Campbell Scientific SDM-AO4 User Manual

SDM-AO4 Four Channel Analog

12V

C1
C2
C3

Output Module

SDM-AO4

4 CHANNEL ANALOG OUTPUT

Revision: 4/09

AO1

AO2

AO3

A04

SN: 2270

MADE IN USA

Copyright © 1986-2009

Campbell Scientific, Inc.

Warranty and Assistance

The SDM-AO4 FOUR CHANNEL ANALOG OUTPUT MODULE is
warranted by CAMPBELL SCIENTIFIC, INC. to be free from defects in
materials and workmanship under normal use and service for twelve (12)
months from date of shipment unless specified otherwise. Batteries have no
warranty. CAMPBELL SCIENTIFIC, INC.'s obligation under this warranty is
limited to repairing or replacing (at CAMPBELL SCIENTIFIC, INC.'s option)
defective products. The customer shall assume all costs of removing,
reinstalling, and shipping defective products to CAMPBELL SCIENTIFIC,
INC. CAMPBELL SCIENTIFIC, INC. will return such products by surface
carrier prepaid. This warranty shall not apply to any CAMPBELL
SCIENTIFIC, INC. products which have been subjected to modification,
misuse, neglect, accidents of nature, or shipping damage. This warranty is in
lieu of all other warranties, expressed or implied, including warranties of
merchantability or fitness for a particular purpose. CAMPBELL SCIENTIFIC,
INC. is not liable for special, indirect, incidental, or consequential damages.

Products may not be returned without prior authorization. The following
contact information is for US and International customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company
serves your country. To obtain a Returned Materials Authorization (RMA),
contact CAMPBELL SCIENTIFIC, INC., phone [phone]. After an
applications engineer determines the nature of the problem, an RMA number
will be issued. Please write this number clearly on the outside of the shipping
container. CAMPBELL SCIENTIFIC's shipping address is:

CAMPBELL SCIENTIFIC, INC.

RMA#_____
815 West 1800 North
Logan, Utah 84321-1784

CAMPBELL SCIENTIFIC, INC. does not accept collect calls.

SDM-AO4 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. Function........................................................................1

2. Specifications ..............................................................1

3. Power Supply...............................................................1

4. Physical Connections .................................................2

5. Addressing...................................................................3

6. Programming ...............................................................6

6.1 CRBasic....................................................................................................6

6.1.1 SDMAO4 Instruction......................................................................6

6.1.2 SDMSpeed Instruction....................................................................7

6.2 Edlog.........................................................................................................8

6.3 Programming Examples............................................................................8

6.3.1 CR5000 Program Example.............................................................9

6.3.2 CR10X Program Example ............................................................10

List of Figures

1. Front Panel of the SDM-AO4.....................................................................3

2. Locational Diagram for the Address Jumpers ............................................5

List of Tables

1. Description of Terminal Block Connections..............................................3

2. SDM-AO4 Addressing...............................................................................4

3. Bit Period Value .........................................................................................7

4. Description of Instruction 103....................................................................8

i

SDM-AO4 Four Channel Analog Output

1. Function

The SDM-AO4 is designed to output four continuous voltages at levels set by
a Campbell Scientific datalogger.

2. Specifications

Power Requirements
Operating voltage: 12 VDC Nominal (9.6 V - 16 V)
Typical current drain: 10.5 mA

3. Power Supply

Physical Specification
Size: 6.1" X 2.7" X 1.1"
Weight: 0.9 lbs.

Analog Output
Range: ±5000 mV
Resolution 2.5 mV
Maximum Current 1 mA
Accuracy ± (0.5% of |Vout| +5 mV)
Minimum load
(for above accuracy) 75, 000 ohms
Output Resistance

Temperature Range

-25 to +55

1

Output resistance can be viewed as a series resistance with the load the SDM­AO4 is driving. A low resistance load will cause appreciable error due to the
voltage drop across the 200 ohm resistance. For example, the error (in addition
to the accuracy specification above) with a 4800 ohm load = 200 / (4800 +

200) * Vout = 4 % of Vout

It is often convenient to power the SDM-AO4 from the datalogger power
supply, but when doing so consideration must be given to the SDM-AO4's

10.5 mA continuous current drain. The alkaline supply available with the
datalogger has 7.5 Amp-hours and will power one SDM-AO4 for less than one
month. This supply is not recommended for continuous long-term operation.
The rechargeable lead acid option, float charged by an AC supply or solar
panel, may be used for long term operation.

o

C

1

200 Ohms

The SDM-AO4 may also be powered from an external 12 Volt supply,
independent from the datalogger supply. The low side of an external 12 Volt
supply should be connected to datalogger ground and not directly earth
grounded. Slight alterations in ground potential across the 21X terminal strip
are created when the 21X 12 Volt supply is used to power peripherals.
Therefore, low level voltage measurements (e.g., thermocouples, thermopiles,
and radiometers) should be made differentially when powering the SDM-AO4
with the 21X 12 Volt output.

1

SDM-AO4 Four Channel Analog Output

4. Physical Connections

Figure 1 shows the front panel of the SDM-AO4. The terminal block on the
left is used for connection to the datalogger and the terminal block on the right
provides the continuous analog output. The two ground ports on the left block
are identical and at the same potential.

Table 1 describes the terminal block connections. Multiple SDM-AO4s may
be used by connecting the datalogger side of one SDM-AO4 to the next.
Campbell Scientific does not recommend connecting more than six SDM­AO4s to one datalogger.

The CABLE5CBL-L or similar cable is used to connect the module to the
datalogger. A 1-ft cable length should be sufficient when both datalogger and
module are housed within an ENC12/14 enclosure; a 2-ft length may be
required if the datalogger and SDM-AO4 are housed at opposite ends of an
ENC16/18 enclosure.

CRBasic dataloggers should use the SDMSpeed instruction if the cable length
is longer than 20 feet (see Section 6.1.2). The maximum recommended cable
length for the CR7 is 600 ft. For other Edlog dataloggers, the maximum
recommended cable length is 20 feet.

CAUTION

CAUTION

Cables connecting the terminals of the datalogger and
SDM device should be as short as possible to minimize the
risk of corruption of the signal and damage from induced
surges.

With power supplied to an SDM-AO4 and before execution of the datalogger
program, a random voltage between ±5 Volts will be output. To avoid
outputting erroneous voltages to the receiving device, connect the SDM-AO4
to the datalogger, start the program, and then connect the receiving device.

The order of connections is critical. ALWAYS CONNECT
GROUND FIRST, followed by 12V and then the Control
Ports.

2

SDM-AO4 Four Channel Analog Output

FIGURE 1. Front Panel of the SDM-AO4

TABLE 1. Description of Terminal Block Connections

CAUTION

5. Addressing

Datalogger Connections
12V - 12 volt supply

- ground

- ground
SDM-C1 (CR3000, CR5000) or C1 - SDM control port #1
SDM-C2 (CR3000, CR5000) or C2 - SDM control port #2
SDM-C3 (CR3000, CR5000) or C3 - SDM control port #3

Analog Output Connections
AO1 - analog output #1

- ground
AO2 - analog output #2

- ground
AO3 - analog output #3

- ground
AO4 - analog output #4

- ground

The SDM-AO4 will not function correctly unless the case is
fully assembled and the case screws are fully tightened.

The SDM-AO4 is a synchronously addressed datalogger peripheral. Control
Ports 1, 2, and 3, are used to address an SDM-AO4 and send out the digital
millivolt readings for subsequent analog output. Addressing allows multiple
SDM peripherals to be connected to one datalogger.

3

SDM-AO4 Four Channel Analog Output

The SDM-AO4 has sixteen possible addresses, as shown in Table 2. The
address for an SDM-AO4 is hardware selectable using jumpers at locations J12
and J8, as shown in Figure 2. The jumper at location J12 represents the least
significant digit (LSD), and the jumper at location J8 is the most significant
digit (MSD). The digit zero (0) is nearest the edge of the board, and the digit
three (3) is the innermost jumper on the board. All SDM-AO4s are shipped
with the address set at zero (00).

Table 2. SDM-AO4 Addressing

Base 10

[CRBasic Loggers]

Base 4 [CR10(X),

21X, CR23X]

MSD

J8

LSD

J12
0 0 0 0
1 1 0 1
2 2 0 2
3 3 0 3
4 10 1 0
5 11 1 1
6 12 1 2
7 13 1 3
8 20 2 0
9 21 2 1

10 22 2 2
11 23 2 3
12 30 3 0
13 31 3 1
14 32 3 2
15 33 3 3

MSD = most significant digit LSD = least significant digit
Multiple SDM-AO4s connected to one datalogger must have

separate and sequentially increasing addresses.

4

SDM-AO4 Four Channel Analog Output

FIGURE 2. Locational Diagram for the Address Jumpers.

5

SDM-AO4 Four Channel Analog Output

6. Programming

NOTE

This section is for users who write their own datalogger
programs. A datalogger program can be generated using
Campbell Scientific’s SCWIN Short Cut Program Generator.
You do not need to read this section to use Short Cut.

The datalogger is programmed using either CRBasic or Edlog. Dataloggers
that use CRBasic include our CR800, CR850, CR1000, CR3000, and CR5000.
Dataloggers that use Edlog include our CR7, CR10X, CR10, CR23X, and
21X. Both CRBasic and Edlog are included in PC400 and LoggerNet
datalogger support software.

In both CRBasic and Edlog, the datalogger programming instruction allows the
user to set four separate voltage levels in one SDM-AO4, or move voltage
levels with multiple SDM-AO4s. Voltage levels are reset each time the
instruction is executed. The voltage range is ±5 Volts; voltage levels sent to
the SDM-AO4 which are out of the range limits will appear as either + 5 Volts
or - 5 Volts depending on whether it is overranged or underranged.

6.1 CRBasic

6.1.1 SDMAO4 Instruction

The SDMAO4 instruction is used to set the voltage to an SDM-AO4 four
channel analog output device.

NOTE

The SDMAO4 instruction was at one time named the AO4
instruction. Please change your program accordingly.

The SDMAO4 instruction has the following syntax:

SDMAO4(Source

Description of the parameters follows:

Source: The Source parameter is the variable or variable array that holds the
voltage(s), in millivolts, that will be sent to the SDM-AO4(s). If multiple
SDM-AO4s are to be triggered with one instruction, this parameter must be
dimensioned to the total number of channels for all the devices being set (e.g.,
if all four channels are being set on two SDM-AO4 devices, Source must be
dimensioned to eight).

Reps: The Reps parameter determines the number of SDM-AO4 output
channels that will be set. If this parameter is greater than four (i.e., voltage is
being set for more than one SDM-AO4 device), voltage is set on the next
consecutively addressed SDM-AO4 device. In this case, the SDM-AO4s must
have sequential SDM addresses.

, Reps, SDMAddress)

6

SDMAddress: The SDMAddress parameter defines the address of the SDM­AO4 to which a voltage should be applied. Valid SDM addresses are 0 through

14. Address 15 is reserved for the SDMTrigger instruction. CRBasic
dataloggers use base 10 when addressing SDM devices (see Table 2).

6.1.2 SDMSpeed Instruction

The SDMSpeed instruction is used to change the bit period that the datalogger
uses to clock the SDM data. Slowing down the clock rate may be necessary
when long cable lengths are used to connect the datalogger and SDM devices.

The syntax of this instruction is as follows:

SDM-AO4 Four Channel Analog Output

SDMSpeed (BitPeriod

The BitPeriod argument can be an integer or a variable. If the SDMSpeed
instruction is not in the program, a default bit period is used. If 0 is used for
the argument, the minimum allowable bit period is used. Table 3 shows the
default, minimum allowable, and maximum bit period for each of our CRBasic
dataloggers.

Datalogger

CR800, CR850
CR1000
CR3000
CR5000

The equation used to calculate the bit rate depends on the datalogger used.
The datalogger will round down to the next faster bit rate.

Equation for CR800, CR850, and CR1000:

)

TABLE 3. Bit Period Values

Default
Bit Period

26.04 μsec 8.68 μsec

26.04 μsec 8.68 μsec

26.04 μsec 8.68 μsec
30 μsec 8 μsec

Minimum Allowable
Bit Period

Maximum
Bit Period

2.2 msec

2.2 msec

2.2 msec
3 msec

bit_rate=INT((k*72)/625)*Resolution

Where:
k= the value entered in BitPeriod

Resolution=8.68 microseconds

Equation for CR3000:

bit_rate=INT((k*144)/625)*Resolution

Where:
k= the value entered in BitPeriod
Resolution= 4.34 μsec.

7

SDM-AO4 Four Channel Analog Output

Equation for CR5000:

bit_rate=INT(k*20)*Resolution

Where:
k= the value entered in BitPeriod
Resolution=50 nsec.

6.2 Edlog

The Edlog dataloggers are programmed with the SDM-AO4 Instruction 103
(See Table 4):

SDM-AO4 (P103)
1: 1 Reps
2: 00 SDM Address
3: 0000 Loc [ _________ ]

The number of repetitions, Parameter 01, specifies the total number of SDM­AO4 output channels to be set. The address of the first SDM-AO4 is specified
with Parameter 02, multiple SDM-AO4s must have consecutive addresses.
Parameter 3 is the starting Input Location containing the first millivolt level to
be output on the first channel of the first SDM-AO4. Subsequent millivolt
levels must be contained in consecutive Input Locations immediately after the
first Input Location specified in Parameter 3.

For example, two SDM-AO4s can be used to output eight voltage levels which
are contained in Input Locations 15 through 22. There are eight repetitions, so
eight (8) will be entered for Parameter 1. The SDM-AO4s must have
consecutive addresses (e.g., 31 and 32), and Parameter 2 would contain 31 in
this case. Fifteen (15) will be entered for Parameter 3.

TABLE 4. Description of Instruction 103

Par.
No.

Data
Type

escription

D

01: 2 Reps - Number of analog outputs.
02: 2 Address of SDM-AO4 in base 4 (00 to 33)
03: 4 Input Location containing millivolt output level

Execution Time: 1.0 ms + (0.8 ms) * R (R=Repetitions)

6.3 Programming Examples

The following program examples are given to help the user understand the
general principles involved in the use of the SDM-AO4 with CSI dataloggers.

Both of the example programs are for weather stations with a datalogger
measuring wind speed, wind direction, temperature, and relative humidity.
Each parameter is then scaled to 0 to 1000 mVDC, and output to a strip chart
recorder through the SDM-AO4.

8

SDM-AO4 Four Channel Analog Output

6.3.1 CR5000 Program Example

Although this program is for a CR5000 datalogger, programming for other
CRBasic dataloggers is similar.

'CR5000 SDM-AO4 Program Example

Public WS_ms
Public WD_0_360
Public Temp_C
Public RH
Public WD_0_540
Public Flag
Public AO4Output(4)

Alias AO4Output(1) = WSOut
Alias AO4Output(2) = WDOut
Alias AO4Output(3) = TempOut
Alias AO4Output(4) = RHOut

'Code for DataTable OneMin

DataTable(OneMin,1,-1)
DataInterval(0,1,Min,0)
WindVector (1, WS_ms,WD_0_360, IEEE4, 0, 0, 0, 0)
Average(1,Temp_C,IEEE4,0)
Sample(1,RH, IEEE4
EndTable

BeginProg
Scan(1,Sec,1,0)

' Code for 03001 wind measurements, WS_ms & WD_0_360:

PulseCount(WS_ms, 1, 1, 1, 1, 0.75, 0.2)
BrHalf(WD_0_360, 1, mV1000, 1, 1, 1, 1000, True, 1000, 250, 355, 0)

' Code for CS500 measurement, AirTC and RH:

VoltSE(Temp_C,1,mV5000,3,0, 0, _60Hz,0.1,-40.0)
VoltSE(RH,1,mV5000,2,0, 0, _60Hz,0.1, 0)

' Call Data Table

CallTable(OneMin)

' Convert 0-360 WD to 0-540:

If WD_0_540 >= 270 and WD_0_360 <180 Then
WD_0_540 = WD_0_360 + 360
Else
WD_0_540 = WD_0_360
EndIf

' Scale the measurements for the SDM-AO4 to output 0-1000 mV

WSOut = WS_ms*20 'WS: 0-50 m/s = 0-1000 mV
WDOut = WD_0_540 *1.859 'WD: 0-540 deg = 0-1000mV
TempOut= 10*(Temp_C+40) 'Temp: -40-60 deg C = 0-1000 mV
RHOut = RH *10 'RH: 0-100 % RH = 0-1000 mV

' Send mV outputs to SDM-SIO4

SDMAO4 (AO4Output(),4,12)
NextScan
EndProg

9

SDM-AO4 Four Channel Analog Output

6.3.2 CR10X Program Example

Although this program is for a CR10X, programming for other Edlog
dataloggers is similar.

;{CR10X}

*Table 1 Program
01: 1.0000 Execution Interval (seconds)

; Code for 03001 wind measurements, WS_ms & WindDir:

1: Pulse (P3)
1: 1 Reps
2: 1 Pulse Channel 1
3: 21 Low Level AC, Output Hz
4: 1 Loc [ WS_ms ]
5: 0.75 Mult
6: 0.2 Offset

2: Excite-Delay (SE) (P4)
1: 1 Reps
2: 5 2500 mV Slow Range
3: 1 SE Channel
4: 1 Excite all reps w/Exchan 1
5: 2 Delay (0.01 sec units)
6: 2500 mV Excitation
7: 2 Loc [ WD_0_360 ]
8: 0.142 Mult
9: 0 Offset

; Code for CS500 measurement, AirTC and RH:

3: Volt (SE) (P1)
1: 1 Reps
2: 25 2500 mV 60 Hz Rejection Range
3: 3 SE Channel
4: 3 Loc [ Temp_C ]
5: 0.1 Mult
6: -40.0 Offset

4: Volt (SE) (P1)
1: 1 Reps
2: 25 2500 mV 60 Hz Rejection Range
3: 2 SE Channel
4: 4 Loc [ RH ]
5: 0.1 Mult
6: 0 Offset

; Output Data Every Minute

10

SDM-AO4 Four Channel Analog Output

5: If time is (P92)
1: 0 Minutes (Seconds --) into a
2: 1 Interval (same units as above)
3: 10 Set Output Flag High (Flag 0)

6: Set Active Storage Area (P80) ;Set array ID to 101
1: 1 Final Storage Area 1
2: 101 Array ID

7: Real Time (P77) ; Output Year, Day, Hour/Minute
1: 1110 Year,Day,Hour/Minute (midnight = 0000)

8: Wind Vector (P69) ; Output Average WS, WD, StdDev WD
1: 1 Reps
2: 0 Samples per Sub-Interval
3: 0 S, theta(1), sigma(theta(1)) with polar sensor
4: 1 Wind Speed/East Loc [ WS_ms ]
5: 2 Wind Direction/North Loc [ WD_0_360 ]

9: Average (P71) ; Output Average Temperature
1: 1 Reps
2: 3 Loc [ Temp_C ]

10: Sample (P70) ; Sample RH
1: 1 Reps
2: 4 Loc [ RH ]

; Routine to convert 0-360 deg. Direction to 0-540 deg.

11: Do (P86)
1: 21 Set Flag 1 Low

12: If (X<=>F) (P89) ; Set Flag 1 if previous
1: 9 X Loc [ WD_0_540 ] ; reading was > 270
2: 3 >=
3: 270 F
4: 11 Set Flag 1 High

13: Z=X (P31) ; Set 0-540 value to current 0-360 reading
1: 2 X Loc [ WD_0_360 ]
2: 9 Z Loc [ WD_0_540 ]

14: If (X<=>F) (P89) ; If current reading is <180
1: 9 X Loc [ WD_0_540 ]
2: 4 <
3: 180 F
4: 30 Then Do

15: If Flag/Port (P91) ; And if previous reading
1: 11 Do if Flag 1 is High ; was > 270
2: 30 Then Do

11

SDM-AO4 Four Channel Analog Output

16: Z=X+F (P34) ; Add 360 to the current reading
1: 9 X Loc [ WD_0_540 ] ; otherwise, the current reading
2: 360 F ; is left alone
3: 9 Z Loc [ WD_0_540 ]

17: End (P95)

18: End (P95)

; Scale the measurements for the SDM-AO4 to output 0 to 1000 mV

19: Z=X*F (P37) ; Scale WS: 0-50 mps = 0-1000 mV
1: 1 X Loc [ WS_ms ]
2: 20 F
3: 5 Z Loc [ WSoutput ]

20: Z=X*F (P37) ; Scale WD: 0-540 deg = 0-1000 mV
1: 9 X Loc [ WD_0_540 ]
2: 1.859 F
3: 6 Z Loc [ WDoutput ]

21: Z=X+F (P34) ; Scale Temperature: -40-60 deg C = 0-1000 mV
1: 3 X Loc [ Temp_C ]
2: 40 F
3: 7 Z Loc [ TempOut ]

22: Z=X*F (P37)
1: 7 X Loc [ TempOut ]
2: 10 F
3: 7 Z Loc [ TempOut ]

23: Z=X*F (P37) ; Scale RH: 0-100 % RH = 0-1000 mV
1: 4 X Loc [ RH ]
2: 10 F
3: 8 Z Loc [ RHout ]

; Send mV outputs to SDM-AO4

24: SDM-AO4 (P103)
1: 4 Reps
2: 30 SDM Address
3: 5 Loc [ WSoutput ]

End Program

12

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