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This manual is intended to provide a technical reference for configuring and operating the newest Sensortech
ST-3300 Series Smart RF Sensors and software. Installation guidelines are provided in the Wiring and Installation
document provided with the Sensor. New and experienced users will benefit from the detailed technical
information and operating instructions for Sensortech hardware and software options and accessories.
In this manual, the ST-3300 Series Smart RF Sensors are also referred to by the general term “Gauge”.
Hardware Revisions and Software Versions covered by this manual:
ST-3300 Series Hardware Revision: A (and above)
ST-3300 Series Firmware Version: 0.04 (and above)
ST-3300 Series Configuration Software Version: 1.000 (and above)
The manual is organized as follows:
1. Quick Start Guide
2. Sensor and hardware installation information.
3. Sensortech software installation and PC requirements.
4. Overview of the Sensor and software configuration.
5. Overview of Product Calibration using the Sensor.
About The Manual ..............................................................................................................................................3
Table of Contents .......................................................................................................................................................4
System Overview ........................................................................................................................................................6
Theory of Operation ................................................................................................................................................ 20
Radio Frequency Dielectric Measurement ...................................................................................................... 20
Moisture Determination by Dielectric Measurement ..................................................................................... 21
Connecting to the Sensor using the RS-485 Interface ............................................................................................. 23
RS-485 Serial Communication - Host PC/PLC/Controller to I/O Unit .............................................................. 23
ST-3300 Configuration Program Operation ............................................................................................................. 24
Main Screen – at Startup ................................................................................................................................. 24
Main Screen – Sensor Connected .................................................................................................................... 25
Linear Mode ..................................................................................................................................................... 38
Thank you for choosing Sensortech for your moisture measurement and analysis needs. The Sensortech ST-3300
Series of Smart RF Sensors are designed for use in industrial environments and provide the most sophisticated
on-line Sensors available, offering unmatched accuracy and reliability.
The Sensors are shipped with all the accessories and custom options ordered. Please compare the contents with
the packing list to ensure all items are accounted for. If any items are missing or damaged, please contact
Sensortech immediately for further assistance.
Sensor Physical Installation
Every Sensor installation is unique and specific installation instructions are provided for the most common and
custom Sensor Application Interfaces. Please refer to the ST-3300 Wiring and Installation Guide for your specific
application.
System Overview
The ST-3300 Series Sensor is a complete measurement and interface system where all signal processing and
control functions are self-contained. It features multiple interface protocols including one isolated 4-20mA
output, an RS-485 serial communication port, a Digital Input and a Product Temperature Input. Optional
communications protocols include OI-6000 Operator Interface, Ethernet TCP/IP, DeviceNet, PROFIBUS,
PROFINET and EtherNet/IP as well as digital inputs and outputs for external sample gating and control.
The ST-3300 System is composed of the following components:
Sensor Antenna - an antenna that is located in close proximity to the Product being measured and is either
directly attached for low temperature applications or remotely located for high temperature applications. The
Sensor Antenna is connected to the Sensor Electronics Unit through coaxial cables.
Sensor Electronics Unit - a NEMA rated metal enclosure which houses 2 PCB’s – the RF PCB and the Processor
PCB. The RF PCB generates signals sent to the Sensor Antenna and provides frequency and voltage signals to the
Processor PCB for moisture and temperature value calculations. It connects to the I/O Unit and the Sensor
Antenna via M12 for power and signals as well as coaxial cables to measure product moisture. The Processor
PCB controls the RF PCB and to read and manage data on the analog and digital interfaces.
I/O Unit - a NEMA rated metal enclosure which provides +/-15VDC power to the Sensor and allows the user to
install wires onto the terminal blocks and connectors mounted on the I/O Unit PCB to provide AC power and
external analog and digital interfaces.
Product Temperature Transducer - a user defined peripheral pyrometer or transducer module that connects to
the Sensor Electronics Unit via a M4 x 4 pin connector for 4-20mA or voltage input via an M12 x 4 cable.
The heart of the ST-3300 is a sophisticated dielectric Sensor. The Sensor utilizes state of the art phase lock loop
technology. High speed logic and ultra-high bandwidth operational amplifiers enhance performance. A
microprocessor controls the RF measurement circuit and communicates with user defined protocol interfaces.
Figure 3 shows a block diagram of the Sensor electronics.
Measurement is made by switching between one of three RF channels: CA, CH, CL and Sensortech Systems
developed and patented a specific method of dielectric determination using radio frequency. This is known as
the resonant frequency technique. The purpose of the reference channels is to stabilize the Sensor over a wide
range of ambient conditions. The three frequencies are measured by an onboard microprocessor and form the
inputs to a proprietary algorithm used to eliminate most drift factors.
CA connects to the Sensor Antenna element which is in close proximity to the product being measured. CH
connects to the High Reference element and CL connects to the Low Reference element for precision reference
calculations.
Only one channel is switched in circuit per measurement sample, this forms a parallel tuned circuit with the
inductor. The resonant frequency of this network constitutes the "lock frequency" of the phase lock loop.
The Sensor measurement results are sent from the Sensor Electronics Unit to the I/O Unit via RS-485 interface.
The I/O Unit provides +/-15V power supply for the Sensor Electronics Unit and terminal board connectors for
connection of the analog and digital interface signals to the user’s process control systems.
The I/O Unit also provides local push button controls for performing the Zero and Standardize calibrations of the
Sensor. The user opens the lid of the enclosure and presses the Zero button with nothing over the Sensor and
the Status LED next to the button lights up to indicate a Zero calibration has been performed. The user then
places a Standardization Plate over the Sensor and presses the Standardize button. The Status LED next to the
button lights up to indicate a Standardize calibration has been performed.
Numerous methods have been used to determine dielectric constant of a material. Radio frequency is often
used for its ability to penetrate a material to a substantial depth and to be able to measure without contacting
the material. Sensortech Systems developed and patented a specific method of dielectric determination using
radio frequency. This is known as the resonant frequency technique.
Figure 5: Parallel Plate Capacitor with Dielectric Medium
Figure 4: Parallel Plate Capacitor with Air Medium
As previously stated, dielectric is a material property affecting the way it behaves in an electric field. A parallel
plate capacitor is shown in figure 2(a). If the medium separating the plates is air or a vacuum, the capacitance is
given by:
C = (ε
A) / d
⋅
o
where:
ε
= permitivitty of free space = 8.854 x 10
o
-12
A = Area of plate
d = separation distance of plates
When a dielectric medium separates the plates as in figure 2(b), capacitance becomes:
C = (ε
o
⋅
ε
r
A) / d
⋅
where:
ε
= dielectric constant
r
Thus, capacitance is directly proportional to the dielectric constant of the material in the electric field.
C = K
ε
⋅
r
Parallel plate capacitance Sensors are rarely used for industrial applications; single-sided Sensors being
preferred.
Figure 6 is schematic representation of a parallel plate capacitor showing uniform electric flux lines except at the
edges where fringing occurs. The fringe field is generally undesirable in a capacitor, but in a single-sided
capacitance Sensor, it is the only useful field.
Figure 7 is a cross-sectional view of a planar Sensor, most frequently used for gypsum board applications. A
central element propagates an electric field to the grounded side plates. A small proportion of the field is
directly between electrodes, but most is the fringe field used to penetrate the board. Figure 8 shows an example
of an Open Frame Planar Sensor Antenna.
Figure 8: Example of an Open Frame Planar Sensor Antenna
Electrically, the Sensor Antenna, is simply a capacitor. The electrical analogy of the gypsum product is itself a
capacitance with parallel resistance. The resistance or conductance represents the ionic conductance or
dielectric loss in the board.
Figure 9: Electrical Schematic of Product Coupling
Figure 10: Electrical Schematic of Equivalent Resonant Circuit
Figure 9 shows the electrical schematic of the product coupled to the capacitive Sensor. Air gap capacitance (
couples the product (
C
) to the Sensor (
p
C
) and must, therefore, be kept constant. Mounting the Sensor
s
between conveyor rollers, spaced perhaps 6mm below the plane of the rollers, ensures a constant coupling
C
capacitance, provided rollers are reasonably true. The capacitances may be combined as one (
mathematically incorrect, may simplistically be represented as
CT = Cs + C
.
p
) which, while
T
Figure 10 illustrates the resonant network formed by Sensor capacitance in parallel with product capacitance
also in parallel with inductor (L). This network has a unique resonant frequency at which inductive reactance
cancels capacitive reactance and network impedance is at a maximum. Impedance at resonance is actually
The resonant network is driven from a suitable RF signal through a pure fixed resistor (Ro) as shown in Figure 11.
As frequency increases, the network is first of all inductive with a leading phase angle. At resonance all reactive
components cancel and the circuit is purely resistive. At resonance, the signal amplitude across the resonant
network is a function of only R
, Rp and amplitude of the driving signal. Ro and Rp behave as a simple potential
o
divider.
Using a precision phase lock loop to adjust signal frequency to maintain zero phase angle across resistor R
o
ensures the network is always at resonance.
Resonant frequency is defined as:
f
= 1 / [2π√(L
o
)]
C
⋅
T
The Sensor measures this frequency and a proprietary measurement algorithm combines Sensor frequency with
two reference frequencies to produce a dielectric value that is essentially independent of ambient temperatures
and component aging.
The resulting raw dielectric can be seen to be a function of Sensor capacitance (with product) and precision
reference capacitors. Inductance and stray capacitance are eliminated.
Moisture is directly proportional to the raw dielectric.
Given a linear relationship, the instrument can now be calibrated from analytical data to fit a linear function of
the form:
Moisture = a
D + b
⋅
Since capacitance C
of Sensor capacitance. This is achieved by measuring Sensor capacitance when no product is present (D
is a composite of both the Sensor and the product, it is necessary to remove the influence
T
) and
z
subtracting this from future measurement in a similar way to performing a tare on a weigh scale. This action is
termed 'Pre-zero' and should be performed periodically to compensate for antenna changes and product buildup on the antenna.
The primary moisture measurement of the Sensor uses the principle of dielectric determination. Since moisture
has a much higher relative dielectric than most solids, it is possible to relate to moisture content. Radio
frequency moisture determination, which is a penetrating measurement, has to take into account the mass of
the product being measured in order to provide a percentage measurement. This is because the Sensor
effectively counts the water molecules within the Sensor field. If more product is squeezed into that field, it will
produce a higher moisture reading, even though the percentage water figure may be constant. In order to
correct for this, the product mass, weight or density must be taken into consideration.
Figure 13: Open Frame Sensor - Radio Frequency Field Penetrating Through Product
The Figure 13 shows the typical radio electric field passing through a product. The dielectric effect of the product
will be a function of its dielectric constant and the length of flux paths passing through the product (fringe field
lines). The latter will be a function of product thickness and distance from the Sensor. If a parallel plate Sensor
were used, the field lines would be uniform and a doubling in product thickness would produce a doubling in
dielectric. The Sensor shown is a single sided or Planar Sensor Antenna, with a non-linear field. Doubling of
product thickness will cause an increase in dielectric, but not by a factor of two. A Planar Sensor Antenna
response would be of the form:
where:
Mass = weight, density, thickness etc.
Kw = coefficient determined by antenna geometry (less than 1)
The value of Kw coefficient will depend upon antenna geometry, product presentation and form of mass
measurement e.g. thickness, weight etc. To determine Kw, a constant moisture product of varying mass is
presented to Sensor. A graph of log (Sensor response) vs. log (mass) must be plotted. Kw is given by the slope of
this line (see Figure 14).
The product dielectric is coupled to the antenna via an interface such as air. In some cases, direct contact may
be made, or a fixed interface such as a Teflon or Ceramic window may isolate the Sensor from the product. The
important thing is that the interface between product and Sensor, must remain constant in order for the
interface dielectric to be cancelled out of the product measurement. In the case of direct contact or a window,
this would be the case. If an air gap exists between product and Sensor and the air gap distance varies, due to
mechanical vibration or board bounce, the total dielectric for the measurement will change. If the gap can be
measured, it can be compensated.
If the antenna were a point source, then the RF energy would decrease according to the inverse square law and
a simple compensation based upon the square of the distance would be possible. In practice the antenna is a
finite width radiator producing a more complex relationship. It is further complicated by field distortion through
the product.
Instrument
Mass
Figure 14: Plots of Sensor Measurement vs. Product Mass
Kw = log(y)/log(x)
log (Instrument)
y
x
log (Mass)
Figure 13 shows the typical field pattern emanating from a planar electrode, but this is somewhat idealized, as
the field is actually distorted or refracted within the product. The amount of distortion is a function of product
dielectric and is both density and moisture dependent. This distortion will also affect the field in the air gap and
the distance relationship.
In practice, the product density usually remains fairly constant at a fixed point in the process, and the moisture
similarly should not vary too greatly. If this is the case, distance may be corrected by an equation of the form:
If moisture and density are uncontrolled such as raw material measurement, it is better to control or constrain
the distance variation rather than try to compensate for it.
The example to the left shows three Sensor measurements of differing
moisture, at varying distances from the Sensor. No compensation is
applied and an inverse relationship is apparent.
10
0 .25 .50 .75
Distance
. In this next example the same three Sensor measurements are
20
performed at varying distances. The Sensor has a compensation
15
equation:
10
Mc = Mu (D + 0.14)2
5
The offset coefficient Kd (.14) is determined by trial and error to obtain
0 .25 .50 .75
Distance
flattest response.
Figure 15: Plot of Sensor
Measurement vs. Product
Distance
From an electronic standpoint, antenna is a misnomer. A truer description would be electrode or
probe, since antennae tend to denote devices designed for maximum propagation efficiency, usually
achieved by standing wave theory.
For dielectric measurement, standing waves are to be avoided at all cost since this would produce nonuniform energy distribution. The Sensortech Systems probe is essentially a deliberately mismatched
antenna to provide broadband uniform dielectric coupling to product.
Antenna geometry (shape, size, etc.) is mainly a function of application, since provided the above
criteria are met, it is largely a matter of mechanical design as how best to couple to the product.
Sensortech Systems, Inc. has over a period of years, developed many unique electrode designs
including: parallel plate, planar, cylindrical (pipeline), probe and co-axial types. The most widely used
style is the planar type shown in figure 2. Consisting of a central electrode between two ground planes,
or multiple electrodes interspersed with ground plane, this style provides a single sided measurement
preferred in most industrial applications.
Figure 17:Electric field interaction with an atom under the classical dielectric model
In the classical approach to the dielectric model a material is made up of atoms. The atoms consist of a positive
point charge at the center surrounded by a cloud of negative charge. The cloud of negative charge is bound to
the positive point charge. The atoms are separated by enough distance such that they do not interact with one
another. This is represented by the top left of the figure aside. Note: Remember the model is not attempting to
say anything about the structure of matter. It is only trying to describe the interaction between an electric field
and matter.
In the presence of an electric field the charge cloud is distorted, as shown the top right of Figure 17 above.
This can be reduced to a simple dipole using the superposition principle. A dipole is characterized by its dipole
moment. This is a vector quantity and is shown as the blue arrow labeled M. It is the relationship between the
electric field and the dipole moment that gives rise to the behavior of the dielectric. Note: The dipole moment
is shown to be pointing in the same direction as the electric field. This isn't always correct, but it is a major
simplification, and it is suitable for many materials.
When the electric field is removed the atom returns to its original state.
Dielectric is the electrical property of a material relating to its behavior when subject to an electric field. Figure
17 illustrates the dielectric model of a material. Dielectric Constant or Relative Dielectric relates to the ease with
which a material polarizes relative to a vacuum or, more practically, air. Table 1 shows the dielectric constants of
a few common materials. Generally, solids exhibit relatively low dielectric constants. Exceptions include
Titanium Dioxide (110) and many titanates.
Water exhibits a very high dielectric; much higher than gypsum and most other solids. Thus, dielectric
measurement can accurately resolve very low quantities of free water. Dielectric testing is particularly suited to
determine moisture content in gypsum board and other gypsum products. The dielectric figure for gypsum itself
varies. It is a function of crystal structure and, in the case of finished board, a function of density. For a particular
product, these values are normally tightly controlled.
Dielectric Constant
The Dielectric Constant for a salt solution is shown to demonstrate how little the dielectric constant is affected
by ion concentration. Note that for liquids, the dielectric constant is given for a specific temperature.
Temperature effect on solids is typically small, but on liquids can be significant. The internal temperature of a
gypsum board after 1st zone drying should be very constant around 100°C, provided the board is not over-dried.
Temperature compensation is therefore not required for gypsum board applications.
A Sensortech USB Drive is included with the Sensor. The USB Drive contains documentation and software to
perform Sensor configuration and display results.
Minimum Host PC Requirements
• IBM PC compatible computer
• Windows 7
• Pentium 4 / 3.00 GHz. or better processor
• 1280 X 1024 pixel resolution, 16-bit color
• 2GB System RAM
• 128MB Video RAM
• 100MB disk space
• 10/100 MB or faster Ethernet card
• USB port
Software installation
Run Setup.exe and follow the installation instructions.
If earlier versions of Sensortech software are installed, they should be detected during the setup procedure and
may be removed. It is recommended to back-up and remove any earlier known versions prior to installing the
software.
Starting the software
At the completion of software installation, an icon will appear on the desktop of the host PC.
Figure 18: Sensor Configuration Program Icon
Double clicking the icon above will start the configuration program and display the Screen shown in Figure 18.
Note: The Sensor Configuration program is used to perform Sensor configuration and calibration. It is not
intended as an HMI or logging program. For continuous monitoring of the Sensor(s), Sensortech provides 420mA outputs or the user may use the Modbus digital interface for continuous monitoring on the user
PLC/Controller. An Operator Interface unit or process controller may also be connected to the Sensor digital
interface for Sensor configuration, calibration and monitoring measurements.
Connecting to the Sensor using the RS-485 Interface
The default Sensor configuration provides for serial communication via the RS-485 interface using a M12 x 5
connector or the terminal block connectors on the I/O Unit. Optional communication protocols may be added to
a I/O Unit to provide Ethernet TCP/IP, DeviceNet, PROFIBUS, or EtherNet/IP interface for digital interface. See
the Sensor Configuration Detail sheet provided with the Sensor to determine if a custom protocol option that
was installed.
RS-485 Serial Communication - Host PC/PLC/Controller to I/O Unit
On Sensors using an I/O Unit the digital interface is provided by RS-485 full duplex Modbus protocol. The
starting point for Sensor configuration would be to connect the Sensor to a host PC/PLC/Controller using the
M12 x 5 connector or the terminal blocks on the I/O Unit.
If the ST-3300 I/O Unit is not being used, the user must directly wire an M12 x 12 connector cable to a RS-485 to
USB converter on a host PC and provide power and ground for +/-15VDC power.
Connect the host PC to the Sensor using the factory default settings below:
See the APPENDIX for wiring and connector information.
Host PC
PLC/Controller
Figure 19: Digital RS-485 Serial Interface Connection
Figure 20: Main Screen at Startup - Not Connected to an Sensor
To initiate connection between the host PC and Sensor click on "Find Networked Gauges" button on the lower
left of the Main Screen. When using a USB to RS-485 converter, select the COM port where the USB Converter is
installed on the host PC. All Sensors connected to the host PC will be displayed in the "Gauge List" box located to
the right of the "Find Networked Gauges" button. Then connect to a Sensor using the serial interface COMx
(where x = 1 - 9), highlight the COMx by double-clicking on the COMx listed in the "Gauge List" box and the
selected COMx port will appear in the “Selected Gauge” field.
Press the red "Connect" button at the lower left. When a Sensor is connected, the “Connect” button will change
color from red to green and the information fields to the right of the "Connect" button will display the data read
from the connected Sensor.
Figure 21: Main Screen Time Plot with Sensor Connected
To commence a time plot, press the "Start" button after the “Connect” button has turned green. When a
measurement has started, the “Start” button will change color from red to green and the displays on the upper
right will indicate the measured value selected and the trend plot in the upper left will begin to display the
measured value and time plot as shown in the Main Screen above.
The Main Screen above is shown after a Sensor is connected to the host PC/Controller, the user has logged in
using the factory default password and a moisture measurement has started.
The Main Screen configuration and field descriptions are as follows (beginning at upper left of Screen):
1. Sensortech Configuration Software Version is displayed in upper bar.
2. At startup, the Main Screen shows three tabs in the upper left, namely: Main and Diagnostics. The Sensor
configuration functions are password protected for security. Entering the appropriate password enables
more tabs at the top of the Main Screen for access to additional Sensor functions: Configuration, Calibration
and Maintenance screens. Select the tab for each of the Diagnostics,Configuration, Calibration and Maintenance screens to select the Sensor configuration desired.
3. Trend Chart Display of time vs. measured value plot of all selected constituents to be measured and
displayed.
4. Digital Display of Measurement Values for selected constituents.
5. Y Axis Min: Minimum value of lowest measured value to display. User defined.
6. Y Axis Max: Maximum value of highest measured value to display. User defined.
7. Change button: sends the new ‘Y Axis Min’ and ‘Y Axis Max’ values to configure the plot display.
8. Enable/Disable Logging button: starts or stops the data log, which stores measurement data directly into
a text file. Pressing the red “Enable Logging” button will open a window where you can create and name
the file. Once the file is named, press ‘Open’ to activate this function. Press the Start/Stop button to
begin data logging. The measurements will be stored in the data log file until the user presses “Disable
Logging” button or the Configuration program is closed.
9. Drop-down menu (1 second) selects the time interval for updating the displays for each constituent and
the sample rate used for data log of measurements.
10. Start/Stop button: begins the display and plot of a measurement on the Main Screen. It also starts and
stops the data log of measurements.
11. Password entry field and Login/Log Out button: Press the Login button after entering the Engineering
password “engpass”
and the button changes from red to green. The default is operator level control
when no password is entered. Note: Log out each time you are finished to prevent unauthorized access
to Sensor configuration settings.
12. Find Networked Gauges button: Queries all of the Sensors connected to the host PC and displays a list of
Sensors that are detected and can be connected to the host PC using the Configuration program.
13. Gauge List field: Displays a list of the GaugeID names for all Sensors currently available that can be
selected to connect to the Configuration program. Only one Sensor may be connected at a time to the
Configuration program.
14. Connect button: initiates the data connection between the host PC and Sensor. The button is red when
not connected to an Sensor and changes to green when an Sensor is connected.
15. Selected Gauge: Displays the GaugeID name of the Sensor currently connected to the host PC using the
Configuration program.
16. Fields displaying information of Connected Gauge, Firmware Version, Hardware Revision, Model
Number and Serial Number for the Sensor.
17. Product Select: Drop-down menu (1 Corn Germ) to select the Product configuration to be used for the
current measurement.
18. Current Product: Displays the Product name of the currently active product configuration.
19.
Lower status display bar is updated with current Sensor and measurement status. See Table 2 for Sensor
status and error messages.
The Setup Screen is shown above. From the Setup Screen it is possible to create a new user password, which will
change the factory default password. The Setup Screen descriptions are as follows (from upper left of Screen):
Change Eng Password Box - allows you to change your engineering level password for access to all screens.
1. Old Password: Enter the factory default or a previously entered user defined password.
2. New Password: Enter a new user defined password (alphanumeric characters).
3. Repeat New Password: Re-enter new user defined password.
4. Change button: Sends and stores the new password entered.
5. Auto Connect Mode checkbox: When selected, will automatically connect to Ethernet TCP/IP devices
connected to the Ethernet port such as an Operator Interface unit.
6. Data Folder: specifies the pathname where all gauge data will be stored.
The Diagnostics Screen is shown above. The Diagnostic values are updated when the “RUN” button is pressed
and the current Sensor information will be displayed. The Diagnostics Screen field descriptions are as follows
(from upper left of Screen):
1.
Fs: Sensor frequency count value of the Antenna channel. The Fs frequency count should be approx. equal
to the Fl frequency count when there is no product over the Sensor. The Fs frequency count should be lower
than the Fl frequency count when there is product over the Sensor.
2.
Fl: Sensor frequency count value of the Low Reference channel. The Fl frequency count should be approx.
equal to the Fs frequency count when there is no product over the Sensor.
3.
Fh: Sensor frequency count value of the High Reference channel. The Fh frequency count will be higher than
the Fl frequency count with or without product over the Sensor, the higher Fh frequency count value will
always be higher and will be different values depending on the Sample Period and Sensor Antenna design.
4.
Dr: calculated Raw Dielectric value. The Dr value should be approx. 1 with no product on the Sensor.
Dz: stored Raw Dielectric value from ZERO calibration. The Dr value should be approx. 1 after Sensor
calibration.
6.
Moisture: current moisture measurement.
7.
Delta Freq Fl – Fs: difference in frequency count of Fl minus Fs.
8.
Standardization: stored STD factor value from Standardize calibration. The STD value will always be a
positive value between 0 and 100.
9.
Product Temperature: optional Product Temperature measurement in degrees C.
10.
Gauge Temperature: current internal temperature in degrees C of Sensor Electronics Unit enclosure.
11.
+3.3V Volt Reading: current internal +3.3V power supply voltage monitor.
12.
-+5V Volt Reading: current internal +5V power supply voltage monitor.
13.
+12 Volt Reading: current internal +12V power supply voltage monitor.
14.
-12 Volt Reading: current internal -12V power supply voltage monitor.
15.
Digital Input: current logic state of external DIG_IN input.
16.
Freq Lock Mode: Pull down menu for selecting Normal mode of operation or to lock the measurement to a
single channel for Sensor (Fs), Low Reference (Fl) and High Reference (Fh). Normal mode should be selected
for process measurements.
After entering the engineering password, click on the ‘Configuration’ tab, the Measure Configuration Screen
shown above will be displayed. The Screen allows the user to select the mode of measurement and to set
various parameters associated with this mode.
The Measure Configuration settings are pre-set at the factory for your application. Care must be taken if any
values are changed due to the significant effect on Sensor moisture measurement results. The user may change
measure configuration controls on the Screen.
The Measure Configuration Screen descriptions are as follows (from upper left of Screen):
1. Measure Method: drop-down menu selects the measurement mode of the Sensor. A Sensor can be
configured to operate in one of 5 different measurement modes as described in Table 1.
Signal Gated An external input signal is provided to the Sensor, which enables a measurement
sample for a true logic input voltage. A false logic input voltage disables
measurement and the last measurement is held.
Auto Product Detect Similar to signal gated, but gating is enabled by using the “Delta Freq Fl – Fs” value
from the Diagnostics Screen. A frequency count change threshold is programmed in
the “Product Loss Threshold” field where a frequency count change that is greater
than the threshold value starts a measurement (sample) and a frequency count
change that is less than the threshold value ends the measurement (hold).
Timed Sample This is used when a sampling device is attached to the Sensor such as a Snorkel
Sampler, which collects a material sample for measurement, performs a
measurement then purges the sample container to begin a new measurement.
Programmable functions for this mode include Fill Time, Measure Time and Purge
Time.
Gated Timed Sample An external input signal is provided to the Sensor, which enables measurement
sample for a timed interval for a true logic input voltage. The Measure Time interval
is programmable.
Product Tare A measurement is made on with or without product as a reference for a zero value
measurement. This value is stored and sets the zero value offset for additional
measurements.
Table 1.
2. Batch Mode checkbox: this can be applied to all measurement modes except for Continuous. The
measurement will be averaged during the period that the “gate” is active. The average of the measured
values will be displayed when the gate is inactive.
3. Fill Time (seconds): used in Timed Sample mode to define the period (in seconds) to collect a material
sample for measurement. no measurements are made during this period.
4. Measure Time (seconds): used in Timed Sample mode to define the period (in seconds) to measure a
sample.
5. Purge Time (seconds): used in Timed Sample mode to define the period (in seconds) to purge a material
sample collected for measurement. No measurements are made during this period.
6. Product Loss Threshold: used in Auto Product Detect mode to define the frequency count change in the
“Delta Freq Fl – Fs” value which is used to start (sample) and end (hold) a measurement. Used to detect the
leading edge of wallboard when the “Delta Freq Fl – Fs” value exceeds the threshold value to begin a
measurement and ends the measurement when the wallboard trailing end causes the “Delta Freq Fl – Fs”
value to fall below the threshold value.
7. Sample Period (msec): The Sensor circuitry can be configured to sample every 5, 10, 20, 50 or 100
milliseconds (5ms = 200 samples/sec.). The Sensor is capable of handling this sampling rate, but in many
applications a slower rate is desirable.
8. Sensor Measurements per cycle: number of sequential samples of Sensor moisture measurements to be
made before a Low Reference or High Reference measurement is repeated. For example, if the number of
Sensor Measurements per cycle=98 and Sample Period=10mS, then 98 moisture measurements plus 1 High
and 1 Low Reference measurement is made each cycle for a total of 100 measurements per second (98
Sensor measurements plus 2 Reference measurements).
9. Reference Buffer Size: number of reference measurements to use for calibration.
10. Reference Moisture: value of the dielectric reference used for Standardize calibration. A Standardization
plate would have a dielectric reference value of 25.
11. Median Filter Size: median averaging allows the user to smooth the response of the moisture display by
calculating the median average of successive samples. For example, if a Median Filter Size value of 10 is
entered, then the Median average of the last 10 measurement samples is displayed. Median Filter Size has a
smoothing effect on the Sensor response to measurement changes. A large Median Filter Size value will
slightly delay the response to measurement changes. The measurement sample update rate is not affected
by the Median Filter Size value. Each new sample is added to the buffer and the oldest sample is discarded.
Median Filter Size is determined by the amount of Median averaging required, but the maximum Median
Filter Size is 100. Thus at Sample Period=10mS, Median Filter Size=10, Mean Filter Size=1, Sensor
Measurements per cycle=98 and Damping Filter Size=1 would equate to 0.1 seconds of averaging. Only
integer values may be entered between 1 and 31.
12. Mean Filter Size: mean averaging allows the user to smooth the response of the moisture display by
averaging successive samples. For example, if a Mean Filter Size value of 10 is entered, then the mean
average of the last 10 measurement samples is displayed. Mean Filter Size has a smoothing effect on the
Sensor response to measurement changes. A large Mean Filter Size value will slightly delay the response to
measurement changes. The measurement sample update rate is not affected by the Mean Filter Size value.
Each new sample is added to the buffer and the oldest sample is discarded. Mean Filter Size is determined
by the amount of mean averaging required, but the maximum Mean Filter Size is 100. Thus at Sample
Period=10mS, Median Filter Size=1, Mean Filter Size=10, Sensor Measurements per cycle=98 and Damping
Filter Size=1 would equate to 0.1 seconds of averaging. Only integer values may be entered between 1 and
100.
13. Damping Filter Size: damping or averaging allows the user to smooth the response of the moisture display
by averaging successive samples. For example, if a Damping value of 10 is entered, then the average of the
last 10 measurement samples is displayed. Damping has a smoothing effect on the Sensor response to
measurement changes. A large Damping value will delay the response to measurement changes. The
measurement sample update rate is not affected by the Damping value. Each new sample is added to the
buffer and the oldest sample is discarded. Damping Filter Size is determined by the amount of damping
required, but the maximum Damping Filter Size is 500. Thus at Sample Period=10mS, Median Filter Size=1,
Mean Filter Size=1, Sensor Measurements per cycle=98 and Damping Filter Size=500 would equate to 8.33
seconds of averaging. Only integer values may be entered between 1 and 500.
14. Damping Bypass: a moisture threshold value where any moisture measurement changes smaller than the
Damping Bypass value will have the Damping Filter applied. However, measurement changes exceeding the
Damping Filter Size value will bypass or disable the Damping Filter function. In this way, small, steady state
fluctuations are smoothed by damping, but moisture measurement changes greater than the Damping
Bypass value are immediately displayed.
Note: Each Sensor is set at the factory for the Sensor configuration ordered and predefined values have been
set according to the product and measurement requirements specified. Care should be taken when changing
any factory configuration or preset values to ensure that the Sensor will perform the measurement correctly
and in the mode desired.
The “Get” button loads information from the Sensor and the “Send” button writes to the Sensor.
The Product Configuration Screen allows the user to define measurement settings for up to 50 unique Product
Codes being measured.
The Product Configuration Screen descriptions are as follows (from upper left of Screen):
1. Product: drop-down menu that allows the user to select the Product information to be displayed. Up to 50
unique Product Codes may be defined. The Product Name can be set by entering the name of the product in
Product Name field.
2. Coefficient B: user programmable positive value that defines the measurement slope. A higher ‘B’ value
increases Sensor sensitivity.
3. Coefficient C: user programmable positive or negative value that defines the measurement offset.
4. Product Name: user defined name composed of alphanumeric characters.
The “Get” button loads information from the Sensor and the “Send” button writes to the Sensor.
The I/O Configuration Screen allows the user to configure the Sensor 4-20mA output to be either the moisture
value or Product Temperature value.
The I/O Configuration Screen descriptions are as follows (from upper left of Screen):
1. 4-20mA Select port 1: a pull down selection of either moisture measurement or Product Temperature sent
to the 4-20mA output.
2. 4-20mA Select port 2: not used.
3. Levels Corresponding to 4-20mA: port 1 4mA: moisture value corresponding to a 4mA output.
4. Levels Corresponding to 4-20mA: port 1 20mA: moisture value corresponding to a 20mA output.
5. Digital Output 1: not used.
6. Digital Output 2: not used.
The “Get” button loads information from the Sensor and the “Send” button writes to the Sensor
The Calibration Screen enables the user to recalibrate the instrument by recording measurements of physical
samples and comparing them to a laboratory analysis.
The screen descriptions are as follows (from upper left of Screen):
1. Constituent Select: One constituent at a time is selected for Sensor calibration. (i.e. Moisture)
2. Calibration Mode: There are two modes which can be employed: Linear and Offset. Each method is outlined
later in this chapter.
3. Delete Sample: Deletes any previous sample measurement.
4. Sample: This field displays the real-time measurement.
5. Average: This field displays the average between start and stop of the measurement.
6. Start / Stop button: By pressing the ‘Start’ button, the calibration measurement is initiated. The button
toggles to ‘Stop’, which will complete the sample measurement when pressed.
7. Store Sample: This button stores the average value obtained during the sample period into the data table.
8. Create Sample: This is used for manual entry of values in the Gauge and corresponding Lab field.
9. Recalculate Coefficients: Recalculates coefficients A, B and C after all of the sample measurement and
corresponding lab data has been collected.
10. Send Coefficients: Using this function, the recalculated coefficients are stored in the Sensor, completing the
calibration procedure.
11. Correlation: This shows the quality data fit between the Sensor and Lab data. The optimum value for
correlation is 1.
12. Standard Error: The standard deviation before recalculation.
13. Recalculated Standard Error: The standard error resulting from the new values determined for coefficients
A, B and C after recalculation.
14. Clear Samples: This function will clear the data relating to the current Calibration. Note: All data will be lost
unless saved to file.
15. Save To File: After performing the calibration, the coefficient values can be saved in the host PC for future
use.
16. Load from File: This function is used to load previously saved calibrations.
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Figure 28: Effect of Coefficient B on Slope
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Figure 29: Effect of Coefficient C on Offset
Offset Mode
The simplest mode of calibration is the ‘Offset’ method. This method assumes that the Sensor has been
previously calibrated and the slope (Coefficient B) has already been established. It is primarily intended for
online calibration to compensate for process variables such as interface between Sensor and product, density,
product height, flow speed, Sensor installation misalignments, etc.
In most cases, the Sensor has been statically calibrated in our factory for your application. Once the Sensor has
been installed on-line, a single sample comparison with the measurement value will determine if an offset is
necessary.
2. While material is over the Sensor, press the ‘Start’ button and wait until the measured value is
displayed.
3. Press the ‘Stop’ button and immediately collect a sample from the line at the Sensor and place it in an
airtight container or plastic bag. Completely fill the container and remove any excess air.
4. Press ‘Store Sample’ to record the reading in the Calibration screen data table.
5. Perform a lab analysis on your sample (for moisture this is typically a weight loss oven test), then enter
the lab analysis value into the data table under the ‘Lab’ column.
6. Press ‘Recalculate Coefficients’ and note that the ‘C’ coefficient value has been corrected.
7. Press ‘Send Coefficients’ to conclude the calibration procedure
Linear Mode
Linear regression establishes the direct correlation between two data series. A correlation coefficient indicates
the quality of correlation. This value is between 0 and 1, with 1 being perfect.
In addition to determining the quality of fit, the regression function calculates the slope and intercept of the
calibration line. These two values are the ‘B’ and ‘C’ coefficients, respectively.
Linear mode should only be used with an adequate range and moisture levels
The following steps will provide an example of how to perform a Product Calibration:
1. Select the Calibration screen tab.
2. Select the constituent to calibrate using the ‘Constituent Select’ drop-down menu.
3. Select the calibration mode using the ‘Calibration Mode’ drop-down menu.
4. Place the sample material to be calibrated under the Sensor Light Tube / Viewing Window.
5. Press the ‘Start’ button. The ‘Sample’ and ‘Average fields will change color to green and the current
measured value is displayed. The ‘Start’ button changes to ‘Stop’ during the measurement.
6. Press the ‘Stop’ button. The ‘Sample’ and ‘Average’ displays will change color to red and the average of
all the readings, obtained during the sample period, is displayed in the ‘Average’ field. The ‘Sample’ field
will be cleared. Press ‘Store Sample’ button. The sample measurement is stored to the table.
7. Repeat this procedure to get at least 3 sample measurement readings. A minimum of six sample
measurements is recommended for good calibration data sample set. Samples should be reasonably
distributed through the calibration range.
8. The stored samples will be displayed with time and date information in the table fields as shown in
Figure 30.
9. Initially, the ‘Gauge’ value is entered into the ‘Lab’ field also. The actual ‘Lab’ value is manually entered
following the laboratory analysis. Position cursor over desired ‘Lab’ value in table and click field. A data
entry window will open to allow entry of the actual ‘Lab’ value.
10. Press the ‘Recalculate Coefficients’ button. The ‘Gauge’ values and the ‘Lab’ values will be used to
recalculate the coefficient values to find the best fit. The new ‘Gauge’ coefficient values appear in the
‘Recalculated’ fields.
11. To complete the Product Calibration, click on the ‘Send Coefficients’ button. The new coefficient values
will be sent to the Sensor and overwrite the previous coefficient values stored in the Sensor.
Figure 30: Example of the Calibration Screen after Product Calibration has been performed
The graphical representation is useful in selecting bad data points. If a data point appears to be an outlier it may
be temporarily disabled by clicking on the appropriate checkbox in the table. Press ‘Recalculate Coefficients’
button to check if correlation value is significantly improved. If not, uncheck the disable checkbox. If disabling a
data point significantly improves correlation, that data point may be permanently removed by highlighting the
row in the table and pressing the ‘Delete Sample’ button.
a) Take the sample as close to the Sensor as possible.
b) Process as large a sample as possible.
c) If using damping, take a series of samples over the range of the sampling period. Example: 30 secs damping -
take a sample every 5 secs for 30 seconds.
d) Use a homogenous sample representative of the whole. In the above example, thoroughly mix 30 sec
sample.
e) If using small samples, test samples two or three times (to show repeatability) and average results if
necessary.
f) Use the most accurate testing method available. An oven dry test with a 100g sample is generally more
accurate than a lamp dry test with a 10g sample.
Note: The calibration can only be as accurate as the sampling method.
Figure 31: Maintenance Screen for Pre-Zero and Standardize Calibrations
The Maintenance Screen is provided for the user to perform Pre-Zero and Standardize Calibrations of the Sensor
during periodic routine maintenance. The user will press the “Pre-ZERO” or “STANDARDIZE” button on the left
side of the screen to initiate the Sensor calibration algorithms.
The screen descriptions are as follows (from upper left of Screen):
1. Pre-Zero Button: when pressed performs the Pre-Zero Calibration.
2. Standardize Button: when pressed performs the Standardize Calibration.
3. Current Value: current moisture measurement with B coefficient = 1 and C coefficient = 0.
4. Dz: stored Pre-Zero dielectric value from last Pre-Zero Calibration.
CAUTION! This is a critical calibration parameter and will affect all calibrations.
The purpose of the Pre-Zero Calibration is to remove the influence of the surrounding environment upon the
Sensor e.g. a metal beam located three inches from the face of the Sensor, or a plastic window between Sensor
and sample. If this residual dielectric were not negated, it would cause problems when calibrating for product
moisture.
The Pre-Zero Calibration allows the user to “Zero” or “Tare” the Sensor after system installation and during
routine maintenance. With no product or debris on the Sensor Antenna, the Pre-Zero value is a single dielectric
measurement which is stored in memory, this Pre-Zero value is subsequently subtracted from all subsequent
measurements.
The value for displayed Moisture is calculated from the equation:
Moisture = STD x B coefficient x (D
Where: B coefficient = slope
calibration coefficient for Product selected (SPAN)
– Pre-Zero) + C coefficient
R
C coefficient = offset calibration coefficient for Product selected (ZERO)
STD = Standardization Factor (calculated)
DR = raw dielectric value
Pre-Zero = calculated raw dielectric value with empty Sensor – air only from Pre-Zero Calibration
There are two methods of performing a Pre-Zero Calibration:
1. Using the Configuration Program the user would connect a host PC / laptop to the RS-485 interface and
run the Configuration Program to select the Maintenance Screen to control the Sensor. The user will
press the Pre-ZERO button on the Maintenance Screen with nothing over the Sensor to complete the
Pre-Zero calibration.
2. The I/O Unit also provides local push button controls for performing the Zero and Standardize
calibrations of the Sensor. The user opens the lid of the enclosure and presses the ZERO button with
nothing over the Sensor and the Status LED next to the button lights up to indicate a Pre-Zero calibration
has been performed. The Status LED next to the ZERO button lights up to indicate a Standardize
calibration has been performed.
CAUTION! This is a critical calibration parameter and will affect all calibrations.
DO NOT STANDARDIZE UNIT WITHOUT A STANDARDIZATION PLATE, TUBE, ETC. AS the SENSOR WILL CAUSE
ERRONEOUS READINGS. PLEASE CONTACT SENSORTECH SHOULD YOU HAVE ANY QUESTIONS.
The purpose of the Standardize calibration is to provide uniformity of calibration between Sensors, and to
provide a repeatable reference for all Sensors at the same location. The Standardization factor, STD is used as a
secondary span coefficient, and may be considered as a scaling factor. See following equation:
Moisture = STD * B coefficient * (DR – Pre-Zero) + C coefficient
Where: B coefficient = slope
calibration coefficient for Product selected (SPAN)
C coefficient = offset calibration coefficient for Product selected (ZERO)
STD = Standardization Factor (calculated)
D
= raw dielectric value
R
Pre-Zero = calculated raw dielectric value with empty Sensor – air only from Pre-Zero Calibration
Due to manufacturing and component tolerances, no two Sensors will be identical. The scaling or
Standardization factor will compensate for these differences. During the Standardize calibration, dielectric span
is forced to one (1), and dielectric zero forced to zero (0). The equation becomes:
Moisture = STD * (D
– Pre-Zero)
R
Transposing equation gives:
STD = Moisture / (D
– Pre-Zero)
R
Using a known dielectric reference, the Standardize calibration allows the user to enter that moisture value and
the Sensor will calculate STD value from the above equation. A Standardization Plate or other reference
materials are available with very stable dielectrics, which can also be used as dielectric standards
The Standardize Calibration is performed by the user to produce a moisture display value of 25 when a
Standardization Plate (dielectric reference) is placed on the Sensor Antenna.
There are two methods of performing a Standardize Calibration:
1. Using the Configuration Program the user would connect a host PC / laptop to the RS-485 interface and
run the Configuration Program to select the Maintenance Screen to control the Sensor. The user places
a Standardization Plate over the Sensor and the user will press the STANDARDIZE button on the
Maintenance Screen to complete the Standardize calibration.
2. The I/O Unit also provides local push button controls for performing the Zero and Standardize
calibrations of the Sensor. The user would perform the Pre-Zero Calibration followed by the Standardize
calibration. The user places a Standardization Plate over the Sensor and the user opens the lid of the
enclosure and presses the Standardize button. The Status LED next to the button lights up to indicate a
Standardize calibration has been performed.
Pre-Zero Calibration Procedure - using the Configuration Program
1. Log in to the Configuration Program using the engineering password. Select the Maintenance Screen.
2. Ensure that the Sensor Antenna is clean, dry and free of debris. No Product or Standardization Plate
should be present on the Sensor Antenna.
3. The ‘Pre-ZERO’ button is pressed on the Maintenance Screen using the Configuration Program. The Pre-
ZERO button will change color to red for several seconds. If there is an error the Current Value field will
turn red to indicate a problem occurred.
4. Verify the Current Value displayed equals 0.
If the Current Value displayed is not 0 after the Pre-Zero Calibration do each of the following steps and repeat
the Pre-Zero Calibration procedure.
1. Remove all product, debris, Standardization Plate, etc. on the Sensor Antenna. Check the Sensor is
clean and dry.
2. Check the coaxial cables are undamaged, connected and securely tightened on the Sensor
Electronics Unit.
3. Check the M12 cables are undamaged, connected and securely tightened on the Sensor Electronics
Unit and the I/O Unit. Where possible open the enclosures to check for debris or moisture.
Standardize Calibration Procedure - using the Configuration Program
1. Log in to the Configuration Program using the engineering password. Select the Maintenance Screen.
2. Ensure that the Sensor Antenna is clean, dry and free of debris. No Product or Standardization Plate
should be present on the Sensor Antenna.
3. Place the Standardization Plate on conveyor/rollers/belts positioned in the center of Sensor Antenna.
4. The ‘Standardize’ button is pressed on the Maintenance Screen using the Configuration Program. The
Standardize button will change color to red for several seconds. If there is an error the Standardization
Factor field will turn red to indicate a problem occurred.
5. Verify the Current Value displayed equals 25. This is the dielectric reference value of the Standardization
Plate.
6. Verify the Standardization Factor value displayed is between 0 – 100.
If the Current Value displayed is not 25 after the Standardize Calibration do each of the following and repeat the
Standardize Calibration procedure.
1. Remove all product, debris, Standardization Plate, etc. on the Sensor Antenna. Check the Sensor and
plate are clean and dry. Place the Standardization Plate back over the center of the Sensor Antenna.
2. Check the coaxial cables are undamaged, connected and securely tightened on the Sensor
Electronics Unit.
3. Check the M12 cables are undamaged, connected and securely tightened on the Sensor Electronics
Unit and the I/O Unit. Where possible open the enclosures to check for debris or moisture.
Pre-Zero Calibration Procedure - using the I/O Unit Push-buttons
1. Ensure that the Sensor Antenna is clean, dry and free of debris. No Product or Standardization Plate
should be present on the Sensor Antenna.
2. The user opens the lid on the I/O Unit and the ‘ZERO’ pushbutton is pressed and held for 1 second.
a. Good Calibration: The STATUS LED will turn green and remain on for several seconds.
b. Poor Calibration: the STATUS LED will blink on/off 10 times to indicate a problem occurred.
3. Verify the Current Value displayed equals 0.
If the Current Value displayed is not 0 after the Pre-Zero Calibration, do each of the following steps and repeat
the Pre-Zero Calibration procedure.
1. Remove all product, debris, Standardization Plate, etc. on the Sensor Antenna. Check the Sensor is clean
and dry.
2. Check the coaxial cables are undamaged, connected and securely tightened on the Sensor Electronics
Unit.
3. Check the M12 cables are undamaged, connected and securely tightened on the Sensor Electronics Unit
and the I/O Unit. Where possible open the enclosures to check for debris or moisture.
Standardize Calibration Procedure - using the I/O Unit Push-buttons
1. Ensure that the Sensor Antenna is clean, dry and free of debris.
2. Place the Standardization Plate on conveyor/rollers/belts positioned in the center of Sensor Antenna.
3. The user opens the lid on the I/O Unit and the ‘ZERO’ pushbutton is pressed and held for 1 second.
a. Good Calibration: The STATUS LED will turn green and remain on for several seconds.
b. Poor Calibration: the STATUS LED will blink on/off 10 times to indicate a problem occurred
4. Verify the Current Value displayed equals 25. This is the dielectric reference value of the Standardization
Plate.
5. Verify the Standardization Factor value displayed is between 0 – 100.
If the Current Value displayed is not 25 or the Standardization Factor less than 0 or greater than 100 after the
Standardize Calibration do each of the following and repeat the Standardize Calibration procedure.
1. Remove all product, debris, Standardization Plate, etc. on the Sensor Antenna. Check the Sensor and
plate are clean and dry. Place the Standardization Plate back over the center of the Sensor Antenna.
2. Check the coaxial cables are undamaged, connected and securely tightened on the Sensor Electronics
Unit.
3. Check the M12 cables are undamaged, connected and securely tightened on the Sensor Electronics Unit
and the I/O Unit. Where possible open the enclosures to check for debris or moisture.
Sensortech Systems, Inc. is disclosing this manual to you solely for use to operate with Sensortech
hardware devices. You may not reproduce, distribute, republish, download, display, post, or
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the documentation. Sensortech Systems reserves the right, at its sole discretion, to change the
documentation without notice at any time. Sensortech Systems assumes no obligation to correct
any errors contained in the documentation, or to advise you of any corrections or updates.
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STATUTORY, REGARDING THE DOCUMENTATION, INCLUDING ANY WARRANTIES OF
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ST-3300 MODBUS-RTU Serial Communications Interface
External devices can communicate with the ST-3300 via Serial RS485 using a simple
Modbus RTU protocol
The ST-3300 Modbus RTU protocol is very simple. It is further simplified by the fact that we
support only two Modbus function codes - 03 (Multiple Register Read) and 16 (Multiple Register
Write).
For function code 03, the host computer sends out:
Slave Address (8 bits) – the gauge address set in the serial configuration screen
Function Code (8 bits. Value = 03)
Start Address (High byte)
Start Address (Low Byte) normally set to 0
Number of registers (High byte)
Number of registers (Low byte) normally set to 16
CRC (16 bits)
The gauge responds with:
Slave Address (8 bits)
Function Code (8 bits. Value = 03)
Byte Count (8 bits) (2* number of registers) normally 32
Data High
Data Low
...
Data High
Data Low
CRC (16 bits)
For function code 16, the host computer sends out:
Slave Address (8 bits) – the gauge address set in the serial configuration screen
Function Code (8 bits. Value = 16)
Start Address (High byte)
Start Address (Low Byte) normally 0
Number of registers (High byte)
Number of registers (Low byte) normally 4
Byte Count (8 bits) (2* number of registers) normally 8
Data High
Data Low
...
Data High
Data Low
CRC (16 bits)
The gauge responds with:
Slave Address (8 bits)
Function Code (8 bits. Value = 03)
Start Address (High byte)
Start Address (Low Byte)
Number of registers (High byte)
Number of registers (Low byte)
CRC (16 bits)
CRC Generation, Code Examples
CRC Calculation Basics
The CRC calculation is started by first preloading a 16-bit register to all 1's. Then a process
begins of applying successive eight-bit bytes of the message to the current contents of the register.
During generation of the CRC, each eight-bit character is XOR’d with the current register
contents. The result is shifted in the direction of the least significant bit (LSB), with a zero filled into the most
significant bit (MSB) position. The LSB is extracted and examined. If the LSB is a 1, the register is XOR’d with a
preset, fixed value. If the LSB was a 0, no XOR takes place. This process is repeated until eight shifts have been
performed. After the last (eighth) shift, the above process repeats for the next byte in the message. The final
contents of the register, after all bytes of the message have been applied, is the CRC value.
Step by Step:
1. Load a 16-bit register with 0xFFFF (all 1's). Call this the CRC register
2. XOR the first eight-bit byte of the message with the low order byte of the 16-bit CRC register,
putting the result in the CRC register
3. Shift the CRC register one bit to the right (toward the LSB), zerofilling the MSB. Extract and
examine the LSB
4. If the LSB is 0, repeat Step 3 (another shift). If the LSB is 1, Exclusive OR the CRC register with the polynomial
value 0xA001 (1010 0000 0000 0001)
5. Repeat Steps 3 and 4 until eight shifts have been performed. When this is done, a complete eight bit byte will
have been processed
6. Repeat Steps 2 … 5 for the next eight-bit byte of the message. Continue doing this until all
Bytes have been processed.
• Result
The final contents of the CRC register is the CRC value. When the CRC is placed into the
message, its upper and lower bytes must be swapped as described in chapter 9-1 “Modbus Protocol”
(CRC).
The following example calculates the CRC using the method described earlier.
Note: This function performs the swapping of the high/low CRC bytes internally. Therefore the
CRC value returned from the function can be directly placed into the message for transmission.
The function returns the CRC as a type UINT16, and takes two arguments:
• UINT8 *pabMessage;
A pointer to the message buffer containing binary data to be used for generating the CRC.
• UINT16 iLength;
The quantity of bytes in the message buffer.
Typedefs
UINT8 = Unsigned 8 bit ( e.g. unsigned char )
UINT16 = Unsigned 16 bit ( e.g. unsigned short )
This example uses another approach to calculate the CRC; All of the possible CRC values are
Preloaded into two arrays, which are simply indexed as the function increments through the message buffer.
One array contains all of the 256 possible CRC values for the high byte of the 16-bit CRC field, and the other
array contains all of the values for the low byte. Indexing the CRC in this way provides faster execution than
would be achieved by calculating a new CRC value with each new character from the message buffer.
Note: This function performs the swapping of the high/low CRC bytes internally. Therefore the
CRC value returned from the function can be directly placed into the message for transmission.
The function returns the CRC as a type UINT16, and takes two arguments:
Data Object: Measurement Data
Modbus Address: 0x10
Data Size (Bytes): 12 - Read Only
Data Definition:
Moisture Value – IEEE float (4 bytes)
Temperature Value – IEEE float (4 bytes)
Measurement Status – unsigned 32 bit integer (4 bytes) 0 = No Errors
Bit 0-31 definitions:
Bit 0 Set = 3.3 Volt Error
Bit 1 Set = 5 Volt Error
Bit 2 Set = 12 Volt Error
Bit 3 Set = -12 Volt Error
Bit 4 Set = Board Temperature Alarm
Bit 5 Set = Reference Frequency Error
Bit 6 Set = Bad Zero
Bit 7 Set = Bad Standardization
Bits 8-31 reserved for future use
Data Object: Sensor Information
Modbus Address: 0x20 - Read Only
Data Size (Bytes): 20
Data Definition:
Serial Number – unsigned 32 bit integer (4 bytes)
Model – ASCII string (10 bytes)
Hardware Major Version – ASCII character (1 byte)
Hardware Major Minor – numeric byte value (1 byte)
Firmware Version – IEEE float (4 bytes)
Data Object: Diagnostics Data
Modbus Address: 0x150 - Read Only
Data Size (Bytes): 72
Data Definition:
Frequency Fs – unsigned 32 bit integer (4 bytes)
Frequency Fl – unsigned 32 bit integer (4 bytes)
Frequency Fh – unsigned 32 bit integer (4 bytes)
Dr – IEEE float (4 bytes)
Dz – IEEE float (4 bytes)
Standardization – IEEE float (4 bytes)
Board Temperature – IEEE float (4 bytes)
Moisture – IEEE float (4 bytes)
Uncalibrated Moisture – IEEE float (4 bytes)
Voltage 3.3V – IEEE float (4 bytes)
Voltage 5V – IEEE float (4 bytes)
Voltage 12V – IEEE float (4 bytes)
Voltage -12V – IEEE float (4 bytes)
Product Temperature – IEEE float (4 bytes)
Digital Input 1 - unsigned 16 bit integer (2 bytes)
Digital Input 2 - unsigned 16 bit integer (2 bytes)
Future Use - unsigned 16 bit integer (2 bytes)
Future Use - unsigned 16 bit integer (2 bytes)
Error Status - unsigned 32 bit integer (4 bytes)
0 = No Errors
Bit 0-31 definitions:
Bit 0 Set = 3.3 Volt Error
Bit 1 Set = 5 Volt Error
Bit 2 Set = 12 Volt Error
Bit 3 Set = -12 Volt Error
Bit 4 Set = Board Temperature Alarm
Bit 5 Set = Reference Frequency Error
Bit 6 Set = Bad Zero
Bit 7 Set = Bad Standardization
Bits 8-31 reserved for future use
Data Object: Pre-Zero Command – Sending this message causes the Sensor to perform a Pre-Zero
Modbus Address: 0x60 - Write Only
Data Size (Bytes): 2
Data Definition:
Dummy Value - unsigned 16 bit integer (2 bytes) Set to 0x5555
Data Object: Standardization Command – Sending this message causes the Sensor to perform a Standardization
Modbus Address: 0x65 - Write Only
Data Size (Bytes): 2
Data Definition:
Dummy Value - unsigned 16 bit integer (2 bytes) Set to 0xAAAA
Read/Write Data Objects
The following read/write data objects are read in a single multiple register read and
written in a single multiple register write – no individual registers within a group are
readable or writable. All registers in the write object have to contain valid data. The best way to change
parameters is to perform a read-modify-write: first read the data object into a buffer, modify the parameters
that need to be changed, and then write the entire data object back.
Data Object: Product Code
Read/Change Active Product Code
Modbus Address: 0x50 Read/Write
Data Size (Bytes): 2
Data Definition:
Product Code – 16 bit integer (2 bytes) – the current product code 0-50
Data Object: Measure Configuration Data
Modbus Address: 0x300 Read/Write
Data Size (Bytes): 30
Data Definition:
Measurement Mode – 16 bit integer (2 bytes)
0 – default – Continuous
1- Signal Gated
2- Automatic Product Detect
3- Timed Sample
4- Gated Timed Sample
5- Auto Reference
Sample Period – 16 bit integer (2 bytes)
Milliseconds: 5, 10(default), 20, 50, 100
Sensor Measurements– 16 bit integer (2 bytes)
Sensor measurements per cycle 1-500, default: 98