RST Instruments RST Flexi-Mux User manual

All efforts have been made to ensure the accuracy and
completeness of the information contained in this document. RST
Instruments Ltd reserves the right to change the information at any
time and assumes no liability for its accuracy.
Copyright © 2021. RST Instruments Ltd. All rights reserved.
Document Number: ELM0029B
Release Date: April 12, 2021
RST Flexi-Mux
Instruction Manual

RST Flexi-Mux Instruction Manual
ELM0029B
RST Instruments Ltd.
Page i
REVISION HISTORY
Rev.
Revision History
Date
Prepared By
Approved By
A
Initial Release
2012-Mar-23
TK
TW
B
Removed all references to old Campbell
loggers (CR10X, etc.), updated all schematics
and photos, added more schematic examples,
added an Appendix that includes CRBasic
programming for each new schematic, added
minimum clocking between readings >=500ms,
updated formatting throughout.
2021-Apr-12
JR
JW

RST Flexi-Mux Instruction Manual
ELM0029B
RST Instruments Ltd.
Page ii
TABLE OF CONTENTS
1 OVERVIEW..................................................................................................................1
2 FUNCTION...................................................................................................................1
3 COMPATIBILITY ...........................................................................................................3
4 PHYSICAL DESCRIPTION ..............................................................................................3
4.1 Layout...............................................................................................................3
4.2 Dimensions.......................................................................................................4
4.3 Connection Details............................................................................................4
5 OPERATION ................................................................................................................5
5.1 Control Terminals..............................................................................................6
5.1.1 Reset......................................................................................................6
5.1.2 Clock.......................................................................................................7
5.1.3 Ground....................................................................................................7
5.2 DIP Switch Settings...........................................................................................7
5.3 Connection Examples.......................................................................................8
5.3.1 2-Wire Serial Switching...........................................................................8
5.3.2 4-Wire Serial Switching...........................................................................9
5.3.3 4-Wire Switching with Separate Excitation............................................10
5.3.4 8-Wire Series/Parallel Switching...........................................................13
5.4 Datalogger Programming................................................................................13
6 SPECIFICATIONS........................................................................................................14
SAMPLE PROGRAMMING .............................................................................15
A-1. 2-Wire Serial Switching....................................................................................15
A-2. 4-Wire Serial Switching....................................................................................16
A-3. 4-Wire Switching with Separate Excitation .......................................................17
A-4. 8-Wire Series/Parallel Switching.......................................................................24
LIST OF FIGURES
Figure 2-1 Flexi-Mux cascading feature .....................................................................................2
Figure 4-1 Flexi-Mux layout........................................................................................................3
Figure 4-2 Flexi-mux dimension.................................................................................................4
Figure 4-3 Connector detail........................................................................................................5
Figure 5-1 Flexi-Mux to CR6 datalogger power/control hookup..................................................6
Figure 5-2 DIP switch location....................................................................................................8
Figure 5-3 A CR6 connecting a Flexi-Mux and an MPBX...........................................................9
Figure 5-4 Flexi-Mux with VW instruments and AWV200 .........................................................10
Figure 5-5 Flexi-Mux with biaxial IPIs and VWP.......................................................................11
Figure 5-6 Flexi-Mux IPI27050 series.......................................................................................12
Figure 5-7 Flexi-Mux wired in parallel to switch 8-wires............................................................13

RST Flexi-Mux Instruction Manual
ELM0029B
RST Instruments Ltd.
Page 1
1 OVERVIEW
The RST Flexi-Mux is designed to increase the number of sensors that can be measured
with a datalogger. The Flexi-Mux is located between the datalogger and the sensors and
allows a single channel of a datalogger to be sequentially connected to numerous
sensors. Each Flexi-Mux can sequentially multiplex 5 groups of 4 wire inputs or 10 groups
of 2 wire inputs. Internal DIP switch settings permit the changing of these settings. The
system can be expanded by chaining together multiple Flexi-Muxes allowing the signals to
cascade through the system. This allows a virtually unlimited number of sensors to be
connected to a single channel.
The datalogger program and control ports advance the Flexi-Mux through each sensor.
An added feature of the RST Flexi-Mux is that it contains internal transient protection on
each individual line. Unlike traditional multiplexers, this negates the need for external
transient protection devices to be installed saving cost, wiring and time deploying the
system.
2 FUNCTION
The RST Flexi-Mux allows a single channel of a datalogger, such as a Campbell Scientific
CR6, to be sequentially connected to numerous sensors. Each Flexi-Mux can
sequentially multiplex 5 groups of 4 wire for a total of 20 wires. Alternatively, internal DIP
switch settings permit the multiplexing of 10 groups of 2 wires.
The extremely slim and compact (8.15” H x 1.05” W x 3.07” D) vertical design permits the
Flexi-Mux to occupy minimal space in the control box which allows for more Flexi-Mux
units to be installed. By utilizing a unique cascade feature, there is theoretically no limit to
the number of channels which can be connected to the datalogger. Figure 2-1 highlights
the cascading feature.

RST Flexi-Mux Instruction Manual
ELM0029B
RST Instruments Ltd.
Page 2
FIGURE 2-1 FLEXI-MUX CASCADING FEATURE
Conveniently designed detachable screw terminals allow rapid wiring of large systems,
with straightforward testing and substitution of both sensors and multiplexers. Built-in
transient protection on every line safeguards against damaging power surges, which can
be caused by occurrences such as nearby lightning.
The Flexi-Mux requires only two datalogger control ports: one for “enable” (Reset
Terminal), and a second for channel stepping (Clock Terminal). The Flexi-Mux is
compatible with most sensors including load cells, pressure transducers, vibrating wire
sensors, thermistors, potentiometers, tiltmeters, strain gauges, in-place inclinometers, and
tilt beams.

RST Flexi-Mux Instruction Manual
ELM0029B
RST Instruments Ltd.
Page 3
3 COMPATIBILITY
The Flexi-Mux is compatible with, but not limited to, Campbell’s CR300, CR310,
CR1000/X, and CR6 series dataloggers.
A wide variety of commercially available sensors are supported provided the current
maximums are not exceeded on the relay contacts (see Section 6).
Using a single Flexi-Mux in combination with a Campbell AVW-200 (excluding CR6)
Vibrating Wire Interface, up to 5 RST vibrating wire piezometers can be multiplexed.
Cascading each Flexi-Mux permits a theoretically unlimited number of muxes to be
chained together. Thus, many vibrating wire sensors can be connected to a single
vibrating wire interface.
4 PHYSICAL DESCRIPTION
4.1 LAYOUT
FIGURE 4-1 FLEXI-MUX LAYOUT
1. Grounding spade terminal.
2. Channel assignments
3. Multiplexed terminal channel assignments.
4. Modular 5-pole terminal blocks for multiplexed sensors.
5. Modular 18-pole Mux control terminal.
6. Graphical representation for internal DIP switch settings.
7. Mounting tabs.

RST Flexi-Mux Instruction Manual
ELM0029B
RST Instruments Ltd.
Page 4
4.2 DIMENSIONS
The Flexi-Mux is housed in a slim 15.6cm x 8.1cm x 2.7cm (6.15” x 3.17” x 1.05”)
aluminum case (Figure 4-2). Convenient mounting tabs extend 2.5cm (1”) from each end
and provide simple means of mounting the unit on any flat surface or base plate. The
finished length including the mounting tabs is 20.7cm (8.15”). Mounting holes are 17.9cm
(7.07”) apart.
FIGURE 4-2 FLEXI-MUX DIMENSION
4.3 CONNECTION DETAILS
Connections to the Flexi-Mux are made on the top mounted modular terminal blocks. The
removable 18-pin connector block is dedicated for connecting the datalogger power and
control lines (see Section 5.1). This connector has a tension clamp which is rated to
accept 14-28 AWG wire as shown below:

RST Flexi-Mux Instruction Manual
ELM0029B
RST Instruments Ltd.
Page 5
FIGURE 4-3 CONNECTOR DETAIL
The cable grips are spring loaded and require a small screwdriver to be inserted into the
centre to retract the spring. Once retracted, insert the wire into the round hole and
remove the screwdriver. The spring will grasp the wire.
The five, 5-pole terminal blocks are connection points for the shielded multiplexed sensor
signals destined for the datalogger analog inputs (Section 5.3). The 5-pole blocks have
screw clamps and are rated to accept 14-28 AWG wire. Each sensor line is connected to
a quick-connect terminal block with an integrated stress release system. The tab is
designed to accommodate a tie-wrap to hold the lead wires. The connectors are designed
to be easily disconnected, giving the flexibility to switch or move sensors. Lead wires are
attached using a standard screw terminal on each block. Pin locations are numbered from
the top down, with the shield located in the centre. Ensure that connections are made in
this order.
All terminal blocks are modular and socketed, allowing them to be unplugged. This
provides the flexibility of being able to switch out and entire mux or switch the locations of
instruments without having to rewire.
5 OPERATION
Section 5.1 describes the terminals that control the operation of the multiplexer. These
terminals are located in the 18-pin terminal block labelled “5” attached to the MUX in
Figure 4-1. Section 5.2 discusses the use of the DIP switch settings which control the
behaviour of the measurement terminals.

RST Flexi-Mux Instruction Manual
ELM0029B
RST Instruments Ltd.
Page 6
5.1 CONTROL TERMINALS
The CR6 datalogger (or other Campbell Scientific Datalogger) connects to the Flexi-Mux
as shown in Figure 5-1. Using a CR310, CR300, and CR1000X, a AVW200 is required to
be used. Figure 5-4 further details the configuration.
FIGURE 5-1 FLEXI-MUX TO CR6 DATALOGGER POWER/CONTROL HOOKUP
With the CR6, the Flexi-Mux connects to an available 12V port and a Ground terminal for
power. One control port is used for Reset and another is used for Clock. If two control
ports are not available (depending on the datalogger) a switched excitation channel can
be used. The Flexi-Mux only requires 2 volts to be clocked.
5.1.1 Reset
The reset line is used to activate the Flexi-Mux. A signal in the range of +2.0V to +10VDC
applied to the reset terminal activates the multiplexer. When this line drops lower than
0.9VDC, the multiplexer enters a quiescent, low current drain state. In the quiescent state

RST Flexi-Mux Instruction Manual
ELM0029B
RST Instruments Ltd.
Page 7
the common terminals (A, B, C, D) are electrically disconnected from all the sensor input
channels. Reset should always connect to a datalogger control port. When programming,
a delay (≥100ms) after setting Reset high must be included or the Flexi-Mux will not clock
between ports.
5.1.2 Clock
Pulsing the Flexi-Mux “clock” line high (with “reset” set high) advances the channel.
Whether the Flexi-Mux advances 2 positions or 4 positions depends on the internal DIP
switch settings (Section 5.2). When the reset first goes high, the common terminals A, B,
C and D are disconnected from all sensor input terminals. With the Flexi-Mux set in the 4-
Pole mode, when the first clock pulse arrives the common terminals are switched to
connect with the sensor input channel 1 (consists of 5 wires: A, B, C, D and shield). When
a second clock pulse arrives, the common lines are switched to connect to channel 2.
The multiplexer advances along the leading edge of the positive-going clock pulse. The
voltage level must fall below 1.5VDC and then rise about 2.0VDC to clock the multiplexer.
The clock pulse should be at least 1 ms long. A delay (typically 10 to 20 ms) is inserted
into the datalogger program between the beginning of the clock pulse and the
measurement instruction to ensure sufficient settling time for the relay contacts.
In general, a control port is used to clock the multiplexer. However, switched excitation for
the sensors can also be used (as stated in Section 5.1). See Section 5.3 for more details
on datalogger connections with the Flexi-Mux.
If several multiplexers are required, the Flexi-Mux allows a virtually unlimited number of
units (limited by cable losses) to be connected in series because the Flexi-Mux boosts the
clock and reset signals through its circuitry. Thus, no control voltage is lost through the
ports. An adequate 12VDC power source must be maintained through each multiplexer
for this to function correctly.
5.1.3 Ground
The Flexi-Mux “ground” terminal is connected to the datalogger power ground.
5.2 DIP SWITCH SETTINGS
Internal DIP switches on the Flexi-Mux control whether it switches 2 or 4 wires each time it
is clocked. To change the DIP switch settings, remove the dust cover located on the base
of the unit. The piano-key style DIP switches are accessed through this hole as shown in
Figure 5-2. Adjust the DIP switches as outlined below. There is also a diagram on the
Flexi-Mux itself which reflects these settings (item 6, Figure 4-1).