Campbell Scientific AM16-32B User Manual
AM16/32B Relay Multiplexer
Revision: 4/13
Copyright © 1987-2013
Campbell Scientific, Inc.
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Table of Contents
PDF viewers: These page numbers refer to the printed version of this document. Use the
PDF reader bookmarks tab for links to specific sections.
1. Function....................................................................... 1
1.1 Typical Applications............................................................................1
1.2 Compatibility .......................................................................................2
2. Physical Description...................................................2
3. AM16/32B Specifications ...........................................3
4. Operation.....................................................................5
4.1 The Control Terminals .........................................................................5
4.1.1 Reset..............................................................................................6
4.1.2 Clock.............................................................................................7
4.1.2.1 Mode A...............................................................................7
4.1.2.2 Mode B...............................................................................7
4.1.2.3 Datalogger Connection/Instruction ....................................8
4.1.3 Ground ..........................................................................................9
4.1.4 Power Supply ................................................................................9
4.2 Measurement Terminals.....................................................................10
4.2.1 COM Terminals ..........................................................................11
4.2.2 Sensor Input Terminals...............................................................11
5. Datalogger Programming.........................................12
5.1 CRBasic Programming.......................................................................13
5.1.1 CR1000, CR800, and CR850 Programming ...............................14
5.1.2 CR5000 and CR3000 Programming ...........................................16
5.2 Edlog Programming ...........................................................................17
5.2.1 Single Loop Instruction Sequence ..............................................17
5.2.2 Multiple Loop Instruction Sequence ...........................................22
5.3 General Programming Considerations ...............................................24
6. Sensor Hookup and Measurement Examples ........24
6.1 Single-Ended Analog Measurement without Sensor Excitation ........25
6.2 Differential Analog Measurement without Sensor Excitation............25
6.3 Half Bridge Measurements.................................................................26
6.3.1 Half Bridge Measurement with Completion Resistor at
Datalogger ...............................................................................26
6.3.2 Potentiometer Measurement........................................................27
6.3.3 Four Wire Half Bridge (Measured Excitation Current) ..............27
6.4 Full Bridge Measurements .................................................................28
6.5 Full Bridges with Excitation Compensation.......................................29
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Table of Contents
6.6 Thermocouple Measurement............................................................. 30
6.6.1 Measurement Considerations ..................................................... 30
6.6.2 Single-ended Thermocouple Measurement................................ 32
6.6.3 Differential Thermocouple Measurement .................................. 33
6.7 Mixed Sensor Types.......................................................................... 33
6.7.1 Mixed Sensor Example: Soil Moisture Blocks and
Thermocouples ....................................................................... 33
7. General Measurement Considerations ...................37
8. Installation .................................................................37
8.1 Mounting Tabs .................................................................................. 38
8.2 Controlling Humidity ........................................................................ 38
Appendix
AM16/32B Improvements .......................................A-1
A.
Figures
2-1. AM16/32B Relay Multiplexer............................................................. 3
3-1. AM16/32B relay actuation time vs. temperature and battery
voltage.............................................................................................. 5
4-1. AM16/32B to datalogger power/control hookup using
CABLE4CBL cable ......................................................................... 6
4-2. Diagram showing advancement of channels using clocking
Mode B ............................................................................................ 8
4-3. Power and ground connections for external power supply................ 10
4-4. Typical AM16/32B to datalogger signal hookup (4x16 mode)
using CABLE4CBL cable.............................................................. 11
5-1. SCWin (Short Cut for Windows program builder)............................ 12
5-2. Example “4x16” mode program loops for CR23X, CR10(X),
21X, and CR7 dataloggers............................................................. 20
5-3. Example “2x32” mode program loops for CR23X, CR10(X),
21X, and CR7 dataloggers............................................................. 21
5-4. Wiring diagram for strain gages and potentiometers (uses two
CABLE4CBL cables) .................................................................... 22
6-1. Single-ended measurement without excitation.................................. 25
6-2. Differential measurement without excitation .................................... 25
6-3. Half bridge (modified 107 Temperature Probe) hookup and
measurement .................................................................................. 26
6-4. Potentiometer hookup and measurement (using CABLE4CBL
cable).............................................................................................. 27
6-5. Four wire half bridge hookup and measurement ............................... 28
6-6. Full bridge measurement................................................................... 28
6-7. Full bridge measurement with excitation compensation ................... 29
6-8. Differential thermocouple measurement with reference junction
at the datalogger............................................................................. 31
6-9. Differential thermocouple measurement with reference junction
at the AM16/32B ........................................................................... 31
6-10. AM16/32B aluminum cover plate ..................................................... 32
ii
Table
Table of Contents
6-11. Thermocouple and soil block measurement for CR10X example......34
8-1. Mounting tab hole pattern ..................................................................38
5-1. Single Loop Instruction Sequence......................................................17
iii
Table of Contents
iv
Cautionary Notes
The AM16/32B is not designed to multiplex power. Its intended function is to
switch low level analog signals. Switched currents in excess of 30 mA will
degrade the relay contacts involved, rendering that channel unsuitable for
further low level analog measurement. Customers who need to switch power
are directed to Campbell Scientific’s SDM-CD16AC, A6REL-12, or
A21REL-12 relays.
Changing the setting of the mode switch from “4x16” to “2x32” connects
COM ODD H to COM EVEN H and also COM ODD L to COM EVEN L.
After wiring AM16/32B, exercise due care to avoid inadvertently putting
excess voltage on a line or short circuiting a power supply which might
damage connected devices such as datalogger, wiring panel, sensor, or
multiplexer (not covered under warranty).
v
vi
AM16/32B Relay Multiplexer
1. Function
The primary function of the AM16/32B Multiplexer is to increase the number
of sensors that can be measured by a CR1000, CR3000, CR800, CR850,
CR23X, CR10(X), 21X, or CR7 datalogger. The AM16/32B is positioned
between the sensors and the datalogger. The AM16/32B is a replacement for
Campbell Scientific’s AM16/32A model. The hardware is the same as the
AM16/32A model. The AM16/32B adds a mode to address an individual
relay. Mechanical relays in the AM16/32B connect each of the sensor
channels in turn to a common output destined for the datalogger. The user
program advances the multiplexer through the sensor channels making
measurements and storing data.
A slide switch located on the AM16/32B’s top panel selects one of two modes
of operation. In “2x32” mode the multiplexer can scan 32 sensor input
channels, each with two lines. In “4x16” mode it can scan 16 input channels
with four lines a piece. The datalogger program is written according to the
selected mode and the sensors to be measured.
The maximum number of sensors that can be multiplexed by an AM16/32B
depends primarily on the type(s) of sensors to be scanned. The following
guidelines assume identical sensors:
Up to 32 single-ended or differential analog sensors that do not require
excitation. For example: pyranometers and thermocouples (see Section 6.1,
Single-Ended Analog Measurement without Sensor Excitation, Section 6.2,
Differential Analog Measurement without Sensor Excitation, and Section 6.6,
Thermocouple Measurement).
Up to 32 single-ended sensors that require excitation. Example: some half
bridges (see Section 6.3.1, Half Bridge Measurement with Completion Resistor
at Datalogger).
Up to 16 single-ended or differential sensors that require excitation. Examples:
full bridges and four-wire half bridge with measured excitation (see Section
6.3.3, Four Wire Half Bridge, and Section 6.4, Full Bridge Measurements).
In conjunction with a second AM16/32B, up to 16 six-wire full bridges
(Section 6.5, Full Bridges with Excitation Compensation).
1.1 Typical Applications
The AM16/32B is intended for use in applications where the number of
required sensors exceeds the number of datalogger input channels. Most
commonly, the AM16/32B is used to multiplex analog sensor signals, although
it can also be used to multiplex switched excitations, continuous analog
outputs, or even certain pulse counting measurements (those that require only
intermittent sampling). It is also possible to multiplex sensors of different, but
compatible, types (for example, thermocouples and soil moisture blocks, see
Section 6.7.1, Mixed Sensor Example: Soil Moisture Blocks and
Thermocouples).
1
AM16/32B Relay Multiplexer
NOTE
For a discussion of single-ended versus differential analog
measurements, please consult the measurement section of your
datalogger manual.
As purchased, the AM16/32B is intended for use in indoor, non-condensing
environments. An enclosure is required for field or high humidity use. In
applications where one or two multiplexers are deployed, the ENC10/12
(10” x 12”) enclosure is recommended.
1.2 Compatibility
The AM16/32B is compatible with Campbell’s CR5000, CR800, CR850,
CR3000, CR1000, CR23X, CR10(X), 21X, and CR7 dataloggers.
The AM16/32B is compatible with a wide variety of commercially available
sensors. As long as relay contact current maximums are not exceeded (see
Cautionary Notes, page v), and no more than four lines are switched at a time,
system compatibility for a specific sensor is determined by sensor-datalogger
compatibility.
In CR1000, CR800, CR850, CR3000, CR23X, and CR10(X) applications, the
AM16/32B may be used to multiplex up to 16 Geokon vibrating wire sensors
through one AVW1 vibrating wire interface. The AM16/32B can also be used
to multiplex vibrating wire sensors connected to the AVW200 or AVW206.
2. Physical Description
The AM16/32B is housed in a 10.2 x 23.9 x 4.6 cm (4.0 x 9.4 x 1.8 in)
anodized aluminum case (FIGURE 2-1). The aluminum case is intended to
reduce temperature gradients across the AM16/32B’s terminal strips. An
aluminum cover plate is also included to this end, and its use is extremely
important if thermocouples are being multiplexed (Section 6.6, Thermocouple
Measurement).
The case can be opened for inspection/cleaning by removing two Phillips-head
screws located on the underside of the case. Mounting tabs are provided so the
AM16/32B can be fastened to a flat surface or an enclosure plate (Section 8,
Installation).
All connections to the AM16/32B are made on the top panel terminal blocks.
The island of four terminals located near the mode switch are dedicated to the
connecting of datalogger power and control lines (Section 4.1, The Control
Terminals). The four ODD and EVEN COM terminals on the other side of the
mode switch carry shielded multiplexed sensor signals destined for datalogger
analog inputs. The remaining terminals on the AM16/32B are for sensor and
sensor shield connection (Section 4.2, Measurement Terminals). All of the
inputs of the AM16/32B are protected with gas tubes. The terminals accept
stripped and tinned lead wires up to 16 AWG or 1.6 mm in diameter.
Datalogger-to-AM16/32B cabling requires a minimum of six and as many as
nine individually insulated wires with shields.
2
FIGURE 2-1. AM16/32B Relay Multiplexer
AM16/32B Relay Multiplexer
3. AM16/32B Specifications
Power*: Unregulated 12 Vdc
Minimum
Operating Voltage: from –55° to +40°C = 11.3 Vdc
from +40° to +85°C = 11.8 Vdc
(See FIGURE 3-1 for relay actuation times vs.
Current Drain
Quiescent: <210 µA
Active: 6 mA typical in “2 x 32” mode
11 mA typical in “4 x 16” mode
Reset*: A continuous signal between 3.3 Vdc and
Clock*: On the transition from <1.5 V to >3.3 V, a scan
temperature and supply voltage.)
8 Vdc holds the AM16/32B in an active state
(where a clock pulse can trigger a channel
advance). A signal voltage <0.9 Vdc
deactivates the AM16/32B (clock pulse will
not trigger a scan advance; AM16/32B is also
reset).
advance is actuated on the leading edge of the
clock signal; clock pulse should be a minimum
of 1 ms wide; maximum voltage is 8 Vdc.
Operational Temperature
Standard: –25° to +50°C
Extended: –55° to +85°C
Operational Humidity: 0 to 95%, non-condensing
3
AM16/32B Relay Multiplexer
Dimensions
Length: 23.9 cm (9.4 in)
Width: 10.2 cm (4.0 in)
Depth: 4.6 cm (1.8 in)
Weight: 693 g (1.5 lb) (approx.)
Mounting Tab
Hole Spacing: 1 x 3 x 9 in. Up to 1/8 in or 3 mm diameter
screws (see FIGURE 8-1).
Expandability** (nominal): 2 AM16/32Bs per CR800/CR850
4 AM16/32Bs per CR3000
4 AM16/32Bs per CR5000
4 AM16/32Bs per CR1000
4 AM16/32Bs per CR23X
4 AM16/32Bs per CR10(X)
4 AM16/32Bs per 21X
8 AM16/32Bs per CR7 725 Card
Maximum Cable Length: Depends on sensor and scan rate. In general,
longer lead lengths necessitate longer
measurement delays. Refer to datalogger
manual for details.
Maximum
Switching Current
***
: 500 mA
Contact Specifications
Initial contact resistance: <0.1 ohm max.
Initial contact bounce: <1 ms
Contact material: Gold clad silver alloy
Wiper to N.O. contact
capacitance: 0.5 pF
Typical low-current
(<30 mA) life: 5 x 10
7
operations
Relay Switching
Thermal emf: 0.3 µV typical; 0.5 µV maximum
Characteristics (applying 11.3 – 14 Vdc)
Operate time: <10 ms over temperature and supply ranges
Break-before-make guaranteed by design.
Relays disengage from previous selected
channel before engaging next channel.
ESD
Air Discharge: complies with IEC61000-4-2, test level 4
(±15 kV)
Contact Discharge: complies with IEC61000-4-2, test level 4
(±8 kV)
4
AM16/32B Relay Multiplexer
Surge: Complies with IEC61000-4-5, test level 3
(±2 kV, 2 ohms coupling impedance)
*
Reset and clock protected by 8V varistors; +12V input is protected by +16V transzorb.
**
Assumes sequential activation of multiplexers and that each datalogger channel is uniquely
dedicated. If your application requires additional multiplexing capability, please consult Campbell
Scientific for application assistance.
***
Switching currents greater than 30 mA (occasional 50 mA current is acceptable) will degrade
the contact surfaces of the mechanical relays (increase their resistance). This will adversely affect
the suitability of these relays to multiplex low voltage signals. Although a relay used in this
manner no longer qualifies for low voltage measurement, it continues to be useful for switching
currents in excess of 30 mA.
12.0
10.0
4. Operation
8.0
6.0
4.0
2.0
RELAY ACTUATION TIME (ms)
0.0
10
9.6
10.9
11.3
11.7
12.1
10.4
10.8
12.512.9
11.2
12
13.3
13.7
11.6
14.1
12.4
12.8
14.514.9
13.2
14
15.3
15.7
13.6
16.1
14.4
14.8
16.516.9
15.2
16
17.3
15.6
POWER SUPPLY VOLTAGE
65C 50C 25C -25C
FIGURE 3-1. AM16/32B relay actuation time vs. temperature and
battery voltage
Section 4.1, The Control Terminals, discusses the terminals that control
operation of the multiplexer. These terminals are located at the left-hand side
of the multiplexer as shown in FIGURE 2-1. Section 4.2, Measurement
Terminals, discusses the use of sensor measurement terminals.
4.1 The Control Terminals
The CABLE4CBL cable is used to connect the control terminals. The
CR5000, CR3000, CR800, CR850, CR1000, CR23X, CR10(X), 21X, and CR7
5
AM16/32B Relay Multiplexer
RES
CLK
GND
12V
O
N
dataloggers connect to the AM16/32B as shown in FIGURE 4-1 (“4x16”
mode). FIGURE 4-1 depicts control connections. Measurement connections
are discussed in Section 6, Sensor Hookup and Measurement Examples. The
power, ground, reset, and clock connections remain essentially the same
regardless of datalogger used.
With the CR5000, CR3000, CR800, CR850, CR1000, CR23X, and CR10(X),
the datalogger 12 Vdc supply and ground terminals are connected to the
AM16/32B 12V and ground terminals. One control port is required for
clocking and a second control port for reset. The cable’s shield is grounded on
both ends as illustrated in FIGURE 4-1.
MUXPOWER
SHIELD
CR10X,
CR800,
CR850
G G
12 V 12 V 12 V
CR3000,
CR1000
CR23X,
CR5000
21X
+12 V 12 V
CR7
4.1.1 Reset
G G G
C1-C4 C1-C8 C1-C8 EXCIT 1-4 EXCITATION
C1-C4 C1-C8 C1-C8 C1-C8
725 Card
Control
FIGURE 4-1. AM16/32B to datalogger power/control hookup using
CABLE4CBL cable
With the 21X or CR7, the AM16/32B connects to the 12 Vdc and “
”
terminals for power. One control port is used for reset, and one switched
excitation channel is used for clock (on 725 card with CR7). If a switched
excitation port is not available, an additional control port can be used to
provide clock pulses to the multiplexer.
The reset (“RES”) line is used to activate the AM16/32B. A signal in the range
of +3.3 to +8 Vdc applied to the reset terminal activates the multiplexer. When
this line drops lower than +0.9 Vdc, the multiplexer enters a quiescent, lowcurrent-drain state. In the quiescent state, the common (COM) terminals are
electrically disconnected from all of the sensor input channels. Reset should
always connect to a datalogger control port. The CR800, CR850, CR3000,
CR5000, and CR1000 use the PortSet() instruction to control the reset line.
Instruction Do (P86) (option code 41 – 48 to activate, and 51 – 58 to
deactivate) is generally used to activate/deactivate the multiplexer when using
an Edlog datalogger; however, in the case of the 21X or CR7 with older
PROMS, instruction Set Port (P20) is commonly used.
6
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