IET Labs SCA Series User manual

♦PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT ♦
Email: inf[email protected]
TEL: [phone] • FAX: [phone]
www.ietlabs.com
IET LABS, INC.
SCA Series
Capacitance Standard
Operation Manual
Copyright © 2019 IET Labs, Inc.
Visit www.ietlabs.com for manual revision updates
SCA im/Nov. 2019

♦PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT ♦
Email: inf[email protected]
TEL: [phone] • FAX: [phone]
www.ietlabs.com
IET LABS, INC.

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,
INCLUDING BUT NOT LIMITED TO, ANY IMPLIED WARRANTY OF MERCHANTABILITY OR
FITNESS FOR ANY PARTICULAR PURPOSE.
i

Safety Symbols
General definitions of safety symbols used on the instrument or in manuals are listed below.
Caution symbol: the product is marked with this symbol when it is necessary for the user to
refer to the instruction manual.
Hazardous voltage symbol: the product is marked with this symbol when high voltage maybe
present on the product and an electrical shock hazard can exist.
Indicates the grounding protect terminal, which is used to prevent electric shock from the
leakage on chassis. The ground terminal must connect to earth before using the product
Direct current.
Alternating current.
Frame or chassis terminal. A connection to the frame (chassis) of the equipment which
normally includes all exposed metal structures.
On supply.
Off supply.
Hot surface. Avoid contact. Surfaces are hot and may cause personal injury if touched.
Disposal
Waste Electrical and Electronic Equipment (WEEE) Directive 2002/96/EC
This product complies with the WEEE Directive (2002/96/EC) marking requirements.
The affixed label indicates that you must not discard this electrical/ electronic product in domestic
household waste.
Product Category: With reference to the equipment types in the WEEE directive Annex 1, this product
is classified as a “Monitoring and Control instrumentation” product.
Do not dispose of electrical appliances as unsorted municipal waste, use separate collection facilities.
Contact your local government for information regarding the collection systems available. If electrical
appliances are disposed of in landfills or dumps, hazardous substances can leak into the groundwater
and get into the food chain, damaging your health and well-being.
When replacing old appliances with new one, the retailer is legally obligated to take back your old ap-
pliances for disposal.
Proposition 65 Warning for California Residents
WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov.
This product may contain chemicals known to the State of California to cause cancer, birth defects, or
other reproductive harm

SAFETY PRECAUTIONS
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 specific 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.
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.
The SCA is an indoor use product.
DANGEROUS PROCEDURE WARNINGS
Comply with all WARNINGS - Procedures throughout in this manual and instructions on the instrument prevent
you from potential hazard. These instructions contained in the warnings must be followed.
CAUTION
• DO NOT Operate in an Explosive Atmosphere
• Do not operate the instrument in the presence of inflammable gasses or fumes
• Operation of any electrical instrument in such an environment clearly constitutes a safety hazard
• Use Caution around live circuits and whenever hazardous voltages > 45 V are present
• Operators must not remove instrument covers
• Component replacement and internal adjustments must be made by qualified maintenance personnel only
• DO NOT substitute parts or modify the instrument
• When working with high voltages; post warning signs, train personnel and keep unauthorized personnel away.
Do not apply any voltage or currents to the terminals of the instrument in excess of the maximum limits
indicated in the specifications section of this manual.
To avoid the danger of introducing additional hazards, do not install substitute parts or perform unauthorized
modifications to the instrument.
Return the instrument to an IET Labs for service and repair to ensure that safety features are maintained in
operational condition.

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 qualified personnel
HIGH VOLTAGES MAY BE PRESENTAT 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.
iv

Contents
Chapter 1 Introduction ..............................................................................1
1.1 Description of the SCA Series .............................................................................. 1
1.2 Optional Transit Case............................................................................................ 1
Chapter 2 Specifications ...........................................................................2
Specifications ................................................................................................................ 2
Chapter 3 Operation ..................................................................................3
3.1 Initial Inspection and Setup .................................................................................. 3
3.2 Connections to Capacitor...................................................................................... 3
3.2.1 Low capacitors - 190 pF and under ............................................................ 3
3.2.2 Intermediate Capacitors - from 1 nF to 1 μF ............................................. 4
3.2.3 High capacitors - 1.9 μF and over .............................................................. 4
3.3 Environmental Conditions .................................................................................... 4
3.3.1 Operating Temperature ............................................................................... 4
3.3.2 Storage Temperature ................................................................................... 4
3.4 Shipping and Handling ......................................................................................... 4
Chapter 4 Maintenance..............................................................................5
4.1 Preventive Maintenance........................................................................................ 5
4.2 Calibration............................................................................................................. 5
4.2.1 Calibration Interval..................................................................................... 5
4.2.2 General Considerations............................................................................... 5
4.2.3 Calibration Procedure ................................................................................. 5
4.3 Calibration with Digibridge .................................................................................. 6
4.4 Calibration with GenRad 1620 or AH2500A........................................................ 6
4.5 Replaceable Parts List........................................................................................... 7
v

Figures and Tables
Figure 1-1: SCA Series Resistance Standard .............................................1
Figure 1-2: Optional Transit Case (SRC-100)..............................................1
Figure 2-1: Sample label attached to an SCA unit ......................................2
Figure 3-1: Low SCA capacitor standard with bnc connectors....................3
Figure 3-2: Capacitance shunted by leakage to case .................................3
Figure 3-3: Intermediate SCA capacitor standard with 3 binding posts ......4
Figure 3-4: High SCA capacitor standard with 5 binding posts ...................4
Figure 3-5: SCA as a 5-terminal capacitor ..................................................4
Table 4-1: Replaceable Parts List................................................................6
Figure 4-1: SCA Replaceable Parts ............................................................6
vi

1
SCA Series
1Introduction
Chapter 1
INTRODUCTION
1.1 Description of the SCA Series
The SCA Series (Figure 1-1) are stable, precise,
laboratory or portable capacitance standards. They
are working and laboratory standards grade. The
SCA units are available in values ranging from
1 pF to 10,000 μF with custom values or combinations
available, to satisfy any requirement.
Each value range is built with the type of capacitor
that will provide the best performance for high stabil-
ity, low dissipation, low temperature coefficient, and
high operating voltage. Most are hermetically sealed
and mechanically stabilized.
Low values have bnc connectors to minimize lead
stray capacitance; higher values have two or four
(Kelvin-type) binding posts. All have a ground
terminal.
1.2 Optional Transit Case
Optional Model SRC-100 lightweight transit case
with handle, suitable for transporting and storing two
units. See Figure 1-2. The case provides mechanical
protection and insulation from temperature changes
during transportation or shipping.
Figure 1-1: SCA Series Resistance Standard
Figure 1-2: Optional Transit Case (SRC-100)

2
SCA Series
2 Specifications
Chapter 2
SPECIFICATIONS
For convenience to the user, the pertinent specifications are given in a label, shown in Figure 2-1 affixed to the
case of the instrument.
SPECIFICATIONS
Nominal
value Model
Adjust-
ment to
nominal
Tempera-
ture coef-
ficient
(ppm/°C)
Calibration
Conditions
Dissipa-
tion
(typical)
Stability
(per
year)
Max voltage
Terminals Capacitor
type
Peak (V) Max Fre-
quency
1 pF SCA-1pF ±0.1 pF +20 to +40
30 Vac
Series Model
1 kHz
0.002 ±0.1 pF 500 10 kHz
2 bnc
connectors
+ gnd
Air capacitors
1.9 pF SCA-1.9pF ±0.1 pF +20 to +40 0.002 ±0.1 pF 500 10 kHz
10 pF SCA-10pF ±0.1 pF +20 to +40 0.002 ±0.1 pF 500 10 kHz
19 pF SCA-19pF ±0.1 pF +20 to +40 0.001 ±0.1 pF 500 10 kHz
100 pF SCA-100pF ±0.1 pF 20 0.0005 ±0.1 pF 500 10 kHz
Silvered mica
mechanically
stabilized
hermetically
sealed
190 pF SCA-190pF ±0.1 pF 20 0.0005 ±0.1 pF 500 10 kHz
1.0 nF SCA-1nF ±0.02% 20 0.0003 ±100 ppm 500 10 kHz
1.9 nF SCA-1.9nF ±0.02% 20 0.0003 ±100 ppm 500 10 kHz
10 nF SCA-10nF ±0.02% 20 0.0003 ±100 ppm 500 10 kHz
2 binding
posts + gnd
19 nF SCA-19nF ±0.02% 20 0.0003 ±100 ppm 500 10 kHz
100 nF SCA-100nF ±0.02% 20 0.0003 ±100 ppm 500 10 kHz
190 nF SCA-190nF ±0.02% 20 0.0003 ±100 ppm 500 10 kHz
1 µF SCA-1µF ±0.02% 20 0.0002 ±100 ppm 500 10 kHz
1.9 µF SCA-1.9µF ±0.02% 20 1 Vac
Series Model
1 kHz
0.0002 ±100 ppm 100 10 kHz
4 binding
posts + gnd
Metallized
polypropylene
sulfide
hermetically
sealed
5 µF SCA-5µF ±0.02% ±50 0.0005 ±200 ppm 50 10 kHz
10 µF SCA-10µF ±0.04% ±50
1 Vac
Series Model
100 Hz
(1 kHz data included)
0.0005 ±200 ppm 22 Vrms† 1 kHz
19 µF SCA-19µF ±0.04% ±50 0.0005 ±200 ppm 44 Vrms† 1 kHz
100 µF SCA-100µF ±0.05% ±50 0.001 ±500 ppm 22 Vrms† 1 kHz
190 µF SCA-190µF ±0.05% ±50 0.001 ±500 ppm 22 Vrms† 1 kHz
1,000 µF SCA-1000µF ±0.4% -150 0.001 ±500 ppm 22 Vrms† 1 kHz
5,000 µF SCA-5000µF ±2% -150 0.001 -- 22 Vrms† 1 kHz Polypropyl-
ene
10,000 µF SCA-
10000µF ±2% -150 0.001 -- 22 Vrms† 1 kHz
XXX F SCA-XXX customer-selected value and power specifications
† Maximum allowable Vrms; subject to maximum Vdc = 50 V and max Vrms = (39000/f) for C = 10 μF;
(26000/f) for C = 19 μF; (13000/f) for C ≥100μF, where f = frequency (in Hz).
Environment:
Operating: +10 to +40°C, <80% RH
Storage: -20 to +65°C
Calibration Conditions:
Calibrated at 23°C, <80% RH, Traceable to SI
Mechanical:
Values Dimensions Weight
≤190 µF
8.6 cm H x 10.5 cm W x 12.7 cm D
(3.4” x 4.15” x 5”) 0.73 kg (1.6 lb)
1,000 µF
31 cm W x 8.9 cm H x 10.2 cm D
(12.2" x 3.5" x 4") 1.7 kg (3.8 lb)
5,000 µF
53.3 cm W x 27.3 cm H x 44.5 cm D
(21" x 10.75" x 17.5")
27.2 kg (60 lb)
10,000 µF
36.3 kg (80 lb)
Figure 2-1: Sample label attached to an SCA unit
Date 18-Jan-2010
C (μF) @ 1592 H z 1.000 36
D @ 1592 H z 0.002 430
C (μF) @ 10 kHz 1.000 103
D @ 10 kHz 0.001 023
C (μF) @ 50 kHz 0.999 124
D @ 50 kHz 0.004 013
C (μF) @ 100 kH z 0.996 463
D @ 100 kHz 0.008 931
By NPL/JOS
SC-A Series 1 μF CAPACITANCE STANDARD
SN: B1-0936460
.*91&'8.3(.*91&'8.3(
.*91&'8.3(.*91&'8.3(
.*91&'8.3(
[phone] • FAX: [phone]
534 Main Street, Westbury, NY 11590
Capacitance Type:
Temp. Coefficient:
Operating Temp:
Maximum Voltage:
Test Conditions:
Hermetically sealed silvered mica.
<20 ppm/°C
10°C to 50°C
500 V
Calibrated as a 5-terminal capacitor, series
model, at 1 Vrms.
www.ietlabs.com
SCA Series lbl/1μF/pg1/1-2010

3
SCA Series
3Operation
Chapter 3
OPERATION
3.1 Initial Inspection and Setup
This instrument was carefully inspected before ship-
ment. It should be in proper electrical and mechanical
order upon receipt.
To provide ready reference to specifications, a label,
shown in Figure 2-1, is attached to the case of the
instrument.
3.2 Connections to Capacitor
3.2.1 Low capacitors - 190 pF and under
Low SCA capacitors have 2 bnc connectors labeled
HI and LO, and a ground binding post labeled GND
as shown in figure 3-1.
Figure 3-1: Low SCA capacitor standard with
bnc connectors
The capacitance of the unit is shown as CHL in Figure
3-2. There is additional capacitance to the case shown
by CHG and CLG. These capacitances will add to CHL
unless the 3rd terminal, GND, is connected to the
GUARD of the measuring instrument.
.
Figure 3-2: Capacitance shunted by leakage
to case
CAUTION
Using the unit as a 2-terminal capacitor
will add an error to the standard.
CHL
CLG
CHG
LOWHIGH
GND

4
SCA Series
4 Maintenance
3.2.2 Intermediate Capacitors - from
1 nF to 1 µF
Intermediate SCA capacitors have 3 binding posts
-- HI, LO, and GND -- as shown in figure 3-3.
Figure 3-3: Intermediate SCA capacitor
standard with 3 binding posts
These intermediate values are connected the same
way as low capacitances (Section 3.2.1), except they
use binding posts because lead and stray resistances
are less critical.
3.2.3 High capacitors - 1.9 µF and over
High SCA capacitors have 5 binding posts -- HI
CURRENT, HI SENSE,LO CURRENT, LO
SENSE,and GND -- as shown in figure 3-4.
Figure 3-4: High SCA capacitor standard with
5 binding posts
This 4-terminal connection circuit has special wiring
and low-resistance conductors to minimize dissipa-
tion and parasitic inductance, and improve frequency
characteristics. See Figure 3-5. To use as a 2-terminal
capacitor, connect to only the two SENSE terminals.
CHL
CLG
CHG
CURRENT
LOW
SENSE
LOW
CURRENT
HIGH
SENSE
HIGH
GND
Figure 3-5: SCA as a 5-terminal capacitor
To use as a 2-terminal capacitor, connect to only the two
SENSE terminals.
3.3 Environmental Conditions
3.3.1 Operating Temperature
For optimal accuracy, SCA models should be used
in an environment of 23°C ±5°C. They should be
allowed to stabilize at those temperatures after any
significant temperature variation.
3.3.2 Storage Temperature
The SCA units should be maintained within the stor-
age temperature range of 0°C to 40°C to retain its
accuracy within the specified limits.
3.4 Shipping and Handling
The SCA Series should not be exposed to any excessive
shock or temperature extremes. The option SRC-100, a
lightweight transit case capable of storing two SCA units,
is recommended for shipping or transporting the models.

5
SCA Series
5Maintenance
Chapter 4
MAINTENANCE
4.1 Preventive Maintenance
Keep the unit in a clean environment. This will help
prevent possible contamination.
SCA’s are packaged in a closed case, which limits the
entry of contaminants and dust into the instruments.
If they are maintained in a clean or air-conditioned
environment, cleaning will seldom be required. In a
contaminated atmosphere, cleaning may be required.
4.2 Calibration
The SCA units may be employed as stand-alone
instruments or as integral components of a system.
If used as part of a system, they should be calibrated
as part of the overall system to provide an optimum
system calibration.
4.2.1 Calibration Interval
The recommended SCA Series calibration interval is
twelve (12) months.
The calibration 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.
4.2.2 General Considerations
It is important, whenever calibrating an SCA unit, to
be very aware of the capabilities and limitations of
the test instruments used.
Recommended Instruments:
• IET Model 1689 Digibridge (direct
reading)
or
• IET Model 1620 or 1621 Precision
Capacitance Measurement System
(bridge)
The test instruments must be significantly more ac-
curate than ±(0.1% + 1.0 pF) for all ranges, allowing
for a band of uncertainty of the instrument itself.
It is important to allow both the testing instrument
and the SCA to stabilize for a number of hours at
the nominal operating temperature of 23OC, and at
nominal laboratory conditions of humidity. There
should be no temperature gradients across the unit
under test.
bnc test terminals should be used to obtain accurate
shielded readings on low value SCAs

6
SCA Series
6 Maintenance
4.3 Calibration Procedure with
Digibridge
To calibrate an SCA unit, proceed as follows:
1. SCA capacitors with bnc connectors should
be connected to the Digibridge such that the
shields are connected to both the high and
low terminals.
2. Determine and employ proper metrological
practices.
Allow a confidence band for the uncer-
tainty of the measuring instrument and
setup.
3. Set test conditions:
At 1 Vrms, series model, 23°C
≤190 pF: 3-terminal measurement
bnc connection
1nF - 1μF: 3-terminal measurement
binding post connection
≥1.9 μF: 5-terminal measurement
binding post connection
4. Determine the allowable drift limits for the
capacitance reading.
<(0.1%+0.1pF) per year - up to 1 μF
5. Confirm that the readings fall within these
drift limits, allowing for the uncertainty band.
If the reading falls outside the limits,
it has to be repaired by IET or another
qualified facility.
4.4 Calibration Procedure with
GenRad 1620 or AH2500A/
AH2700A Capacitance Bridge
To calibrate an SCA unit, proceed as follows:
1. SCA capacitors with bnc connectors should
have the shield disconnected at the HItermi-
nal to minimize stray capacitance. The shield
on the LO terminal should be maintained.
This connection mimics the connection on the
IET/GenRad 1404 Standard Capacitor.
2. Determine and employ proper metrological
practices.
Allow a confidence band for the uncer-
tainty of the measuring instrument and
setup.
3. Set test conditions:
At 1 Vrms, series model, 23°C
≤190 pF: 3-terminal measurement
bnc connection
1nF - 1μF: 3-terminal measurement
binding post connection
≥1.9 μF: 5-terminal measurement
binding post connection
4. Determine the allowable drift limits for the
capacitance reading.
<(0.1%+0.1pF) per year - up to 1 μF
5. Confirm that the readings fall within these
drift limits, allowing for the uncertainty band.
If the reading falls outside the limits,
it has to be repaired by IET or another
qualified facility

4.5 Replaceable Parts List
Reference IET Pt No Description
132-21 Binding Post, Red
232-20 Binding Post, Black
332-19 Binding Post, Gold
Not Shown UG-194 bnc connecor
Not Shown SCA-*-Cap SCA capacitor assembly
Replace * with nominal capacitance value
Table 4-1: Replaceable Parts List
Figure 4-1: SCA Replaceable Parts
12
3