IET Labs PRS-202 Series User manual

♦PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT ♦
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www.ietlabs.com
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IET LABS, INC.
PRS-202 SERIES
High Precision
Manual or SCPI Programmable
Decade Resistance Substituters
Operation Manual
Copyright  2002 IET Labs, Inc.
PRS202 IEEE.2 im/October, 2002

CONTENTS
WARRANTY.......................................................................................................... i
WARNING ............................................................................................................ ii
CAUTION ............................................................................................................. ii
CONTENTS......................................................................................................... iii
FIGURES............................................................................................................. iv
TABLES............................................................................................................... iv
Chapter 1: INTRODUCTION ............................................................................... 1
Chapter 2: SPECIFICATIONS............................................................................. 3
2.1 Model Configuration and specifications ........................................................................ 3
2.2 General specifications ................................................................................................... 4
Chapter 3: OPERATION...................................................................................... 6
3.1 Initial inspection and setup ............................................................................................ 6
3.2 Connection .................................................................................................................... 6
3.2.1 General Considerations ................................................................................. 6
3.2.2 Electrical Considerations ............................................................................... 6
3.2.3 Four-Wire Kelvin Lead Connections............................................................. 6
3.2.4 Thermal emf Considerations ......................................................................... 6
3.3 Dial Setting .................................................................................................................... 7
3.4 Environmental Conditions ............................................................................................. 7
3.5 Local Operation ............................................................................................................ 7
3.6 Remote Operation ......................................................................................................... 7
Chapter 4: BCD INTERFACE OPTION .............................................................. 8
4.1 BCD Programming ....................................................................................................... 8
Chapter 5: IEEE INTERFACE OPTION ............................................................ 10
5.1 Introduction ................................................................................................................. 10
5.2 Capabilities .................................................................................................................. 10
5.3 Address Switch and Communications Settings ........................................................... 10
5.4 IEEE Option Operation ............................................................................................... 10
Chapter 6: SERIAL INTERFACE OPTION ....................................................... 11
6.1 Introduction .................................................................................................................. 11
6.2 Capabilities ................................................................................................................... 11
6.3 Signal Interface and Communications Settings ............................................................ 11
6.4 SERIAL Option Operation ........................................................................................... 11

Figures
Figure 1.1 PRS 202 Series High Precision Manual or Programmable
Decade Resistance Substituter ............................................................................ 1
FIGURE 2.1 Typical OPERATING GUIDEAffixed to Unit ...................................... 5
Tables
Table 3.1 BCD INPUT Connector ........................................................................... 8
Table 3.2 BCD INPUT Connector PinAssignments .................................................. 9
Table 4.1 Bus Address Switch Settings ............................................................................10
Chapter 7: PROGRAMMING ............................................................................ 12
7.1 Introduction ................................................................................................................. 12
7.2 Command String Structure .......................................................................................... 12
7.3 Advanced Programming - Software Drivers .............................................................. 13
7.3.1 Determining the PRS Configuration ............................................................ 13
7.3.2 Instrument Initialization ............................................................................... 13
7.3.3 Source Impedance ...................................................................................... 14
Chapter 8: MAINTENANCE .............................................................................. 15
8.1 Verification of Performance ....................................................................................... 15
8.1.1 Calibration Interval ...................................................................................... 15
8.1.2 General Considerations ............................................................................... 15
Appendix A ........................................................................................................ 16
SCPI Command Reference .............................................................................................. 16
Appendix B ........................................................................................................ 18
IEEE-488.2 Common Commands ..................................................................................... 18

WARNING
OBSERVE ALL SAFETY RULES
WHEN WORKING WITH HIGH VOLTAGES OR LINE VOLTAGES.
Dangerous voltages may be present inside this instrument. Do not open the case
Refer servicing to qulified personnel
HIGH VOLTAGES MAY BE PRESENT AT THE TERMINALS OF THIS INSTRUMENT
WHENEVER HAZARDOUS VOLTAGES (> 45 V) ARE USED, TAKE ALL MEASURES TO
AVOID ACCIDENTAL CONTACT WITH ANY LIVE COMPONENTS.
USE MAXIMUM INSULATION AND MINIMIZE THE USE OF BARE
CONDUCTORS WHEN USING THIS INSTRUMENT.
Use extreme caution when working with bare conductors or bus bars.
WHEN WORKING WITH HIGH VOLTAGES, POST WARNING SIGNS AND
KEEP UNREQUIRED PERSONNEL SAFELY AWAY.
CAUTION
DO NOT APPLY ANY VOLTAGES OR CURRENTS TO THE TERMINALS OF THIS
INSTRUMENT IN EXCESS OF THE MAXIMUM LIMITS INDICATED ON
THE FRONT PANEL OR THE OPERATING GUIDE LABEL.
WARRANTY
We warrant that this product is free from defects in material and workmanship and, when properly used, will
perform in accordance with applicable IET specifications. If within one year after original shipment, it is found
not to meet this standard, it will be repaired or, at the option of IET, replaced at no charge when returned to IET.
Changes in this product not approved by IET or application of voltages or currents greater than those allowed by
the specifications shall void this warranty. IET shall not be liable for any indirect, special, or consequential
damages, even if notice has been given to the possibility of such damages.
THIS WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR IMPLIED, INCLUD-
ING BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTIBILITY OR FITNESS FOR
ANY PARTICULAR PURPOSE.

1
INTRODUCTION
PRS-202 Series
Chapter 1
INTRODUCTION
The PRS-202 (Figure 1.1) Series is a broad line of
high precision manual and programmable decade
substituters. They provide straight resistance substi-
tution as well as RTD (Resistance Temperature De-
tector) simulation, in a wide selection of ranges, tol-
erances and ratings.
The PRS-202 substituter is a precision resistance
source with excellent characteristics of stability, tem-
perature coefficient, and power coefficient. High dy-
namic ranges are available, starting as low as 1 mΩ,
and extending to as many as 10 decades. These fea-
tures combined with a low virtually constant “zero
resistance” make for very versatile instruments.
The PRS-202 Series features two optional special
settings. An “open circuit” and a “short circuit”.
These modes are useful for obtaining reproducible
transitions between settings, i.e. break-before-make
or to short between settings. The “short circuit” set-
ting also provides a reduced zero resistance.
Operation is both local using convenient direct read-
ing front panel thumbwheel switches, and remote with
optional parallel BCD or IEEE-4888 interfaces. Both
can provide an optional extra “10” position for each
decade.
The PRS-202 Series employs very low resistance, low
thermal emf relays with gold clad silver alloy con-
tacts. A special design keeps contact resistance to a
minimum. The gold plating keeps the silver contacts
from becoming tarnished when unused, or when only
low currents are passed through them. This is most
often the case when only minute test currents are
drawn by digital multimeters and other test instru-
ments. Contact resistance remains low and repeat-
able.
High quality gold plated tellurium copper five-way
binding posts serve to minimize the thermal emf ef-
fects, which would artificially reflect a change in dc
resistance measurements. All other conductors within
the instrument, as well as the solder employed con-
tain no metals or junctions that could contribute to
thermal emf problems.
With a resolution as low as 1 mΩand a maximum
available resistance of over 100 MΩ, the PRS-202
Series may be used for exacting precision measure-
ment applications requiring high accuracy, good sta-
bility, and low zero resistance. They are suited for
automatic and manual calibration and testing, simu-
lation of RTD’S, programmable loads, and many other
laboratory and industrial applications.
The PRS-202 Series may be rack mounted to serve
as components in measurement and control systems.
Figure 1.1: High Precision Manual or
Programmable Decade Resistance Substituter

2INTRODUCTION
PRS-202 Series
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