IET Labs HACS-Z-A-6E-1pF Troubleshooting guide

PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT 
TEL: [phone] • [phone] • FAX: [phone]
www.ietlabs.com
IET LABS, INC.
HACS-Z-A-6E-1pF
Decade Capacitance System
User and Service Manual
Copyright 2017 IET Labs, Inc.
Visit www.ietlabs.com for manual revision updates
HACS-Z-A-6E-1pF / March 2017

PRECISION INSTRUMENTS FOR TEST AND MEASUREMENT 
TEL: [phone] • [phone] • FAX: [phone]
www.ietlabs.com
IET LABS, INC.

iii
HACS-Z-6E-1pF
Table of Contents
Contents
Chapter 1 Introduction ..............................................................................1
1.1 General Description .............................................................................................. 1
1.2 Switches ................................................................................................................ 1
1.3 Double Shielded Construction .............................................................................. 2
Chapter 2 Specifications ...........................................................................3
Specifi cations ................................................................................................................ 3
Double Shielded Construction ...................................................................................... 3
Chapter 3 Operation ..................................................................................5
3.1 Initial Inspection and Setup .................................................................................. 5
3.2 Switch Setting ....................................................................................................... 5
3.3 Connection to Terminals ....................................................................................... 5
Chapter 4 Maintenance..............................................................................6
4.1 Preventive Maintenance ........................................................................................ 6
4.2 Calibration Interval ............................................................................................... 6
4.3 General Considerations ......................................................................................... 6
4.4 Calibration Procedure ........................................................................................... 7
4.5 Capacitance Adjustment ........................................................................................ 7
4.6 Replaceable Parts .................................................................................................. 9
Figures and Tables
Figure 1-1: HACS-Z-B-6E-1pF ....................................................................1
Figure 1-2: Capacitance Shunted by Leakage to case ...............................2
Figure 1-3: HACS-Z Construction ...............................................................2
Table 2-1: Specifications .............................................................................3
Figure 2-1: Double Shielded Construction ..................................................3
Figure 2-2: Typical Operating Guide Affixed to HACS-Z-A-6E-1pF....................4
Table 4-1: Capacitor type ............................................................................7
Figure 4-1: Screws holding the rear panel ..................................................8
Figure 4-2: Calibration access holes ...........................................................8
Figure 4-3: Screws holding the cabinet .......................................................8
Figure 4-4: 10 nF & 100 nF capacitance sets .............................................8
Table 4-2: Replaceable Parts List................................................................9
Figure 4-5: Replaceable Parts.....................................................................9

iv
HACS-Z-6E-1pF
Table of Contents
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1
HACS-Z-A-6E-1pF
1Introduction
Chapter 1
INTRODUCTION
1.1 General Description
The HACS-Z-A-6E-1pF Decade Capacitance System is
capable of meeting exacting requirements for fi xed or
adjustable calibration capacitance or any applications
requiring precise stable capacitance values.
Unit Features:
• Range: 1 pF - 1.111 11 μF
• Low zero-capacitance
• High accuracy
• Excellent stability
• Low temperature coeffi cient
• High voltage rating
• Bench-top or rack-mount operation
Figure 1-1: HACS-Z-B-6E-1pF
1 pF, 10 pF
For these, the lowest decade steps, trimmable air
capacitors are used. The capacitors are selected for
maximum resolution, high mechanical stability, and
low dissipation factor.
100 pF - 0.1 μF decades
These mid-range decades are implemented with
the highest grade, mechanically stabilized, sealed
India ruby mica capacitors selected for optimum
electrical characteristics and low dissipation. They
are hermetically sealed to prevent intrusion of
moisture and to obtain minimum drift.
Stability
The stability of the capacitors is such that the in-
strument should not require readjustment for the
duration of the recommended calibration interval.
Should recalibration become necessary, easily ac-
cessible trimmer capacitors are provided for the
l pF, 10 pF, 100 pF, and 1000 pF decades. The
other decades may also be calibrated with discrete
padder capacitors.
1.2 Switches
Custom-designed switches are used to connect four ca-
pacitors in a parallel circuit for each decade. These are
weighted in a 1-2-2-5 code to provide all the necessary
combinations for ten equal steps for each decade.
The switch circuit is designed such that each unused
capacitor is completely disconnected from the rest of
the circuit and has its positive terminal connected to
the inner shield. See Figure 1-5.
The stability of the switches is assured by the use of
large gaps and secure mechanical construction.

2
HACS-Z-A-6E-1pF
2 Introduction
1.3 Double Shielded Construction
In order to meet the low residual capacitance require-
ment, the unit utilizes:
• Specially shielded and routed wiring
• The switching scheme described above and
shown in Figure 1-2
• A double-shielded construction to keep the
zero capacitance at an extremely low level
Figure 1-2 demonstrates the need for the double
shielded construction. It shows that a capacitor CHL
would be shunted by the series combination of the
series combination of the capacitances from the HIGH
and LOW terminals to the case. The net capacitance
becomes:
CHL + (CHG in series with CLG)
Clearly it would be very diffi cult to get a very low
residual or zero capacitance, unless the G terminal is
the ground terminal of 3-terminal measurement of
the capacitance.
In order to accomplish this, an inner shield is added
as conceptually shown in Figure 1-3. It is mechani-
cally constructed to shunt away any capacitance
between the HIGH and LOW terminals. This inner
shield shunts this capacitance when it is electrically
connected to the outer shield, forming a 3-terminal
capacitor (5-teminal capacitor for units with 10 μF
steps or higher). All unused capacitors are shorted
to this inner shield at their high ends, and are open
at their low ends.
This inner shield is not actually an internal enclosure
but rather a cellular structure that optimally separates
all conductors and capacitor elements. It also serves
to minimize terminal-to-ground capacitance which is
necessary when measuring small capacitances with
various bridges.
Figure 1-2: Capacitance Shunted by Leakage
to case
Figure 1-3: HACS-Z Construction

3
HACS-Z-A-6E-1pF
3Specifications
Chapter 2
SPECIFICATIONS
For convenience to the user, the pertinent specifi cations are given in an Operating Guide, similar to the one shown
in Figure 2-2, which is affi xed to the case of the instrument.
SPECIFICATIONS
No zero-subtraction required
Range:
0 to 1.111 110 μF, in 1 pF steps
Zero Capacitance:
≤0.1 pF maximum capacitance obtained with all dials set to zero;
Temperature Coeffi cient:
≈20 ppm/°C
Insulation Resistance:
>50,000 MΩ
Operating Temperature Range:
10°C to 40°C
Shielding:
Double-shielded construction; see below.
Dimensions:
Bench: 43.2 cm W x 13.3 cm H x 27.7 cm D (17” x 5.2” x 10.9”)
Rack: 48.3 cm W x 13.3 cm H x 27.7 cm D (19” x 5.2” x 10.9”)
Weight:
8.6 kg (19 lb), for bench version
Connection to Capacitor:
Two bnc connectors labeled HI and LO. The shielding is divided
into the following parts:
The inner shield: minimizes the terminal-to-guard capacitance
Outer shield (the case): minimizes the detector input capacitance
and noise
The outer shell of the HI connector is connected to the switch shaft.
The outer shell of the LO connector is connected to the outer case.
To use the HACS-Z as a 3-terminal capacitance substituter with
very low zero-capacitance connect these two shields together at the
measuring instrument.
DOUBLE SHIELDED CONSTRUCTION
The shielding is divided into two diff erent parts: an inner
shield that minimizes the low terminal-to-guard capaci-
tance, and an outer shield (the case) that minimizes the
detector input capacitance and noise. (See Figure 2-1.)
When these two shields are connected together, the
HACS-Z becomes an excellent 3-terminal capacitance
substituter with low zero capacitance.
LOHI
Inner Shield
Outer Case
CHL
Figure 2-1: Double Shielded Construction
Capacitance
per step
Total decade
capacitance Max voltage Accuracy* Dissipation factor* Stability Capacitor type
HACS-Z-1pF Variable
Decade 1 pF+
500 V peak max up
to 10 kHz
±0.1 pF <0.003 typical
±(100 ppm + 0.1 pF)
per year
Air capacitors
1 pF 10 pF
± (0.05% + 0.5 pF)
<0.002
10 pF 100 pF <0.002
100 pF 1 nF
Position 1: <0.002
All others: <0.001
Silvered mica
Mechanically stabilized
Hermetically sealed
1,000 pF 10 nF
Position 1: <0.001
Position 2: <0.0005
All others: <0.0003
0.01 µF 100 nF <0.0003
0.1 µF 1 µF <0.0004
*1 kHz, 3-terminal measurement; series model; 1 Vrms, 23°C; traceable to SI

4
HACS-Z-A-6E-1pF
4 Specifications
Figure 2-2: Typical Operating Guide Affixed to HACS-Z-A-6E-1pF
HACS-Z-A HIGH ACCURACY DECADE CAPACITANCE SUBSTITUTER
CONSULT INSTRUCTION MANUAL FOR PROPER INSTRUMENT OPERATION
HACS-Z-A Feb 2018
Accuracy:
± (0.05% + 0.5 pF) at 1 kHz* *1 kHz, 3-terminal measurement; series model; 1 Vrms, 23°C; traceable to SI 10 µF steps are measured at 100 Hz
Zero Capacitance:
d0.1 pF maximum capacitance obtained with all dials
set to zero
Operating Temperature Range:
10°C to 40°C
Shielding:
Double-shielded construction
Connection to capacitor:
Two bnc connectors labeled HI and LO located on the
front. The shielding is divided into the following parts:
The inner shield: minimizes the terminal-to-guard capacitance Outer shield (the case): minimizes the detector input capacitance and noise
The outer shells of the HI connectors are connected to the switch shaft.
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.
CAGE CODE: 62015 www.ietlabs.com
IET LABS, INC.
Email: inf[email protected] • [phone]• Fax: [phone]
WARNING
MODEL: HACS-Z-A-6E-1pF
SN: H1-1816441
Capacitance
per step
Total decade
capacitance Max voltage Stability Dissipation factor Temperature
coefficient Capacitor type
1 pF 10 pF
500 V peak max up to 10 kHz
±(100 ppm + 0.1 pF) per year
<0.002
10 pF 100 pF
|20 ppm/°C
Air capacitors
100 pF 1 nF Position 1: <0.002
All others: <0.001
Silvered mica Mechanically stabilized Hermetically sealed
1,000 pF
10 nF
Position 1: <0.001 Position 2: <0.0005 All others: <0.0003
0.01 µF 100 nF <0.0003 0.1 µF 1 µF <0.0004 1 µF 10 µF 50 V peak max
±(200 ppm) per year
<0.0007
-50 ppm/°C Sealed MPPS
10 µF 100 µF
(Vdc+Vac) < 30 V or (Vac) < 22 V
<0.002
The outer shells of the LO connectors are connected to the outer case. To use the HACS-Z as a 3-terminal capacitance substituter with very low zero- capacitance connect the two shields together at the measuring instrument.

5
HACS-Z-A-6E-1pF
5Operation
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.
An OPERATING GUIDE, shown in Figure 2-2, is
attached to the case of the instrument to provide ready
reference to specifi cations.
3.2 Switch Setting
The HACS-Z Precision Capacitor has six capacitance
decades. The actual capacitance for each decade is the
product of the switch setting and the CAPACITANCE
PER STEP indicated below each switch on the front
panel.
Note, however, that if any dial is set on 10, a 1 is added
to the next decade. For example, if the dials are set: to
10-9-9-10-1-1, the resultant capacitance is:
1
1
10
9
9
10
Total 1100011 pF
The zero capacitance of the HACS-Z unit is very low,
but all settings are adjusted to accurately provide their
nominal values, and it is not necessary to subtract the
zero capacitance from any particular setting
Chapter 3
OPERATION
3.3 Connection to Terminals
In order to properly use the HACS-Z capacitor, it is
necessary to understand the use and function of each
of the capacitor terminals. Refer to Figure 1-2 and
note that a basic capacitor is a 2-terminal capacitor
shown as CHL. As described above, CHG and CLG, the
capacitances to the case add to the capacitor CHL un-
less the 3rd terminal G is connected to the guard of
the measuring instrument.
The shielding is divided into two diff erent parts: an
inner shield that minimizes the low terminal-to-
guard capacitance, and an outer shield (the case) that
minimizes the detector input capacitance and noise.
When these two shields are connected together, the
HACS-Z becomes an excellent 3-terminal capaci-
tance substituter with low zero capacitance.
Using the unit as a 2-terminal capacitor will cause an
error of about 100 to 150 pF to be added. This error
is not necessarily the same for every setting. This
also makes the unit susceptible to noise. However,
for high capacitance, the unit may be used as a 2-ter-
minal device.

6
HACS-Z-A-6E-1pF
6 Maintenance
MAINTENANCE
Chapter 4
4.3 General Considerations
It is important, whenever calibrating the HACS-Z
unit, to be very aware of the capabilities and limita-
tions 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 signifi cantly 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 HACS-Z 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.
4.1 Preventive Maintenance
Keep the unit in a clean environment. This will help
prevent possible contamination.
The HACS-Z is packaged in a closed case, which lim-
its the entry of contaminants and dust into the instru-
ment. If it is maintained in a clean or air-conditioned
environment, cleaning will seldom be required. In a
contaminated atmosphere, cleaning may be required.
To clean the front panel, wipe the front panel using
alcohol and a lint-free cloth.
4.2 Calibration Interval
The recommended calibration interval for the
HACS-Z Capacitance Substituter 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 certifi ed calibration laboratory.
If the user should choose to perform this procedure,
then the considerations below should be observed.

7
HACS-Z-A-6E-1pF
7Maintenance
4.4 Calibration Procedure
To calibrate the unit, proceed as follows:
1. Determine and employ proper metrological
practices.
Allow a confidence band for the uncer-
tainty of the measuring instrument and
setup.
2. Set test conditions:
No zero subtraction required
At 1 Vrms, series model, 23°C
3. Using 3-terminal measurement confi rm the
zero capacitance of the unit is ≤0.1 pF.
4. Determine the allowable upper and lower lim-
its for each capacitance setting of each decade
based on the specifi ed accuracy.
For the HACS-Z series, these limits for
any capacitance “C” are:
C±(0.1% + 1.0 pF)
5. Confi rm that the readings fall within these
limits, allowing for the uncertainty band.
6. If any reading falls outside these limits, the
associated step(s) may require adjustment (See
section 4.5 for details).
4.5 Capacitance Adjustment
The various decades are adjustable as follows:
Steps Capacitor Type
1 pF Air capacitor/trimmable
10 pF Air capacitor/trimmable
100 pF Air and mica capacitor/trimmable
1,000 pF Air and mica capacitor/trimmable
0.01 µF Mica capacitor/padders
0.1 µF Mica capacitor/padders
Table 4-1: Capacitor type

8
HACS-Z-A-6E-1pF
8Maintenance
To adjust 1 pF - 1,000 pF decades, proceed as follows:
1. Remove the rear panel; see Figure 4-1.
This exposes the trimmers for each de-
cade; see Figure 4-2.
Figure 4-1: Screws holding the rear panel
2. Adjust each decade in ascending order,
starting with the lowest value of the lowest
decade.
Figure 4-2: Calibration access holes
To make adjustments:
A. Set all dials to zero except for the decade
in question.
B. Set that decade to the value indicated on
the trimmer label, in the nominal order
of 1-2-4-5 starting with the smallest.
When taking a measurement, use a
nonmetallic screw driver or tool.
Screws
holding the
rear panel
To adjust the 10 nF and 100 nF decades - if technical
capability for this process is available - proceed as
follows:
1. Loosen the four 10-32 screws holding the
cabinet and slide the cabinet off the unit; see
Figure 4-3.
Figure 4-3: Screws holding the cabinet
2. Locate the particular capacitance of the 1-2-
4-5 set of the particular decade that needs to
be adjusted. See capacitor-labels; see Figure
4-4
Figure 4-4: 10 nF & 100 nF capacitance sets
3. Locate the padder capacitor if installed across
the particular capacitor in question.
4. Adjust the padder up or down by adding or
removing a capacitor trimmer.
5. Confi rm calibration.
6. Replace the cabinet.
Screws
holding the
cabinet
100 nF
Set
10 nF
Set

9
HACS-Z-A-6E-1pF
9Maintenance
4.6 Replaceable Parts
Model Ref IET Pt No Description
1 0505-4030 Mica Capacitor, 100 pF
1 0505-4031 Mica Capacitor, 200 pF
1 0505-4032 Mica Capacitor, 500 pF
1 0505-4033 Mica Capacitor, 1 nF
1 0505-4034 Mica Capacitor, 2 nF
1 0505-4035 Mica Capacitor, 5 nF
1 0505-4036 Mica Capacitor, 10 nF
1 0505-4037 Mica Capacitor, 20 nF
1 0505-4038 Mica Capacitor, 50 nF
1 0505-4039 Mica Capacitor, 100 nF
1 0505-4040 Mica Capacitor, 200 nF
1 0505-4041 Mica Capacitor, 500 nF
2 4380-3700 Air Capacitor, 2.7-19.6 pF
3 4380-3600 Air Capacitor, 1.7-8.7 pF
4 4380-3500 Air Capacitor, 1.5-5.0 pF
5 HACS-Z-520033 Switch Assembly
6 HACS-Z-4300-KNB Knob Assembly
Not Visible HACS-Z-PE4091 HIGH bnc connector
Not Visible HACS-Z-31-221-RFX LOW bnc connector
Not Visible 1413-BC-14215 Bail assembly
Table 4-2: Replaceable Parts List
Figure 4-5: Replaceable Parts
1
4
5
6
2
3