Campbell AM16/32B User manual

INSTRUCTION MANUAL
AM16/32B Relay Multiplexer
Revision: 7/16
Copyright © 1987-2016
Campbell Scientific, Inc.

Guarantee
This equipment is guaranteed against defects in materials and workmanship.
We will repair or replace products which prove to be defective during the
guarantee period as detailed on your invoice, provided they are returned to us
prepaid. The guarantee will not apply to:

Equipment which has been modified or altered in any way without the
written permission of Campbell Scientific

Batteries

Any product which has been subjected to misuse, neglect, acts of God or
damage in transit.
Campbell Scientific will return guaranteed equipment by surface carrier
prepaid. Campbell Scientific will not reimburse the claimant for costs incurred
in removing and/or reinstalling equipment. This guarantee and the Company’s
obligation thereunder is in lieu of all other guarantees, expressed or implied,
including those of suitability and fitness for a particular purpose. Campbell
Scientific is not liable for consequential damage.
Please inform us before returning equipment and obtain a Repair Reference
Number whether the repair is under guarantee or not. Please state the faults as
clearly as possible, and if the product is out of the guarantee period it should
be accompanied by a purchase order. Quotations for repairs can be given on
request. It is the policy of Campbell Scientific to protect the health of its
employees and provide a safe working environment, in support of this policy a
“Declaration of Hazardous Material and Decontamination” form will be
issued for completion.
When returning equipment, the Repair Reference Number must be clearly
marked on the outside of the package. Complete the “Declaration of
Hazardous Material and Decontamination” form and ensure a completed copy
is returned with your goods. Please note your Repair may not be processed if
you do not include a copy of this form and Campbell Scientific Ltd reserves
the right to return goods at the customers’ expense.
Note that goods sent air freight are subject to Customs clearance fees which
Campbell Scientific will charge to customers. In many cases, these charges are
greater than the cost of the repair.
Campbell Scientific Ltd,
80 Hathern Road,
Shepshed, Loughborough, LE12 9GX, UK
Tel: [phone]
Fax: [phone]
Email: [e-mail]
www.campbellsci.co.uk

PLEASE READ FIRST
About this manual
Please note that this manual was originally produced by Campbell Scientific Inc. primarily for the North
American market. Some spellings, weights and measures may reflect this origin.
Some useful conversion factors:
Area: 1 in2(square inch) = 645 mm2
Length: 1 in. (inch) = 25.4 mm
1 ft (foot) = 304.8 mm
1 yard = 0.914 m
1 mile = 1.609 km
Mass: 1 oz. (ounce) = 28.35 g
1 lb (pound weight) = 0.454 kg
Pressure: 1 psi (lb/in2) = 68.95 mb
Volume: 1 UK pint = 568.3 ml
1 UK gallon = 4.546 litres
1 US gallon = 3.785 litres
In addition, while most of the information in the manual is correct for all countries, certain information
is specific to the North American market and so may not be applicable to European users.
Differences include the U.S standard external power supply details where some information (for
example the AC transformer input voltage) will not be applicable for British/European use. Please note,
however, that when a power supply adapter is ordered it will be suitable for use in your country.
Reference to some radio transmitters, digital cell phones and aerials may also not be applicable
according to your locality.
Some brackets, shields and enclosure options, including wiring, are not sold as standard items in the
European market; in some cases alternatives are offered. Details of the alternatives will be covered in
separate manuals.
Part numbers prefixed with a “#” symbol are special order parts for use with non-EU variants or for
special installations. Please quote the full part number with the # when ordering.
Recycling information
At the end of this product’s life it should not be put in commercial or domestic refuse but
sent for recycling. Any batteries contained within the product or used during the
products life should be removed from the product and also be sent to an appropriate
recycling facility.
Campbell Scientific Ltd can advise on the recycling of the equipment and in some cases
arrange collection and the correct disposal of it, although charges may apply for some
items or territories.
For further advice or support, please contact Campbell Scientific Ltd, or your local agent.
Campbell Scientific Ltd, 80 Hathern Road, Shepshed, Loughborough, LE12 9GX, UK
Tel: [phone] Fax: [phone]
Email: [e-mail]
www.campbellsci.co.uk

Precautions
DANGER —MANY HAZARDS ARE ASSOCIATED WITH INSTALLING, USING, MAINTAINING, AND WORKING ON
OR AROUND TRIPODS, TOWERS, AND ANY ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS,
CROSSARMS, ENCLOSURES, ANTENNAS, ETC. FAILURE TO PROPERLY AND COMPLETELY ASSEMBLE,
INSTALL, OPERATE, USE, AND MAINTAIN TRIPODS, TOWERS, AND ATTACHMENTS, AND FAILURE TO HEED
WARNINGS, INCREASES THE RISK OF DEATH, ACCIDENT, SERIOUS INJURY, PROPERTY DAMAGE, AND
PRODUCT FAILURE. TAKE ALL REASONABLE PRECAUTIONS TO AVOID THESE HAZARDS. CHECK WITH YOUR
ORGANIZATION'S SAFETY COORDINATOR (OR POLICY) FOR PROCEDURES AND REQUIRED PROTECTIVE
EQUIPMENT PRIOR TO PERFORMING ANY WORK.
Use tripods, towers, and attachments to tripods and towers only for purposes for which they are designed. Do not
exceed design limits. Be familiar and comply with all instructions provided in product manuals. Manuals are
available at www.campbellsci.eu or by telephoning [phone] (UK). You are responsible for conformance
with governing codes and regulations, including safety regulations, and the integrity and location of structures or land
to which towers, tripods, and any attachments are attached. Installation sites should be evaluated and approved by a
qualified engineer. If questions or concerns arise regarding installation, use, or maintenance of tripods, towers,
attachments, or electrical connections, consult with a licensed and qualified engineer or electrician.
General
•Prior to performing site or installation work, obtain required approvals and permits. Comply with all
governing structure-height regulations, such as those of the FAA in the USA.
•Use only qualified personnel for installation, use, and maintenance of tripods and towers, and any
attachments to tripods and towers. The use of licensed and qualified contractors is highly recommended.
•Read all applicable instructions carefully and understand procedures thoroughly before beginning work.
•Wear a hardhat and eye protection, and take other appropriate safety precautions while working on or
around tripods and towers.
•Do not climb tripods or towers at any time, and prohibit climbing by other persons. Take reasonable
precautions to secure tripod and tower sites from trespassers.
•Use only manufacturer recommended parts, materials, and tools.
Utility and Electrical
•You can be killed or sustain serious bodily injury if the tripod, tower, or attachments you are installing,
constructing, using, or maintaining, or a tool, stake, or anchor, come in contact with overhead or
underground utility lines.
•Maintain a distance of at least one-and-one-half times structure height, or 20 feet, or the distance
required by applicable law, whichever is greater, between overhead utility lines and the structure (tripod,
tower, attachments, or tools).
•Prior to performing site or installation work, inform all utility companies and have all underground utilities
marked.
•Comply with all electrical codes. Electrical equipment and related grounding devices should be installed
by a licensed and qualified electrician.
Elevated Work and Weather
•Exercise extreme caution when performing elevated work.
•Use appropriate equipment and safety practices.
•During installation and maintenance, keep tower and tripod sites clear of un-trained or non-essential
personnel. Take precautions to prevent elevated tools and objects from dropping.
•Do not perform any work in inclement weather, including wind, rain, snow, lightning, etc.
Maintenance
•Periodically (at least yearly) check for wear and damage, including corrosion, stress cracks, frayed cables,
loose cable clamps, cable tightness, etc. and take necessary corrective actions.
•Periodically (at least yearly) check electrical ground connections.
WHILE EVERY ATTEMPT IS MADE TO EMBODY THE HIGHEST DEGREE OF SAFETY IN ALL CAMPBELL
SCIENTIFIC PRODUCTS, THE CUSTOMER ASSUMES ALL RISK FROM ANY INJURY RESULTING FROM IMPROPER
INSTALLATION, USE, OR MAINTENANCE OF TRIPODS, TOWERS, OR ATTACHMENTS TO TRIPODS AND TOWERS
SUCH AS SENSORS, CROSSARMS, ENCLOSURES, ANTENNAS, ETC.

i
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. Introduction ................................................................1
1.1 Typical Applications ............................................................................1
1.2 Compatibility .......................................................................................1
2. Precautions ................................................................2
3. Initial Inspection.........................................................2
4. QuickStart...................................................................2
5. Overview .....................................................................5
6. AM16/32B Specifications...........................................6
7. Installation ..................................................................8
7.1 Wiring to Datalogger ...........................................................................8
7.1.1 Control Terminals .........................................................................8
7.1.2 COM Terminals ............................................................................8
7.1.3 Measurement Terminals................................................................9
7.2 Grounding ............................................................................................9
7.3 Power Supply.......................................................................................9
7.4 Installation in Enclosure.....................................................................10
8. Operation..................................................................10
8.1 Programming......................................................................................11
8.1.1 General Programming Considerations ........................................12
8.1.2 Mixed Sensor Types ...................................................................12
8.2 General Measurement Considerations ...............................................13
8.2.1 Long Cable Lengths....................................................................13
8.2.2Earth Ground...............................................................................13
8.2.3 Completion Resistors ..................................................................13
8.2.4 Contact Degradation ...................................................................13
Appendices
A. Importing Short Cut Code Into CRBasic Editor ... A-1
B. Example Measurements and Programs................ B-1
B.1 Single-Ended Voltage Measurement................................................B-1
B.2 Differential Voltage Measurement...................................................B-3
B.3 Half-Bridge Measurement................................................................B-4
B.4 Full-Bridge Measurement ................................................................B-6

Table of Contents
ii
B.5 CR5000 Program Example............................................................ B-10
C. Thermocouple Measurement................................. C-1
C.1 Measurement Considerations .......................................................... C-1
C.1.1 Reference Junction ................................................................... C-1
C.1.2 Datalogger Reference............................................................... C-1
C.1.3 AM16/32B Reference .............................................................. C-2
C.1.4 Thermal Gradients.................................................................... C-2
Figures
5-1. AM16/32B Relay Multiplexer............................................................. 6
7-1. Example of AM16/32B-to-datalogger signal connection (4x16
mode) ............................................................................................... 9
B-1. Typical single-ended voltage measurement connection .................. B-1
B-2. Typical differential voltage measurement connection..................... B-3
B-3. Typical half-bridge measurement connection ................................. B-5
B-4. Full-bridge measurement................................................................. B-6
C-1. Differential thermocouple measurement with reference junction
at the datalogger........................................................................... C-2
C-2. Differential thermocouple measurement with reference junction
at the AM16/32B (using 107-L thermistor) ................................. C-2
C-3. AM16/32B aluminum cover plate ................................................... C-3
Tables
7-1. Control Terminal Function and Datalogger Connection ..................... 8
B-1. Wiring for Single-Ended Voltage Measurements CRBasic
Example ....................................................................................... B-2
B-2. Wiring for Differential Voltage Measurements CRBasic
Example ....................................................................................... B-3
B-3. Wiring for Campbell Scientific 107 Temperature Sensors
CRBasic Example ........................................................................ B-5
B-4. Wiring for Load Cells CRBasic Example ....................................... B-7
B-5. Wiring for CS616 Sensor CRBasic Example .................................. B-9
B-6. Wiring for CR5000 Program Example.......................................... B-10
CRBasic Examples
B-1. Single-Ended Voltage Measurements ............................................. B-2
B-2. Differential Voltage Measurements ................................................ B-4
B-3. Campbell Scientific 107 Temperature Sensors ............................... B-5
B-4. Load Cells ....................................................................................... B-7
B-5. CS616 Sensors................................................................................. B-9
B-6. CR5000 Program Example............................................................ B-11

1
AM16/32B Relay Multiplexer
1. Introduction
The primary function of the AM16/32B multiplexer is to increase the number
of sensors that can be measured by CR6-series, CR800-series, CR1000,
CR3000, and CR5000 dataloggers. The AM16/32B is positioned between the
sensors and the datalogger. 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 adds 32 terminal pairs. In 4x16
mode, it adds 16 terminal groups with four terminals each. The datalogger
program is written according to the selected mode and the sensors to be
measured.
The maximum number of sensors multiplexed by an AM16/32B depends
primarily on the type(s) of sensors to be measured.
This manual provides information for CRBasic dataloggers and
serial numbers greater than 5056. The AM16/32B is also
compatible with most of our retired Edlog dataloggers.
For Edlog datalogger support or for specifications on serial
numbers lower than 5056, see an older version of this manual at
www.campbellsci.com/old-manuals.
1.1 Typical Applications
The AM16/32B is intended for use in applications where more terminals are
needed than the datalogger has available. 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 (see
Section 8.1.2, Mixed Sensor Types (p. 12)).
1.2 Compatibility
The AM16/32B is compatible with Campbell Scientific’s CR6-series, CR800-
series, CR1000, CR3000, and CR5000 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
Section 2, Precautions (p. 2)), and no more than four lines are switched at a
time, system compatibility for a specific sensor is determined by sensor-
datalogger compatibility.
NOTE

AM16/32B Relay Multiplexer
2
The AM16/32B is also compatible with the CDM-A108 and
CDM-A116 24-bit analog input modules by using the CRBasic
CDM_MuxSelect() instruction. Refer to the CRBasic Help for
information on using the AM16/32B with these modules. The
CDM-A100 Series manual includes a sample program for the
CDM-A108 and the AM16/32B.
2. Precautions
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 the 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, and
which would not be covered under warranty.
3. Initial Inspection
•The AM16/32B ships with:
o4 each pn 6044, Grommet
o4 each pn 505, Screw
•Upon receipt of the AM16/32B, inspect the packaging and contents for
damage. File damage claims with the shipping company.
•Immediately check package contents. Thoroughly check all packaging
material for product that may be concealed. Check model number, part
numbers, and product descriptions against the shipping documents. Model
or part numbers are found on each product. On cables, the number is often
found at the end of the cable that connects to the measurement device.
Ensure that the expected lengths of cables were received. Contact
Campbell Scientific immediately if there are any discrepancies.
4. QuickStart
Short Cut is an easy way to program your datalogger to make measurements
through an AM16/32B multiplexer. Short Cut is included in installations of
LoggerNet, PC400, PC200W, and RTDAQ. It is also available as a download
on www.campbellsci.com and the ResourceDVD.
This section will guide you through programming a datalogger to measure 6
Campbell Scientific 107 temperature sensors as an example for creating a
program using a multiplexer. With minor changes, these steps can apply to
other measurements and dataloggers.
NOTE

AM16/32B Relay Multiplexer
3
Open Short Cut. From the
LoggerNet toolbar, click Program |
Short Cut. In PC200W and PC400,
click on the Short Cut icon.
Select New Program.
Select your datalogger model in the
Datalogger Model drop-down list.
This tutorial uses the CR6-series
datalogger.
In the Scan Interval box, enter how
frequently the datalogger should
make measurements. When
measuring with an AM16/32B
multiplexer, we recommend an
interval of 30 seconds or longer.
Enter 30 and select Seconds.
Click Next.
NOTE The first time Short Cut is run, a prompt will appear asking for a choice of first notch
frequency. Select 60 Hz Noise Rejection for the United States and areas using 60 Hz
AC voltage. Select 50 Hz Noise Rejection for most of Europe and areas that operate at
50 Hz.
A second prompt lists sensor support options. Campbell Scientific, Inc. (US) is
probably the best fit if you are outside Europe.
To change the first notch frequency or sensor support option for future programs, use
the Program menu.
The next window displays
Available Sensors and Devices.
Expand a folder by clicking on the
symbol. Expand the Devices
folder, then double-click on the
AM16/32 to add it to the Selected
panel.

AM16/32B Relay Multiplexer
4
When the AM16/32 multiplexer is
added as a device, a new AM16/32
tab will appear at the bottom of the
Available Sensors and Devices
pane. With the AM16/32 tab
selected, select the Sensors |
Temperature subfolder. Double-
click on 107 Temperature Probe
(4-wire).
In the resulting window, enter the
number of 107 temperature probes
to measure on this AM16/32B
multiplexer. For this tutorial, enter 6
as the number of 107 (4-wire)
sensors to add. Click OK in the
dialog window to accept the default
name of T107_C and the default
units of Deg C.
After adding the measurements,
click Wiring Diagram to see how
the sensors are to be wired to the
AM16/32B and how the AM16/32B
is to be wired to the datalogger. The
datalogger tab (CR6 Series in this
example) shows the connection
between the AM16/32B and the
datalogger, and the AM16/32 tab
shows the sensor connection to the
AM16/32B.
With power disconnected, wire the
sensors and devices as shown in the
wiring diagrams. Insert the wires,
taking care to tighten the terminals
on the conductors themselves, not
the insulation.

AM16/32B Relay Multiplexer
5
Click on Sensors in the Progress
list to return to the sensor-selection
screen.
Select any other sensors you have in
the Sensors section. Add sensors to
the datalogger by selecting the
datalogger tab (CR6 in this
example). Add sensors to the
multiplexer by selecting the
AM16/32 tab. Finish the remaining
Short Cut steps to complete the
program. The remaining steps are
outlined in Short Cut Help, which is
accessed by clicking on Help |
Short Cut Help | Contents |
Programming Steps.
If LoggerNet, PC200W, PC400, or
RTDAQ is running on your PC and
the PC-to-datalogger connection is
active, you can click Finish in Short
Cut, and you will be prompted to
send the program just created to the
datalogger.
After powering on and sending the program to the datalogger, check the output of sensors in the datalogger
support software data display to make sure they are making reasonable measurements.
5. Overview
Under datalogger control, the AM16/32B sequentially connects terminal pairs
or groups to datalogger terminals. This effectively expands the number of
terminals available on a datalogger.
FIGURE 5-1 shows the wiring panel of the AM16/32B multiplexer. The group
of four terminals located near the mode switch are dedicated to the connection
of datalogger power and control lines. COM ODD and EVEN terminals on the
other side of the mode switch carry multiplexed signals destined for datalogger
terminals. The remaining terminals on the AM16/32B are for sensor and
sensor-shield connection. All of the inputs of the AM16/32B are protected

AM16/32B Relay Multiplexer
6
against surges with transient suppression. Datalogger-to-AM16/32B cabling
requires a minimum of six and as many as nine individually insulated wires
with shields.
FIGURE 5-1. AM16/32B Relay Multiplexer
6. AM16/32B Specifications
Power1, 2: Unregulated 9.6 to 16 Vdc
Current Drain
Quiescent: < 210 µA
Active: 6 mA typical in 2x32 mode
11 mA typical in 4x16 mode
Reset1: A continuous signal between 3.3 Vdc and
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 channel advance; AM16/32B is
also reset).
Clock1: On the transition from <1.5 V to >3.3 V, a
channel 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

AM16/32B Relay Multiplexer
7
Dimensions
Length: 23.9 cm (9.4 in)
Width: 10.2 cm (4.0 in)
Depth: 4.6 cm (1.8 in)
Weight: 680 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.
Expandability3(nominal): 4 AM16/32Bs per CR6
2 AM16/32Bs per CR800/CR850
4 AM16/32Bs per CR3000
4 AM16/32Bs per CR5000
4 AM16/32Bs per CR1000
Maximum Cable Length: Depends on sensor and scan rate. In general,
longer lead lengths necessitate longer
measurement delays. Refer to datalogger and
sensor manuals for details.
Maximum
Switching Current4: 500 mA
Contact Specifications
Initial Contact Resistance: <0.1 Ωmax.
Initial Contact Bounce: <1 ms
Contact Material: Silver Palladium
Wiper to N.O. Contact
Capacitance: 0.5 pF
Typical Low-current
(<30 mA) Life: 5 x 107operations
Relay Switching
Thermal emf: 0.3 µV typical; 0.5 µV maximum
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)
Surge: Complies with IEC61000-4-5, test level 3
(±2 kV, 2 ohms coupling impedance)
1Reset and clock protected by 8 V varistors; +12 V input is protected by +16 V
TransZorb®.
2For power specifications on serial numbers less than 5056, refer to an older version of
this manual at www.campbellsci.com/old-manuals.
3Assumes sequential activation of multiplexers and that each datalogger channel is
uniquely dedicated. If the application requires additional multiplexing capability, please
consult Campbell Scientific for application assistance.

AM16/32B Relay Multiplexer
8
4Switching currents greater than 30 mA (occasional 50 mA current is acceptable) will
degrade the contact surfaces of the mechanical relays and 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.
7. Installation
If you are programming your datalogger with Short Cut, skip Section 7.1,
Wiring to Datalogger. Short Cut creates a wiring diagram for you. See Section
4, QuickStart (p. 2), for a Short Cut tutorial.
7.1 Wiring to Datalogger
Removable terminal strips allow wiring to remain intact while the multiplexer
is used elsewhere. The green terminal strips are easily removed; no tools are
required. Replacement terminal strips may be purchased from Campbell
Scientific.
7.1.1 Control Terminals
TABLE 7-1 depicts control connections to Campbell Scientific dataloggers.
TABLE 7-1. Control Terminal Function and Datalogger Connection1
Control
Terminal Function Datalogger Connection Terminal
12V Power 12V
G
Power
ground G(power ground)
CLK Clock C(control port), Uterminal configured for
control
RES Reset
C
,
U
terminal configured for control
1Connect the cable shield to Gon the AM16/32B and to Gon the CR6 series, CR800
series, CR1000, or CR3000. Connect to
⏚
on the CR5000.
7.1.2 COM Terminals
The four terminals dedicated to multiplexer-datalogger connection are located
under the blue COM label next to the mode switch. The terminals are labeled:
ODD H/L and EVEN H/L. In 4x16 mode, the AM16/32B maintains the four
COM terminals electrically isolated from one another. In 2x32 mode, the
AM16/32B maintains an internal connection between ODD H and EVEN H
and between ODD L and EVEN L. How the COM terminals connect to
datalogger terminals determines the function of the measurement terminals. For
proper function, these terminals must be wired according to the measurement
instructions in the CRBasic program. See Section 8, Operation (p. 10), for details
and Appendix B, Example Measurements and Programs (p. B-1), for examples.
Common
terminals are provided next to the COM ODD and COM EVEN
terminals. They connect internally to the other thirty-two
terminals on the
AM16/32B and are connected at all times (not switched). Their function is to

AM16/32B Relay Multiplexer
9
provide a path to ground for sensor cable shields. A COM
terminal should be
wired to datalogger ground (⏚) as shown in FIGURE 7-1.
FIGURE 7-1. Example of AM16/32B-to-datalogger signal connection
(4x16 mode)
7.1.3 Measurement Terminals
Wire sensors and transducers according to the COM terminal connections and
the measurement instructions in the CRBasic program. See Section 8,
Operation (p. 10) for details and Appendix B, Example Measurements and
Programs (p. B-1), for examples.
7.2 Grounding
The AM16/32B has a ground lug that should be connected to earth ground via
an 8 AWG wire. This connection should be as short as possible. The ground
lug provides a path to dissipate surges that might propagate on a sensor’s shield
line. An 8-V, bi-polar TransZorb® connects shield ground to the ground lug.
The AM16/32B Gterminal is connected to datalogger power ground. The
AM16/32B Gterminal is also connected to the cable shield and, via that, to
datalogger power ground (see TABLE 7-1). If a separate power supply is used,
the AM16/32B ground should also connect to the power supply’s ground. An
AM16/32B COM
terminal should connect to a datalogger signal ground (⏚)
via the cable that connects the COM terminals (see FIGURE 7-1). The
datalogger must connect to earth ground by one of the methods described in the
installation and maintenance section of the datalogger operator’s manual.
7.3 Power Supply
The AM16/32B requires a continuous power supply for operation. The positive
side of the power supply is connected to 12V, and the negative side is
connected to G. Connect the Gwire first for safety.
The average power required to operate an AM16/32B depends on the
percentage of time it is active per time period. At a minimum, the power supply
must be able to sustain the system between site visits anticipating the worst
environmental extremes. Refer to the application note Power Supplies and the

AM16/32B Relay Multiplexer
10
video Power Budgeting , both available at www.campbellsci.com, for more
help in selecting a power supply.
7.4 Installation in Enclosure
The AM16/32B must be protected from moisture. Moisture in the electronics
will seriously damage the AM16/32B. In most cases, protection from water is
easily accomplished by placing the AM16/32B in a weathertight enclosure with
desiccant and elevating the enclosure above the ground. Desiccant in
enclosures should be changed periodically.
Mount the AM16/32B to an enclosure backplate by inserting the included
screws through the mounting holes in the AM16/32B and into the included
nylon anchors.
8. Operation
The reset (RES) line is used to switch on the AM16/32B by applying 3.3 to 8
Vdc. When this line drops lower than 0.9 Vdc, the multiplexer enters a
quiescent, low current-drain state. In the quiescent state, the common (COM)
terminals are electrically disconnected from all of the sensor input channels.
RES should always connect to a datalogger terminal configured for control.
The PortSet() instruction controls the reset line.
After RES has been set high, a pulse on CLK advances the channels. The
voltage level must fall below 1.5 Vdc and then rise above 3.3 Vdc to clock the
multiplexer. In a typical operation, this is accomplished with either the
PulsePort() or PortSet() instruction. Another method of operation uses the
MuxSelect() instruction to advance to a channel specified in the instruction.
When RES first goes high, the COM terminals (ODD H, ODD L and EVEN
H, EVEN L) are disconnected from all measurement terminals. When the first
CLK pulse arrives, the COM terminals are switched to connect with the first
set of measurement terminals according to the mode switch, either 4x16 or
2x32. When a second CLK pulse arrives, the common lines are switched to
connect to the second set of measurement terminals. The multiplexer advances
a channel on the rising edge of the CLK pulse.
The CLK pulse should be at least 1 ms long. A delay (typically 10
ms or more) is inserted between the beginning of the CLK pulse
and the measurement instruction to ensure sufficient settling time
to relay contacts.
The terminals for sensor attachment are divided into 16 groups (panel switch
set to 4x16) or into 32 groups (panel switch set to 2x32). The groups consist of
four or two Simultaneously Enabled Terminals (SETs). With the panel switch
set to 4X16, the blue channel numbers apply. The SETs are numbered starting
at 1(1H, 1L, 2H, 2L) and continuing until SET 16 (31H, 31L, 32H, 32L).
In 4x16 mode, the odd-numbered terminals (example: 5H, 5L)are relay-
switched to the COM ODD terminals while the even terminals (6H, 6L) are
switched to the COM EVEN terminals. When activated by the RES line, as
the AM16/32B receives clock pulses from the datalogger, each SET of four in
turn is switched into contact with the four COM terminals. For example, when
NOTE