SDM-CVO4 4-Channel Current/Voltage Output Module User Guide Issued: 13.3.08 Copyright © 2001-2007 Campbell Scientific Inc. Printed under Licence by Campbell Scientific Ltd.
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Contents 1. Introduction.................................................................. 1 2. Specifications .............................................................. 2 2.1 General Specifications ..............................................................................2 2.2 Output Specifications................................................................................3 2.3 Isolation Specifications.............................................................................3 3.
Contents Tables 4-1. Datalogger to SDM-CVO4 Connections.................................................4 4-2. Switch Position and Addresses .............................................................10 6-1. Description of Instruction 103 ..............................................................
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 analogue output capability of Campbell Scientific dataloggers. Each output can be set to 0-10V or 0-20mA by the datalogger.
SDM-CVO4 4-Channel Current/Voltage Output Module The SDM-CVO4 is a synchronously addressed datalogger peripheral. Datalogger control ports 1, 2 and 3 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 in successive input locations in the datalogger. A total of up to sixteen SDM-CVO4s or other SDM peripherals may be connected and addressed from the same three ‘SDM’ ports.
Instruction Manual 2.2 Output Specifications Voltage Mode: Range: 0 – 10,000 mV Resolution: 2.5 mV Maximum Output Current: 30 mA per channel. Minimum load current: 5 μA if output < 200 mV. Accuracy (+23°C) ±0.02% of set voltage, + (± 2.5 mV). Accuracy (-25 to +50°C) ±0.13% of set voltage, + (± 2.5 mV). Current Mode: Range: 0 – 20 mA Resolution: 5 μA Minimum output current (leakage): 5 μA at +50°C. Accuracy (+23°C) ±0.02% of full scale range, + (± 5 μA). Accuracy (-25 to +50°C) ±0.
SDM-CVO4 4-Channel Current/Voltage Output Module 3. 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 that the power supply can cope with 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.
Instruction Manual insert a small screwdriver into either the top or front slot, as appropriate, and push to open the terminal spring. Strip any insulation from the wire to give 7 to 9 mm bare wire. Push the wire into the opening, and, while holding it in position, withdraw the screwdriver to release the spring. The wire will now be firmly held in place. See Figures 4-1 and 4-2, below. Figure 4-1. Use of the Spring-Loaded Terminal Blocks (Top Position) Figure 4-2.
SDM-CVO4 4-Channel Current/Voltage Output Module 4.2 Output Device Connections For each output channel there are four terminals which are labelled Vo, Id plus ) connections per channel. The two ground terminals there are two ground ( are internally connected; two are provided for convenience. 4.2.1 Voltage Output Mode The Vo terminal is the output for either the preset voltage signal, when the channel is set to operate in voltage mode or an unregulated 15 VDC power source in current mode.
Instruction Manual a) The remote device powers the loop, where, depending on the ground referencing requirements of that device, the connection can be as shown in the diagrams below: Remote Voltage V+ Source +ve + Remote Current Input Id – CVO4 V- or CVO4 Id V+ + Remote Current Input V- b) The SDM-CVO4 provides the voltage source to drive the loop.
SDM-CVO4 4-Channel Current/Voltage Output Module 4.2.3 Shield and Ground Connections It is generally advisable to used shielded (screened) cable when connecting the output to any remote system to reduce the chances of noise pickup. The shield will only be effective if it is connected to a good ground reference point. As a result of the isolation barrier in the SDM-CVO4, the ground terminals associated with the output connector of each channel cannot be considered as good ground reference points.
Instruction Manual Select channel(s) by fitting jumper (s) between appropriate terminals. (Current mode only.) Jumper shown fitted to ‘enable’ Channel 4. Jumper shown fitted in the unconnected ‘stored’ position. CAUTION Figure 4-3. Location of Jumpers on Circuit Board Do not store the jumpers between any other pins in the block as this may switch the module into a factory calibration mode, which may result in abnormal operation and change of output accuracy.
SDM-CVO4 4-Channel Current/Voltage Output Module Table 4-2. Switch Position and Addresses Switch Setting Base 4 Address 0 1 2 3 4 5 6 7 8 9 A B C D E F 00 01 02 03 10 11 12 13 20 21 22 23 30 31 32 33 Use a screwdriver to select address Figure 4-4. Address Selection Switch The address switch has a hexadecimal setting position (0..F). Most datalogger instructions require you to enter the address as a base 4 number. Please see your datalogger manual for more details of the convention required. 4.
Instruction Manual 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. For such applications Campbell Scientific does not supply the device as a stand-alone device which will meet all safety requirements.
SDM-CVO4 4-Channel Current/Voltage Output Module this device is at the low end of its tolerance band (±10%), combined with the normal tolerance of flash test devices, then the spark gap could fire during a 1500 VAC flash test, which may cause an indication of failure. Testing at a slightly lower voltage will confirm whether there is a true fault or not.
Instruction Manual 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. It is worth investigating, therefore, the exact requirements of the sensors you wish to use. For instance, on closer inspection of the specification of many pressure sensors you will often find the recommendation of 10V excitation, but in reality many will accept a lower voltage.
SDM-CVO4 4-Channel Current/Voltage Output Module range of -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. The datalogger limits the output of the SDM-CVO4 so that even if the measured value exceeds the intended range (i.e.
Instruction Manual If the SDM-CVO4 loses power for any reason, when power is restored the outputs will return to the default ‘off’ state. This will be held until the datalogger runs Instruction 103 again to update the output levels required. 6.2 Edlog Program Examples The following program examples are given to help you understand the general principles involved in the use of the SDM-CVO4. 6.2.
SDM-CVO4 4-Channel Current/Voltage Output Module 4: Volt (SE) (P1) 1: 1 Reps 2: 32 50 mV, 50 Hz Reject, Slow Range 3: 3 SE Channel 4: 4 Loc [ Radiation ] 5: 100 Mult 6: 0.
Instruction Manual 7: 8: 9: -1666.67 B3 10 A4 -5000 B4 ; Now update the SDM-CVO4 with the information ; for the four channels 11: SDM-AO4 (P103) 1: 4 Reps 2: 30 SDM Address 3: 5 Loc [ ScldOut_1 ] 6.2.2 Restricted Range Current Output Modes (4-20 mA) When driving a system that requires a restricted current range then the full-scale range is reduced accordingly.
SDM-CVO4 4-Channel Current/Voltage Output Module ; then set the value to –3000 13: Z=F (P30) 1: -3000 2: 00 3: 5 F Exponent of 10 -- Z Loc [ ScldOut_1 ] 14: End (P95) 15: End (P95) ; Now update the SDM-CVO4 with the information ; for the four channels 16: SDM-AO4 (P103) 1: 4 Reps 2: 30 SDM Address 3: 5 Loc [ ScldOut_1 ] 6.2.3 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.
Instruction Manual ; Wait 100 ms for it to power-on and the outputs to stabilize ; You may need to increase this delay if the sensors ; themselves ; have a power-on delay 3: Excitation with Delay (P22) 1: 1 Ex Channel 2: 0000 Delay W/Ex (units = 0.01 sec) 3: 10 Delay After Ex (units = 0.01 sec) 4: 0000 mV Excitation ; Take the four measurements from the Pressure sensors. 4: Volt (Diff) (P2) 1: 4 Reps 2: 04 250 mV Slow Range 3: 1 DIFF Channel 4: 5 Loc [ Press_1 ] 5: 1.0 Mult 6: 0.
SDM-CVO4 4-Channel Current/Voltage Output Module 6.3 CRBasic SDMCVO4 Instruction This instruction is used to control the SDM-CVO4 four channel current/voltage output device. Syntax 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.
Instruction Manual be cycled on the device to return it to its default state. Otherwise, if 0 or 1 is entered it will be ignored and the device will remain in its last override state. Refer to Section 4.2.2 for connection details. 6.4 SDM-CVO4 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.
SDM-CVO4 4-Channel Current/Voltage Output Module EndIf ' Scale the measurements for the SDM-CVO4 to output 0-10000 mV WSOut = WS_ms*200 'WS: 0-50 m/s = 0-10000 mV 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 This is a blank page.
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