Hardy HI 1756-nDF User Manual

HI 1756-1DF and HI 1756-2DF

Corporate Headquarters

9440 Carroll Park Drive, Suite 150
San Diego, CA 92121
Phone: [phone]
FAX: [phone]
Web-site: http://www.hardysolutions.com

Dispenser Filler Control Module

User’s Guide

Hardy Process Solutions Document Number: 0596-0322-01 Revision B

Copyright April 2012 Hardy Process Solutions, Inc. All Rights Reserved.

Local Field Service

Hardy has over 200 field technicians in the U.S., and more positioned throughout the world to assist you in
your support needs. We also have factory engineers who will travel to your facility anywhere in the world
to help you solve challenging applications. We're ready to support you with:

Installation and start-up
Routine maintenance and certification
Plant audits and performance measurement
Emergency troubleshooting and repair

To request Emergency Service and Troubleshooting, Start-up, Installation, Calibration, Verification or to
discuss a Maintenance Agreement please call 800-821-5831 (Standard Hours 6:30 AM to 5:00 PM Pacific
Standard Time).

Outside the U.S

Hardy Process Solutions has built a network of support throughout the globe. For specific field service
options available in your area please contact your local sales agent or our U.S. factory at [phone].

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Contents

Contents

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CONTENTS ........................................................................................................... I

CHAPTER 1 OVERVIEW ..................................................................................... 1

About Hardy Manuals ................................................................................................................................. 1

HI 1756 nDF Overview ................................................................................................................................. 1

Typical Applications ................................................................................................................................... 2

Features and Capabilities ............................................................................................................................. 2

CHAPTER 2 SPECIFICATIONS .......................................................................... 5

Basic Specifications ....................................................................................................................................... 5

General ........................................................................................................................................................ 5

Environmental Requirements ...................................................................................................................... 6

Pending Approvals ...................................................................................................................................... 6

CHAPTER 3 INSTALLATION .............................................................................. 7

Unpacking ...................................................................................................................................................... 7

Installing the HI 1756 nDF ........................................................................................................................... 7

Allen-Bradley ControlLogix Processor or Remote Rack ............................................................................ 7

A ControlLogix Chassis .............................................................................................................................. 7

Removing the Module from the Chassis ..................................................................................................... 8

Installing the Module I/O Connector ........................................................................................................... 8

Load Cell Wiring Diagrams ......................................................................................................................... 9

HI 1756 1DF Valve wiring diagram ............................................................................................................. 9

Hardy HI 215IT Junction Box ................................................................................................................... 10

CHAPTER 4 CONFIGURATION ........................................................................ 11

Power Check ................................................................................................................................................ 11

LEDs ......................................................................................................................................................... 11

Dot Matrix Display .................................................................................................................................... 12

Setting Up Communications ....................................................................................................................... 12

Configuring the HI 1756-nDF Dispenser Filler Module in the RSLogix 5000 for ControlLogix with the

HI 1756-nDF Module Add on Profile ....................................................................................................... 12

Linking the PLC with the HI 1756-nDF Dispenser Filler Control Module ............................................... 15

Overview of Operation ................................................................................................................................ 16

DINT Configuration Parameters used in Flow Rate Control .................................................................... 18

REAL Configuration Parameters used in Flow Rate Control .................................................................... 19

DINT Configuration Parameters used in Auto-Preact ............................................................................... 22

REAL Configuration Parameters used in Auto-Preact .............................................................................. 22

Status Values used in Auto-Preact function .............................................................................................. 23

Assembly Object Instances ......................................................................................................................... 25

First Word – 0: Command Number .......................................................................................................... 27

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Contents

Command Return or Error Codes .............................................................................................................. 29

Second and Third Words - 1, 2: Parameter Number and Value ............................................................. 29

DINT Configuration Parameters ............................................................................................................... 29

REAL Configuration Parameters .............................................................................................................. 34

REAL Status Values .................................................................................................................................. 38

Integrated Technician ................................................................................................................................ 40

CIP Messages ............................................................................................................................................ 41

CHAPTER 5 CALIBRATION .............................................................................. 43

Pre-Calibration Procedures ........................................................................................................................ 43

Electrical Check Procedures ...................................................................................................................... 43

Load Cell/Point Input/Output Measurements ............................................................................................ 43

Load Check ............................................................................................................................................... 44

AOP Calibration .......................................................................................................................................... 44

C2 Calibration ............................................................................................................................................. 44

“THE BUTTON” C2 Calibration .............................................................................................................. 45

C2 Calibration Using Ladder Logic .......................................................................................................... 45

Hard Calibration ......................................................................................................................................... 46

Hard Calibration Ladder Logic Example .................................................................................................. 46

CHAPTER 6 TROUBLESHOOTING ............................................................... 47

Disassembly and Reassembly Notes, Warnings and Cautions ................................................................ 47

Weight and Voltage Testing ....................................................................................................................... 47

IT Test ....................................................................................................................................................... 48

General Troubleshooting Flow Chart Index ............................................................................................. 48

A1 - Guidelines for Instabilities on Formerly Operating System .............................................................. 49

B - Guidelines for Instabilities on Formerly Operating Systems (Cont’d) ................................................ 50

B1 - Guidelines for Instabilities on Formerly Operating Systems (Cont’d) .............................................. 51

B1 - Guidelines for Instabilities on Formerly Operating Systems (Cont’d) .............................................. 52

Testing an individual load cell signal output requires an IT Summing Junction box or millivolt meter. .. 53

Use the load cell certificate to verify the millivolt per volt (mV/V) rating: .............................................. 53

G - Calibration Failed ................................................................................................................................ 54

H - Mechanical Inspection ........................................................................................................................ 55

J - Electrical Inspection ............................................................................................................................. 56

K - Load Sharing and Load Sensor Checkout ........................................................................................... 57

Erratic Flow Rates ...................................................................................................................................... 58

System and Load Cell Tests ........................................................................................................................ 58

INTEGRATED TECHNICIAN (IT®) ...................................................................................................... 59

Stability Test ............................................................................................................................................. 60

Weight and Voltage Test ........................................................................................................................... 60

General Policies and Information .............................................................................................................. 60

Warranty .................................................................................................................................................... 61

For Further Information Contact ............................................................................................................... 61

INDEX ................................................................................................................ 62

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Chapter 1

Chapter 1 Overview

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This manual provides users and service personnel with specifications and procedures for
installing, configuring, operating, maintaining, and troubleshooting the Hardy Process
Solutions HI 1756 nDF Dispenser Filler with WAVERSAVER®, C2®, and
INTEGRATED TECHNICIANTM (IT®) diagnostics.

NOTE WAVERSAVER, C2, and IT are registered trademarks of Hardy Process Solutions, Inc.

To ensure good performance and maximum service life, follow all guidelines described
in this manual. Be sure you understand all cautions, warnings, and safety procedures. If
you find that the information in this manual does not provide the help you need, contact
the HI Customer Service Department at:

Phone: [phone]
FAX: [phone]
Web Site: www.hardysolutions.com
Support e-mail address: [e-mail]

About Hardy Manuals

An overview of each chapter’s contents is listed below:

Chapter One - Provides an overview of HI 1756 nDF capabilities and features
Chapter Two - Provides a overview of HI 1756 nDF specifications
Chapter Three - Describes the steps for installing both the standard and optional HI

1756 nDF equipment, and the HI 215IT series junction box

Chapter Four - Explains how to configure the HI 1756 nDF
Chapter Five - Provides calibration instructions
Chapter Six – Provides troubleshooting procedures for repair of the HI 1756 nDF

HI 1756 nDF Overview

The HI 1756 nDF is a ControlLogix I/O module, which is designed to operate in a local
rack or a remote rack that is connected to the local chassis via a network link.

The module can be inserted and removed under power without disruption of any other
modules in the system (racks). This makes it possible to replace a failed module while
keeping the rest of the system running. Status indicators will be provided on the front of
the module for fault status. A status block will provide information to the processor for
alarming and troubleshooting (IT).

The HI 1756 nDF can be purchased as a single channel (1756 1DF) or dual channel (1756
2DF) module; enabling up to two separate single or multi-cell weight scales to be
monitored at one time. Two relays are assigned to each weigh scale input, and can be
triggered by programmable target weight and preact weight values.

The analog-to-digital converter in the weigh module controller is capable of 8,388,608
counts of resolution which allows the instrument to tolerate large “dead” loads, over
sizing of load cells/sensors, and still have sufficient resolution to provide accurate weight
measurement and control. The analog-to-digital converter can be configured to provide
either 95 or 145 updates per second. The 95 updates per second mode is recommended

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Chapter 1

for nosier environments while the 145 updates per second mode provides a faster
response time to changes in the flow rate.

The module supports both C2 electronic calibration and hard calibration (i.e., traditional
calibration with weights).

Typical Applications

Dispenser filler control can be used in a variety of material-flow applications.
The 1756 nDF Controller can control up to two ingredients per weigh scale channel, in a

filler mode, using two integrated DC or AC relays which can be independently controlled
automatically through programmable set point values or manually. The setpoint values
can be adjusted throughout the fill cycle, however once a relay is OPENED (external
valve is closed) it cannot be CLOSED again until the next fill cycle is started.

Features and Capabilities

C2® Calibration

Traditional calibration uses certified test weights. C2® Electronic Calibration allows a
scale to be calibrated without the need for test weights. A C2® weighing system consists
of up to eight load cell sensors per channel, a junction box, interconnect cable, and an
instrument with C2® capabilities (e.g., the HI 1756 nDF). Each Hardy Process Solutions
C2-certified load sensor outputs digital information used for calculating the calibration.
When the HI 1756 nDF reads the signals from the load sensors, it calibrates the scale
based on the load sensor’s output plus a user-supplied reference point value (from 0 to
any known weight on the scale).

NOTE C2® is registered trademarks of Hardy Process Solutions Inc.

WAVERSAVER®

When measuring small weight changes, the affects of mechanical vibration and noise
from the feeders and plant environment can introduce substantial interference.
WAVERSAVER factors out vibration, noise, and other interference-related signals from
the load cell so the rate controller can better decipher the actual weight data.

While WAVERSAVER can factor out noise with frequencies as low as 0.25 Hz, five cut­off frequencies can be selected, with higher frequencies providing a faster response time.
The default factory setting is 1 Hz vibration frequency immunity.

Integrated Technician™

The HI 1756 nDF Integrated Technician™ (IT®) is built-in system diagnostics that
makes it possible to diagnose weighing system problems. IT allows the reading of
individual load sensor voltages and weights and isolates individual system components
for quick and easy troubleshooting.

Digital Volt Meter (DVM) - Option

DVM requires the HI 215IT Series Junction Box to monitor mV/V readings for each load
sensor and the total system. When the operator detects a problem, the DVM readings help
to isolate the faulty component. Further, the DVM readings can be used to level a system
and to make corner adjustments to platform scales. Accuracy is +/- 2% or better of full
scale.

NOTE If you do not have the HI 215IT Junction Box connected to the module, the reading is the

total for all load cells on the system.

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Chapter 1

Start Refill Weight

Stop Refill Weight

1756-1DF

Weight value

Dispense Valve Control

RA1

RB1

Refill Valve Control

Weighing System Tests - Optional

This test is used to diagnose drifting or unstable weight reading problems. It requires the
HI 215IT Series Junction Box for full utilization. The ability to read the weight seen by
the individual load sensors allows you to use this test for making cornering, leveling and
load sharing adjustments to the weighing system.

The Weighing System Test provides the following problem detection support:

1. Disconnects the controller and engages an internal reference signal to see if the

problem is inside of the instrument.

2. Disconnects the load sensors and engages an internal (in the junction box)

reference signal to see if the cable between the instrument and the Junction Box
is causing the problem.

3. Reads the weight of each load sensor to see if the load sensor might be causing

the problem.

Automatic or Manual Refill

Automatic refill uses user-selectable refill points to start and stop the refill process
between dispense cycles. Automatic refill is only set for Dispense single speed mode.
The relay B is the default refill relay in single mode and dribble feed in the dual mode. A
command status of -1 will be set when the automatic refill is incorrectly configured.
Automatic refill is not usable in the filler mode as the refill source vessel weight is not
monitored by the HI 1756 nDF.

In the automatic refill mode, if weight at the end of a single speed dispense cycle is equal
to or below the start refill weight parameter value, then the dispense cycle is disabled
and the refill cycle started automatically; once the weight reaches the stop refill weight
parameter value the refill cycle is stopped. Once the refill cycle is complete the dispense
cycle is once again enabled. In this mode relay RA on the weigh scale channel would be
used for the dispense cycle and relay RB on the same weigh scale channel would be used
for the refill cycle.

An Automatic Refill Example

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Chapter 1

The Manual Refill option allows for manual refill at any time, via the STARTREFILL
command; the refill cycle will automatically stop when the weight reaches the stop refill
weight parameter value. The STOP command will set both relays to their default (OPEN)
state.

The SETRELAY command can also be used to directly control the relay states regardless
of weight value.

In the filler mode the PLC will need to remotely detect the level in the dispensing vessel
and implement a manual refill operation.

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Chapter 2

Chapter 2 Specifications

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Chapter 2 provides specifications for the HI 1756 nDF Dispenser-Filler and other
equipment that may come with the package. The specifications listed are designed to
assist in the installation, operation and troubleshooting of the instrument. All service
personnel should be familiar with this section before installing or repairing the
instrument.

Basic Specifications

General

Resolution

Internal:1:8,388,608

Input

Up to four 350-ohm Full Wheatstone Bridge, Strain Gauge Load Sensor/Cells (5 volt
excitation) can be connected to each weigh scale channel

Non-Linearity

0.0015% of Full Scale

Common-Mode Rejection

110dB at or below 60 Hz

Common-Mode Voltage Range

2.5VDC maximum (with respect to earth ground)

Backplane Input Voltage

5 VDC and 24 VDC

Backplane Current Load

<1 Amp at 5 VDC

0.0125 Amps at 24 VDC (with 4-350 Ohm Load Cells)

Backplane Power Load

< 5W at 5 VDC
< .3W at 24 VDC with 4-350 Ohm Load Cells

C2 Calibration Input

Isolation from digital section 1000 VDC minimum.

Cable lengths

1000 feet maximum of C2 authorized cable
250 feet maximum of C2 authorized cable (Maximum of 4 load sensors) with IT Junction
box.

Load Cell Excitation

5 VDC +/- 1.15 VDC maximum.
Isolation from digital section 1000 VDC minimum

C2 Calibration Output

Isolation from digital section 1000 VDC minimum

Number of Channels

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Chapter 2

HI 1756 1DF 1 Weigh Scale Channel
HI 1756 2DF 2 Weigh Scale Channels

Update Rate

95(10.5ms) or 145(6.9ms) Updates per Second

Averages

1-255 User-selectable in Single Increments

WAVERSAVER®

User Selectable
OFF

7.50 Hz

3.50 Hz

1.00 Hz (Default)

0.50 Hz

0.25 Hz
Digital Voltmeter (Integrated Technician – Diagnostic Mode Only)

Accuracy ± 2% of full scale

Relay

Two integrated solid state DC or AC relays per weigh scale channel
Default state of relays will be OPEN (Form A - NO).
For resistive loads only. Cannot mix AC and DC relays on same module.

DC Relay

Capable of switching 5 to 30 VDC
Maximum current rating 3A @ 25oC, 2A @ 40oC, and 1A @ 60oC
Minimum load current 2mA

AC Relay

Capable of switching 24-280 (47-63Hz) VAC
Maximum current rating 0.5A @ 60oC
Minimum load current 70mA

Environmental Requirements

Operating Temperature Range

0 to 60º C (32º F to 140º F)

Temperature Coefficient

Less than 0.005% of full scale per degree C for Cal-LO and Cal-HI reference points

Storage Temperature Range

-40 to 85º C (-40 to 185º F)

Humidity Range

0-90% (non-condensing)

Pending Approvals

UL, CUL, and CE

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Chapter 3

Step 1. Make sure that the module is

oriented correctly for installation.

Step 2. Gently slide the module into the

Chassis.

Step 3. Slide the digital board between the

PCB Guides on the top plate and
bottom plate of the chassis to line up
the module connector with the
backplane connector

Inserting the module

Chapter 3 Installation

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Chapter 3 covers unpacking, cabling, interconnecting, configuring, and installing the
Weigh Scale Module. User and service personnel should read this chapter before
installing or operating the Weigh Scale module.

Unpacking

Step 1. Before signing the packing slip, inspect the packing and contents for damage of

any kind. Report any damage to the carrier company immediately.

Step 2. Verify that everything in the package matches the bill of lading.
Step 3. Write down the Model and Serial number of the module. Store this information

in a convenient location for reference when contacting The Customer Support
Department for parts or service.

Step 4. Be sure to complete the warranty registration on the Hardy web site.

Installing the HI 1756 nDF

Allen-Bradley ControlLogix Processor or Remote Rack

WARNING Electrostatic discharge may damage semiconductor components in the module. DO NOT

TOUCH THE CONNECTOR PINS, and observe the following handling precautions:

Wear an approved wrist-strap grounding device when handling the module.
Touch a grounded object or surface to rid yourself of any electrostatic

discharged prior to handling the module.

Handle the module from the bezel in front away from the connector. Do not

touch the connector pins.

Do not install the module right next to an AC or high voltage DC module.
Route all the load voltage cables away from high voltage cables.

A ControlLogix Chassis

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Chapter 3

Module release(s)

Module installed in chassis

The I/O connector at the front of the module
connects the module to a load sensor, or the HI
215IT Series Junction Box, depending on how
many load sensors are installed in the weighing
system. (See the pin-out diagram below.) A pin­out diagram is also located on the inside of the
module door.

Open the module door to access to the I/O
connector.

Step 1. Install the cable and connector so it
allows the module door to be shut.

Step 2. With the plug oriented correctly (See
the pin-out diagram below), plug the I/O male
connector into the I/O connector at the front of
the module.

HI 1756 1DF with door open

Step 4. When the module connector is touching the backplane connector, firmly but

carefully push toward the chassis until the pins are plugged in and the top and
bottom module releases are snapped into place.

Removing the Module from the Chassis

Step 1. Press down on the top and bottom module releases simultaneously until the

module can be pulled away from the chassis. (See Figure above.)

Step 2. Pull the module out of the chassis.
Step 3. Store in a safe, secure location in an anti-static bag or the original enclosure.

Installing the Module I/O Connector

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Chapter 3

Check to be sure that the connector is completely
plugged in before operating the module.

NOTE Most module-related problems are due to loose

connections. Be sure to check the I/O connection first
in the event you have a problem receiving
information from the load cells or if the relays do not
operate correctly.

Single Channel

Pin 1 Exc+

Pin 2 Sense+

Pin 3 Sig+

Pin 4 Sig-

Pin 5 Sense-

Pin 6 Exc-

Pin 7 C2+

Pin 8 C2-

Pin 9 Shield

Industry standard load cells wiring

Hardy load sensor/c2 wiring

+Exc

-Exc

+Sen

+Sig

-Sig

-Sen

+C2

-C2

Shield

RA1 IP

RA1 OP

RA1 COM

RB1 IP

RB1 OP

RB1 COM

1756-1DF

C2

Shield

Load Cell

(0-24Vdc, 3.5A)

Valve

1

(0-24Vdc, 3.5A)

Valve

2

Control Voltage 2

Control Voltage 1

COM2

COM1

Load Cell Wiring Diagrams

The diagrams below show how Hardy Load Sensor with C2 wiring differs from standard
Load Cell wiring. C2 wiring is required when using a Integrated Technician summing
junction box. The C2 wires are used fro communicating IT and C2 commands.

HI 1756 1DF Valve wiring diagram

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Chapter 3

L o a d C e l

l

C o n n e c t o r

J

1

1756 1DF

The simple wiring diagram above shows how to connect a single load cell to a single
channel 1756 1DF module. Note, when connecting the 1756 1DF to a junction box, the
sense lines would be connected to +Sen and –Sen Connections in the diagram.

The solid state relays used in the 1756 nDF require a 2mA minimum load. When
switching a light load with a solid state relay across the line, you must look at the rated
dropout current of the load. If it is less than 2mA it may not turn off. The solution is to
put a loading resistor in parallel with the light load, to be sure leakage current is sufficient
to the solid state relay is turned off.

CAUTION: INSTRUMENT POWER AND RELAY WIRES SHOULD BE ROUTED AWAY FROM ALL

OTHER SIGNAL CABLES TO AVOID ELECTRICAL INTERFERENCE.

Hardy HI 215IT Junction Box

Hardy HI 215IT Junction Box Wiring Diagram

NOTE When connecting the Hardy HI 215IT Junction Box, you must remove the two factory

installed jumpers on pins 1&2 and on pins 5&6 on the module and install C2 and sense
wires. C2 wires carry the commands for Integrated Technician and the C2 calibration
information.

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Chapter 4

To make or change settings, there
must be power to both the PLC and
the module. Verify that the LEDs
are lit for normal operation.

Module LEDs

Chapter 4 Configuration

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Chapter 4 covers the settings used to prepare the controller for calibration and operation.
The Setup procedures require Allen-Bradley’s RS Logix 5000, Allen-Bradley RSLinx™
or RSLinx™ Lite.

Power Check

LEDs

Scale Data LEDs

Flashing Green Dispenser/Filler is active (on)
Steady Green Running (Normal)
Steady Red Device Failure. Contact HI Customer Support
Flashing Red Read Convert Error.
LED is Off Channel is Inactive

OK Module Status LED

Brief Steady During power up the LED lights Red for about one second.
Flashing Green In Program mode. (Normal)
Steady Green In Run Mode. (Normal)
Steady Red Device Failure. Contact HI Customer Support.
Flashing Red Communication Error.
At power-up, the module runs through an initial self-diagnostic check. If the module does

not have valid calibration data the scale data LED will flash green at a rate of about once
a second.

The door will open to the right revealing two groups of connectors and one red button for
C2 calibration at the “cal low weight” parameter value. The number of pins in the
connector will depend on the number of channel options obtained. The left group of
connectors will be for weigh scale inputs and the group of connectors on the right will be
for relay I/O.

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Chapter 4

Display

Comment

_

Not Active, OPEN

A

Active, CLOSED

X

Not being used

Dot Matrix Display

Four 3x7 dot matrix displays provide individual status on the relays assigned to each
weigh scale channel.

The three operational states are defined in the following table.

Setting Up Communications

Configuring the HI 1756-nDF Dispenser Filler Module in the RSLogix
5000 for ControlLogix with the HI 1756-nDF Module Add on Profile

To set up communications between the ControlLogix processor and the dispenser/Filler
Control module using the Add on Profile (AOP), you will need to do the following in
RSLogix 5000.

Step 1. Download the AOP files from the Hardy Process Solutions web site,

hardysolutions.com and install.

Note: If a password is requested use hi1756 (all lower case).

Step 2. Under the project, right click on the I/O Configuration and from the list box

select “New Module”. The “Select Module Type” dialog box appears.

Step 3. Scroll down and find the “Hardy” modules and expand this category. Select the

HI 1756-nDF module and click on the OK button. The module properties dialog
box appears.

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Chapter 4

Step 4. Click in the Name text field. Enter a descriptive name for the module. We used

HI1756DF for example. Click in the Description box and enter a description if
desired. Insure the slot selection is correct.

Step 5. If you have a dual channel module, you should click on the “Change” button and

select “Two Channel”.

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Chapter 4

Step 6. On the Connection tab, set the RPI time to 10.0 ms.

The remaining tabs will allow the user to fill out the parameter settings for the module.

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Chapter 4

Linking the PLC with the HI 1756-nDF Dispenser Filler Control
Module

To set parameters for the weigh scale module, you must establish communications with a
ControlLogix PLC. Follow the steps below to set up the communication link without
using the AOP. You will need a new or open RS Logix® 5000 project. For instructions,
see your RS LOGIX 5000 manual.

Step 1. Look for a list of folders on the left side of the screen. Scroll to and select the

I/O Config folder, which will open a menu.

Step 2. Select New Module to display a list of modules.
Step 3. Select the Generic 1756 module to open the Module Properties form.
Step 4. Enter the following connection parameters in the appropriate fields:

Name of Module
Description of Module (Optional)
Slot ID
Input Assembly Instance:101 Size = 16
Output Assembly Instance: 100 Size = 16
Configuration Assembly Instance: 102 Size = 200 for a single channel

(1756 1DF) or 400 for a dual channel (1756 2DF)

Step 5. Select DATA REAL from the Comm Format pull-down list.
Step 6. Open the Connection Tab.
Step 7. Set the RPI to 5 milliseconds or greater Do not set this parameter lower than 5

milliseconds.

Step 8. Click Finish.

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Chapter 4

Weigh Filter
NumAVg

Weight

Conditioning

Weight

Calculation

Weight
Value

Flow Rate

Calculation

Flow Rate Time Base

Weight Unit

Flow Rate

Filter

Flow Rate
Value

Load Cell

Signal

Flow Rate Update Period
Flow Rate Filter
Material

ADC

Weight Update Rate

Current
Flow Rate

Auto_Preact

Calculation

Auto_Preact

stable
capture time

p gain
i gain
frc tolerance

variation
capture
steady period

auto preact config
start wait
fast adjust

Overview of Operation

The HI 1756 nDF will calculate Gross weight, Net weight, & Flow Rate (FR) outputs
simultaneously, as shown in the simplified block diagram below.

Overview of Weight Calculation

The ADC data can be filtered to reduce short term disturbances caused by system noise,
vibration noise, and local short term disturbances that could affect the weigh
measurement.

The most robust method to reduce these system disturbances is Waversaver®, but this
mode has the longest delay which is directly proportional to the bandwidth selected as the
algorithm requires at least one full cycle of the lowest frequency to be able to remove the
noise and harmonics from the weight measurement. On the other hand the raw data
sample mode provides the fastest response with no additional delay but does not filter out
any noise from the sampled data. As a compromise a low pass filter can be selected to
provide noise shaping across multiple samples centered on the current weigh value; this
mode has a fixed delay of 100mS.

The filter selection will depend upon the environment and the desired response time to
changes in weight.

Simplified block diagram for the 1756-1DF

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Chapter 4

Weight
Filter

Delay (ms)

Quality Comment

0 0 Poor, no filtering

1

100

Fair, narrow filter window

2

270 – 2000

Excellent, Waversaver® filter selection

Parameter

Default

Description

steady period

128

Sets the number of samples used to calculate the steady
weight value used in the auto-preact function.

variation

*1

Sets the peak to peak variation in weight values which will
be processed

capture

*2

Sets the peak to peak variation in processed weight values
that will be used to calculate the weight value on the scale
after in flight material has settled.

Note: ADC delay in not included in delay calculation as this delay is

consistent regardless of filter mode selected.

In addition a second filtering stage can be enabled which averages the current and
preceding ADC samples. This is a simple method to remove harmonics from the data
stream without introducing delay into the data path. For example, if NumAverages
parameter is set to 10 (default) and the weight update rate is 100Hz, a frequency notch
will occur every 10Hz in the sampled spectrum. This simple but effective filter is ideal
for removing harmonics at known frequencies within the sampled spectrum.

To calculate the preact value to compensate for in flight material, it is necessary to set
tolerances so that the weight processing algorithm can detect when amount of inflight
material falls within a user specified tolerance over a set number of samples. The
required parameters are shown in the following table. This processing does not add delay
into the signal processing path.

*1: Default value set to 1/2,500 of maximum capacity of the load cell.
*2: Default value set to 1/10,000 of maximum capacity of the load cell

Overview of Flow Rate Control

The default setting for the flow rate will be kilograms per second (kg/sec); however the
time interval will be programmable to also include kilograms per minute (kg/min) and
kilograms per hour (kg/hr) and the weight value can be programmed to be in pounds
enabling lbs/sec, lbs/min, and lbs/hr flow rate to be generated.

The flow rate calculation is a filtering operation tailored to provide an accurate
measurement of the material flow rate over the specified period of time. As the update
period is typically faster than the flow rate unit of time, the HI-1756 nDF will scale the
current calculation to match the programmed flow rate unit of time, albeit hours, minutes,
or seconds.

The time base value sets the number of samples that will be reviewed each time a flow
rate calculation is made.