DCM 4800
LOAD CELL SUMMING TRANSMITTER
USER’S GUIDE
www.cooperinstruments.com
PH: 540-349-4746 • FAX: 540-347-4755
CONTENTS
1.0 GENERAL DESCRIPTION.............................................................................................................. 3
1.1 Features ........................................................................................................................................................ 3
1.2 Application.................................................................................................................................................... 3
1.3 Brief Description.......................................................................................................................................... 3
1.4 Operation ...................................................................................................................................................... 3
1.5 Specifications............................................................................................................................................... 3
1.6 Instrument Layout ....................................................................................................................................... 5
2.0 INSTALLATION ............................................................................................................................... 5
2.1 Unpacking the DCM 4800 ........................................................................................................................... 5
2.2 Mounting ....................................................................................................................................................... 5
2.3 Electrical Connection.................................................................................................................................. 5
3.0 SETUP.............................................................................................................................................. 7
3.1 Setting the Excitation Voltage.................................................................................................................... 7
3.2 Single Load Cell System Adjustment....................................................................................................... 7
3.3 Multiple Load Cells Adjustment (Cornering the scale) .......................................................................... 8
3.4 Troubleshooting .......................................................................................................................................... 9
4.0 OPTIONS........................................................................................................................................ 10
4.1 Enclosures.................................................................................................................................................. 10
2. Dual Set Point Relays.................................................................................................................................. 10
5.0 WARRANTY REPAIR POLICY..................................................................................................... 10
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1.0 GENERAL DESCRIPTION
1.1 Features
• Summing of up to 4 load cells
• Complete strain gage bridge signal conditioner
• High gain, low drift, low temperature coefficient precision amplifiers, with low input current (10 pA typical)
• Wide input range from 5 mV to 50 mV full scale
• Very stable bridge balance with 80% tare offset capability
• 4-20 mA or 0-20 mA output
Capable of driving 1000 ohm loop
• 2 to 10 V or 0 to 10 V output
• Excitation supply capable of driving four load cells
o Typical 0.001% temperature coefficient
o Wide adjustment voltage range
o Long distance remote sense capability
o Very good line and load regulation
• Both AC & DC power capability
Surge voltage suppression
• Input, output and power three way isolation
• NEMA 4 enclosure for use in rugged environments
1.2 Application
• Precision weighing with load cells
• Process control add-on loops
• Can be used with all types of low output sensors
1.3 Brief Description
The DCM 4800 is an AC or DC powered Summing Transmitter for up to four load cells with output options of 0 to 20 mA,
and 0 to 10 V or 4 to 20 mA, and 2 to 10 V. All input/output options are included on one board so there is no need to
specify input/output parameters with the DCM 4800.
The DCM 4800 has a built in excitation supply capable of delivering up to 120 mA from 5 to 10 V, more than enough
current to drive four 350 ohm load cells.
The DCM 4800 offers three way isolation, input to output and power, eliminating unwanted ground loop problems. Overall
accuracy over the normal room temperature range is excellent at <±0.1% of full scale. The high gain, very low drift and
very low temperature coefficient of the DCM 4800 amplifier allows full scale live load signals as low as 5 mV to be
amplified to 20 mA or 10 V.
Designed with large and very stable tare offset requirements in mind, the 4800 can tare off up to 80 % of the output of a 3
mV/V load cell (at 10 V excitation).
If high/low setpoint alarms/controls are desired, the 4800 board is laid out to accept Opto-22 output relays. Potentiometers
are accessible to adjust the high and low trip points.
1.4 Operation
The 4800 accepts DC mV signals from up to four load cells which are summed together, then amplified, isolated and
filtered. The 4800 features a very stable on-board excitation supply and precision amplifier. They are designed for very low
drift and a small temperature coefficient, critical for high accuracy. The full scale output is either 20 mA or a 10 V signal for
industrial control. A wide AC and DC power voltage range is allowed for convenience.
1.5 Specifications
NOTE: Unless otherwise noted, specifications apply after half hour warm up at 23°C ±2 °C ambient. Temperature
Coefficients apply between 0°C and 55°C ambient.
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ACCURACY
10 TO 30oC, at 10 V Excitation Less than ±0.1%
Total Temperature Coefficient (TC) 0.0025%/oC typ
ISOLATION
AC or DC Powered – Three Way Isolated
AC to Input and Output 750 VAC
DC to Input to Output
300 VDC
500 pF
AMPLIFIER SECTION
Gain
Input Range 5 mV to 50 mV Full Scale
Linearity ±0.01% of Full Scale
TC 0.0015%/oC typ
Input Noise – 0.1 Hz to 10 Hz 2µV PP
Tare Adjustment Range
(Bridge Offset)
(Equals 80% F.S. of 3 mV/V cell at 10 V)
-3 mV to +6.5 mV
+6.5 mV to +16 mV
+16 mV to +25 mV
Temperature Coefficient 0.0015%/oC typ
Common Mode Rejection
Common Mode Input Voltage
100 dB Min
+5 Volts Max
OUTPUT
Zero Selection
Temperature Coefficient
Test Signal Output
Current Output Span
Current
Compliance Voltage
0 or 4 mA
0 or 2 V
0.001%/
o
C typ
Add 8 mA or 4 V to output
0 or 4 to +20 mA
Available 0 to -0.3 mA for zero monitor
0 to +20 Volts
Available 0 to -0.3 V for zero monitor
Loop Resistance 0 to 1000 ohms
Voltage Output Span
Voltage 0 or 2 to 10 V
Maximum Load Current 5 mA
Frequency Response
2 Poll roll off -dB at 10 Hz typ
Response Time
Rise Time 10% to 90%
To 0.1% of Final value
35 mS
100 mS
COMPARATOR OUTPUT Optional with Opto22 I/O Module
Comparative Voltage
Hysteresis Voltage
Comparator Output
Input/Output Isolation
BRIDGE EXCITATION SUPPLY
Voltage Adjustment Range
Temperature Coefficient
Load Current
Remote Sense for Excitation Supply
Current Leads Volt Drop
0 to 10 V
0.07 V typ
See the specification of OPTO22 output module
300 V
5 to 10 V
0.001% typ at 10 V
0 to 120 mA
Max 1 V drop
Sensing Leads Resistance Max 1 kohm
Line Regulation
Load Regulation
Output Noise
120 Hz Bandwidth
Less than 0.01%, typ 0.002%
Less than 0.03%, typ 0.005%
1 mV RMS, typ
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POWER INPUT
AC
DC
ENVIRONMENT
Operating Temperature
Storage Temperature
WEIGHT
JUNCTION BOX
TOTAL SIZE
LED power on indicator
115 V (90 to 130 V) /
230 V (180 to 260 V)
50/60 Hz, 10 W typ
11 to 30 V, 8 W
o
-25
C to +55oC
o
-25
C to +85oC
10.5 lb (4.7 kg)
10”L x 8” W x 4” H, NEMA 4 Box or NEMA 4X
Stainless Steel Box
12.5” x 9” x 4.4” (318 mm x 229 mm x 112 mm)
1.6 Instrument Layout
The components are assembled on one printed circuit board which is mounted inside of the NEMA 4 box. The T & B NonMetallic Liquidtight Strain Relief Connectors are used for weatherproofing and corrosion resistance. Four connectors on
one side of the box are used for load cell connections. Two connectors on another side of the box are used for output
signals, relay outputs and power connections.
2.0 INSTALLATION
2.1 Unpacking the DCM 4800
Item Check List:
• 4800 Load Cell Summing Transmitter
• AC Power Cord
• Grounding Kit for NEMA 4 Box
• Operation Manual
• Hole Plugs
2.2 Mounting
Mount the NEMA 4 Box using four screws in a location where water will not drip or run directly onto it.
Connect the box to the scale frame work ground using the “Grounding Kit” and a low resistance ground strap (e.g. #10 or
larger wire). A terminal “GND” on “Power Input” connector can also be used for ground connection.
2.3 Electrical Connection
Note: All the terminals are marked clearly on the printed circuit board. Be sure all terminal strip connections are tight and
the cable conductors are not cut or damaged. Use strain relief connectors, tighten securely. Remove any unused strain
reliefs and replace with provided hole plugs.
A. Connect the power to Model 4800
If you use AC power line, connect the two AC power leads to “AC” pin and ground lead to “GND” pin. Set the “AC
Switch” to your power line voltage(115 or 230 V) before you plug in the power cord.
If you use DC power, connect the DC power supply plus lead to “DC+” pin and negative lead to “DC-” pin.
B. Pre-set the excitation voltage
Connect “RSE.+”(Remote sensing) to “EXC.+”(Excitation), on “Remote Sense” connector “TR5”, and connect “RSE.-”
to “EXC.-”.
Turn on the power to Model 4800. Measure the voltage at the remote sensing pins. Adjust the excitation supply
voltage with the “EXC. V” potentiometer “R131”.
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This step is necessary to avoid overdriving the load cells.
Note that all four load cell connectors “TR1-4” use the same excitation supply in parallel, so the excitation supply
voltage is always adjusted at “EXC. V” potentiometer “R131” regardless of the number of cells.
*CAUTION: Turn off the power!
C. Connect the load cells to the Model 4800
“EXC.+” and “EXC-.” pins, see Fig.1 to Fig.3 for different applications.
Figure 1.
Remote Sense for Single Load Cell
Figure 2.
Remote Sense for Mutiple Load Cells
Figure 3.
Non-remote Sense for Mutiple Load Cells
D. Remote Excitation
Excitation Supply is a high performance, remote sensing supply for long lead applications. Remote sensing mode is
recommended for single load cell applications and also for up to four load cell applications where long leads are
present.
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The total voltage drop of excitation leads should be less than 1 V. An application example: if excitation leads are
copper wire AWG No. 16, 1000 feet resistance is 4.016 ohm, round trip resistance is 8.032 ohm, then the voltage drop
at 120 mA excitation current is less than 1 V.
If remote sensing is desired, disconnect “RSE.+” from “EXC.+”, on “Remote Sense” connector “TR5”, and disconnect
“RSE.-” from “EXC.-”.
Connect “RSE.+” and “RSE.-” to the excitation leads where you want the voltage to be controlled. Usually these two
points are close to the load cell. See Fig. 2 for single load cell and Fig. 3 for multiple load cell connections.
If remote sensing is not used, skip step D.
E. Connect each load cell to the related amplifier input pins “SIG.+” and “SIG.-” on connectors “Load Cell-1” to
“Load Cell-4”.
If a single load cell is used, connect it to “Load Cell-1” connector. (Other connectors “Load Cell-2 to 4” and switch “LC2
to 4” can also be used.)
All wires used in connecting up the Model 4800 should be of the same material. If any intervening connections have to
be made, such as a terminal block, the terminal block connecting points should have good thermal contact so they will
always be at the same temperature to minimize thermal-electric effects.
F. “SW1” has eight dip switches for four load cells.
Turn on two switches “LC1” on “SW1”. This connects the cell output signals to the amplifier input.
G. We strongly recommend you use the 4800 excitation supply to ensure high accuracy. In case the amplifier is
used without the 4800 excitation supply, the external power supply low side must be connected to the “EXC.-”
terminal on “Remote Sense” connector.
3.0 SETUP
3.1 Setting the Excitation Voltage
A. Turn on power to the 4800.
B. Measure the voltage at the remote sensing points or at the sense terminal on “Remote Sense” connector. Adjust
the excitation supply voltage with the “EXC. V” potentiometer “R131”.
3.2 Single Load Cell System Adjustment
A. Select the expected full scale signal range according to table 1 with SW2-”FS1", “FS2” and “FS3”. If the output
from the load cell is not known, set SW2 for the 40-50 mV range.
Table 1. Input Range Selection for Full Scale
Range 0-20 mA/0-10 V 2-10 V/4-20 mA FS1 FS2 FS3
1 5 to 10 mV 5 to 8 mV OFF OFF OFF
2 10 to 20 mV 8 to 16 mV OFF OFF ON
3 20 to 40 mV 16 to 32 mV OFF ON ON or OFF
4 40 to 50 mV 32 to 50 mV ON ON or OFF ON or OFF
B. Select Zero Output
Set SW2-”4mA” on for 4 mA or 2 V output or SW2-”4mA” off for 0 mA or 0 V output. Note actual output may not equal
desired value, follow the steps below for adjustment.
C. Select Tare Range on “SW2” according to Table 2.
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Table 2. Tare Range Selection
TARE 1 TARE 2
-3 to 6.5 mV OFF OFF
6.5 to 16 mV OFF ON
16 to 25 mV ON ON or OFF
D. Apply no load or dead weight to load cell.
E. For voltage output: Connect the “Hi” lead of a digital voltmeter to the “10V”, connect the “Lo” lead of the digital
voltmeter to the “OGND” of “OUTPUT” connector “TR6”.
For current output: Connect the “Hi” lead of a current meter to the “I-OUT”, connect the “Lo” lead of the current meter
to the current return terminal “I-RET” of “OUTPUT” connector “TR6”.
There will be a small difference between current output and voltage output. Select current or voltage output for
adjustment.
F. Adjust “TARE COARSE” and “TARE FINE” potentiometers for the ZERO current (0 or 4 mA) or ZERO voltage (0
or 2 V).
G. Test signal: Turn on Switch “SW2”-”8mA” to output a change of 8 mA or 4 V for monitoring system check. See Table
3.
Table 3. Calibration Output Selection
“SW2” – “4 mA” OFF “SW2” – “4 mA” ON
“SW2” – “8 mA” OFF 0 4 mA and/or 2 V
“SW2” – “8 mA” ON 8 mA and/or 4 V 12 mA and/or 6 V
Turn “SW2”-”8mA” off, after the completion of system check.
H. Apply rated load cell full scale load. Adjust “SENSIT.1” (“R2”) to get the maximum sensitivity.
I. Apply rated load cell full scale load. Adjust “FS COARSE” and “FS FINE” (GAIN) potentiometers for the desired full
scale output voltage or current. Set full scale range switches as required in Table 2.
J. Remove full scale load and check ZERO output voltage or current. Adjust “TARE FINE” potentiometer if required.
K. Recheck full scale as in Step 2.I.
3.3 Multiple Load Cells Adjustment (Cornering the scale)
Note: The full scale weight of a system with multiple load cells is the multiple of rated full scale of each load cell.
A. Turn on two “SW1”-”LC1" switches only, turn off other “SW1” switches. Follow steps 2.A. to 2.I.. Note: Apply a
load of 20 to 100 % of the rated full scale capacity of each load cell (not the full scale of system) for corner adjustment.
Record the output voltage with and without load.
B. Turn on two “SW1”-”LCn” (n=2, 3, or 4) switches only, turn off all other “SW1” switches. Apply same load as in
step A. Adjust “SENSIT. n” to get the maximum sensitivity. Record the output voltages with and without load for each
load cell.
C. Calculate the span, the difference of output voltage between no load and loaded for each corner load cell.
The sensitivity adjustment range for 350 ohm load cells is 7%. If the spread of the difference of output voltage
between corner load cells is larger than 7%, check the mechanical installation of load cells and the specifications of
load cells. Usually the corner load cells should be matched to each other within ±3%.
D. Select the lowest cell output span as the span reference. Do not adjust the load cell sensitivity pot for this cell.
CF 30 8 C0001 1.8.01
Turn on two “SW1”-”LCn” (n=1, 2, 3, or 4) switches only. Turn off all other “SW1” switches. Apply no load and 20% to
100 % of full scale of load cell (Not system full scale). Adjust “SENSIT. n” potentiometer to lower down the sensitivity
for the output span to be the same value as span reference voltage.
E. If there is no way to put known weight on each corner, apply 20 to 100 % of full scale of system load instead of
20% to 100 % of full scale of load cell. Then follow the steps A to D.
F. Turn on all “SW1”-”LC1", “LC2” ......”LCn” switches which are used. Remove all load and check ZERO output
voltage or current. Adjust “TARE COARSE” and “TARE FINE” potentiometer for zero output.
G. Apply rated system full scale load. Adjust “FS COARSE” and “FS FINE” (GAIN) potentiometers for the desired full
scale output voltage or current. Set full scale range switches as required in Table 2.
H. If necessary, repeat step 3.E and 3.F.
Note: Do not try to equalize the dead load outputs of each cell. The dead load does not need to be the same for proper
operation of the summing board.
3.4 Troubleshooting
A. The scale seems to be reading incorrectly
a. Check for correct wiring.
b. Unload the scale and check for a zero reading.
c. Check the input range switches according to Table 2.
d. Be sure that the object being weighed is completely on the scale.
B. The scale corner readings are not equal
a. Repeat step 3. multiple load cells adjustment.
b. Check the installation of load cells.
c. Check the load cells for damage.
C. The scale readings drift rapidly
a. Check for water in the junction box.
b. Isolate one load cell at a time from the summing box by turning off the two related switches “LCn”(n=1 to 4). If the
scale reading becomes stable, then the isolated load cell is probably defective or not installed properly.
c. Use a load cell simulator to verify that the DCM 4800 is stable and operating correctly.
D. Test the load cell zero shift
a. Remove the load from the load cell.
b. Turn on the two related switches “LCn”, turn off all other switches.
c. Measure the output voltage on “Output” connector. If it is less than 15 % of full scale output, it is not zero shifted. If
the output is 15 to 50 % of full scale, the load cell has been zero shifted, but will probably still work. If the output is
larger than 50 % of full scale, the load cell should be replaced with a known good unit. If the zero shift of the load
cell is caused by a mechanical overload, the reason for the overload should be determined before a new load cell is
installed.
E. Test load cell resistance
a. Disconnect the load cells from the junction box.
b. Measure the resistances of load cell and compare to the load cell specifications. Water leakage into the load cell or
damaged cable can cause problems.
c. If a load cell does not pass the resistance test, replace it with a known good unit.
d. Defective load cells can usually be repaired.
CF 30 9 C0001 1.8.01
4.0 OPTIONS
4.1 Enclosures
4800-W4: Continuous Hinge NEMA 4 Box
4800-WS: Continuous Hinge NEMA 4 Stainless Steel Box
2. Dual Set Point Relays
A. Opto-22 G4ODC5 *
Opto-22 G4OAC5 *
* Not included with the 4800
B. Installation
Plug the Opto-22 output modules into “RELAY1” and “RELAY2” on the printed circuit board. Tighten the screw on top
of the module lightly.
C. Adjusting Set Point Values
If you need the Relay outputs, connect the “Hi” lead of a digital voltmeter to the “TP1”. Connect the “Lo” lead of the
digital voltmeter to the “O-GND” on “OUTPUT” connector “TR6”. Test the voltage at “TP1” and adjust the “COMP. V1”
potentiometer “R66” to set the Comparator voltage for the low set point. If the output voltage at “OUTPUT” connector
“TR6” is lower than the Comparator voltage at “TP1”, this means the output is lower than the low set point, and the
output of Relay 1 will be “ON”. The two “RL1” on “RELAY OUTPUT” connector “TR7” are the Opto-22 Output
contacts.
Use the digital voltmeter to set the voltage at “TP2” with “COMP. V2” potentiometer “R75” for high set point. If the
output voltage at “OUTPUT” on connector “TR6” is higher than the Comparator voltage at “TP2”, this means the
output is higher than high set point, and the output of Relay 2 will be “ON”. The two “RL2” on “RELAY OUTPUT”
connector “TR7” are the Opto-22 Output contacts.
In order to prevent relay chatter, typically there are 0.07 V hysteresis voltage. There may be a very small difference
between the output voltage and the voltage at “TP1” or “TP2” for turn on or off. The output voltage for turn on or off
can be set precisely by adjusting the “COMP. V1” potentiometer “R66” for the low set point or “COMP. V2”
potentiometer “R75” for high set point.
5.0 WARRANTY REPAIR POLICY
Limited Warranty on Products
Any Cooper Instruments product which, under normal operating conditions, proves defective in material or in workmanship
within one year of the date of shipment by Cooper will be repaired or replaced free of charge provided that a return
material authorization is obtained from Cooper and the defective product is sent, transportation charges prepaid, with
notice of the defect, and it is established that the product has been properly installed, maintained, and operated within the
limits of rated and normal usage. Replacement or repaired product will be shipped F.O.B. from our plant. The terms of
this warranty do not extend to any product or part thereof which, under normal usage, has an inherently shorter useful life
than one year. The replacement warranty detailed here is the buyer’s exclusive remedy, and will satisfy all obligations of
Cooper whether based on contract, negligence, or otherwise. Cooper is not responsible for any incidental or
consequential loss or damage which might result from a failure of any and all other warranties, express or implied,
including implied warranty of merchantability or fitness for particular purpose. Any unauthorized disassembly or attempt to
repair voids this warranty.
Obtaining Service under Warranty
Advance authorization is required prior to the return to Cooper Instruments. Before returning the item, contact the Repair
Department c/o Cooper Instruments at (540) 349-4746 for a Return Material Authorization number. Shipment to Cooper
shall be at buyer’s expense and repaired or replacement items will be shipped F.O.B. from our plant in Warrenton,
Virginia. Non-verified problems or defects may be subject to a $100 evaluation charge. Please return the original
calibration data with the unit.
CF 30 10 C0001 1.8.01
Repair Warranty
All repairs of Cooper products are warranted for a period of 90 days from date of shipment. This warranty applies only to
those items that were found defective and repaired; it does not apply to products in which no defect was found and
returned as is or merely recalibrated. It may be possible for out-of-warranty products to be returned to the exact original
specifications or dimensions.
* Technical description of the defect: In order to properly repair a product, it is absolutely necessary for Cooper to receive
information specifying the reason the product is being returned. Specific test data, written observations on the failure and
the specific corrective action you require are needed.
CF 30 11 C0001 1.8.01
Cooper Instruments & Systems
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