Omega Stud Sensor DMD 476 User Manual

Users Guide  
®
An OMEGA Technologies Company  
DMD-476 Bridgesensor  
AC Powered Signal Conditioner  
 
Description  
Specifications  
NOTE: Unless otherwise noted, specifications apply after one hour  
warm up at 25°C ambient. Temperature coefficients apply between  
0°C and 55°C ambient.  
The Model DMD-476 is a self contained, AC  
powered signal conditioner for bridge type  
instrumentation. It contains a precision  
instrumentation amplifier with isolated, filtered  
outputandahighlyregulated,lownoise,adjustable  
output bridge excitation source. The unit is  
completely encapsulated for use in rugged  
environments.  
Isolation  
700 VDC  
60pF  
Input to Output  
Amplifier  
Gain  
Adjustment Range  
Input for 4 - 20 mA Output  
5 mV to 50 mV  
±0.01% of Full Scale  
Linearity  
Features  
Temperature Stability  
50 PPM (0.005%/°C)  
Input Noise  
n Complete Strain Gage  
Bridge Signal Conditioner  
.1 Hz to 10 Hz  
2 V P-P  
Tare Adjustment Range  
n Isolated 4-20 mA or 0-20 mA Output  
-3 mV to +25 mV  
(Equals 80% F.S. of  
3 mV/V cell)  
Bridge Offset  
n Output Capable of Driving 1000 ohm Loop  
Input Resistance  
n Bridge Balance with 80%  
Tare Offset Capability  
Differential and Common Mode 1000 megohm  
Common Mode Rejection, DC  
Common Mode Input  
Output  
100 dB minimum  
+ 5 Volts  
n High Gain Amplifier; Can Accept Full Scale  
Live Load Signals as Low as 5 mV and  
Provide 16 mA Output Span  
Zero Adjust  
0 or 4 mA  
Temperature Coefficient  
Current Output Span  
Compliance Voltage  
1mA/ C  
4 to 20 mA or 0 to 20 mA  
-1 to +20 Volts  
n Excitation Supply Capable of Driving  
Four Load Cells  
-1 mA to +20 mA  
0 to 1000 ohms  
10 Hertz, 2 Pole Roll Off  
Current  
n AC Powered  
Loop Resistance  
Frequency Response, -3dB  
n Rugged Epoxy Encapsulated Design  
Response Time  
Rise Time 10% to 90%  
To 0.1% of Final Value  
35 ms  
100 ms  
Applications  
Bridge Supply  
Voltage Adjustment Range  
Temperature Coefficient  
Fixed  
5 to 10 Volts  
n Weighing with Load Cells  
n Process Control Add-on Loops  
100 PPM Typical  
10.2V ±2.5%  
Temperature Coefficient  
Load Current  
60 PPM Typical  
0 to 120 mA  
n Can Be Used With All Types of  
Low Output Sensors  
Regulation - Load and Line  
Output Noise  
0.02% maximum  
120 Hz Bandwidth  
1 mV RMS, maximum  
115 VAC, ±10V 50/60 Hz  
@ 7 VA  
Power Input  
Optional  
100, 220 or 230 VAC, –10%  
Line Isolation  
Capacitance  
Dielectric Withstand  
Environment  
Ambient Operating  
Storage  
60 pF  
1100 Volts RMS  
-25°C to +55°C  
-25°C to +85°C  
18 oz. (510 grams)  
Weight  
3.75" L x 2.0" W x 2.87" H  
(9.53 cm x 5.1 cm x 7.62 cm)  
Size  
3
 
MODEL DMD-476 Block Diagram  
SWB - Excitation Voltage  
Mechanical Specifications  
SWB-1  
ON  
OFF  
Excitation Voltage  
Fixed 10 Volts  
Adjustable  
SWA - Control Switch  
SWA-1  
OFF  
Tare Range  
-3mV to +15 mV  
ON  
+15 mV to +25 mV  
SWA-2  
OFF  
Zero Current  
4 mA  
Terminal Strip Assignments  
Screw  
ON  
0 mA  
Screw  
Terminal  
Function  
Function  
Terminal  
1
2
3
4
5
-SENSE  
-EXCITATION  
+SENSE  
6
7
AC  
SWA-4 SWA-5  
Span Range  
40 mV to 50 mV  
20 mV to 40 mV  
10 mV to 20 mV  
5 mV to 10 mV  
+SIGNAL  
-SIGNAL  
OUTPUT  
RETURN  
ON  
OFF  
ON  
ON  
ON  
OFF  
OFF  
8
+EXCITATION  
AC  
9
10  
OFF  
4
 
Getting Started with the Model DMD-476  
1. Excitation Supply. If remote sensing is not used, connect +Sense to +Excitation, terminal 3 to 4, and  
connect -Sense to -Excitation, terminal 1 to 2.  
2. Apply power to the DMD-476 and adjust the Excitation supply. Turn SWB-1 “ON” for a fixed 10 Volts.  
This will set the supply to 10.2 ±2.5% and provide the best temperature stability. For voltages between  
5 and 10 Volts, place SWB-1 in the “OFF” position and set the Excitation Supply with potentiometer  
E. SWB-2 may be in either position.  
3. Turn the power to the DMD-476 off and connect the load cell to the DMD-476 Excitation terminals and  
the Amplifier Inputs.  
4. Turn on power to the DMD-476.  
5. Turn SWA-3 “ON”. (To set output ZERO current with pot D.)  
6. Select the expected full scale signal range according to the table with SWA-4 and  
SWA-5. If the output from the load cell is not known, set both SW-4 and  
SW-5 “ON” for the 40-50mV range.  
7. Set SWA-2 “OFF” for 4mA or SWA-2 “ON” for 0mA output ZERO.  
8. Adjust D potentiometer for desired ZERO current.  
9. Turn SWA-3 “OFF”. Expect output current to change.  
10. Apply no load or dead weight to load cell.  
11. Adjust TARE potentiometers A and B for the same ZERO current set in Step 8.  
SWA-1 “OFF” provides a bridge output balance of -3mV to +15mV, and “ON” between +15mV and  
+25mV.  
12. Apply full scale load and adjust SPAN (GAIN) potentiometer C for the desired full scale output current.  
Set Range switches SWA-4 and SWA-5 as required.  
13. RemovefullscaleloadandcheckZEROoutputcurrent. AdjustFINETAREpotentiometerAifrequired.  
14. Recheck full scale as in Step 12.  
15. End.  
Note: If the amplifier is used without using the DMD-476 Excitation Supply, the external power supply low  
side must be connected to the -EXCITATION terminal 2 on the Model DMD-476, or one of the inputs  
must be tied to terminal 2, -EXCITATION. This provides a DC return path for the finite amplifier input  
current.  
5
 
Amplifier  
The amplifier is a true differential input, low drift Instrumentation Amplifier with less than 100pA input  
current. It has a common mode range of 5 Volts with respect to the - EXCITATION supply terminal and  
a minimum of 100dB rejection of the common mode voltage. The input amplifier and excitation supply are  
DC isolated from the AC line and the current output.  
The isolated output current source has a compliance of 20 Volts to allow the Model DMD-476 to operate  
with zero to 1000 Ohms of loop resistance.  
Tare Weight Compensation  
The Model DMD-476 has two different zero controls. One is called the OUTPUT zero and can be set to  
0mA or 4mA with SWA-2. The other zero control is called TARE. SWA-1 allows the selection of one of  
two TARE ranges, -3mV to 15mV or +15mV to +25mV. Potentiometers are available for COARSE and  
FINE TARE adjustments.  
Connecting to a Sensor  
AnyamplifierhasafiniteinputcurrentwhichmusthaveDCreturnpathtotheamplifierpowersupplies. This  
path is automatically provided when the Model DMD-476 Bridge Excitation Supply is used to excite the  
sensor. If an external supply is used, one side of the external supply must be connected to the DMD-476  
common, Terminal 2. Be sure that the common mode voltage limits are observed. This would generally  
limit the external power supply to 10 Volts assuming that half the voltage would be common mode, as is  
the case when exciting a full bridge.  
When the full scale output of a sensor is measured in millivolts, say 10 millivolts, care must be exercised  
-6  
in wiring systems. At 10 millivolts full scale, each microvolt (10 volts) contributes 0.01% of full scale  
output. Wire connections can generate microvolts of potential due to contact potentials. These will also  
be thermoelectric potentials and thus vary with temperature differences. All wires used in connecting up  
the Model DMD-476 should be of the same material. If any intervening connections are 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 and thus cancel each other.  
Transducer Excitation  
The bridge excitation supply voltage is set by SWB-1 and potentiometer E. Set SWB-1 ON for a fixed 10  
Volts. This will provide the best temperature stability. The supply can be adjusted between 5 and 10 Volts  
by setting SWB-1 OFF and adjusting potentiometer E. The supply will deliver up to 120mA current at any  
voltage setting to power up to four 350 ohm sensors.  
6
 
WARRANTY/DISCLAIMER  
OMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship for a period  
of 13 months from date of purchase. OMEGA Warranty adds an additional one (1) month grace period to the  
normal one (1) year product warranty to cover handling and shipping time. This ensures that OMEGA’s  
customers receive maximum coverage on each product.  
If the unit malfunctions, it must be returned to the factory for evaluation. OMEGA’s Customer Service Department  
will issue an Authorized Return (AR) number immediately upon phone or written request. Upon examination by  
OMEGA, if the unit is found to be defective, it will be repaired or replaced at no charge. OMEGA’s WARRANTY  
does not apply to defects resulting from any action of the purchaser, including but not limited to mishandling,  
improper interfacing, operation outside of design limits, improper repair, or unauthorized modification. This  
WARRANTY is VOID if the unit shows evidence of having been tampered with or shows evidence of having  
been damaged as a result of excessive corrosion; or current, heat, moisture or vibration; improper specification;  
misapplication; misuse or other operating conditions outside of OMEGA’s control. Components which wear  
are not warranted, including but not limited to contact points, fuses, and triacs.  
OMEGA is pleased to offer suggestions on the use of its various products. However, OMEGA neither assumes  
responsibility for any omissions or errors nor assumes liability for any damages that result from the use of its  
products in accordance with information provided by OMEGA, either verbal or written. OMEGA warrants only  
that the parts manufactured by it will be as specified and free of defects. OMEGA MAKES NO OTHER  
WARRANTIES OR REPRESENTATIONS OF ANY KIND WHATSOEVER, EXPRESS OR IMPLIED, EXCEPT THAT  
OF TITLE, AND ALL IMPLIED WARRANTIES INCLUDING ANY WARRANTY OF MERCHANTABILITY AND  
FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED. LIMITATION OF LIABILITY: The remedies  
of purchaser set forth herein are exclusive, and the total liability of OMEGA with respect to this order, whether  
based on contract, warranty, negligence, indemnification, strict liability or otherwise, shall not exceed the  
purchase price of the component upon which liability is based. In no event shall OMEGA be liable for  
consequential, incidental or special damages.  
CONDITIONS: Equipment sold by OMEGA is not intended to be used, nor shall it be used: (1) as a “Basic  
Component” under 10 CFR 21 (NRC), used in or with any nuclear installation or activity; or (2) in medical  
applications or used on humans. Should any Product(s) be used in or with any nuclear installation or activity,  
medical application, used on humans, or misused in any way, OMEGA assumes no responsibility as set forth  
in our basic WARRANTY / DISCLAIMER language, and, additionally, purchaser will indemnify OMEGA and  
hold OMEGA harmless from any liability or damage whatsoever arising out of the use of the Product(s) in such  
a manner.  
RETURN REQUESTS/INQUIRIES  
Direct all warranty and repair requests/inquiries to the OMEGA Customer Service Department. BEFORE  
RETURNING ANY PRODUCT(S) TO OMEGA, PURCHASER MUST OBTAIN AN AUTHORIZED RETURN (AR)  
NUMBER FROM OMEGA’S CUSTOMER SERVICE DEPARTMENT (IN ORDER TO AVOID PROCESSING DELAYS).  
The assigned AR number should then be marked on the outside of the return package and on any correspondence.  
The purchaser is responsible for shipping charges, freight, insurance and proper packaging to prevent breakage  
in transit.  
FOR WARRANTY RETURNS, please have the  
following information available BEFORE contacting  
OMEGA:  
FOR NON-WARRANTY REPAIRS, consult OMEGA  
for current repair charges. Have the following  
information available BEFORE contacting  
OMEGA:  
1. Purchase Order number under which the  
product was PURCHASED,  
1. Purchase Order number to cover the COST  
of the repair,  
2. Model and serial number of product, and  
3. Repair instructions and/or specific problems  
relative to the product.  
2. Model and serial number of the product  
under warranty, and  
3. Repair instructions and/or specific problems  
relative to the product.  
OMEGA’s policy is to make running changes, not model changes, whenever an improvement is possible. This affords our  
customers the latest in technology and engineering.  
OMEGA is a registered trademark of OMEGA ENGINEERING, INC.  
Copyright 1999 OMEGA ENGINEERING, INC. All rights reserved. This document may not be copied, photocopied,  
reproduced, translated, or reduced to any electronic medium or machine-readable form, in whole or in part, without the  
prior written consent of OMEGA ENGINEERING, INC.  
©
7
 
Where Do I Find Everything I Need for  
Process Measurement and Control?  
OMEGA...Of Course!  
TEMPERATURE  
þ Therm ocou p le, RTD & Therm istor Probes, Connectors, Panels & Assem blies  
þ Wire: Therm ocou p le, RTD & Therm istor  
þ Calibrators & Ice Point References  
þ Record ers, Controllers & Process Monitors  
þ Infrared Pyrom eters  
PRESSURE, STRAIN AND FORCE  
þ Transd u cer & Strain Gau ges  
þ Load Cells & Pressu re Gau ges  
þ Disp lacem ent Transd u cers  
þ Instru m entation & Accessories  
FLOW/LEVEL  
þ Rotam eters, Gas Mass Flow m eters & Flow Com p u ters  
þ Air Velocity Ind icators  
þ Tu rbine/ Pad d lew heel System s  
þ Totalizers & Batch Controllers  
pH/CONDUCTIVITY  
þ p H Electrod es, Testers & Accessories  
þ Benchtop / Laboratory Meters  
þ Controllers, Calibrators, Sim u lators & Pu m p s  
þ Ind u strial p H & Cond u ctivity Equ ip m ent  
DATA ACQUISITION  
þ Data Acqu isition & Engineering Softw are  
þ Com m u nications-Based Acqu isition System s  
þ Plu g-in Card s for Ap p le, IBM & Com p atibles  
þ Datalogging System s  
þ Record ers, Printers & Plotters  
HEATERS  
þ H eating Cable  
þ Cartrid ge & Strip H eaters  
þ Im m ersion & Band H eaters  
þ Flexible H eaters  
þ Laboratory H eaters  
ENVIRONMENTAL  
MONITORING AND CONTROL  
þ Metering & Control Instru m entation  
þ Refractom eters  
þ Pu m p s & Tu bing  
þ Air, Soil & Water Monitors  
þ Ind u strial Water & Wastew ater Treatm ent  
þ p H , Cond u ctivity & Dissolved Oxygen Instru m ents  
M-3241  
8
 

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