IET Labs HPRS Series Troubleshooting guide

PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT 
Email: inf[email protected]
TEL: [phone] • FAX: [phone]
www.ietlabs.com
IET LABS, INC.
Copyright © 2018 IET Labs, Inc.
Visit www.ietlabs.com for manual revision updates
HPRS im/Sept. 2018
HPRS SERIES
High-Power Decade
Resistance Substituter
User and Service Manual

Email: inf[email protected]
TEL: [phone] • FAX: [phone]
www.ietlabs.com
IET LABS, INC.

3
HPRS Series
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 specifi cations. 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 specifi cations 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,
INCLUDING BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR
FITNESS FOR ANY PARTICULAR PURPOSE.

4
HRRS Series
Revision History:
Date Description By
March 2013 Initial release LB
Sept 2018 Major update for standardization of marking
and required information in the manual
BB

5
HRRS Series
SAFETY SUMMARY
The following general safety precautions must be observed during all phases of operation,
service, and repair of this instrument. Failure to comply with these precautions or with
specifi c WARNINGS elsewhere in this manual may impair the protection provided by the
equipment. Such noncompliance would also violate safety standards of design, manufacture,
and intended use of the instrument.
IET Labs assumes no liability for the customer’s failure to comply with these precautions.
The HPRS Series comply with INSTALLATION CATEGORY I as well as POLLUTION
DEGREE 2 as defi ned in IEC61010-1.
Voltages of up to 1000 Vdc maybe present at measurement terminals.
If an instrument is marked CAT I (IEC Measurement Category I), or it is not marked with a
measurement category, its measurement terminals must not be connected to line-voltage
mains and it is not designed for use as for measurements within measurement categories
II, III and IV,
The HPRS Series are an indoor use product.
DANGEROUS PROCEDURE WARNINGS
Comply with all WARNINGS - Procedures throughout in this manual prevent you from
potential hazard. These instructions contained in the warnings must be followed.
BEFORE APPLYING POWER
Verify that all safety precautions are taken. Make all connections to the instrument
before applying power. Note the instrument’s external markings described under “Safety
Symbols”.
GROUND THE INSTRUMENT
This is a Safety Class I instrument. To minimize shock hazard, the instrument chassis and
cabinet must be connected to an electrical ground. The power terminal and the power
cable must meet International Electrotechnical Commission (IEC) safety standards.

6
HRRS Series
SAFETY SUMMARY CONTINUED
CAUTION
• DO NOT Operate in an Explosive Atmosphere
• DO NOT operate the instrument in the presence of infl ammable gasses or fumes
• Operation of any electrical instrument in such an environment clearly constitutes a
safety hazard
• Use Caution around live circuits
• To prevent electrical shock operators must not remove instrument covers
• Component replacement and internal adjustments must be made by qualifi ed
maintenance personnel only
• DO NOT substitute parts or modify the instrument
• There are no user serviceable parts inside.
• Refer servicing to qualifi ed personnel.
• Only replaced fuses with correct size and rating to prevent electrical shock
To avoid the danger of introducing additional hazards, do not install substitute parts or perform
unauthorized modifi cations to the instrument.
Return the instrument to an IET Labs for service and repair to ensure that safety features are
maintained in operational condition.

7
HRRS Series
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 qualifi ed 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.

Contents
WARRANTY ............................................................................................ 3
Revision History ....................................................................................... 4
Safety Summary ........................................................................................ 5
WARNING ................................................................................................ 7
Chapter 1
INTRODUCTION ............................................................................ 9
Chapter 2
SPECIFICATIONS ........................................................................ 10
Chapter 3
INSTALLATION .......................................................................... 12
3.1 Initial Inspection ................................................................. 12
3.2 Installation .......................................................................... 12
3.3 Storage ................................................................................ 12
Chapter 4
OPERATION .................................................................................. 13
4.1. General Considerations ....................................................... 13
4.2 Duty Cycle ........................................................................... 13
4.3 Electrical Considerations ..................................................... 13
4.4 Dial Setting .......................................................................... 13
4.5 Environmental Conditions ................................................... 13
Chapter 5
MAINTENANCE ........................................................................... 14
5.1 Preventive Maintenance ....................................................... 14
5.2 Verifi cation of Performance ................................................. 14
5.2.1 Calibration Interval ..................................................... 14
5.2.2 General Considerations ............................................... 14
5.2.3 Procedure ..................................................................... 14
5.3 Schematic and Replacement Parts ....................................... 15
5.4 Troubleshooting .................................................................. 15
5.5 Disassembly, Component Replacement, and Reassembly ... 15
5.5.1 Disassembly ................................................................ 15
5.5.2 Component Replacement ............................................ 15
5.5.3 Reassembly .................................................................. 15
5.6 Customer Service ................................................................ 15
5.7 Instrument Return ............................................................... 16

9
INTRODUCTION
HPRS Series
Chapter 1
INTRODUCTION
The High-Power Decade Resistance Substituter
(HPRS) Series is a family of instruments off ering a
broad choice of high-power, excellent-performance
resistance sources (Figure 1.1). High-power resistors
are made available without sacrifi cing other electrical
properties. Any number of decades is available in a
choice of two accuracies.
The HPRS Series employs state-of-the-art precision
resistors of various types for high accuracy, high
stability, and low temperature and power coeffi cients-
of-resistance.
The standard models off er a choice of three to nine
decades. The panels are clearly labeled showing the
step size and maximum voltage and current limita-
tions for each decade.
With a resolution as low as 1 m and a maximum
resistance of 10 M , the HPRS Series may be used
as a general purpose substituter as well as a high-
power load for testing power supplies and for other
high-power applications.
Applications include calibration of meters and instru-
ments. HPRS instruments are useful development
tools wherever precise resistances with high-power
handling capacity are required.
It is important to keep the amount of time power is
applied the the HPRS within the duty cycles below.
The duty cycles assume an ambient temperature of
around 230C.
Power Time on Time off
<101 W continuous none
>101 W 5 minutes 10 minutes
Exceeding the time on can cause damage to the
resistors.
If continuous use is required to full rated power see
DRS-900 High Power Resistance Substituter.
Figure 1.1 DRS-900 High-Power Decade
Resistance Substituter
The HPRS series complements the HRRS and HARS
series, providing resistance steps as low as 1 m The
units may be rack-mounted to serve as components
in measurement and control systems.
This series is part of a family of resistance substitut-
ers suited to fi ll many engineering and testing needs.
Consult IET for:
High power substituters - up to 400 W
High resistance substituters - to 1 T
RTD simulators
Laboratory-standard-gradesubstituters- to 20 ppm
accuracy
Programmable substituters - IEEE-488, USB or
Ethernet.
Figure 1.2 HPRS Series High-Power Decade
Resistance Substituter

10 SPECIFICATIONS
HPRS Series
Chapter 2
SPECIFICATIONS
ORDERING INFORMATION
Model*
(1.0% accuracy shown)
Total
resistance
()
No of
Dials
Resolution
()
HPRS-F-3-0.001 0.999 3 0.001
HPRS-F-3-0.01 9.99 3 0.01
HPRS-F-3-0.1 99.9 3 0.1
HPRS-F-3-1 999 3 1
HPRS-F-3-10 9.99 k 310
HPRS-F-3-100 99.9 k 3 100
HPRS-F-3-1K 999 k 31k
HPRS-F-3-10K 9.99 M 3 10 k
HPRS-F-4-0.001 9.999 4 0.001
HPRS-F-4-0.01 99.99 4 0.01
HPRS-F-4-0.1 999.9 4 0.1
HPRS-F-4-1 9.999 k 4 1
HPRS-F-4-10 99.99 k 4 10
HPRS-F-4-100 999.9 k 4 100
HPRS-F-4-1K 9.999 M 4 1 k
HPRS-F-5-0.001 99.999 5 0.001
HPRS-F-5-0.01 999.99 5 0.01
HPRS-F-5-0.1 9.999 9 k 5 0.1
HPRS-F-5-1 99.999 k 5 1
HPRS-F-5-10 999.99 k 5 10
HPRS-F-5-100 9.999 9 M 5 100
Model*
(1.0% accuracy shown)
Total
resistance
()
No of
Dials
Resolution
()
HPRS-F-6-0.001 999.999 6 0.001
HPRS-F-6-0.01 9.999 99 k 6 0.01
HPRS-F-6-0.1 99.999 9 k 6 0.1
HPRS-F-6-1 (HPRS-150) 999.999 k 6 1
HPRS-F-6-10 9.999 99 M 6 10
HPRS-F-7-0.001 9.999 999 k 7 0.001
HPRS-F-7-0.01 (HPRS-200) 99.999 99 k 7 0.01
HPRS-F-7-0.1 999.999 9 k 7 0.1
HPRS-F-7-1 9.999 999 M 7 1
HPRS-F-0.001 99.999 999 k 8 0.001
HPRS-F-8-0.01 999.999 99 k 8 0.01
HPRS-F-8-0.1 (HPRS-200W) 9.999 999 9 M 8 0.1
* For 0.5% accuracy, substitute "C" for "F" in part number
Options:
-RM for rack mountable version
For programmable versions see PRS-300 and PRS-200/202
Accuracy:
after subtraction of zero resistance, at 23°C; traceable to SI
Option F: ±(1% + 20 mΩ)
Option C: ±(0.5% + 20 mΩ)
Zero Resistance:
<5 mΩ per decade
Terminals:
Two fi ve-way binding posts and one ground post electrically
connected to case.
Dimensions:
43.9 cm W x 8.9 cm H x 10.2 cm D (17.3" W x 3.5" H x 4" D)
Weight:
2.4 kg (5.3 lbs), nominal
SPECIFICATIONS
Resistance
per step
Total
decade
resistance
Max
current*
Max power
per step*
(W)
Temperature
coefficient
(ppm/°C)
Resistor
Type
1 m0.009 8 A 0.036 ±50
Resistance
Wire
10 m0.09 6 A 0.36 ±50
100 m0.9 6 A 3.6 ±20
1 9 5 A 25 -20 to +80
Power
Film
10 90 1.5 A 25 -20 to +80
100 900 0.5 A 25 -20 to +80
1 k9 k150 mA† 25† -20 to +80
10 k90 k50 mA† 25† -20 to +80
100 k900 kV limit† V limit† -20 to +80 Wirewound/
metal film
1 M9 MV limit† V limit† ±50 Wirewound/film
*Subject to maximum of 250 W max. per unit
†Subject to 1000 V (dc+ac) peak max

11
SPECIFICATIONS
HPRS Series
Figure 2.1. Typical Operating Guide Affixed to Unit
1 mȍ0.009 ȍ8 A 0.036 ±50
10 mȍ0.09 ȍ6 A 0.36 ±50
100 mȍ0.9 ȍ6 A 3.6 ±20
1 ȍ9 ȍ5 A 25 -20 to +80 10 ȍ90 ȍ1.5 A 25 -20 to +80 100 ȍ900 ȍ0.5 A 25 -20 to +80
1 kȍ9 kȍ150 mA†25†-20 to +80
10 kȍ90 kȍ50 mA†25†-20 to +80 100 kȍ900 kȍV limit†V limit†-20 to +80 Wirewound/
metal film
1 Mȍ9 MȍV limit†V limit†±50 Wirewound/film
*Subject to maximum of 250 W per unit †Subject to 1000 V (dc+ac) peak max
Max
current*
Power
Film
Resistance
per step Power
per step*
(W)
Resistance
Wire
Temp.
coeffieient
(ppm/°C)
Resistor
type
Total
decade
resistance
MODEL: HPRS-F-6-0.1
SN: E1-18361535
Accuracy:
at 23°C; traceable to SI HPRS-F Series: ±(1% + 20 mΩ) after subtraction of zero resistance HPRS-C Series: ±(0.5% + 20 mΩ) after subtraction of zero resistance
Zero Resistance:
<5 mΩper decade
Terminals:
Two five-way binding posts and one ground post electrically connected to case.
HPRS SERIES HIGH POWER DECADE RESISTANCE SUBSTITUTER
WARNING
Observe all safety rules when working with high voltages or line voltages. Connect the (G) terminal to earth ground in order to maintain the case at a safe voltage. Whenever hazardous voltages (>45 V) are used, take all measures to avoid accidental contact with any live components: a) Use maximum insulation and minimize the use of bare conductors. b) Remove power when adjusting switches. c) Post warning signs and keep personnel safely away.
HPRSLBL/p1/HPRS-genl/62%/03-22-13
IET LABS, INC.IET LABS, INC. IET LABS, INC.IET LABS, INC.
IET LABS, INC.
CAGE CODE: 62015
CONSULT INSTRUCTION MANUAL FOR PROPER INSTRUMENT OPERATION
WARNING
BURN HAZARD
CASE MAY BE HOT UNDER POWER
Long Island, NY • Email: [email protected] • [phone]• Fax: [phone]
www.ietlabs.com
HPRS SERIES HIGH POWER DECADE RESISTANCE SUBSTITUTER

12
INSTALLATION
HPRS Series
Chapter 3
INSTALLATION
3.1 Initial Inspection
IET instruments receive a careful mechanical and
electrical inspection before shipment. Upon receipt,
verify that the contents are intact and as ordered.
The instrument should then be given a visual and
operational inspection.
If any shipping damage is found, contact the carrier
and IET Labs. If any operational problems are en-
countered, contact IET Labs and refer to the warranty
at the beginning of this manual. IET Labs will work
with you until you are satisfi ed that your instrument
is operating to fulfi ll the needs of your applications.
Save all original packing material for convenience
in case shipping of the instrument should become
necessary.
3.2 Installation
For a rack-mounted model, installation in a 19-inch
rack may be made using the slots in the rack mounting
ears. A mounting location that does not expose the
unit to excessive heat is recommended.
For bench models, no installation as such is required,
because this instrument series is not powered. Since
it is a high-accuracy instrument, bench space should
be provided that will not expose it to abuse and keep
it protected from temperature extremes and contami-
nants.
3.3 Storage
If this instrument is to be stored for any lengthy
period of time, it should be sealed in plastic and
stored in a dry location. It should not be subjected
to temperature extremes beyond the specifi cations.
Extended exposure to such temperatures can result
in an irreversible change in resistance, and require
repair and/or recalibration

13
OPERATION
HPRS Series
Chapter 4
OPERATION
4.1 General Considerations
The HPRS Series Decade unit provides three termi-
nals labeled H (high), L (low), and G (ground.) The
H and L terminals are connected to the ends of the
resistor being set. the G terminal is connected to the
case. The G terminal may be used as a guard or shield
terminal. It may also be connected using a shorting
link to either terminal to allow two-terminal as op-
posed to three-terminal measurement. See Figure 5.1.
In order to make proper use of the full performance
capabilities of the HPRS unit, especially if low re-
sistance or high power are important, take care in
connecting to the terminals of the decade box.
In order to keep contact resistance to a minimum,
make the most substantial and secure connection to
the binding posts. They accept banana plugs, tele-
phone tips, spade lugs, alligator clips, and bare wire.
The largest or heaviest mating connection should be
made, and, where applicable, the binding post should
be securely tightened.
4.2 Duty Cycle
It is important to keep the amount of time power is
applied the the HPRS within the duty cycles below.
The duty cycles assume an ambient temperature of
around 230C.
Power Time on Time off
<101 W continuous none
>101 W 5 minutes 10 minutes
Exceeding the time on can cause damage to the resis-
tors. If continuous use is required to full rated power
see DRS-900 High Power Resistance Substituter.
4.3 Electrical Considerations
As a good safety practice, the case should be grounded
using the G terminal.
Since high voltages may be present, it is important to
observe all precautions and safety rules.
• CONNECT THE G (GND) TERMINAL TO
EARTH OR OTHER SUITABLE GROUND IN
ORDER TO MAINTAIN THE CASE AT A SAFE
VOLTAGE.
• 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.
• - REMOVE POWER WHEN SETTING
SWITCHES.
• EXERCISE CARE WHEN HANDLING UNIT.
CASE - ESPECIALLY REAR AND BOTTOM
MAY BECOME HOT IF HIGH POWER IS AP-
PLIED FOR AN EXTENDED PERIOD.
• POST WARNING SIGNS AND KEEP
PERSONNEL SAFELY AWAY.
4.4 Dial Setting
Whenever the dials are used for positions 0-9, the
resulting resistance is simply read from the panel dial
setting directly. Both the decimal point and the steps
are clearly marked on the panel.
4.5 Environmental Conditions
For optimal accuracy, the decade box should be used
in an environment near 230C and <50% RH. It should
be allowed to stabilize at those conditions for at least
two hours after any signifi cant temperature variation.

14 MAINTENANCE
HPRS Series
Chapter 5
MAINTENANCE
5.1 Preventive Maintenance
The HPRS Decade Substituter is packaged in a ven-
tilated case. If it is maintained in a generally clean
or air-conditioned environment, cleaning will seldom
be necessary. In a contaminated atmosphere, cleaning
may be required.
To maintain optimal accuracy and stability, it is best
not to open the case of the unit. In normal service,
the switches require no additional lubrication. Dur-
ing the manufacturing process, a light lubrication is
applied which in most instances is suffi cient for the
service life of the switches, and yet will not tend to
collect dust.
5.2 Verification of Performance
5.2.1 Calibration Interval
The HPRS Series instruments should be verifi ed for
performance at a calibration interval of twelve (12)
months. This procedure may be carried out by the
user, if a calibration capability, is available, by IET
Labs, or by a certifi ed calibration laboratory. If the
user should choose to perform this procedure, then
the considerations below should be observed.
5.2.2 General Considerations
It is important, whenever testing the HPRS Series
Decade Units, to be very aware of the capabilities
and limitations of the test instruments used. There
are a some bridges and direct reading resistance me-
ters or digital multimeters available that can verify
the accuracy of these units, especially when used in
conjunction with standards that can serve to confi rm
or improve the accuracy of the testing instrument.
Such instruments would have to be significantly more
accurate than the specifi ed accuracies for all appli-
cable ranges, in order to perform this task, allowing
for a band of uncertainty of the instrument itself. A
few commercial models, bridges and meters, do exist
that can do this; consult IET Labs for information.
It is important to allow both the testing instrument
and the HPRS Substituter to stabilize for a number of
hours at the nominal operating temperature of 230C,
and at < 50% RH. There should be no temperature
gradients across the unit under test.
Proper metrology practices should be followed in
performing this verifi cation.
5.2.3 Procedure
1. Confi rm the zero resistance of the unit.
2. Determine the allowable upper and lower
limits for each resistance setting of each de-
cade following the specifi ed accuracy given
in the Specifi cations Section of Chapter 2.
3. Confi rm that the resistances fall within these
limits.
4. If any resistances fall outside these limits, the
associated switch assembly may be trimmed,
repaired or replaced.

15
MAINTENANCE
HPRS Series
5.3 Schematic and Replacement Parts
Refer to Figure 5.1 for a basic schematic of the HPRS
decade unit.
If you must order parts, give the model number and
serial number from the bottom label. and a detailed
description of the part or assembly.
5.4 Troubleshooting
If the verifi cation procedure results in a failure, disas-
semble the unit as described below, and examine the
parts in question to determine the necessary repair
or replacement.
5.5 Disassembly, Component
Replacement, and Reassembly
It is recommended that service be performed only by
IET Labs or by qualifi ed personnel.
5.5.1 Disassembly
Referring to Figure 5.2 to locate part numbers, pro-
ceed as follows:
1. Work in a clean environment.
2. Place the instrument on a fl at surface and remove
the 4 housing screws from the bottom of the instru-
ment. The housing may now be removed.
5.5.2 Component Replacement
Determine and locate any faulty component that
requires replacement.
To remove a decade switch assembly proceed as
follows:
1. Label and unsolder the bus wires connecting the
switch assembly to the resistive loads.
2. Loosen the screw holding the knob on the switch
shaft and remove the knob.
3. Remove the nut holding the switch assembly on
the front panel and remove the assembly.
4. Replace the assembly by reversing the above steps,
making certain that the knob screw is aligned with
the fl at portion of the switch shaft.
5.5.3 Reassembly
1. Make certain that the 4 standoff s have not become
loose; tighten as required.
2. Replace the housing: line up the holes in the
standoff s with the holes in the case, and install the 4
housing screws.
5.6 Customer Service
The IET warranty attests to the quality of materials
and workmanship in our products. For application
assistance or if diffi culties occur, our engineers will
assist in any way possible. If you cannot eliminate the
diffi culty, please e-mail, FAX, or phone our Service
Department, giving full information of the trouble
and of steps taken to remedy it. Be sure to include
the type and serial number of the instrument.
Call 516-334-5959 for technical support or customer
service
www.ietlabs.com

16 MAINTENANCE
HPRS Series
5.7 Instrument Return
Before returning an instrument to IET for service
please call our Service Department at 516-334-5959
for Return Material Authorization (RMA) or visit
www.ietlabs.com to request an RMA online.
Include a Purchase Order Number to insure expedi-
ent processing.
Units under warranty will be repaired at no charge.
For any questions on repair costs or shipment instruc-
tions, please contact our Service Department at the
above number or visit www.ietlabs.com to request
an RMA online.
To safeguard an instrument during shipment, please
use packaging that is adequate to protect it from
damage, (i.e., equivalent to the original packaging)
and mark the box “Delicate Electronic Instrument”.
Return material should be sent freight prepaid to:
IET Labs, Inc.
1202 VFW Parkway
West Roxbury, MA 02132
Attention: RMA #

17
MAINTENANCE
HPRS Series
Figure 5.1. HPRS Series Schematic Diagram