Hardy HI 2204LT User Manual

HI 2201LT Loop Powered Level Weight Transmitter For

Hazardous Areas

HI 2204LT Loop Powered Level Weight Transmitter

OPERATION AND INSTALLATION

MANUAL

Corporate Headquarters

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

Hardy Instruments Document Number: 0596-0138-01 Rev E

Copyright November 1999 H ard y Inst rum ents, Inc. All Rights Reserved. Printed i n the U .S.A . (941 028)

1-2

Table of Contents

Table of Contents
Overview - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -1
Specifications - - - - - - - - - - - - - - - - - - - - - - - - - - - - -2

Physical Dimensions - - - - - - - - - - - - - - - - - - - - - - - -2
Power Requirement - - - - - - - - - - - - - - - - - - - - - - - -2
Load Cell Excitation - - - - - - - - - - - - - - - - - - - - - - - -2
Zero Offset Range - - - - - - - - - - - - - - - - - - - - - - - - -2
Sensitivity - - - - - - - - - - - - - - - - - - - - - - - - - - - - -2
Linearity - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -2
Operating Temperature Range - - - - - - - - - - - - - - - - - - -2
Temperature Coefficient - - - - - - - - - - - - - - - - - - - - - -3
Signal Current Ripple - - - - - - - - - - - - - - - - - - - - - - -3
Power Supply Rejection - - - - - - - - - - - - - - - - - - - - - -3
Approvals (HI 2201LT Only) - - - - - - - - - - - - - - - - - - - -3
Approvals HI 2201LT & HI 2204LT - - - - - - - - - - - - - - - - -3

Installation - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -3

Junction Box with Strain Gage Summing Board
(HI 2201LT-A3 or HI 2201LT-A5) - - - - - - - - - - - - - - -3

Input - Strain Gage Transducer - - - - - - - - - - - - - - - - - - -4
Output/Power Loop - - - - - - - - - - - - - - - - - - - - - - - -4
Earth Ground and Signal Return - - - - - - - - - - - - - - - - - -6
Precautions on Grounding - - - - - - - - - - - - - - - - - - - - -7
Isolation - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -7

Calibration - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -7

Calibration Controls - - - - - - - - - - - - - - - - - - - - - - - -8

Coarse (Zero) - - - - - - - - - - - - - - - - - - - - - - - - -8
Fine (Zero) - - - - - - - - - - - - - - - - - - - - - - - - - - -8
Span - - - - - - - - - - - - - - - - - - - - - - - - - - - - -8

Calibration Procedures - - - - - - - - - - - - - - - - - - - - - - -8

Example - - - - - - - - - - - - - - - - - - - - - - - - - - - -9

Trouble Shooting Procedures - - - - - - - - - - - - - - - - - - - -10

Malfunction: No Output - - - - - - - - - - - - - - - - - - - - - - -10
Malfunction: No Change in Input - - - - - - - - - - - - - - - - - -10
Malfunction: Output Drifts - - - - - - - - - - - - - - - - - - - - -10

Factory Mutual (FM) Approval (HI 2201LT Only) - - - - - - - - - - -11

i

HI 2201 LT

ii

HI 2201LT/HI 2204LT

Overview The model HI 2204LT Loop Powered Level Weight

Transmitter and model HI 2201LT Loop Powered
Level Weight Transmitter for Hazardous Areas fur­nish power to strain gage transducers, measure the
return voltage, and adjust the 4-20 milli amp loop cur­rent to be proportional to the transducer signal.

The HI 2201LT is Factory Mutual approved and safe
to use in hazardous operating environments. The HI
2204LT IS NOT Factory Mutual approved and
should not be used in a hazardous environment.

The HI 2201LT/HI 2204LT can be used to transmit
any strain gage signal with a bridg e resistance of more
than 88 ohms. This allows transmission of pressure,
load, weight, force and torque signals including up to
four 350 ohm, full bridge, load cells.

The HI 2201LT/HI 2204LT powers itself and the
attached strain gage transducers from the 4-20 ma
loop power. This allows sensitive strain gage signals
to be transmitted over long distances without the
expense of installing additional power to remote loca­tions. A common, low-cost power supply can be
placed anywhere in the 4-20 ma loop.

As the power supply provides loop power, the HI
2201LT/HI 2204LT controls the current flow (4-20
ma) representing the strain gage signal and receiving
devices can be placed anywhere along the loop to
monitor current flow. Typical receiving devices
include:

• Chart Records

• Panel Meters

• Bar Graphs

• Programmable Controllers

•Computers

• Relay Set Point Modules

Most receiving devices may be characterized as a load
resistor allowing the 4-20 ma signal t o cause a propor­tional voltage drop across it. Multiple receivers may
be placed on the loop provided the loop p ower su pply
can drive the combined loads. this can be calculated
by adding the voltage requirements of the HI 2201LT/

1

HI 2201LT/HI 2204LT

Specifications

HI 2204LT (14 VDC) to that of each receiving device
(loop resistance x 20 ma).

The Level Indicator applies power to each transducer
in pulses a few milliseconds long at a rate of 90 pulses
per second. The Level Indicator measures the voltage
across the output terminals of the transducer with
each power pulse, and it converts the average into a
smooth current that varies with the transducer signal.
This method of powering the transducer allows the
Level Indicator to power up to four load cells . Though
each load cell requires more than 4 ma excitation, the
Level Indicator itself draws no more than 4 ma aver­age current at zero weight load, and no more than 20
ma average current at full scale.

The Level Indicator is potted and sealed to withstand
typical industrial environments. It is small enough to
be mounted on a load cell summing board inside of a
standard 5” x 7” x 3.5” NEMA 4 enclosure.

Physical
Dimensions

Power
Requirement

Load Cell
Excitation

Zero Offset Range Coarse: 2 mV/V

Sensitivity 3 mV/V (Continuously Adjustable from 2 mV/V to 3

Linearity 0.11% of full scale*

2

Length: 4.50 Inches (114.3 mm)
Width: 2.15 Inches (54.6 mm)
Height: 1.30 Inches 33.02 mm)
Weight: 8 oz. (.227 Kgs)

Minimum: 15 VDC
Maximum: 50 VDC
Zero Scale: 4 ma
Full Scale: 20 ma

5 V (pulsed) , 90 hz

fine: 0.04 mV/V

mV/V)

* Some barrier protectio n is required where the 2201
is located in a hazardous area.

HI 2201LT/HI 2204LT

Operating
Temperature
Range

Temperature
Coefficient

Signal Current
Ripple

Power Supply
Rejection

Approvals (HI
2201LT Only)

Approvals HI
2201LT & HI
2204LT

Installation The Loop Powered Level Weight Transmitter is usu-

0o C to +60o C (+32o F to +140o F)

0.025% per degree Celsius

20 mV p-p at 20 ma into 500 ohms

0.015% (max) 20 to 30 V

0.10% (max) 15 to 50 V
FM approved

CE

ally installed close to the strain gage(s) to minimize
the expense of special wiring, such as load cell cable.
Wiring positions are indicated on the top surface next
to each terminal strip.

Junction Box with
Strain Gage
Summing Board
(HI 2201LT-A3 or
HI 2201LT-A5)

The transmitter is available in a NEMA 4 junction
box.(See Fig. 1)

3

HI 2201LT/HI 2204LT

FIG. 1 HI 2201LT/HI 2204 (-A3 OR -A5) IN

NEMA 4 JUNCTION BOX/TOP VIEW

The HI 2201/2204LT-A3 and HI 2201/2204LT-A5
Loop Powered Level Weight Transmitter comes
mounted on a load cell summing board within a
NEMA 4 junction box. The load cell summing board
is designed to allow balancing pots to be instal led if
required. (See Fig. 2)

FIG. 2 TRANSMITTER INSTALLED ON LOAD

CELL SUMMING BOARD (-A3 OR -A5

OPTION)

Input - Strain Gage
Transducer

Output/Power
Loop

4

Strain Gage signals are typically very low in voltage
causing them to be susceptible to noise. It is a good
practice to isolate strain gage signals from high volt­age (110 VAC) lines. It is highly recommended that
the transducer signal wire be routed in its own con­duit. The transducer cable should have a shield which
can be earth grounded near the transmitter.

The loop power connection provides power to the HI
2201LT/HI 2204LT and provides the 4-20 mA signal.
The transmitter must have from 15 VDC to 50 VDC
across its LOOP terminals at up to 20 mA (full scale
output). since all devices in the output/power loop are
in series minimum pow er supply voltage, at 2 0 mA,
must equal the total voltage drop across all of the
other devices in the loop, plus 15 VDC for the HI
2201LT.

HI 2201LT/HI 2204LT

Loop Powered Level

Weight Transmitter

+-

Power

Supply

Receiver

#3

-

+

Receiver

#1

Receiver

#2

4mA-20mA

The transmitter output loop can be wired with any two
conductor shielded cable. The two inner conductors
are connected to the output of the transmitter at the
two terminals marked LOOP. (See Fig. 3 & 4)

Note which wire is connected to each terminal to
maintain correct polarity within the loop.

FIG. 3 OUTPUT LOOP TERMINAL S

5

HI 2201LT/HI 2204LT

DC

Power

Supply

+

Loop Powered Level

Weight Transmitter

+

Isolator

+

+

Relays

Set

Point

RCVR

+

RCVR+110

VAC

110

VAC

110

VAC

110

VAC

FIG. 4 OUTPUT/POWER LOOP WIRING

NOTE: Be sure to shield the tie point for CE compliance.

Earth Ground and
Signal Return

“Earth Ground” is used here to indicate a point actu­ally connected to a path into the Earth’s ground. The
term “signal return” is used to indicate a return path
for signals to the negative side of th e power supply, or
in the case of the output/loop, signal return means the
more negative side of the voltage being measured.
(See Figs. 4 & 5)

FIG. 5 TYPICAL SYST EM WIRING WITH ISOLATION

NOTE: Be sure to shield the tie point for CE compliance.

Receivers may be inserted into the minus or the plus
power supply/transmitter path, or both. It is not neces­sary that one of the transmitter output leads be con­nected directly to ground.

6

Appropriate grounding and shielding helps to protect
the signals from noise. However, it may be necessary
to try various ground/shiel d configur atio ns to find the
best one for a particular installation. Figures 4 & 5 are
examples only.

The transducer cable shield should be connected to
either the earth ground or the signal return, on the
input side of the transmitter to protect against noise,
but not to both. The recommended configuration con­sists of the transducer cable shield connected to the
output/power cable shield and to the signal return.

HI 2201LT/HI 2204LT

Precautions on
Grounding

NOTE: Only the one point where the loop is alr eady gr ounded

Isolation The AC power sources for this instrument must be

1. Do not connect the signal return to the earth
ground at more than one point in the output/
power loop.

2. Any receiver or electronic device inserted in the
output/power loop must be designed so that the
connections to the loop are isolated from gro und .

can accept a grounded lead.

3. Do not connect the earth ground to the signal
return in the transmitter input circuit.

4. Do not connect any of the transducer signal wires
to the earth ground.

separate and isolated from the power supplied to any
switches, relays, solenoids, or motors which can intro­duce excessive noise into the instrument’s circuits.

Load cells and load cell signal wires are not typically
grounded, and they are not typically connected to
their shields or to the load cell case. If the recommen­dations given in the grounding and shielding section
are followed, there will be no need for isolation in the
transmitter/load-cell circuit. In fact, in the load cell
circuit, isolation adds to the cost and inaccuracy and is
not recommended.

It is generally not necessary to provide isolation in the
output loop. However, when ground-loop problems
do occur, a Loop isol ator d e sign ed t o hand le the 4 ma
to 20 ma Loop Powered Level Weight Transmitter
signal may be installed. (See Fig. 5)

Calibration The HI 2201LT Loop Powered Level Weight Trans-

mitter is calibrated at the factory for 4 ma current out­put with zero millivolts input and 20 ma output for 15
mV input (based on a 3mV/V input source and 5 V
excitation). In most cases, the transmitter will require
a very simple recalibration to the system in which it is
installed. The calibration procedure provided is
designed to be used either in new installations or for
recalibration of existing systems, and will work with 3
mV/V or 2 mV/V load cells. Be sure to read all cali-

7

HI 2201LT/HI 2204LT

Calibration
Controls

Coarse (Zero) The Coarse Control is used to remove large deadloads

Fine (Zero) This control is a fine offset adjustment. Its range is

Span The Span Control adjust the gain of the transmitter. It

brations instructions before attempting to calibrate the
instrument.

or offsets such as the weight of the scale’s platform,
container or any other constant weight on the load
cells which is part of the weighing equipment itself.
This control can subtract as much as 65% of full scale
from the transmitter’s output.

sufficient to fine tune the COARSE adjustment.

determines how many millivolts (of transducer signal)
per volt (of transducer excitation) will be represented
by the 4 ma to 20 ma output range.

The gain can be adjusted from 3 mV input per volt of
excitation to as high as 0.8 mV input per volt of exci­tation. This broad range of sensitivity allows for the
wide variation in transducer range that remains after
deadload compensation is subtracted by the COARSE
Zero adjustment.

Calibration
Procedures

8

The measuring instruments used in the following pro­cedure must be designed so that test leads are isolated
from ground. These are either “floating” and/or “iso­lated” and/or “differential” types.

Insertion of any measuring device, or voltage drop­ping resistor for a measuring devic e in the output/
powers loop requires that t he power sup ply voltage be
high enough to supply the extra voltage (See Input­Strain Gage T ransducer). The following is an example
using load cells in a weighing application.

Step 1. Remove any weight from the scale. Allow

deadload to remain. If deadload is counter ­balanced, also allow counterbalancing to
remain.

HI 2201LT/HI 2204LT

Step 2. Install a milli ammeter, in series, into the

output/power loop of the transmitter. If a
voltmeter is to be used for measurements,
and a resistor for calibration is not already
installed in the system, install a 100 ohm,
+- 0.1%, 1/4 W resistor, in series, into the
output/power loop of the transmitter. Volt­meter readings are show in parentheses.

Step 3. If a voltmeter is used, attach the voltmeter

across the 100 ohm resistor.

Step 4. Adjust the transmitter FINE control for a 4

ma (1/4 V) reading on the meter. If neces­sary, center the FINE control, and adjust
COARSE control first.

Step 5. Place a know weight on the scale. If possi-

ble, use a full scale weight for best results.

Step 6. Adjust the SPAN for 20 ma (2V) for full-

scale.

• Divide: Calibration Weight/Full­Scale
Weight = (F)raction of full scale.

• Multiply: (F) (16 ma) = 1, the cur­rent caused by the calibration
weight.

• Add: 1 + 4 ma = Calibration Cur­rent, 1c

• Adjust the SPAN to produce the
Calibration Current, 1c, in the out­put/power loop.

Example Calibration Weight = 750 pounds

Full Scale Capacity = 1000 pounds

Adjust SPAN for:

(750/1000) (16 ma) + 4 ma = 1c

(0.75) (16 ma) + 4 ma = 1c

12 ma + 4 ma = 1c

16 ma = 1c

9

HI 2201LT/HI 2204LT

Step 7. Remove the calibration weight and

recheck that the zero reading is still 4 ma
(0.4 V). Adjust the FINE control if neces­sary.

Step 8. Place the calibration weight back on the

scale and recheck that the calibration read­ing is still correct. Adjust the SPAN con­trol if necessary.

Step 9. Repeat steps 7 & 8 until no further adjust-

ment is necessary to keep both measure­ments within the system tolerances.

Step 10. Calibration is complete.

Trouble Shooting
Procedures

Malfunction: No
Output

Malfunction: No
Change in Input

This section is intended to provide assistance in solv­ing minor system problems.

Checks to be made:

1. Check voltage at + & - loop connections. You
should get a reading of 15 VDC to 50 VDC.

2. Verify load cell connections.

3. Using an Oscilloscope, verify that you have a
pulsed 5 VDC between terminals labeled - & +
excitation.

Checks to be made:

1. Load Cell signal output below original setting. If
the signal level returned by the Load Cells is
below the previous deadload setting, measure
approximately 2.3 ma between the loop + & - ter­minals.

2. Load Cell signal output above original setting. If
the signal level returned by the load cell is above
the previous Span setting, measure approxi­mately 23 ma between the loop + & - terminals.

Malfunction:
Output Drifts

10

Checks to be made:

1. Verify load cell connections.

2. V erify Power Supply output and confirm that it is
outputting a constant voltage.

HI 2201LT/HI 2204LT

Factory Mutual (FM)
Approval (HI 2201LT
Only)

The HI 2201L T is FM approved and inst rinsically safe
for Class I, II, III, Division I, Division II, Groups
A,B,C,D,E,F and G hazardous locations in accor­dance with entity requirements and Hardy drawing
No. 0582-0563.

The HI 2201LT is approved with the MTL 705 Barrier
(See Fig. 6) or with any other FM-approved barrier
provided that the maximum entity parameters are met.
(See Fig. 7)

FIG. 6 MTL705 BARRIER

FIG. 7 FM APPROVED BARRIER

11

HI 2201LT/HI 2204LT

12