Campbell Scientific AM416 User Manual
INSTRUCTION MANUAL
AM416 Relay Multiplexer
Revision: 2/96
Copyright (c) 1987-1996
Campbell Scientific, Inc.
Warranty and Assistance
The AM416 RELAY MULTIPLEXER is warranted by CAMPBELL
SCIENTIFIC, INC. to be free from defects in materials and workmanship under
normal use and ser vice for twelve (1 2) 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.ca mpbellsci.co m 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
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write this number clearly on the outside of the shipping container.
CAMPBELL SCIENTIFIC's shipping address is:
CAMPBELL SCIENTIFIC, INC.
RMA#_____
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CAMPBELL SCIENTIFIC, INC. does not accept collect calls.
AM416 RELAY MULTIPLEXER MANUAL
TABLE OF CONTENTS
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PAGE
1. FUNCTION
1.1 Typical Applications....................................................................................................................1
1.2 Compatibility...............................................................................................................................1
2. PHYSICAL DESCRIPTION.....................................................................................................1
3. AM416 SPECIFICATIONS......................................................................................................3
4. OPERATION................................................................................................................................3
4.1 The Control Terminals ...............................................................................................................3
4.2 The Measurement Terminals.....................................................................................................6
5. DATALOGGER PROGRAMMING
5.1 Single Loop Instruction Sequence .............................................................................................6
5.2 Multiple Loop Instruction Sequence...........................................................................................9
5.3 General Programming Considerations.....................................................................................10
6. SENSOR HOOK-UP AND MEASUREMENT EXAMPLES
6.1 Single-Ended Analog Measurement without Sensor Excitation...............................................10
6.2 Differential Analog Measurement without Sensor Excitation ...................................................11
6.3 Half Bridge Measurements.......................................................................................................11
6.4 Full Bridge Measurements .......................................................................................................13
6.5 Full Bridges with Excitation Compensation..............................................................................13
6.6 Thermocouple Measurement...................................................................................................14
6.7 Mixed Sensor Types ................................................................................................................16
7. GENERAL MEASUREMENT CONSIDERATIONS.......................................................18
8. INSTALLATION
8.1 Environmental Constraints ................................................................................................................18
APPENDIX A. AM416 STUFFING CHART AND SCHEMATICS....................................A-1
APPENDIX B. DIFFERENCES BETWEEN THE AM416 AND AM32............................B-2
LIST OF FIGURES
1. Plan View of the AM416 Relay Multiplexer ................................................................................2
2. Hook-up Diagrams for Datalogger - AM416 Connections..........................................................4
3. Power and Ground Connections for External Power Supply......................................................5
4. Actuation Time of Relays vs. Temperature (
5. Single Loop Instruction Sequence .............................................................................................6
6. Example Program Loops for CR10(X), 21X, and CR7 Dataloggers ..........................................8
o
) and Battery Voltage..........................................6
i
7. Wiring Diagram for Strain Gages and Potentiometers...............................................................9
8. Single-ended Measurement without Excitation........................................................................11
9. Differential Measurement without Excitation............................................................................11
10. Half Bridge (Modified 107 Temperature Probe) Hook-up and Measurement ..........................12
11. Potentiometer Hook-up and Measurement..............................................................................12
12. Four Wire Half Bridge Hook-up and Measurement..................................................................13
13. Differential Measurement with Sensor Excitation.....................................................................13
14. Full Bridge Measurement with Excitation Compensation.........................................................14
15. Differential Thermocouple Measurement with Reference Junction at the Datalogger.............15
16. Differential Thermocouple Measurement with Reference Junction at the AM416...................15
17. Thermocouple and Soil Block Measurement ...........................................................................16
ii
CAUTIONARY NOTES
The AM416 is not designed to multiplex power. Its intended function is to switch low level analog
signals. Switched current in excess of 30 mA will degrade contacts and render them unsuitable for
future low level analog measurements. Customers who need to switch power are directed to CSI's
A6REL-12 or A21REL-12 relays.
Adjacent AM416 channels may be shorted together for up to 5 ms during the clocking procedure. Users
should consider this when assigning AM416 input channels. Sensors that are capable of sourcing
current should not be assigned input terminals adjacent to sensors that can sink current.
This is a blank page.
AM416 RELAY MULTIPLEXER
1. FUNCTION
The primary function of the AM416 Multiplexer
is to increase the number of sensors that may
be scanned by Campbell's CR10(X), 21X and
CR7 dataloggers. The AM416 is positioned
between the sensors and the datalogger;
mechanical relays are used to switch the
desired sensor signal(s) through the system.
Most commonly, users will multiplex signals
from analog sensors into single-ended or
differential datalogger channels. Four lines are
switched simultaneously; a maximum of sixteen
sets of (four) lines may be scanned, hence the
name A(nalog) M(ultiplexer) 4(lines x) 16(sets).
Therefore, a total of 64 lines may be
multiplexed.
The maximum number of sensors that can be
multiplexed through one AM416 depends
primarily upon the type(s) of sensors to be
scanned. Some examples (assuming identical
sensors) follow:
1. Up to 32 single-ended or differential
sensors that do not require excitation (e.g.
pyranometers, thermocouples; Sections
6.1, 6.2, and 6.6).
2. Up to 48 single-ended sensors that require
excitation (e.g. some half bridges; Section
6.3.1).
3. Up to 16 single-ended or differential
sensors that require excitation (e.g. full
bridges, four-wire half bridge with measured
excitation; Section 6.3.3 and 6.4).
4. In conjunction with an AM32 multiplexer, up
to 16 six-wire full bridges (Section 6.5).
1.1. TYPICAL APPLICATIONS
The AM416 is intended for use in applications
where the number of required sensors exceeds
the number of datalogger input channels. Most
commonly, the AM416 is used to multiplex
analog sensor signals, although it also may be
used to multiplex switched excitations,
continuous analog outputs, or even certain
pulse counting measurements (i.e. those that
require only intermittent sampling). It is also
possible to multiplex sensors of different, but
compatible, types (e.g. thermocouples and soil
moisture blocks, see Section 6.6).
NOTE: For a discussion of single-ended
versus differential analog measurements,
please consult the Measurement Section of
your datalogger manual.
As purchased, the AM416 is intended for use in
indoor, non-condensing environments. An
enclosure is required for field use. In nonthermocouple applications where a single
multiplexer is deployed, the AM-ENC enclosure
is recommended. In thermocouple applications,
CSI recommends use of the AM-ENCT
enclosure. If several multiplexers are deployed
at the same site in a non-thermocouple
application, the 024 or 030 enclosures provide
cost-effective housing options.
1.2 COMPATIBILITY
The AM416 is compatible with Campbell's
CR10(X), 21X or CR7 dataloggers.
The AM416 is compatible with a wide variety of
commercially available sensors. As long as
current limitations are not exceeded, and no
more than four lines are switched at a time,
system compatibility for a specific sensor is
determined by sensor-datalogger compatibility.
In CR10(X) applications, the AM416 may be
used to multiplex up to 16 Geokon vibrating wire
sensors through one AVW-1 vibrating wire
interface.
2. PHYSICAL DESCRIPTION
The AM416 is housed in a 21 cm x 16.5 cm x
3.5 cm (8.2" x 6.5" x 1.5") anodized aluminum
case (Figure 1). The aluminum case is
intended to reduce temperature gradients
across the AM416's terminal strips. This is
extremely important when thermocouples are
being multiplexed (Section 6.6). The case may
be opened by removing the four #1 phillipshead screws located at the corners of the case.
Disassembly of the case may be required to
mount the AM416 to a plate or an enclosure
(Section 8).
A strain-relief flange is located along the lower
edge of the top panel of the case. Several
plastic wire ties are included with the AM416 to
attach wires to this flange.
1
AM416 RELAY MULTIPLEXER
Wires from sensors and datalogger are
connected to the gray terminal strips. The set
of four terminals located near the strain-relief
flange are the connections for datalogger
control of the AM416 (Section 4.1). The
terminal strips that run the length of the AM416
are for measurement connections (Section 4.2).
AM416
RELAY MULTIPLEXER
16
SHIELD
15
14
SHIELD
13
L2
H2
L1
H1
L2
H2
L1
H1
L2
H2
L1
H1
L2
H2
L1
H1
12
SHIELD
11
SHIELD
COM
10
SHIELD
9
L2
H2
L1
H1
L2
H2
L1
H1
L2
H2
L2
H2
L1
H1
L2
H2
L1
H1
The sensor inputs are not spark gapped. All
terminals accept stripped and tinned lead wires
up to 1.5 mm in diameter. The datalogger is
connected to the AM416 through a minimum of
seven, but generally nine, individually insulated
lead wires.
L2
H2
L1
H1
SHIELD
L2
H2
L1
H1
L1
SHIELD
H1
L2
H2
L1
H1
SHIELD
L2
H2
L1
H1
8
7
COM
6
5
L2
H2
L1
H1
SHIELD
L2
H2
L1
H1
L2
H2
L1
H1
SHIELD
L2
H2
L1
H1
4
3
2
1
12V
CLK
RES
GND
MADE IN USA
FIGURE 1. Plan View of the AM416 Relay Multiplexer
2
3. AM416 SPECIFICATIONS
POWER*: unregulated 12 VDC (9.6 V to 16 V)
- See Figure 4 for implications of low power to
relay actuation
CURRENT DRAIN:
Quiescent: < 100 uA
Active: 17 mA (typical)
RESET*: a continuous signal of 3.5VDC <
voltage < 16 VDC holds AM416 in an active
state (i.e. a clock pulse can trigger a scan
advance). A signal voltage of < 0.9VDC
deactivates the AM416 (clock pulse will not
trigger a scan advance; AM416 is also reset).
CLOCK*: on the transition from <1.5 V to >3.5
V, scan advance is actuated on the leading
edge of the clock signal; clock signal must be a
minimum of 5 ms in width.
OPERATIONAL TEMPERATURE: -40oC to
+65oC
OPERATIONAL HUMIDITY: 0 - 95%, noncondensing
DIMENSIONS (without field enclosure):
length - 21 cm (8.2")
width - 16.5 cm (6.5")
depth - 3.5 cm (1.5")
AM416 RELAY MULTIPLEXER
*
Reset, Clock, and +12V inputs are limited to
+16V by 1.5KE20A transzorbs.
**
Assumes sequential activation of multiplexers
and that each datalogger channel is uniquely
dedicated. If your application requires
additional multiplexing capability, please consult
CSI for application assistance.
***
Switching currents greater than 30 mA
(occasional 50 mA is acceptable) will degrade
the contact surfaces of the mechanical relays
(i.e. increase their resistance). This process will
adversely affect the suitability of these relays to
multiplex low voltage signals. Although a relay
used in this manner will not be of use in future
low voltage measurements, it may continue to be
used for switching current in excess of 30 mA.
CONTACT SPECIFICATIONS
Initial contact resistance: 50 mohm max.
Initial contact bounce: 1 ms max.
Contact material: Gold clad silver alloy
Electrostatic capacitance: 3pF
Minimum expected life:
Mechanical (at 50cps): 108 open
Electrical (at 20cps): 2 x 10
CHARACTERISTICS (at 25oC, 50% Relative
Humidity)
Operate time 8 to 15 ms approx. (See Figure 4)
Release time 5 ms approx.
5
(with field enclosure i.e. box size):
length - 25.4 cm (10.0")
width - 20.3 cm (8.0")
depth - 10.2 cm (4.0")
WEIGHT: 1.5 lbs (approx.)
(in enclosure): 10.0 lbs (approx.)
EXPANDA BILITY**(nominal):
3 AM416'S/CR10(X)
4 AM416'S/21X
8 AM416's/CR7 725 Card
MAXIMUM CABLE LENGTH: sensor & scan
rate dependent (in general, longer lead lengths
necessitate longer measurement delays. Refer
to datalogger manual for additional details).
MAXIMUM SWITCHING CURRENT
***
: 500 mA
4. OPERATION
Subsection 4.1 discusses the use of the
terminals that control operation of the
multiplexer. These terminals are located along
the lower left side of the multiplexer as shown in
Figure 1. Subsection 4.2 discusses the use of
terminals used in sensor measurement.
4.1. THE CONTROL TERMINALS
The CR10(X), 21X and CR7 dataloggers should
be connected to the AM416 as shown in Figure
2. This figure depicts control connections;
measurement connections are discussed in
Section 6. The power, ground, reset, and clock
connections remain essentially the same
regardless of datalogger used.
In a CR10(X) application, the datalogger 12VDC
supply and ground terminals are connected to
the AM416 12V and ground terminals. Two
control ports are used for clock and reset.
3
AM416 RELAY MULTIPLEXER
FIGURE 2. Hook-up Diagrams for Datalogger - AM416 Connections
CR10(X) Hook-up 21X Hook-up
CR7 Hook-up
The 21X or CR7 (with a 725 Card) can be used
to connect 12VDC supply and ground to the
AM416. One control port is used for reset, and
one switched excitation channel is used for
clock. If switched excitations are unavailable, a
control port may be used to provide clock
pulses to the multiplexer.
4.1.1 RESET
Reset (RES) controls activation of the
multiplexer. A voltage (3.5VDC <voltage<
16VDC) applied to this terminal activates the
multiplexer. When this line is dropped to
<0.9VDC, the multiplexer enters a quiescent,
low current drain state. Reset is always
connected to a datalogger control port.
Instruction 86 (option code 41 - 48 [activate]
and 51 - 58 [deactivate]) is generally used.
With a 21X or CR7 with older PROMS,
Instruction 20 is commonly used to activate and
deactivate the multiplexer (set port high to
4
activate the multiplexer or low to enter
quiescent mode).
4.1.2 CLOCK
The multiplexer clock line (CLK) controls the
switching between sequential sets of relays.
When reset is set high and the multiplexer is
activated, the multiplexer's common lines (COM
H1, COM L1 COM H2, COM L2) are not
connected to any of the sensor input terminals.
When the first clock pulse is received, the
common lines are switched into connection with
multiplexer channel 1 (H1,L1,H2,L2). When a
second clock pulse is received, the common
lines are connected to multiplexer channel 2
(H1,L1,H2,L2). Adjacent Multiplexer input
channels are momentarily shorted to each other
during the switch (e.g. channel 1 H1 to channel
2 H1, channel 1 L1 to channel 2 L1, etc. See
Cautionary Notes). The multiplexer is clocked
on the leading edge of the voltage pulse. The
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