Campbell Manufacturing SDM-SW8A User Manual
SDM-SW8A 8 Channel
Switch Closure Module
Revision: 7/07
Copyright © 1987-2007
Campbell Scientific, Inc.
Warranty and Assistance
The SDM-SW8A SWITCH CLOSURE INPUT 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 (435) 753-2342. 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-SW8A 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 ..............................................................2
3. Power Supply Considerations....................................3
4. Connections.................................................................4
4.1 Connections to Dataloggers and Other SW8As........................................4
4.2 Sensor Connections ..................................................................................4
5. Internal Jumpers..........................................................4
5.1 Address Jumpers.......................................................................................4
5.2 Measurement Jumpers..............................................................................6
6. Datalogger Programming............................................6
6.1 CRBasic Programming.............................................................................6
6.2 Edlog Programming.................................................................................. 7
7. Datalogger Program Details .......................................9
7.1 Datalogger Scan Rate ...............................................................................9
7.2 First Scan..................................................................................................9
7.3 Watchdog Reset........................................................................................9
8. Measurement Applications.......................................10
8.1 SPDT Switch Closure.............................................................................10
8.2 SPST Switch Closure..............................................................................11
8.3 DC Voltage Pulse ...................................................................................11
8.4 Duty Cycle..............................................................................................11
9. Theory of Operation ..................................................12
Appendix
A. Program Example.................................................... A-1
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SDM-SW8A Table of Contents
List of Tables
List of Figures
1. Datalogger to SDM-SW8A Connections...................................................2
2. SDM-SW8A to SDM-SW8A Connections................................................ 3
3. Address Jumpers........................................................................................ 5
4. Measurement Jumpers................................................................................ 6
5. Instruction 102 – SDM-SW8A .................................................................. 7
1. SDM-SW8A Front Panel........................................................................... 1
2. SDM-SW8A Address and Port Configuration Jumpers with
Sensor Wiring Examples......................................................................... 5
3. SPDT Signal Conditioning by SDM-SW8A............................................ 10
A-1. Example Program Flow Chart ........................................................... A-2
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SDM-SW8A Switch Closure Input Module
1. Function
The 8 channel SDM-SW8A Switch Closure Input Module (see Figure 1)
measures up to 8 channels of switch closure or voltage pulse inputs. Each
channel may be configured to read single-pole double-throw (SPDT) switch
closure, single-pole single-throw (SPST) switch closure, or voltage pulse.
Output options include counts, duty cycle, and state.
The SW8A is addressed by the datalogger, allowing multiple SW8As to be
connected to one datalogger (refer to Theory of Operation, Section 9). Sixteen
addresses are available, but for most applications, Campbell Scientific, Inc.
recommends no more than 4 SW8As be connected to one datalogger. If more
SW8As are required, please consult Campbell Scientific's Marketing
Department.
In October, 1988, the SDM-SW8A was introduced. Edlog Instruction 102 is
used for communication with the SW8A. CRBasic dataloggers use the
SDMSW8A instruction. Previous to October, 1988, the SDM-SW8 (no "A")
was offered for use only with the CR10, utilizing CR10 I/O Instruction 15.
SDM-SW8As are not compatible with CR10s containing Instruction 15,
and SDM-SW8s are not compatible with CR10s containing Instruction
102. Contact Campbell Scientific's Marketing Department for update options
if incompatibilities exist.
FIGURE 1. SDM-SW8A Front Panel
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SDM-SW8A Switch Closure Input Module
2. Specifications
Operating voltage: 12 VDC nominal (9.6 to 16)
Current drain: 3 mA quiescent, 6 mA active (max)
Environmental: -25 to +50
Measurement types: Switch closure (SPDT, SPST) DC voltage
Input voltage threshold: From below 0.9 to above 4.0 VDC,±20
Maximum input frequency: 100 Hz (50% duty cycle)
Minimum input pulse width: 5 ms high, 5 ms low
Maximum bounce time: 3 ms open without counting
Output options: State, duty cycle, counts
Max count/port: 65535
Internal sampling frequency: 500 Hz
Watchdog reset: Yes
Total length of connecting cables: 20 feet
Dimensions: 0.9"(H), 6.2"(L), 2.7"(W)
Weight 0.5 lbs. (0.23 kg)
Compatible dataloggers: CR10(X), CR800, CR850, CR1000, 21X,
o
C, 0 to 90% RH,
noncondensing
pulse
VDC max
CR23X, CR3000, CR5000, and CR7
TABLE 1. Datalogger to SDM-SW8A Connections
Datalogger
SDM-SW8A
+12
CR7
CR1000,
CR800,
CR850,
CR23X,
CR10(X)
CR3000,
CR5000
21X
+12 12 V 12 V +12
(see Note 1)
G G
C3 C3 C3 SDM-C3 C3
C2 C2 C2 SDM-C2 C2
C1 IN C1 C1 SDM-C1 C1
C1 OUT not used
(see Note 2)
not used
(see Note 2)
not used
(see Note 2)
1H
(see Note 2)
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SDM-SW8A Switch Closure Input Module
TABLE 2. SDM-SW8A to SDM-SW8A Connections
SDM-SW8A
SDM-SW8A that’s connected to
a CR10(X), CR800, CR850,
CR1000, CR23X, CR3000,
CR5000, or CR7
SDM-SW8A that’s
connected to a 21X
+12 12 V +12
C3 C3 C3
C2 C2 C2
C1 IN C1 IN C1 IN
C1 OUT not used (see Note 2) C1 OUT (see Note 3)
Notes:
(1) If using an auxiliary power supply, instead of connecting the datalogger’s
12 V or +12 terminal to the SW8A, connect the power supply’s positive “+”
wire to the SW8A’s +12 terminal. The power supply’s ground “-” wire
connects to the SW8A’s
datalogger’s G or
terminal.
terminal along with the wire that connects to the
(2) When using a CR10(X), CR800, CR850, CR1000, CR23X, CR3000, or
CR7, a jumper wire is used to connect the C1 IN to the C1 OUT. SDMSW8As shipped after March 1, 2006, include this jumper.
(3) If you’re using a 21X and the SDM-SW8A was shipped after March 1,
2006, remove the jumper connecting C1 IN to C1 OUT.
3. Power Supply Considerations
Due to the 3 mA continuous and 6 mA active current drain, an auxiliary 12
VDC power supply is recommended for powering the SW8A in remote, long
term applications.
For some applications it may be convenient to use the datalogger supply to
power the SW8A. For long term applications where AC power is available, or
where a solar panel can be used for recharging, the lead acid power supply
available with Campbell Scientific, Inc. dataloggers could be used. For short
term applications only, the alkaline power supply available with Campbell
Scientific, Inc. dataloggers could be used to power the SW8A.
If the 21X power supply is used to power the SW8A, all low level analog
measurements (thermocouples, pyranometers, thermopiles, etc.) must be made
differentially. This results from slight ground potentials created along the 21X
analog terminal strip when the 12 V supply is used to power peripherals. This
limitation reduces the number of available analog input channels and may
mandate an external supply for the SW8A.
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SDM-SW8A Switch Closure Input Module
4. Connections
All connections to the datalogger, power supply, and other SW8As are made
from terminals located under "TO DATALOGGER" on the SW8A (refer to
Figure 1). Sensor connections are made at the remaining terminals.
4.1 Connections to Dataloggers and Other SW8As
Connections between an SW8A and the CR10 and 21X dataloggers are shown
in Table 1. Connections to multiple SW8As are shown in Tab le 2 .
CAUTION
1. The order in which connections are made is critical.
ALWAYS CONNECT GROUND FIRST, followed by 12 V
and then the Control Ports.
2. The sum of all the cable lengths connecting SW8As or
other SDM devices and a datalogger should not exceed 20
feet. Lengths in excess of 20 feet may prevent
communication.
4.2 Sensor Connections
Figure 2 shows the connections between the SW8A and compatible sensor
types.
5. Internal Jumpers
Inside the SW8A, jumpers must be set to configure the Module address and the
channel measurement type for each channel. Remove the two panel screws
and lift the cover to access the jumpers. Figure 2 shows jumper location.
5.1 Address Jumpers
Each module can have 1 of 16 addresses (00 to 33, Base 4). The address is
factory set to 00. Figure 2 shows the location of the address jumper block.
Table 3 lists the jumper settings for each address.
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