 Instruction Example

    6.2 SDMCVO4 Instruction Example This program example is for a weather station measuring wind speed, wind direction, temperature, and relative humidity. Each parameter is scaled to 0 to 10000 mVDC, and output to a SCADA system through the SDM-CVO4. Public WS_ms Public WD_0_360...

  • Page 20: Sdmspeed Instruction

    WDOut = WD_0_540 *18.59 'WD: 0-540 deg = 0-10000mV TempOut= 100*(Temp_C+40) 'Temp: -40-60 deg C = 0-10000 mV RHOut = RH *100 'RH: 0-100 % RH = 0-10000 mV ' Send mV outputs to SDM-CVO4 using the option to override the switch settings SDMCVO4 (CVO4Output(),4,0,10) NextScan EndProg 6.3 SDMSpeed Instruction...

  • Page 21: Description Of Instruction 103

    -20°C to +50°C would be scaled so at -20C the output is 0 mV and at +50°C the output is 10000 mV. To do this with the SDM-CVO4 you would use the mathematical functions of the datalogger to calculate a scaled value in a new input location, so that the value is -5000 when the temperature is -20°C and +5000 at +50°C.

  • Page 22: Edlog Program Examples

    SDM-CVO4 4-Channel Current/Voltage Output Module Setting the Reps parameter to 0 (Zero) will cause the addressed SDM-CVO4 to shut down, turning off all its outputs. It will turn on channels 1 and 2 at the next execution of Instruction P103 where the reps parameter is 1 or 2. If the reps parameter is greater than 2, then all the channels will be turned on.
  • Page 23 S, é1, & å(é1) Polar 4: 1 Wind Speed/East Loc [ WindSpeed ] 5: 2 Wind Direction/North Loc [ WindDir ] 8: Average (P71) 1: 2 Reps 2: 3 Loc [ AirT ; Now the code to scale the values and update the SDM-CVO4...

  • Page 24: Restricted Range Current Output Modes (4-20 Ma)

    B1 ; WS Offset 4: 27.7778 5: -5000 6: 133.333 7: -1666.67 B3 8: 10 9: -5000 ; Now update the SDM-CVO4 with the information ; for the four channels 11: SDM-AO4 (P103) 1: 4 Reps 2: 30 SDM Address...
  • Page 25 SDM-CVO4 4-Channel Current/Voltage Output Module ; Then apply the scaling with one instruction P53 ; The readings are scaled -3000 to +5000, i.e. to ; cover the range which would equate to ; 4-20 mA in current mode. ; Windspeed to cover the range 0-100 m/s ;...

  • Page 26: Providing Isolated Power Supplies To Sensors

    Loc [ ScldOut_1 ] 6.5.3 Providing Isolated Power Supplies to Sensors This program example sets all the outputs of the SDM-CVO4 to 10 V to provide isolated power supplies to four separate sensors. The program includes code to put the SDM-CVO4 into standby mode after the measurements are made.
  • Page 27 DIFF Channel 4: 5 Loc [ Press_1 ] 5: 1.0 Mult 6: 0.0 Offset ; Now turn off the SDM-CVO4 by using the command with 0 reps. 5: SDM-AO4 (P103) 1: 0 Reps 2: 00 SDM Address 3: 1 Loc [ Scale_1 ] ;...
  • Page 28 SDM-CVO4 4-Channel Current/Voltage Output Module...
  • Page 30 Campbell Scientific Companies Campbell Scientific, Inc. (CSI) 815 West 1800 North Logan, Utah 84321 UNITED STATES www.campbellsci.com • info@campbellsci.com Campbell Scientific Africa Pty. Ltd. (CSAf) PO Box 2450 Somerset West 7129 SOUTH AFRICA www.csafrica.co.za • cleroux@csafrica.co.za Campbell Scientific Australia Pty. Ltd. (CSA)

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