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User’s Guide

DBX, DBQ, DBA, DBBHigh-Accuracy Decade Box

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i

Contents

Contents ................................................................................................. iWARNING ............................................................................................... iiCAUTION................................................................................................ iiChapter 1

INTRODUCTION .......................................................................... 1Chapter 2

SPECIFICATIONS ......................................................................... 2Chapter 3

OPERATION ................................................................................... 53.1 Initial Inspection and Setup .................................................... 53.2. Connection ............................................................................ 5

3.2.1 General Considerations ................................................. 53.2.2 Electrical Considerations ............................................... 53.2.3 Four-Wire Kelvin Lead Connections ............................. 53.2.4 Thermal emf Considerations ......................................... 63.3 Dial Setting ....................................................................... 6

3.4 Environmental Conditions ...................................................... 6Chapter 4

MAINTENANCE ............................................................................ 74.1 Verification of Performance ................................................... 7

4.1.1 Calibration Interval ........................................................ 74.1.2 General Considerations ................................................. 74.1.3 Procedure ...................................................................... 7

4.2 Schematic .............................................................................. 7

FiguresFigure 1.1 DBX Series High-Accuracy Decade Box .............................. 1Figure 2.1 Typical Operating Guide Affixed to Unit ................................. 4Figure 3.1 Optimal 4-Wire Kelvin Lead Connection ................................. 6Figure 4.1 DBX Series Schematic Diagram ............................................ 8

ii

WARNING

OBSERVE ALL SAFETY RULES‘WHEN WORKING WITH HIGH VOLTAGES OR LINE VOLTAGES.

ELECTRICAL SHOCK HAZARD. DO NOT OPEN CASE.REFER SERVICING TO QUALIFIED PERSONNEL.

HIGH VOLTAGE MAY BE PRESENT WITH HIGH VOLTAGE OPTIONS.

WHENEVER HAZARDOUS VOLTAGES (> 45 V) ARE USED, TAKE ALL MEASURES TOAVOID ACCIDENTAL CONTACT WITH ANY LIVE COMPONENTS:

- USE MAXIMUM INSULATION AND MINIMIZE THE USE OF BARECONDUCTORS.

REMOVE POWER WHEN HANDLING UNIT.

POST WARNING SIGNS AND KEEP PERSONNEL SAFELY AWAY.

CAUTION

DO NOT APPLY ANY VOLTAGES OR CURRENTS TO THE TERMINALS OF THISINSTRUMENT IN EXCESS OF THE MAXIMUM LIMITS INDICATED ON

THE FRONT PANEL OR THE OPERATING GUIDE LABEL.

1INTRODUCTION

Chapter 1

INTRODUCTION

The Omega DB series of resistance decade boxesis a family of instruments providing a very broad choiceof high-performance resistance sources. Any num-ber of decades from one to eleven is available in achoice of accuracies.

The Omega DB decade box is a precision resis-tance source with excellent characteristics of stabil-ity, temperature coefficient, power coefficient, andfrequency response.

The Omega DB Series employs very-low-resistanceswitches with silver alloy contacts. A special designkeeps zero resistance to less than 1 mΩ per decade.Self cleaning keeps the silver contacts from becom-ing tarnished when unused, or when only low cur-rents are passed through them. This is most often thecase when only minute test currents are drawn bydigital multimeters or other test instruments. Contactresistance is stable and remains low and repeatable.

High-quality gold-plated tellurium-copper binding postsserve to minimize the thermal emf effects which wouldartificially reflect a change in dc resistance measure-ments. All other conductors within the instrument, aswell as the solder employed, contain no metals or junc-

tions that could contribute to thermal emf problems.

The standard models offer a choice of one througheleven decades. The panels are clearly labeled show-ing the step size and maximum voltage and currentlimitations for each decade.

With a resolution as low as 1 mΩ and a maximumavailable resistance of over 111 MΩ, the Omega DBseries may be used for exacting precision measure-ment applications requiring high accuracy, good sta-bility, and low zero-resistance. They can be used ascomponents of dc and ac bridges, for calibration, astransfer standards, and as RTD simulators.

The Omega DB Series may be rack-mounted toserve as components in measurement and control sys-tems.

Figure 1.1. DBX Series High Accuracy Decade Box

2 SPECIFICATION

Chapter 2

SPECIFICATIONS

For convenience to the user, the pertinent specifications are given in an OPERATING GUIDE affixedto the case of the instrument. Figure 2.1 shows a typical example.

Accuracy: After subtraction of zero resistance, at 23°C;traceable to NIST.

DBX: ±(0.01% + 2 mΩ)

DBA: ±(0.05% + 2 mΩ)

DBQ: ±(0.02% + 2 mΩ)

Zero Resistance:

3SPECIFICATION

Total Res.(ΩΩΩΩΩ)

No. ofDecades

Model*(0.01% Accuracy)

DBX-1-0.001 0.01 1 0.001DBX-1-0.01 0.1 1 0.01DBX-1-0.1 1 1 0.1DBX-1-1 10 1 1DBX-1-10 100 1 10DBX-1-100 1 k 1 100DBX-1-1K 10 k 1 1 kDBX-1-10K 100 k 1 10 kDBX-1-100K 1 M 1 100 kDBX-1-1M 10 M 1 1 MDBX-1-10M 100 M 1 10 MDBX-2-0.001 0.11 2 0.001DBX-2-0.01 1.1 2 0.01DBX-2-0.1 11 2 0.1DBX-2-1 110 2 1DBX-2-10 1.1 k 2 10DBX-2-100 11 k 2 100DBX-2-1K 110 k 2 1 kDBX-2-10K 1.1 M 2 10 kDBX-2-100K 11 M 2 100 kDBX-2-1M 110 M 2 1 MDBX-3-0.001 1.11 3 0.001DBX-3-0.01 11.1 3 0.01DBX-3-0.1 111 3 0.1DBX-3-1 1.11 k 3 1DBX-3-10 11.1 k 3 10DBX-3-100 111 k 3 100DBX-3-1K 1.11 M 3 1 kDBX-3-10K 11.1 M 3 10 kDBX-3-100K 111 M 3 100 kDBX-4-0.001 11.11 4 0.001DBX-4-0.01 111.1 4 0.01DBX-4-0.1 1.111 k 4 0.1DBX-4-1 11.11 k 4 1

Resolution(ΩΩΩΩΩ)

Single Decade DBX Unit

SINGLE DECADE UNITS

ORDERING INFORMATION

Single-decade units are available withresistance as low as 1 mΩ per step toas high as 10 MΩ per step. These unitssatisfy many system applications re-quiring only a single decade whilemaintaining all the quality features ofthe DB series.

Each decade is enclosed in an alumi-num case which can serve as a shield.

It may be panel mounted and inte-grated with additional units to formpotentiometer circuits or other con-figurations.

Each unit consists of low-inductanceresistors in series, with a high-perfor-mance solid-silver-alloy-contactswitch.

* For less exacting applications, more economical tolerances are available:- For 0.02% accuracy substitute DBQ in part number in lieu of DBX- For 0.05% accuracy substitute DBA in part number in lieu of DBX- For 0.1% accuracy substitute DBB in part number in lieu of DBX

OPTIONS- RM Rack mountable case for standard 19" rack- K Kelvin type 4-terminal binding posts- RO Rear output binding posts

DBX-4-10 111.1 k 4 10DBX-4-100 1.111 M 4 100DBX-4-1K 11.11 M 4 1 kDBX-4-10K 111.1 M 4 10 kDBX-5-0.001 111.11 5 0.001DBX-5-0.01 1.1111 k 5 0.01DBX-5-0.1 11.111 k 5 0.1DBX-5-1 111.11 k 5 1DBX-5-10 1.1111 M 5 10DBX-5-100 11.111 M 5 100DBX-5-1K 111.11 M 5 1 kDBX-6-0.001 1.111 11 k 6 0.001DBX-6-0.01 11.1111 k 6 0.01DBX-6-0.1 111.111 k 6 0.1DBX-6-1 1.111 11 M 6 1DBX-6-10 11.1111 M 6 10DBX-6-100 111.111 M 6 100DBX-7-0.001 11.111 11 k 7 0.001DBX-7-0.01 111.1111 k 7 0.01DBX-7-0.1 1.111 111 M 7 0.1DBX-7-1 11.111 11 M 7 1DBX-7-10 111.1111 M 7 10DBX-8-0.001 111.111 11 k 8 0.001DBX-8-0.01 1.111 111 1 M 8 0.01DBX-8-0.1 11.111 111 M 8 0.1DBX-8-1 111.111 11 M 8 1DBX-9-0.001 1.111 111 11 M 9 0.001DBX-9-0.01 11.111 111 1 M 9 0.01DBX-9-0.1 111.111 111 M 9 0.1DBX-10-0.001 11.111 111 11 M 10 0.001DBX-10-0.01 111.111 111 1 M 10 0.01DBX-11-0.001 111.111 111 11 M 11 0.001

Total Res.(ΩΩΩΩΩ )

No. ofDecades

Model*(0.01% Accuracy)

Resolution(ΩΩΩΩΩ )

4S

PE

CIF

ICA

TIO

N

CONSULT INSTRUCTION MANUAL FOR PROPER INSTRUMENT OPERATIONDBX SERIES HIGH ACCURACY DECADE BOX

Temperature Coefficient:

5OPERATION

Chapter 3

OPERATION3.2.2 Electrical Considerations

In order to make proper use of the full performancecapabilities of the DBX unit, especially if low resis-tance or low-resistance increments are important,care must be taken in connecting to the terminals ofthe decade box.

In particular, in order to keep contact resistance toa minimum, the most substantial and secure connec-tion to the binding posts should be made. They ac-cept banana plugs, telephone tips, spade lugs, alli-gator clips, and bare wire. The largest or heaviestmating connection should be made, and, where ap-plicable, the binding posts should be securely tight-ened.

These considerations may be relaxed wheneversingle milliohms are considered significant for the taskbeing performed.

3.2.3 Four-Wire Kelvin Lead Connections

Whenever possible, 4-wire Kelvin leads, the idealconnection, should be employed. Such a connec-tion minimizes the effects of contact resistance andapproaches ideal performance.

If the four terminals are available as clamps similarto alligator clips, they may be connected to the necksof the binding posts. If the four terminals are avail-able separately, the optimal connection is shown inFigure 3.1, where the current leads are introducedinto the top of the binding posts, and the voltageleads at the necks.

3.1 Initial Inspection and Setup

This instrument was carefully inspected before ship-ment. It should be in proper electrical andmechanical order upon receipt.

An OPERATING GUIDE is attached to the caseof the instrument to provide ready reference to speci-fications.

3.2 Connection

3.2.1 General Considerations

The DBX Series Decade unit provides three termi-nals labeled H (high), L (low), and G (ground). TheH and L terminals are connected to the ends of theresistance being set; the G terminal is connected tothe case. The G terminal may be used as a guard orshield terminal. It may also be connected (using ashorting link) to either terminal to allow two-termi-nal as opposed to three-terminal measurements.

In order to make the most stable measurements,determine which is the more sensitive of the two userleads, i.e. the one going into a higher impedance.This lead should be connected to the more protectedone of the two DBX terminals. That would eitherbe the DBX terminal that is shorted to the case, orthe LOW DBX terminal whenever neither is con-nected to the case.

6 OPERATION

3.2.4 Thermal emf Considerations

The highest-quality low-ernf components are usedin the DBX Series. There nevertheless may be someminute thermal emf generated at the test leads wherethey contact the gold banana jacks.

This emf will not reflect itself if an ac measurementinstrument is employed. It will also be eliminated if ameter with so called “True Ohm” capability is used.Otherwise it may represent itself as a false compo-nent of the dc resistance measurement.

3.3 Dial Setting

Whenever the dials are used in positions 0-9, theresulting resistance is simply read directly. Both thedecimal point and the steps are clearly marked onthe panel.

For additional flexibility and range, each decade pro-vides a “10” position setting. This “10” position onany one decade equals the “1” position on the nexthigher decade. It adds about 11% to the nominaltotal decade resistance.

To determine the resistance obtained when one ormore “10” settings are used, simply add “1” to thenext higher decade. For example, a setting of3-6-10-0-10 Ω becomes:

3 3 0 0 0 06 6 0 0 0

10 1 0 0 00 0 0

10 1 0 ____________________________

TOT 3 7 0 1 0

and a setting of 10-10-10-l0-10.10 Ωbecomes:

10 1 0 0 0 0 0.010 1 0 0 0 0.010 1 0 0 0.010 1 0 0.010 1 0.0

.10 1.0 ________________________________

TOT 1 1 1 1 1 1.0

3.4 Environmental Conditions

For optimal accuracy, the decade box should be usedin an environment of 23oC. It should be allowed tostabilize at that temperature after any significant tem-perature variation.

Humidity should be maintained at laboratory condi-tions. This is especially important if high resistancesare involved.

Figure 3.1 Optimal 4-Wire Kelvin Lead Connection

7MAINTENANCE

Chapter 4

MAINTENANCE

4.1 Verification of Performance

4.1.1 Calibration Interval

The DB Series instruments should be verified forperformance at a calibration interval of twelve (12)months. This procedure may be carried out by theuser if a calibration capability is available, by Omega,or by a certified calibration laboratory.

If the user should choose to perform this procedure,then the considerations below should be observed.

4.1.2 General Considerations

It is important, whenever testing the DBX SeriesDecade Units, to be very aware of the capabilitiesand limitations of the test instruments used. A resis-tance bridge may be employed, and there are di-rect-reading resistance meters or digital multimetersavailable that can verify the accuracy of these units,especially when used in conjunction with standardsthat can serve to confirm or improve the accuracyof the testing instrument

Such test instruments must be significantly more ac-curate than ±(l00ppm+2 mΩ) for all applicableranges, allowing for a band of uncertainty of the in-strument itself. A number of commercial bridges andmeters exist that can perform this task; consultOmega.

It is important to allow both the testing instrumentand the DBX Substituter to stabilize for a numberof hours at the nominal operating temperature of23OC, and at nominal laboratory conditions of hu-midity. There should be no temperature gradientsacross the unit under test.

Substantial Kelvin type 4-wire test terminals shouldbe used to obtain accurate low-resistance readings.It is convenient, once the zero resistance has beendetermined, to subtract it from the remaining mea-surements. This can be automatically done in manyinstruments which have an offset subtraction capa-bility.

4.1.3 Procedure

1. Confirm the zero resistance of the unit.2. Determine the allowable upper and lower

limits for each resistance setting of each decadefollowing the specified accuracy. For theDBX series, these limits for any resistance“R” are [R±(0.0001 R + 2 mΩ)]. For the A,B, or Q series, see specifications.

3. Confirm that the resistances fall within theselimits after subtraction of the zero resistance.

4. If any resistances fall outside these limits, theassociated switch assembly may requirereplacement.

4.2 SchematicRefer to Figure 4.1 for a schematic of the DB de-cade unit.

8 MAINTENANCE

Figure 4.1. DB Series Schematic Diagram

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WARRANTY/DISCLAIMEROMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship for aperiod of 25 months from date of purchase. OMEGA’s WARRANTY adds an additional one (1) monthgrace period to the normal two (2) year product warranty to cover handling and shipping time. Thisensures that OMEGA’s customers receive maximum coverage on each product. If the unit malfunctions, it must be returned to the factory for evaluation. O M E G A’s Customer ServiceDepartment 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 nocharge. O M E G A’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 operatingconditions outside of O M E G A’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 anydamages that result from the use of its products in accordance with information provided byOMEGA, either verbal or written. OMEGA warrants only that the parts manufactured by it will beas specified and free of defects. OMEGA MAKES NO OTHER WARRANTIES OR R E P R E S E N TATIONS OF ANY KIND WHATSOEVER, EXPRESS OR IMPLIED, EXCEPT THAT OF TITLE,AND ALL IMPLIED WARRANTIES INCLUDING ANY WARRANTY OF MERCHANTABILITY AND FITNESS FOR A PA RTICULAR PURPOSE ARE HEREBY DISCLAIMED. LIMITATION OF L I A B I L I T Y: 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 “BasicComponent” under 10 CFR 21 (NRC), used in or with any nuclear installation or activity; or (2) in medicalapplications or used on humans. Should any Product(s) be used in or with any nuclear installation ora c t i v i t y, medical application, used on humans, or misused in any way, OMEGA assumes no responsibilityas set forth in our basic WA R R A N TY/ DISCLAIMER language, and, additionally, purchaser will indemnifyOMEGA and hold OMEGA harmless from any liability or damage whatsoever arising out of the use of theProduct(s) in such a manner.

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FOR WARRANTY RETURNS, please have the following information available BEFORE contacting OMEGA:1 . Purchase Order number under which the product

was PURCHASED,2. Model and serial number of the product under

warranty, and3. Repair instructions and/or specific problems

relative to the product.

FOR NON-WARRANTY REPAIRS, consult OMEGAfor current repair charges. Have the followinginformation available BEFORE contacting OMEGA:1. Purchase Order number to cover the COST

of the repair,2. Model and serial number of the product, and3. 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 affordsour customers the latest in technology and engineering.OMEGA is a registered trademark of OMEGA ENGINEERING, INC.© Copyright 2001 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 theprior written consent of OMEGA ENGINEERING, INC.

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Omega im bk 02-02.pdfContentsContents iCAUTION Chapter 1Chapter 2 SPECIFICATIONS Chapter 33.1 Initial Inspection and Setup 53.2.1 General Considerations 5 3.2.2 Electrical Considerations 3.4 Environmental Conditions 6Chapter 4 4.1.1 Calibration Interval 4.1.3 Procedure 4.2 Schematic