Rice Lake SCT-30 User Manual
SCT Weight Transmitter
30 Series
Installation & Operator’s Manual
159585
Technical training seminars are available through Rice Lake Weighing Systems.
Course descriptions and dates can be viewed at www.ricelake.com/training
or obtained by calling 715-234-9171 and asking for the training department.
Contents
1.0 Introduction............................................................................... 1
1.1 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Electrical Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.4 Analog Output Type Selection . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.5 Instrument Commissioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.0 Calibration ................................................................................ 9
2.1 Real Calibration (With Sample Weights) . . . . . . . . . . . . . . . . . 9
2.2 Theoretical Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3 Digital Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.0 RS-485 Serial Connection ...................................................... 11
3.1 Continuous One Way Transmission Protocol . . . . . . . . . . . . 11
3.2 Modbus-RTU Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3 Alarms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.0 Reserved for the Installer ....................................................... 14
4.1 Restoring Factory Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.2 Calibration and RS-485 Port Setting Access Limitation . . . . 14
© Rice Lake Weighing Systems. All rights reserved. Printed in the United States of America.
Specifications subject to change without notice.
Rice Lake Weighing Systems is an ISO 9001 registered company.
December 05, 2013
i
ii SCT-30 Weight Transmitter Manual
Rice Lake continually offers web-based video training on a growing selection
of product-related topics at no cost. Visit www.ricelake.com/webinars.
1.0 Introduction
WARNING
Important
WARNING
1.1 Safety
1.1.1 Safety Symbol Definitions:
Indicates a potentially hazardous situation that, if not avoided,
could result in death or serious injury, and includes hazards that
are exposed when guards are removed.
Indicates information about procedures that, if not observed,
could result in damage to equipment or corruption to and loss of
data.
1.1.2 Safety Precautions
Failure to heed may result in serious injury or death.
Do not operate or work on this equipment unless you have read
and understand the instructions and warnings in this manual.
Contact any Rice Lake Weighing System dealer for replacement
manuals. Proper care is your responsibility.
qualified service personnel for service.
The unit has no power switch. To completely remove D/C power from the unit,
disconnect the D/C power cable from the main socket.
DO NOT allow minors (children) or inexperienced persons to operate this unit.
DO NOT operate without all shields and guards in place.
DO NOT use for purposes other then weighing applications.
DO NOT place fingers into slots or possible pinch points.
DO NOT use this product if any of the components are cracked.
DO NOT make alterations or modifications to the unit.
DO NOT remove or obscure warning labels.
DO NOT use near water.
Risk of electrical shock. No user serviceable parts. Refer to
Introduction 1
1.1.3 Equipment Recommendations
Important
Failure to follow the installation recommendations will be
considered a misuse of the equipment.
To Avoid Equipment Damage
• Keep away from heat sources and direct sunlight.
• Protect the instrument from rain.
• Do not wash, dip in water or spill liquid on the instrument.
• Do not use solvents to clean the instrument.
• Do not install in areas subject to explosion hazard.
1.1.4 Correct Installation of Weighing Instruments
• The terminals indicated on the instrument’s wiring diagram to be connected to
ground must have the same potential as the scale structure (ground). If you are
unable to ensure this condition, connect a ground wire between the instrument
and the scale structure.
• The load cell cable must be run separately to the instrument input and not share a
conduit with other cables. A shielded connection must be continuous without a
splice.
• Use “RC” filters (quench-arcs) on the instrument-driven solenoid valve and
remote control switch coils.
• Avoid electrical noise in the instrument panel; if inevitable, use special filters or
sheet metal partitions to isolate.
• The panel installer must provide electrical protection for the in struments (fuses,
door lock switch, etc.).
• It is advisable to leave equipment always switched on to prevent the formation of
condensation.
• Maximum cable lengths:
- RS-485: 1000 meters with AWG24, shielded and twisted cables
- Analog current output: up to 500 meters with 0.5 mm
- Analog current output: up to 300 meters with 0.5 mm
2
cable
2
cable
1.1.5 Correct Installation of the Load Cells
Installing Load Cells:
The load cells must be placed on rigid, stable structures within .5% of plumb and
level. It is important to use mounting modules for load cells to compensate for
misalignment of the support surfaces.
Protection Of The Load Cell Cable:
Use waterproof sheaths and joints in order to protect the cables of the load cells.
Mechanical Restraints (pipes, etc.):
When pipes are present, we recommend the use of hoses, flexible couplings and
rubber skirted joints. In case of rigid conduit and pipes, place the pipe support or
anchor bracket as far as possible from the weighed structure (at a distance at least 40
times the diameter of the pipe).
2 SCT-30 Weight Transmitter Manual
Connecting Several Cells in Parallel:
Uses ground plate
to continue ground.
Uses structure to continue ground.
Connect several load cells in parallel by using, if necessary, a watertight junction box
with a terminal box. The load cell connection extension cables must be shielded,
placed individually into their piping or conduit, and laid as far as possible from the
power cables (in case of 4-wire connections, use cables with 4 x 1 sq.mm minimum
cross-section).
Welding:
Avoid welding with the load cells already installed. If this cannot be avoided, place
the welder ground clamp close to the required welding point to prevent sending
current through the load cell body.
Windy Conditions - Shocks - Vibrations:
The use of weigh modules is strongly recommended for all load cells to compensate
for misalignment of the support surfaces. The system designer must ensure that the
scale is protected against lateral shifting and tipping relating to shocks and vibration,
windy conditions, seismic conditions and stability of the support structure.
Grounding The Weighed Structure:
By means of a 10 AWG solid or braided wire or braided grounding strap, con nect the
load cell upper support plate with the lower support plate, then connect all the lower
plates to a single earth ground. Once installed, electrostatic charges are discharged to
the ground without going through or damaging the load cells. Failure to implement a
proper grounding system might not affect the operation of the weighing system; this,
however, does not rule out the possibility that the load cells and connected instrument
may become damaged by ESD. It is forbidden to ensure grounding system continuity
by using metal parts contained in the weighed structure(see Figure 1-1).
Figure 1-1. Installation Recommendations
Introduction 3
1.1.6 Load Cell Testing
Important
ANALOG OUTPUT
(Current and Voltage)
PLC
MAX 8 LOAD CELLS IN
PARALLEL
RS-485
Modbus RTU
SERIAL PORT
DC power
supplier
(12-24 Volt )
Load Cell Resistance Measurement (Use a Digital Multimeter):
• Disconnect the load cells from the instrument and check that there is no moisture
in the load cell junction box caused by condensation or water infiltration. If so,
drain the system or replace it if necessary.
• The value between the positive signal wire and the negative signal wire must be
equal or similar to the one indicated in the load cell data s heet (output resis tance).
• The value between the positive excitation wire and the negativ e excitation wire
must be equal or similar to the one indicated in the load cell data sheet (input
resistance).
• The insulation value between the shield and any other load cell wire, and
between any other load cell wire and the body of the load cell, must be higher
than 20 Mohm (mega ohms).
Load Cell Voltage Measurement (Use a Digital Multimeter):
• Remove weight of scale from load cell to be tested.
• Make sure that the excitation wires of the load cell connected to the instrument is
5 Vdc +/- 3%.
• Measure the millivolt signal between the positive and the negative signal wires
by directly connecting them to the multi-meter, and make sure it reads between 0
and 0.5 mV (thousandths of a volt).
• Apply load to the load cell and make sure that there is a signal increment.
If one of the above conditions is not met, please contact the
technical assistance service.
1.2 Specifications
• Analog/serial weight transmitter suitable for assembly on back panel fitted
Omega/DIN rail. Dimensions: 90x93x65 mm.
• Current or voltage 16 bit analog output.
• RS-485 serial output with Modbus RTU or continuous transmission protocol.
• Zero and full scale setting.
• Simultaneous display of the load cell reading in mV and of the analog output
reading.
• Operating mode selection via 3-position selector switch, DIP switches, knob
control and 2 line, 8 column alphanumeric display.
4 SCT-30 Weight Transmitter Manual
Loading...