IET Labs HRRS SERIES Troubleshooting guide

HRRS SERIES
High Resistance
Decade Substituter
User and Service Manual
♦PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT ♦
TEL: [phone] • [phone] • FAX: [phone]
www.ietlabs.com
534 Main Street, Westbury, NY 11590
IET LABS, INC.
Copyright © 2001 IET Labs, Inc.
HRRS im/February, 2001

iii
HRRS 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 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.

iv
HRRS Series
Contents
WARRANTY ..........................................................................................iii
Contents ............................................................................................... iv
Figures and Tables .................................................................................... v
WARNING .............................................................................................. vi
CAUTION ............................................................................................... vi
Chapter 1
INTRODUCTION ............................................................................ 1
Chapter 2
SPECIFICATIONS .......................................................................... 2
Chapter 3
INSTALLATION .............................................................................. 4
3.2 Initial Inspection ................................................................... 4
3.2 Installation ............................................................................ 4
3.3 Repackaging for Shipment ................................................... 4
3.4 Storage .................................................................................. 5
Chapter 4
OPERATION .................................................................................... 6
4.1. Connection ............................................................................ 6
4.1.1 General Considerations ................................................. 6
4.1.2 Electrical Considerations .............................................. 6
4.2 Dial Setting ............................................................................ 7
4.3 Environmental Conditions ..................................................... 7
Chapter 5
MAINTENANCE ............................................................................. 8
5.1 Preventive Maintenance ........................................................ 8
5.2 Verificaition of Performance.................................................. 8
5.2.1 Calibration Interval ....................................................... 8
5.2.2 General Considerations ................................................. 8
5.2.3 Procedure ...................................................................... 9
5.3 Schematic and Replacement Parts ......................................... 9
5.4 Troubleshooting .................................................................... 9
5.5 Disassembly, Component Replacement, and Reassembly .... 9
5.5.1 Disassembly .................................................................. 9
5.5.2 Component Replacement .............................................. 9
5.5.3 Reassembly ................................................................... 9

v
HRRS Series
Figures and Tables
Figure 1.1. HRRS Series High Resistance Decade Substituter ................ 1
Figure 2.1 Operating Guide Affixed to Unit ........................................... 3
Figure 5.1 HRRS Series Schematic Diagram ........................................ 10
Table 5.1 Model Reference Codes ......................................................... 11
Table 5.2 Replacement Parts List ........................................................... 11
Table 5.3 Commercial and Government Entity CAGE Codes ............... 12
Figure 5.2 Assembly Diagram ................................................................ 13

vi
HRRS Series
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 TO
AVOID ACCIDENTAL CONTACT WITH ANY LIVE COMPONENTS:
- USE MAXIMUM INSULATION AND MINIMIZE THE USE OF BARE
CONDUCTORS.
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 THIS
INSTRUMENT IN EXCESS OF THE MAXIMUM LIMITS INDICATED ON
THE FRONT PANEL OR THE OPERATING GUIDE LABEL.

1
INTRODUCTION
HRRS Series
Chapter 1
INTRODUCTION
The High Resistance Decade Substituter (HRRS Se-
ries) is a family of instruments offering a broad choice
of high range, excellent performance resistance
sources (Figure 1.1). High resistance value resistors
are made available without sacrificing other electri-
cal properties
The HRRS Series employs state of the art precision
resistors, of various types for high accuracy, high sta-
bility, and low temperature and voltage coefficients
of resistance.
The standard models offer a choice of one to seven
decades. The panels are clearly labeled showing the
step size and maximum voltage limitations for each
decade.
The binding posts are insulated with Kel-F high re-
sistance non moisture absorbing material to ascer-
tain that no leakage occurs between them.
With a resolution as low as 10 Ωand a maximum
available resistance of over 1 TΩ(= 1000 GW = 1000
kMΩ), the HRRS Series may be used for exacting
precision high value resistance applications. Maxi-
mum voltage capacities of 5 kV or higher are avail-
able. See Chapter 2.
Applications include calibration of meters and
meghommeters, checking of electrochemical and bio-
medical sensors and instruments. These instruments
are useful developments tool wherever small currents
and high resistances are required, such as insulation
testing, low power circuits, and high impedance am-
plifiers.
The HRRS series complements the HARS series
which provides resistance steps as low as 1 mΩ. The
units may be rack mounted to serve as components
in measurement and control systems.
Figure 1.1. HRRS Series High Resistance Decade
Substituter

2SPECIFICATIONS
HRRS Series
Chapter 2
SPECIFICATIONS
SPECIFICATIONS
HRRS-F-1-100G(-5KV) 1 T 1 100 G
HRRS-B-2-1M(-5KV) 110 M 2 1 M
HRRS-B-2-10M(-5KV) 1.1 G 2 10 M
HRRS-B-2-100M(-5KV) 11 G 2 100 M
HRRS-B-2-1G(-5KV) 110 G 2 1 G
HRRS-B-2-10G(-5KV) 1.1 T 2 10 G
HRRS-B-3-100K 111 M 3 100 k
HRRS-B-3-1M 1.11 G 3 1 M
HRRS-B-3-10M(-5KV) 11.1 G 3 10 M
HRRS-B-3-100M(-5KV) 111 G 3 100 M
HRRS-B-3-1G(-5KV) 1.11 T 3 1 G
HRRS-B-4-10K 111.1 M 4 10 k
HRRS-B-4-100K 1.111 G 4 100 k
HRRS-B-4-1M 11.11 G 4 1 M
HRRS-B-4-10M(-5KV) 111.1 G 4 10 M
Resolution
(Ω)
No.
of
Decades
Model*
(For 5 kV version add
-5KV where shown.)**
ORDERING INFORMATION
Total
Resistance
(Ω)
Zero Resistance: <3 mΩper decade at dc.
Operating Conditions: 10°C to 23 °C; <50% RH.
Terminals: Two five-way binding posts on 2 special, low leakage,
Kel-F insulating sockets and one metal ground post electrically
connected to the case.
Setting of value:
Standard: 11 positions, "0"-"10"; silver contacts, ceramic dielectric switch.
Single Decade Version See HARS-X data sheet.
OPTIONS
-RM Rack mountable case for standard 19" rack
-K Kelvin type 4-terminal binding posts
-RO Rear outputs
* Replace "B" with "Q" for higher grade accuracy;
replace "B" with "F" for 1% accuracy.
Resolution
(Ω)
No.
of
Decades
Model* Total
Resistance
(Ω)
HRRS-B-5-1K 111.11 M 5 1 k
HRRS-B-5-10K 1.111 1 G 5 10 k
HRRS-B-5-100K 11.111 G 5 100 k
HRRS-B-5-1M 111.11 G 5 1 M
HRRS-B-6-10 11.111 1 M 6 10
HRRS-B-6-100 111.111 M 6 100
HRRS-B-6-1K 1.111 11 G 6 1 k
HRRS-B-6-10K 11.111 1 G 6 10 k
HRRS-B-6-100K 111.111 G 6 100 k
HRRS-B-7-10 111.111 1 M 7 10
HRRS-B-7-100 1.111 111 G 7 100
HRRS-B-7-1K 11.111 11 G 7 1 k
HRRS-B-7-10K 111.111 1 G 7 10 k
Model Dimensions Weight
3 decades 31.2 cm W x 8.9 cm H x 10.2 cm D 1.4 kg
(12.3" x 3.5" x 4.0") (3.0 lb)
4 decades 37.5 cm W x 8.9 cm H x 10.2 cm D 1.6 kg
(14.8" x 3.5" x 4.0") (3.5 lb)
5 decades 1.9 kg (4.0 lb)
6 and 7 43.9 cm W x 8.9 cm H x 10.2 cm D 2.0 kg
decades (17.3" x 3.5" x 4.0") (4.5 lb)
Decade Resistance Accuracy Option** Max Voltage 5 kV Max Temp. Voltage Stability
Resistance Per Step (Per Step) Voltage Coefficient Coefficient
Available ±ppm/°C ±ppm/V ±ppm/year
100 Ω10 Ω±0.01% ±0.03% ±0.1% 2.5 V N 15 0 10
1 kΩ100 Ω±0.01% ±0.03% ±0.1% 8 V N 5 0 10
10 kΩ1 kΩ±0.01% ±0.03% ±0.1% 23V N 5 0 10
100 kΩ10 kΩ±0.01% ±0.03% ±0.1% 70 V N 5 0 10
1 MΩ100 kΩ±0.01% ±0.03% ±0.1% 333 V* 5000 V 5 0 10
10 MΩ1 MΩ±0.03% ±0.1% ±0.5% 1000 V* 5000 V 10 0.2 10
100 MΩ10 MΩ±0.03% ±0.1% ±1% 1000 V* 5000 V 10 0.2 25
1 GΩ100 MΩ±0.1% ±0.2% ±1% 1000 V* 5000 V 25 1.5 100
10 GΩ1 GΩ±0.2% ±0.5% ±1% 1000 V* 5000 V 80 5 500
100 GΩ10 GΩ±0.5% ±1% ±1% 1000 V* 5000 V 80 5 500
1 TΩ100 GΩ±0.5% ±1% ±1% 1000 V* 5000 V 200 5 500
* Subject to maximum of 1000 V (dc + ac peak);
** Traceable to NIST.
Q B F
For convenience to the user, the pertinent specifications are given in an OPERATING GUIDE, shown
in Figure 2.1, affixed to the case of the instrument.

3
SPECIFICATIONS
HRRS Series

4OPERATION
HRRS Series
Chapter 3
INSTALLATION
Minimize handling of the binding post area and es-
pecially the Kel-F insulating washers.
3.3 Repackaging for Shipment
If the instrument is to be returned to IET Labs, con-
tact the Service Department at the number or address,
shown on the front cover of this manual, to obtain a
“Returned Material Authorization” (RMA) number
and any special shipping instructions or assistance.
Proceed as follows:
1. Attach a tag to the instrument identifying the owner
and indicate the service or repair to be accomplished.
Include the model number, the full serial number of
the instrument, the RMA number, and shipping ad-
dress.
2. Wrap the instrument in heavy paper or plastic.
3. Protect the front panel and any other protrusions
with cardboard or foam padding.
4. Place instrument in original container or equally
substantial heavy carton.
5. Use packing material around all sides of instru-
ment.
6. Seal with strong tape or bands.
7. Mark shipping container “DELICATE INSTRU-
MENT,” “FRAGILE,” etc.
3.2 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 opera-
tional 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 war-
ranty at the beginning of this manual. IET Labs will
work with you until you are satisfied that your in-
strument is operating to fulfill the needs of your ap-
plications.
Save all original packing material for convenience in
case shipping of the instrument should become nec-
essary.
3.2 Installation
For a rack mounted model, installation on a 19 inch
rack may be made using the slots in the rack mount-
ing 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, it is recommended
that a bench space be provided that would not ex-
pose it to abuse and keep it protected from tempera-
ture extremes and contaminants.
For all high resistance instruments, it is highly rec-
ommended that they be stored sealed in a plastic bag
or other well sealed environment to minimize any
contamination that would lead to electrical leakage
and degradation of performance.
Keep unit in a sealed environment when
not in use.
Maintain binding post area clean for
minimum electrical leakage.

5
OPERATION
HRRS Series
3.4 Storage
If this instrument is to be stored for any lengthy pe-
riod of time, it should be sealed in plastic and stored
in a dry location. It should not be subjected to tem-
perature extremes beyond the specifications. Ex-
tended exposure to such temperatures can result in
an irreversible change in resistance, and require
recalibration

6OPERATION
HRRS Series
Chapter 4
OPERATION
4.1. Connection
4.1.1 General Considerations
The HRRS 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 Gterminal 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 the most stable measurements, de-
termine which is the more sensitive of the two user
leads, i.e. the one going into a higher test instrument
impedance. This lead should be connected to the
HRRS terminal that is shorted to the case, or the L
terminal whenever neither is connected to the case,
i.e. the more protected one of the two HRRS termi-
nals.
4.1.2 Electrical Considerations
In order to make proper use of the full performance
capabilities of the HRRS unit, care should be taken
to obtain good results with the very high resistance
values involved.
Whenever possible, shielding should be employed.
The case itself can be grounded using the Gtermi-
nal, and shielded cables to the other terminals should
be employed.
Because of the high resistances involved, leakage
from all sources should be kept to a minimum. The
ambient humidity should be under 50% RH. Also,
the instrument should be kept clean, and should not
be handled at the terminals. Any contamination could
act as a leakage across the device resistance. The
unit may be cleaned with alcohol or naphtha.
Since high resistance applications are invariably as-
sociated with high voltages, 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 ADJUSTING
SWITCHES.
- POST WARNING SIGNS AND KEEP
PERSONNEL SAFELY AWAY.
Keep unit in a sealed environment when
not in use.
Maintain binding post area clean for
minimum electrical leakage.

7
OPERATION
HRRS Series
4.2 Dial Setting
Whenever the dials are used for positions 0-9, the
resulting resistance is simply read off from the panel
dial setting in a direct fashion. Both the decimal point
and the steps are clearly marked on the panel.
For additional flexibility and range, each decade pro-
vides a “10” position setting. This “10” position on
any one decade equals the “ 1” position on the next
higher decade. It adds about 11% to the nominal to-
tal decade resistance.
To determine the resistance obtained when any one
or more “10” settings are used, simply add 1 to the
next higher decade. For example, a setting of
3-6-10-0-10 MΩbecomes:
3 30000
66000
10 1000
000
10 1 0
TOTAL 37010
and 10-10-10-10.-10 MWs become
10 100000.0
10 10000.0
10 1000.0
10 100.0
10 1 0 . 0
.10 1 . 0
TOTAL 111111.0
4.3 Environmental Conditions
For optimal accuracy, the decade box should be used
in an environment of 230C. It should be allowed to
stabilize at that temperature for at least two hours
after any significant temperature variation. Humid-
ity should be maintained <50% RH.

8MAINTENANCE
HARS-X Series
Chapter 5
MAINTENANCE
5.1 Preventive Maintenance
The HRRS Decade Substituter is packaged in a closed
case which will limit the entry of contaminants and
dust to the inside of the instrument. If it is main-
tained in a generally clean or air conditioned envi-
ronment, cleaning will be seldom required. In a con-
taminated atmosphere, cleaning may be required.
It is important to avoid handling the binding posts
and to keep them clean to minimize the possibility of
shunt leakage across the internal resistors. Wiping
with alcohol or naphtha, is recommended. House-
hold cleaners or any solvents that leave a residue
should not be used.
To maintain optimal accuracy and stability, it is best
not to open the case of the unit. If it is opened, then
it is necessary to handle the internal components with
clean rubber or cotton gloves.
In normal service, the switches require no additional
lubrication. During the manufacturing process, a light
lubrication is applied which in most instances is suf-
ficient 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 HRRS Series instruments should be verified 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 certified 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 HRRS 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
meters or digital multimeters available that can verify
the accuracy of these units, especially when used in
conjunction with standards that can serve to confirm
or improve the accuracy of the testing instrument.
Such instruments would have to be significantly more
accurate than the specified 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 ex-
ist that can do this; consult IET Labs for informa-
tion.
It is important to allow both the testing instrument
and the HRRS 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 verification.

9
MAINTENANCE
HARS-X Series
5.2.3 Procedure
1. Confirm the zero resistance of the unit.
2. Determine the allowable upper and lower
limits for each resistance setting of each de-
cade following the specified accuracy given
in the Specifications Section of Chapter 2.
3. Confirm 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. Refer to the
Parts List below for the appropriate part num-
ber.
5.3 Schematic and Replacement Parts
Refer to Figure 5.1 for a schematic of the HRRS de-
cade unit. In order to locate the replacement parts
associated with a particular model in the HRRS se-
ries, use Table 5.1 to locate the code letter for the
relevant model, and then see Tables 5.2 and 5.3 for
the parts which apply to the model code letter. See
Figure 5.2 for an assembly diagram of the unit.
It is recommended that service be performed only by
IET Labs or by qualified personnel.
5.4 Troubleshooting
If the verification procedure results in a failure, use
the schematic of Figure 5.1 to determine the suspect
decade or component. In a clean environment, and
using gloves, disassemble the unit as described be-
low, and examine the parts in question to determine
the necessary repair or replacement.
5.5 Disassembly, Component
Replacement, and Reassembly
5.5.1 Disassembly
Referring to Figure 5.2 to locate part numbers, pro-
ceed as follows:
1. Work in a clean environment, and use gloves to
handle any components.
2. Place the instrument on a flat surface and remove
the 4 housing screws (HARS-X-3200) from the bot-
tom of the instrument. The housing ((HRRS-30*0)
may now be removed.
5.5.2 Component Replacement
Determine and locate any faulty component that re-
quires replacement as described in the troubleshoot-
ing section 5.4.
To remove a decade switch assembly
(HRRS-6500-*), proceed as follows:
1. Desolder the bus wire connecting the switch as-
sembly.
2. Pry off the cap from the knob
(HARS-X-4300-CAP), and remove the nut under it.
3. Pull off the knob (HARS-X-4300-KNB), and re-
move the nut under it.
4. The decade switch assembly may now be removed.
5. Replace the assembly by reversing the above steps.
6. Replace the knob and cap, making certain that the
figure dial (HARS-X-4300-FD) and the stator
(HARS-X-4300-ST) are properly aligned for the par-
ticular switch setting.
5.5.3 Reassembly
1. Make certain that the 4 standoffs (HARS-X-3300)
have not become loose. If so tighten them.
2. Replace the housing, match the holes, and attach
the 4 housing screws.

10 MAINTENANCE
HARS-X Series
Figure 51. HRRS Series Schematic Diagram

11
MAINTENANCE
HARS-X Series

12 MAINTENANCE
HARS-X Series

13
MAINTENANCE
HARS-X Series