Sutron MONITOR Manual

MONITOR®
Data Logger
OPERATIONS &
MAINTENANCE MANUAL
Part No. 8800-1174
Revision – 1.04
Oct 20, 2008
1

Table Of Contents
Introduction......................................................................................................................... 4
Models............................................................................................................................. 4
Connections......................................................................................................................... 5
Power/SDI/TB Terminal Block ...................................................................................... 5
DB9 Connector ............................................................................................................... 6
Sensor Connections......................................................................................................... 7
Measurements ..................................................................................................................... 9
Sensors ............................................................................................................................ 9
Inputs available ............................................................................................................... 9
Setup ................................................................................................................................. 10
Measurement setup ....................................................................................................... 10
Other Setup ................................................................................................................... 27
Measurement Setup Examples.......................................................................................... 30
RM Young Wind Speed and Direction......................................................................... 30
Thermistor..................................................................................................................... 31
Pressure Transducer (Analog Bridge Sensor)............................................................... 32
Thermocouple Sensor ................................................................................................... 34
Tipping Bucket.............................................................................................................. 35
Solar Radiation Sensor.................................................................................................. 36
SDI-12 Multi-Parameter Sensor ................................................................................... 37
Logging............................................................................................................................. 39
SD Card Interface ............................................................................................................. 41
MONITOR Time .............................................................................................................. 42
SDI Clock Synchronization .......................................................................................... 42
MONITOR Errors............................................................................................................. 44
Clearing errors .............................................................................................................. 44
Measurement errors ...................................................................................................... 44
System errors ................................................................................................................ 45
Front Panel Interface......................................................................................................... 46
Navigating the Menus................................................................................................... 46
Turning Display On/Off................................................................................................ 46
Backlight....................................................................................................................... 46
Contrast......................................................................................................................... 47
Viewing Data ................................................................................................................ 47
Front Panel Menu Tree ................................................................................................. 48
RS232 Command Line Interface ...................................................................................... 49
Status............................................................................................................................. 49
Setup ............................................................................................................................. 50
Measurements ............................................................................................................... 51
Recording...................................................................................................................... 51
Downloading the Log ................................................................................................... 51
Examples....................................................................................................................... 52
Machine to Machine Communication........................................................................... 53
Auto Output .................................................................................................................. 53
RS232 Command Reference......................................................................................... 53
2

Setup Transfer via HyperTerminal ............................................................................... 57
Upgrading Firmware..................................................................................................... 57
Connecting a Modem.................................................................................................... 58
More about SDI-12 ........................................................................................................... 61
Overview....................................................................................................................... 61
Wiring Guidelines......................................................................................................... 62
Connector...................................................................................................................... 62
SETUP of SDI sensors.................................................................................................. 62
Useful SDI commands .................................................................................................. 63
GPS ................................................................................................................................... 64
Timekeeping ................................................................................................................. 64
GPS Installation and Setup ........................................................................................... 64
GPS Positioning............................................................................................................ 65
GPS Operation .............................................................................................................. 65
GPS Errors .................................................................................................................... 65
Jumpers ......................................................................................................................... 66
RJ45 to RS232 Connector............................................................................................. 66
Modbus ............................................................................................................................. 68
Modbus Menu Tree....................................................................................................... 68
Modbus Menu Options ................................................................................................. 68
Modbus Function Codes ............................................................................................... 70
Get Log Command........................................................................................................ 73
Appendix A – Monitor Specifications .............................................................................. 75
Appendix B – Sutron Customer Service Policy................................................................ 77
Appendix C – Commercial Warranty ............................................................................... 78
Sutron Manufactured Equipment.................................................................................. 78
Non-Sutron Manufactured Equipment.......................................................................... 78
Repair and Return Policy .............................................................................................. 78
Extended Warranty and On-Site Maintenance ............................................................. 78
INDEX .............................................................................................................................. 79
3

Introduction
MONITOR is Sutron’s most easy-to-use and affordable data logger. It is designed to
measure common hydrologic and meteorological sensors and log the data into its flash
memory. The general purpose version of MONITOR supports up to 16 sensors with its
analog, digital and SDI-12 interfaces. The built-in display/keypad makes it simple to set
the station up and perform routine maintenance. MONITOR includes an SD memory slot
for downloading data or setups. MONITOR can be used standalone or connected to
wireless modems for integration into automatic data collection systems.
Models
MONITOR comes in several versions to meet varied customer needs. The table below
shows the models currently offered. Check with Sutron for additional models or for a
customized version of MONITOR.
MONITOR-1
Display/Keypad, qty 2 0-5VDC inputs, qty 3 (+39mV, +312mV or +2.5V inputs, qty 1 4-
20ma input, qty 1 tipping bucket, qty 1 freq/period, 5x5x4” fiberglass NEMA box with
qty 2 cable glands.
MONITOR-4
Same as MONITOR-1 but housed in a 12x14x8 NEMA box. Also includes a 7amp-hr
battery and Raven CDPD modem.
MONITOR-1
4

Connections
Power/SDI/TB Terminal Block
Power (Battery), SDI and tipping bucket sensors are wired to a terminal block inside
MONITOR. Connections are made to this terminal block with bare wires using a small
flat blade screwdriver (3.5mm or 0.125” wide). The connections on the terminal block
are as follows:
Connector name Description
1 Battery + Power +12V (supplies
power to MONITOR).
2 Battery GND Power ground
3 SDI Data SDI-12 data
4
SDI +
12V output for SDI-12
sensors (always on,
toggles on Monitor reset)
5 SDI Ground SDI-12 ground
6 TB + Tipping Bucket +
7 TB Ground Tipping Bucket ground
Power Connections
MONITOR requires external +12V power to operate. The most common power source is
a lead-acid battery. Connect the battery to pins labeled Battery + and Battery Ground the
external terminal strip.
SDI-12 Connections
The SDI-12 interface has only 3 connections – GND, +12V and Data. Wire these
connections directly to the SDI-12 connections on a compatible sensor. Please see the
SDI-12 measurement type for more information.
Tipping Bucket Connections
The tipping bucket connections are configured to measure the closure of a dry contact
switch. In most circumstances it doesn’t matter which side of the switch is connected to
+ or Ground. For measurement setup, please see the precipitation section.
5

DB9 Connector
MONITOR comes with a DB9F connector for connection to RS-232 devices. The DB9F
can be connected to the serial port on most PCs using a straight cable. A null modem
adapter is needed to connect to most PDAs and modems. There is a command line
interface that allows communication via RS-232.
The following table shows the pin assignments in the DB9F connector.
DB9F Pin Name Notes
1 N/C No Connection
2 RXD Data from MONITOR
3 TXD Data to MONITOR
4 DTR Signal to MONITOR
5 Ground
6 N/C No Connection
7 RTS Request to Send, signal to MONITOR
8 CTS Clear to Send, signal from MONITOR
9* VOUT
Jumper selectable for 5V or VBAT
(100ma max)
*Pin 9 can be used to provide 12V, 5V or no voltage. Certain devices, such as Bluetooth
dongles require power on that pin. Any setting will work for talking to a PC.
What voltage is output is controlled by an internal jumper. To setup the jumper, the case
must be opened. Once the case is open, the jumper is easily accessible. The Jumper in
question is J19, and is located next to the RS232 connector. Set the jumper across pins 1
and 2 to provide 12V, across pins 2 and 3 to provide 5V, or remove jumper to have no
voltage output.
Another jumper J16 (located near J19) determines when MONITOR outputs the voltage
on pin 9. If the jumper is across pins 1 and 2, MONITOR will always output the voltage
on pin 9. Any other configuration will cause MONITOR to output the voltage only when
it is using the RS232 port (such as when it’s talking to a PC or a GPS).
6

Sensor Connections
Two terminal blocks are provided for making connections to analog and digital sensors.
These blocks are located inside MONITOR, behind the front panel. The terminals are
numbered 1 to 22. The following table gives a short description of each of the terminals.
Detailed notes describing how to connect sensors to the terminal blocks are provided in
the setup section of this manual.
Terminal
Block Description Notes
1 AGND Analog ground
2 Analog 0-5V ‘A’ Voltage input for sensors with 0-5V output
3 Analog 0-5V ‘B’ Voltage input for sensors with 0-5V output
4 AGND Analog ground
5 VREF 2.5V output (turned on during warmup and analog sensor
measurement)
6 DIFF ‘C’ (+) Differential voltage input for bridge type sensors
7 DIFF ‘C’ (- )
8 DIFF ‘D’ (+) Differential voltage input for bridge type sensors
9 DIFF ‘D’ (- )
10 24V (4-20ma) 24 Volt output for 2 wire 4-20ma sensor
11 I-Input (4-20ma) Current input for 2 wire 4-20ma sensor
12 Counter Input Frequency/period measurements
13 Gnd Digital ground
14 SW’D Batt Switched battery (turned on during warmup and analog sensor
measurement)
15 4-20ma Output (+) Connect 2 wire ‘VOLTAGE’ wire here (eq. 24 Volts) – not
used by MONITOR
16 4-20ma Output (-) Connect 2 wire ‘-‘ terminal here – not used by MONITOR
17 GND Digital ground
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Terminal
Block Description Notes
18 DIFF ‘E’ (+) Differential voltage input for bridge type sensors
19 DIFF ‘E’ (- )
20 I/O ‘F’ Digital input (discrete)
21 I/O ‘G’ Digital input (discrete)
22 GND Ground
8

Measurements
A measurement is the process of collecting data from a sensor. MONITOR provides the
ability to setup multiple measurements, each with its unique setup. Each measurement
will occur periodically and provide one or more results, which are usually related to
weather conditions. Measurement results are always logged. The log can hold almost
250,000 unique readings.
Sensors
As a data logger, MONITOR’s primary function is to measure and log data from sensors.
All commonly used environmental sensors are supported.
Here is a list of some of the many sensors supported by MONITOR and available through
Sutron:
•AT/RH (Air Temperature and Relative Humidity) - using analog or SDI-12
sensors
•Precipitation – using a tipping bucket
•Wind Speed / Wind Direction - RM Young or Gill ultrasonic via frequency,
analog, and SDI-12 inputs (includes vector averaging)
•Stage - using SDI-12 Shaft Encoder, Radar Level Recorder, Stage Discharge
Recorder, analog submersible, Bubbler
•Barometric Pressure - using the SDI-12 Accubar
•Solar Radiation via Differential Analog Input
Inputs available
Each of these inputs is capable of having one sensor connected to it, except for SDI-12
which can connect to multiple sensors.
Analog inputs
•Two 0-5 V single ended analog input
•Three Differential Analog Inputs (for bridge type sensors)
•One 4-20mA input
Digital inputs
•One counter digital input (used for tipping bucket)
•One frequency/period input (used for wind speed)
•Two discrete digital inputs (read line state as 1 or 0)
SDI-12 input
•SDI-12 V1.3 compliant supports multiple sensors all connected to the same
bus
9

Setup
Once it is powered on, how MONITOR behaves is controlled by its setup. The user has
the option of changing any part of the setup. MONITOR’s setup is stored in non-volatile
memory and will not be affected when the unit loses power.
Setup can be changed while MONITOR is collecting data. However, if MONITOR is in
the middle of making a measurement when the affecting setup is changed, unexpected
effects may occur. Even if unexpected effects occur, MONITOR will correctly make the
next measurement.
Changes to setup will not affect previously logged data.
Every time setup is changed, it is noted in the log with the entry ‘setup changed’. Details
of the setup change are not logged.
If a password is enabled, changes to setup cannot be made until the password is entered.
MONITOR’s setup is broken into two sections:
•measurement setup
•other setup
Measurement setup
How a measurement behaves is governed by its setup. Each of the 16 measurements has
its own setup. Changing the setup of one measurement will not affect other
measurements (except for Meta measurements).
To access the measurement setup using the front panel, press UP or DOWN until the
Station Setup menu shows. Press RIGHT and the Measurement Setup will show. Press
RIGHT again, and choose which of the 16 measurements to setup by pressing UP or
DOWN. Once the desired measurement is selected, press RIGHT. You may then press
UP or DOWN to choose one of the measurement settings, and press SET to change the
setting. Please see the front panel interface section for more information.
When using the command line, M1, M2, M3... M16 are used to designate the 16 different
measurements. Type M1 to see the setup of measurement one. Type M1 WIZARD to
setup the measurement. Please see the section on command line for more details.
Names and descriptions of each measurement setup field are below.
Active
Will MONITOR make this measurement? If a measurement is not active, it will
not be measured or logged. Making a measurement active is the first step in
setup.
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Label
User set name given to measurement, up to 7 bytes. This is used to identify and
differentiate measurements. This value will be placed in the log each time a
measurement is made, so that changing a label will not affect previously logged
data. Example labels: AT, Stage, Baro, Precip, Batt.
Measurement Type
This field defines what kind of measurement to make. The available options are
•Precip Accumulation
•Precip Rate
•SDI-12
•Analog
•Battery Voltage
•Wind
•Digital
•Meta
For details on each of the types, see the section Measurement Types below.
Measurement Interval
Measurement Time
Measurement interval and time dictate when the measurement will be made. The
interval controls how often the measurement is made, and the time controls when
the measurement is started.
•E.g. time 00:00:00 interval 00:10:00
•00:10:00 data measured and logged
•00:20:00 data measured and logged
•00:30:00 data measured and logged
•and every ten minutes afterwards…
•E.g. time 00:00:30 interval 00:05:00
•00:00:30 data measured and logged
•00:05:30 data measured and logged
•00:10:30 data measured and logged
•and every five minutes afterwards…
Averaging Time
Sampling Interval
Subsamples
MONITOR is capable of collecting multiple samples and averaging them in order
to produce a measurement result. Averaging is useful for measuring changing
conditions, such as wind and water level. For example, correctly measuring the
level of choppy water requires that wave action be cancelled. That can be
accomplished by averaging over several minutes.
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Setting the Averaging Time to zero means that only one sample is to be
collected (no averaging). This is the default setup. If Averaging Time is zero,
Sampling Interval and Subsamples will not show in the setup.
When averaging, MONITOR will take multiple samples and average them into a
final result. Each sample may additionally be composed of a number of
Subsamples.
•Averaging Time determines how long to collect samples for.
•Sampling Interval dictates how often to collect each sample.
•Subsamples tell how many sensor readings to include in each sample. Do
not use Subsamples unless you need two levels of averaging.
The simplest averaging requires only the use of Averaging Time. If one wanted to
know the average temperature for an hour, one would setup the Averaging Time to
one hour. Sampling Interval or Subsamples would not need to be changed.
MONITOR will collect sensor data all throughout the hour as fast as possible.
However, if the power consumption for measuring the sensor continuously for an
hour were unacceptable, one would use the Sampling Interval. If it were
sufficient to take one sample every minute, the Sampling Interval should be set to
one minute. That way, MONITOR will take 60 samples every hour, with
approximately a minute break between each sample.
If the sensor being used were noisy and needed filtering, MONITOR could take
several Subsamples and average them into each sample. In the setup for
temperature above, if the number of Subsamples were set to five, MONITOR
would take five readings at the start of every minute and average them. That
result would be used as a sample. Once an hour, 60 samples would be averaged
into a final result.
If Details is enabled (see below), MONITOR can record and display the
minimum and maximum sample collected. Individual samples are not recorded.
Minimum and maximum Subsamples are not recorded.
E.G. Averaging Time 1 minute, Sampling Interval 15 seconds Subsamples set to
one. For each measurement, four samples will be collected; each sample has
only one subsample.
12:00:00 1st sample is collected
12:00:15 2nd sample is collected
12:00:30 3rd sample is collected
12:00:45 4th sample is collected
12:00:45 all samples are averaged; result is time-stamped 12:00:00
Setting the Averaging Time to zero means that only one sample is to be collected
and is the equivalent of disabling averaging.
12

Setting the Sampling Interval to zero allows the system to collect samples as fast
as possible. If Sampling Interval is zero, Subsamples will not show.
Setting the Subsamples to one means that each sample will consist of only one
data point (default).
The number of samples collected will be logged if the setting Details (see below)
is enabled. Additionally if Details is enabled, it can be accessed by typing LAST
in the command line. Regardless of whether Details is enabled, the number of
samples can be seen using the Diagnostic Menu->Measurement Details menu via
the front panel.
Slope
Offset
Every measurement is computed by taking the sensor reading, multiplying it by
slope and adding offset to it.
Measurement result = (sensor output)*slope + offset
Slope defaults to 1.0 and offset defaults to 0.0, meaning they will not affect
measurement result by default.
Traditionally, when using an analog sensor, slope and offset are required to
convert the voltage output by the sensor into desired units. The required slope
and offset are provided by the sensor manufacturer.
Note that MONITOR supports more complex equation processing (see Equations
below). Slope and offset are applied after equations.
The reading before slope and offset are applied is referred to as the raw reading.
For example, if an analog sensor were to provide a voltage of 2 volts, and the user
had setup the Slope as 5 and Offset as 1, the final reading would be 11 (2*5 + 1).
The raw reading would be 2. The raw reading can be viewed using Diagnostic
Menu->Measurement Details menu via the front panel. Additionally, if Details is
enabled, the raw reading is displayed on the command line by typing MEAS or
LAST.
MONITOR offers easy ways to change the current reading of the measurement by
modifying just the offset or both the slope and offset. Please see the sections on
measurement calibration and two point calibration.
Use Equation
Equation
MONITOR allows the data collected from sensors to be processed by an equation.
If the reading provided by the sensor needs more than just an offset and a slope
applied, equations provide that functionality.
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Equations are supported only by the first eight measurements. Equations
may only be entered using the command line interface. The front panel may not
be used to enter equations.
The field Use Equations can be set to enabled or to disabled. It determines
whether equation processing is to be applied to the raw data. The field Equation
can be set to an ASCII string no longer than 128 bytes (per measurement). That
field contains the equation to be applied.
If both Equations and Slope and Offset are used, Slope and Offset are applied after
the equation is processed.
E.g. to convert Fahrenheit to Celsius, type into command line:
M1 EQUATION = (X-32.0)*5/9
In the example above, X refers to the sensor reading.
Note: Equation processing can take a while to complete (up to several seconds).
If you are using a lengthy equation, Monitor may not be able to complete a
measurement every second, or even every two seconds (see Bad Schedule in the
Error section).
Equation Syntax
The equation is expressed in terms of "X" which will be applied to incoming
sensor data. You may also reference each measurement by its label or by the M1,
M2... designator. The expression is not case sensitive.
The following functions are available:
SIN, COS, TAN, ARCTAN, e.g. COS(90) = 0
SQRT is square root, e.g. SQRT(9) = 3
To raise a number to a power, use ^. For example X^2 is x squared. 2^X is 2 to the
power of X.
EXP, if EXP(x) = y, then LN(y) = x, e.g. EXP(1) = 2.718282
LN, natural log, e.g. LN(2.718282) = 1
LOG, 10 based log, e.g. LOG(10) = 1
INT returns the integral portion of a real number
INT(11.456) = 11.000 INT(-1.345) = -1.000
FRACT returns the fractional portion of a real number.
FRACT(11.456) = 0.456 FRACT(-1.345) = -0.345
ABS returns the absolute value of a real number.
ABS(11.456) = 11.456 ABS(-1.345) = 1.345
POLY is used to compute up to a 5th level polynomial equation:
POLY(x, A, B, C, D, E, F) equates to A + Bx + Cx^2 + Dx^3 + Ex^4 + Fx^5
STEINHART(x, A, B, C) is used for Steinhart-Hart equations,
where x is the resistance and result is the temperature in Celsius
A, B and C are thermistor specific constants
Steinhart result is computed like so: 1/(A + B*ln(x) +C*(ln(x)^3)) - 273.15
VREF = Internal value of VREF (about 2.5Volts)
Example: X/VREF*355 (for wind direction scaling)
14

Comparison can be performed using <, >, <=, >=, !=, and =. The result of a comparison is
1 for true or 0 for false.
The following bitwise boolean operators are supported: AND, OR, XOR, SHL, and SHR.
The last two are shift-left and shift-right. For instance (X SHL 4) would shift X left by 4
bits. AND & OR can also be used in logical expressions. For instance
(X>100) OR (X<50)
would result in 1 if X is above 100 or below 50; otherwise it would result in 0.
The NOT operator is logical not bitwise. This means that NOT 0 is 1 and NOT 1 is 0.
Also, the NOT of any non-zero number is 0.
eg. (X AND 128) != 0results in a 1 if bit 7 in X is set or 0 if bit 7 is clear. The bit mask
128 is 2^7. This assumes bit 0 is the least significant bit. In general, the bit mask for any
bit N is 2^N.
Equations can also contain references to other sensors: e.g. (X + AirTemp)/2
would add X to the AirTemp value and divide by 2. You may also use the M1, M2..
designators instead of measurement labels: e.g. (X+M4)/2 would add X to the result of
measurement four and divide it all by two.
Comments can be contained within braces { }
{convert from degrees Celsius to degrees Fahrenheit} X*9/5+32
Other examples:
SIN(X)+COS(X)+X^3+LOG(X)
(X>1000)*1000 + (X<=1000)*X {would limit the value so that it could never be greater
than 1000}
STEINHART(10000*X/(2.5-X),0.001127098,0.000234445,0.0000000865403)
{temperature sensor}
Details
Details can be enabled or disabled. If disabled (which is the default), the final
result is the only data logged after a measurement completes. If Details are
enabled, several readings are logged along with the final result:
•Minimum (the lowest sample collected)
•Maximum (the highest sample collected)
•Number of samples collected
Details can only be enabled if averaging (see above) is taking place; otherwise,
the number of samples would be 1 and the minimum and maximum would be
equal to the final result. Details are useful for diagnostics and for capturing the
minimum and maximum values.
Log Error Value
When MONITOR is unable to get valid data from a sensor (more specifically,
whenever a sensor failure error occurs), MONITOR will change the sensor
reading to match the user set Log Error Value which defaults to -99999. Such
outlandish numbers are used to attract the user’s attention when viewing the log.
15

Right Digits
The number of digits shown after the decimal place is referred to as the right
digits. To make the measurement read 10.12 rather than 10.12345, set the right
digits to 2. Note that MONITOR will round to the requested number of digits
before logging the data.
Multiple Measurements Using the Same Sensor
Feel free to setup multiple measurements with the same input. For example, to
log the daily rainfall and the rainfall during the last hour, setup two
measurements: one a precip rate with an interval of one hour, and another as
precip rate with an interval of one day.
To log the daily temperature as well as the hourly temperature, only one sensor is
needed. Setup two measurements with the same setup, except for the
Measurement Interval and the Averaging Time and use a different Label for each.
One would happen once a day (measurement interval 24 hours, averaging interval
24 hours), and the other once an hour (measurement interval 1 hour, averaging
time 1 hour). It would be a good idea to setup the sampling Interval to one minute
for both sensors in order to save power (see section on averaging).
If two separate measurements are scheduled to measure the same sensor at the
same time (as they will in the examples above), only one reading of the sensor is
made and the result is shared by both measurements.
Measurement Types
The Measurement Type setting will determine what kind of measurement is made.
Each of the different types will unlock other settings. For example, choosing
Analog as the Measurement Type will unlock the Analog Type setting.
Below are listed all the Measurement Types available.
Precip Accumulation
Precip Rate
Connection: Tipping bucket type sensor connected to terminals 6-7
MONITOR can be setup with a tipping bucket in order to measure rainfall.
Precipitation accumulation is used to tally the total amount of precipitation since
the station has powered up. Count is set to zero whenever the station resets.
Precipitation rate, unlike precipitation accumulation, measures the precipitation
that has occurred since the last measurement. So, if the measurement interval is
15 minutes, this measurement will report the rainfall in the last 15 minutes only.
Feel free to setup multiple measurements with the same input. For example, if
you wanted to know the daily rainfall and the rainfall during the last hour, setup
16

two measurements: one a Precip Rate with an interval of one hour, and another as
Precip Rate with an interval of one day.
Usually, a slope is applied to convert the counts from the tipping bucket into
inches of rain. For example, setting the Slope to 0.01 means that one hundred
counts from the tipping bucket equal to one inch of rain.
SDI-12
SDI-12 is a standardized three wire digital interface. Many manufacturers
provide SDI-12 sensors that measure different environmental effects. SDI-12
sensors provide digital data which improves their reliability and accuracy in terms
of logger sensor communications. For more details on SDI-12, please refer to the
More About SDI-12 section and to the wiring section. Also see how to read
multiple parameters from the same sensor.
Setting up an SDI-12 sensor requires the use of these unique setup fields:
SDI-12 Address
Multiple sensors can be connected to the same SDI-12 bus. However, each sensor
needs a unique address. The address is a single ASCII character. Most sensors
default with the address 0. If you are connecting multiple sensors, connect them
one at a time. As each sensor is connected, issue the 0Ax! command, changing
the sensor’s address from 0 to x, where x is a unique number or letter of your
choice. The front panel Diagnostics->SDI Find menu can help do this.
SDI-12 Command
When the measurement type is set to “SDI-12”, data is obtained by sending a
command to the SDI-12 sensor. The sensor will reply with the measured data.
The command is set by the user through the “SDI-12 Address” and “SDI-12
Command” fields. For example, if the address is set to “0” and the command is
set to “M!”, “0M!” will be sent to the sensor.
SDI-12 Param
Some sensors will respond with multiple data values. The “SDI-12 Param”
designates which of these data values the user is interested in.
The common setup for SDI-12 sensors is to specify the “SDI-12 Address” as “0”,
“SDI-12 Command” as “M!” and the “SDI-12 Param” as “1”. This commands
SDI-12 device at address 0 to make a measurement and to take the first value
returned. Newer SDI-12 devices support the following additional commands:
MC Measure and include CRC in reply
C Measure concurrent
CC Measure concurrent and include CRC in reply
R Read real-time
Some SDI-12 devices can return more than one sensor reading, such as a water
quality probe that returns Dissolved Oxygen, Conductivity, Temperature etc.
Some of these devices will return more than one reading when issued a single
17

measurement command and others require that multiple measurement commands
be given.
In the case of the devices that return more than one reading to a single measure
command, the “SDI-12 Param” specifies which of the sensor readings returned by
the SDI-12 device to use. Setting the parameter to 1 tells MONITOR to use the
first value returned from the device; setting parameter to 3 tells MONITOR to use
the third value returned from the device. If more than one parameter needs to be
measured, a different measurement needs to be set up for each parameter. These
measurements should have identical setups, except for the “SDI-12 Param”. Be
sure to keep the measurement time and interval the same for these measurements.
If you vary the time and interval, MONITOR will end up taking multiple sensor
measurements even though one would have sufficed (thus slowing down the
system and using more power). Also see how to read multiple parameters from
the same sensor.
In the case of devices which require multiple commands to be issued (e.g. 0M1!
Retrieves pressure, 0M2! Retrieves temperature) multiple measurements need to
be set up. It does not matter if these measurements are scheduled for the same
time, as MONITOR will have to issue multiple commands to the sensors.
When multiple measurements of type SDI-12 are scheduled to go at the same
time, MONITOR orders the measurement commands so that concurrent
measurements are commanded first. Non-concurrent measurements occur while
waiting for concurrent results. Also, MONITOR is able to recognize when two
different measurement schedules rely on data from a single measurement
command (e.g., measurement 1 commands “0M!” and expects parameter 1 while
measurement 2 commands the same and expects parameter 2, both scheduled at
the same time). In such cases, MONITOR outputs the measurement command
only once.
Analog
Analog measurements involve reading a voltage or current provided by a sensor.
Analog sensors come with instructions that provide information on how to
translate the output voltage into desired units. Translating the analog sensor
output into environmental units can be done via slope and offset for simple
sensors, and via equations for non-linear sensors.
Analog Type
This setting directs the input channel to which the sensor should be connected and
the type of analog measurement to make. These options are available
•0-5V A
•0-5V B
•Diff C
•Diff D
•4-20 mA
18

•Diff E
0-5VA and 0-5VB
Connection: A (2), B (3)
May also use AGND (1), GND (13), SW’D battery (14).
Analog
Sensor
(0-5v)
A
1 2
Gn
d
Gn
d
Inputs 0-5V A and 0-5B are designed to be general purpose 0-5 Volt DC input.
While sometimes referred to as a single ended input, it is designed to measure
voltage with respect to analog ground. These inputs have a high impedance (>2
Meg Ohms) and will not load down or draw significant current. The input range
is 0V to 5V.
19

Diff C, Diff D, Diff E
Connection: Diff C (6-7)
Diff D (8-9)
Diff E (18-19)
Optional connection to VREF (5) and AGND (4) as needed
Excitation
(VREF)
Analog
Gnd
_
SDR with Analog
Input Option.
4 5 6 7
+
Measurements Diff C, Diff D and Diff E are designed to operate with a special
type of analog output found on many sensors that use a “bridge” configuration or
any sensor that outputs a very small voltage. This input type has a “+” and “-“
input that connects to the sensor output.
Typically a bridge sensor will be powered on “VREF” (sometimes referred to as
excitation), have a “signal +” and “signal –“, and provide a wire for the analog
ground. NOTE: If after wiring the sensor, it displays a negative reading, you may
reverse the “+” and “-“ leads coming from the sensor.
NOTE: The common mode voltage for differential sensors is 0.5V to 3.7V. If the
sensor is floating, it should be tied to VREF and not to AGND in order to
maintain this common mode voltage. Sensors that are not powered by
MONITOR are generally floating (such as a pyranometer).
Input Range
This setting is relevant only to analog differential measurements. The following
options are available:
•-39 to +39mV
•-312 to +312mV
20