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Defib Test Fixture – Specification and Validation
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Datascope Engineering Form E112.5
DIVISION
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0454-00-0034
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Defib Test Fixture – Specification and Validation
TABLE OF CONTENTS
1.0 Introduction .......................................................................................... 3
2.0 Theory of Operation ............................................................................. 3
3.0 Test Fixture Configurations ................................................................ 6
3.1 Defibrillator Load Configuration ...................................................... 6
3.2 Limiting Resistor Configuration ....................................................... 6
3.3 Polarity Configuration ...................................................................... 6
3.4 Inductor Configuration ..................................................................... 7
4.0 Construction Notes ............................................................................... 7
4.1 High Voltage Nodes of Interest ........................................................ 7
4.1.1 Defib configuration Jacks and Jumpers .................................................. 7
4.1.2 Wiring Concerns ............................................................................. 7
4.2 User Safety Concerns........................................................................ 7
5.0 Operating Instructions ......................................................................... 8
6.0 Validation .............................................................................................. 8
5.1 Validation Procedure (AAMI) .......................................................... 8
5.2 Validation Procedure (IEC) ............................................................ 10
APPENDIX A - SCHEMATICS ................................................................ 12
APPENDIX B – ENERGY CALCULATION .......................................... 14
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1.0
Introduction
This document describes the design, construction and validation of the Defib Test Fixture. The
Defib Test Fixture is a test device that shall be used to implement the various defibrillator test
circuits specified in AAMI and IEC standards.
2.0
Theory of Operation
The Defib Test fixture must conform to the following configurations:
Figure 1 - EC13 Figure 9A
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Figure 2 - EC13 Figure 9B
Figure 3 - IEC601-2-27 Figure 106A
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Figure 4 - IEC601-2-27 Figure 106B
The parameters of the Defib Test Fixture can be configured to conform to a number of different
effective circuits shown in the above figures. These different configurations are described in
section 3.0 of this document.
When attached to the high voltage generator, current will flow through R1 (125k) and initially
flow through resistor R2 (125k). Holding down the momentary push button “Charge” switch
will cause the normally closed relay, SW2, to open allowing the high voltage capacitor, C1, to
charge up with an RC time constant of R1*C1 = 125K*32uF = 4s. (Ignoring the negligible DC
resistance of inductor L1) After holding down the charge switch for 4 time constants or 16
seconds, the capacitor (C1) will have charged up to within 1% of 5kV.
The timing Relay, TM1, must be configured to allow current to flow through the coil of relay
SW1 for 200ms ± 100ms. The timing relay can be configured to produce this effect. The
operating mode of the relay must be set to “C002.1”, where the significant digits on the relay
must be set to “002”, and the multiplier on the relay must be set to “0.1s”. By configuring TM1
in this manner, in the circuit described in Appendix A of this document, SW 1 will switch from
R1 over to R3 for 200ms.
Without the inductor, L1, there would simply be a capacitive discharge with an RC time
constant of R3*C1=100*32uF=3.2ms. However, due to L1, which will resist the immediate
change in current through the circuit, a waveform is obtained similar to that shown in figure 5.1
of this document.
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3.0
Test Fixture Configurations
3.1
Defibrillator Load Configuration
The test figure can be configured to deliver the energy across a 100 Ohm load, R3, or the test
fixture can be configured to apply the 5KV across a 100k load, R4. To use the test fixture in
the first configuration, a high voltage jumper must be places from J1 to J2. To use the test
fixture in the second configuration, a high voltage jumper must be placed from J1 to J3 instead.
J1, J2 and J3 are labeled as follows inside the test fixture: If there is no jumper in place, the
energy will simply be drained by R2 when the charge button is released.
J1
J2
J3
COM
100 OHM
100K
3.2
Limiting Resistor Configuration
The limiting resistor can be configured to 50 Ohms (R5), 400 Ohms (R5+R6) or 50K
(R5+R6+R7, where R5 and R6 are insignificant compared to the tolerance of R7).
To configure the test fixture for 50 Ohms, a high voltage jumper is placed between J4 and J6,
shorting out R6 and R7, leaving only R5.
To configure the test fixture for 400 Ohms, a high voltage jumper is placed between J5 and J6,
shorting out R7, leaving R5 and R6.
To configure the test fixture for 50K, no high voltage jumper is placed in the circuit.
J4, J5, and J6 are labeled inside the test fixture as follows:
J4
50 Ohms
J5
400 Ohms
J6
COM
A sticker specifying “50K if open” is also placed inside test fixture.
The inductor has to be configured according to the standard the test is going to be carried with.
The jumpers JA and JB are used to switch between AAMI and IEC standards respectively.
3.3
Polarity Configuration
The test fixture can be configured for either positive or negative polarity. If configured for
positive polarity, the positive side of capacitor C1 is applied to the limiting resistor preceding
P1 and the negative side of capacitor C1 is applied to P2. If configured to negative polarity, the
negative side of the capacitor is applied to the limiting resistor preceding P1, and the positive
side of capacitor C1 is applied to P2.
This configuration is changed by switch SWXX on the top of the test fixture, labeled
“POLARITY”. When configured for positive polarity, this switch is in the open position and
no current flows through the coil of high voltage relay SW3. In its normal position, SW3 will
create the positive polarity situation described above. When switch SWXX is placed in the
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negative position, or closed, current will flow through the coil of relay SW3, and the negative
polarity situation, described above, will be created.
3.4
Inductor Configuration
The wave-shaping inductor can be configured to whatever is needed for the current test being run. While the
AAMI EC-13 test procedure chooses to test with a more realistic defibrillator wave-shape using an inductor on the
order of 25mH (this inductor value may be changed so long as the wave-shape still meets requirements defined in
the validation section of this document per EC13), the IEC tests use a potentially more destructive wave-shape
formed by a 500uH inductor.
The
4.0
Construction Notes
4.1
High Voltage Nodes of Interest
4.1.1 Defib configuration Jacks and Jumpers
The J1, J2, J3, J4, J5, and J6 jacks are used to configure the test fixture, as needed by
various industry standards. Be advised that the jacks, as well as the jumper used to
connect them, will reach relatively high voltages as well as relatively high instantaneous
current. Throughout the entire test fixture, it is important to place components not rated
for greater than 5000V at a distance great enough from one another to prevent arcing.
In general, if adequate spacing is observed between high voltage parts of the test fixture,
the rated voltage on single conductor component, such as jacks and plugs, can be
ignored.
4.1.2
Wiring Concerns
All high voltage wiring within the test fixture should be done with a wire rated for
greater than 5000V, such as Rowe Industries part number R800-1022-100-9, rated at
10kV. Any open solder points should be kept at a distance great enough to prevent a
5kV arc from any other conductive point.
Also, all high voltage nodes should be kept an a great enough distance from any wires
carrying low voltage signals, such as relay controls. It may be helpful to route low
voltage signals around the sides of the box and high voltage in the center.
4.2 User Safety Concerns
User safety must be of primary concern when laying out the defib test fixture. The following
guidelines should be followed:
 User controls should be kept on the opposite end of the test fixture from any points of the
test fixture reaching high voltages.
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

5.0
“Charge” and “Fire” switches should be kept on opposite sides of the test fixture from one
another such that the operator cannot physically operate the unit without both hands being
away from the high voltage.
Any high voltage monitoring should be kept isolated from low voltages points that may
leave the box at unsafe places. For example – by operating the Capacitor charge
monitoring circuit shown in Appendix A from a 9 volt battery, there is no worry of high
voltages harming the 12v power supply or the operator whom might be in the vicinity of the
12v power supply.
Operating Instructions
Step 1 – Attached cable marked “HV INPUT” on the Defib Test Fixture to connector J2 labeled
“HIGH VOLTAGE” on the high voltage generator.
Step 2 – Attach the wires labeled “High Voltage Enable” to screw terminals 14 and 15 on the
“TB 1 – I/O INTERFACE” on the back of the high voltage generator.
Step 3 – Attach a 12V power supply to the banana plug input labeled “+12V” on the top of the
Defib Test Fixture.
Step 4 – Attach the device under test to the Defib Test Fixture according to the procedure being
followed.
Step 5 – Attach a calibrated DVM to the banana plug output labeled “CAP MONITOR”.
Step 6 – While holding down both “CHARGE” buttons on the side of the Defib Test Fixture,
push the “HV ON” button on the High Voltage power supply and set the output to 5kV. Once
the DVM reads 4.95 – 5.05 volts, press the “FIRE” button on the Defib Test Fixture to
discharge the Capacitor across the patient load.
6.0
Validation
5.1
Validation Procedure (AAMI)
Step 1 – Configure Defibrillator Load in the test fixture to 100 Ohms. Configure the Limiting
resistor to 400 Ohms. Plug jumper J to select the inductor for AAMI configuration. Configure
the Polarity to Positive.
Step 2 – Using a Tektronix 744A 4-channel digitizing oscilloscope and the Tektronix High
Voltage Differential Probes, monitor the differential “Output Monitor”.
Step 3 – Set up the scope such as to capture an amplitude of approximately 8 volts over a total
time of approximately 100ms. Note: These settings are only an approximate starting point, set
up the scope, such as to capture the measurements required below. (Table 1)
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Step 4 – When the Unit is operated per the operating instructions, capture to following
approximate output waveform from the oscilloscope:
Figure 5 – Defib Test Fixture Waveform Output
Step 5 – Attach a calibrated multimeter to the “capacitor monitor” output. Charge the capacitor
to 5000V by holding down the momentary push button “Charge” switch until the multimeter
reads 5v. Short out the signal generator by closing the switch (If signal generator is connected).
Depress the momentary push “fire” switch to discharge the capacitor.
Step 6 – Take the following measurements, as indicated in the figure above, and verify that all
measurements are within the specified tolerances. The figure is labeled in current, the table
accounts for a test across a 100 Ohm load and is labeled in voltage.
Waveform
Parameter
VP
VR
V20max
tr
t50
t10
Minimum
Acceptable
2645 volts
N/A
N/A
0.30 ms
2.30ms
4.00ms
Measured
Value
Maximum
Acceptable
4849 volts
0.4 * Vp
0.4 * Vp
1.25ms
6.40ms
19.60ms
Pass/Fail
Table 1
VP – Peak voltage of the waveform
VR – Maximum reverse voltage of the waveform. Note: Test fixture may not result in any
reverse voltage at all.
V20max – Maximum voltage after 20ms.
tr – 10% to 90% rise time of the first lobe of the waveform.
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t50 – time between 50% of VP on the rising edge of the first lobe and 50% VP on the falling
edge of the first lobe.
t10 - time between 10% of VP on the rising edge of the first lobe and 10% VP on the falling
edge of the first lobe
Step 7 – Save the output of the defib test fixture as seen on the scope into a “.cvs” format and
using excel calculate the energy delivered. Integrating V2/R over time will give the energy
delivered. Verify that the energy delivered is within 10% of 400J. (See appendix A for a more
detailed description of the required calculation)
Parameter
Energy
Minimum
Acceptable
360 Joules
Measured
Value
Maximum
Acceptable
440 Joules
Pass/Fail
Table 2
5.2
Validation Procedure (IEC)
Step 1 – Configure Defibrillator Load in the test fixture to 100 Ohms. Configure the Limiting
resistor to 400 Ohms. Plug jumper J to select the inductor for IEC configuration. Configure
the Polarity to Positive.
Step 2 – Using a Tektronix 744A 4-channel digitizing oscilloscope and the Tektronix High
Voltage Differential Probes, monitor the differential “Output Monitor”.
Step 3 – Set up the scope such as to capture an amplitude of approximately 8 volts over a total
time of approximately 100ms. Note: These settings are only an approximate starting point.
Step 4 – Attach a calibrated multimeter to the “capacitor monitor” output. Charge the capacitor
to 5000V by holding down the momentary push button “Charge” switch until the multimeter
reads 5v. Short out the signal generator by closing the switch (If signal generator is connected).
Depress the momentary push “fire” switch to discharge the capacitor.
Step 5 – Save the output of the defib test fixture as seen on the scope into a “.cvs” format and
using excel calculate the energy delivered. Integrating V2/R over time will give the energy
delivered. Verify that the energy delivered is within 10% of 400J.
Parameter
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Minimum
Acceptable
Measured
Value
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Acceptable
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Energy
360 Joules
440 Joules
Table 3
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APPENDIX A - SCHEMATICS
Figure 6
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Figure 7
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APPENDIX B – ENERGY CALCULATION
In order to validate the Defib Test Fixture we must measure the total energy delivered by the output
waveform. However, we do not have a direct method by which to measure the energy. Instead we
must integrate the output power waveform. Unfortunately, we cannot even measure the output power
directly either. The only quantity that we can measure directly is Voltage as a function of time, by
hooking up high voltage differential probes to the V+ / V- output monitor on the test fixture. However,
we know that this voltage is being applied across a 100-ohm resistor. Knowing voltage and resistance
we can easily derive the current and power.
Current = Voltage / Resistance
Power = Voltage * Current = Voltage^2/Resistance
Using a Tektronix 744A oscilloscope, we can Save the waveform to a CSV file. This CSV file can be
opened using Excel to do all the necessary calculations. The steps are as follows:
1) Open the CSV file with Excel (or any other spreadsheet application) The first column of data
will be the voltages sampled by the scope, the second column will be the time. Since the
sampling is linear, we only need the difference between any two adjacent time values. We will
refer to this as the Sampling Period.
2) First, since the Output monitor is 1/1000 the actual output voltage, due to the voltage divider in
the test fixture, we must multiply column A by 1000. This can be done as B1=A1*1000 and
using the Fill Down command.
3) Next, we must calculate the power that each of these voltages corresponds to. This can be
calculated by D1 = C1^2/100 and using the Fill Down command. Column D is now
instantaneous samples of the power waveform. We can view this waveform by graphing
column D if we desire.
4) We want to find the integral of power with respect to time. Because this is defined as the area
under the power-time curve. To find this, first we must multiply each instantaneous power
measurement by the sampling period. For example, if the sampling period is 20us then we can
use E1 = D1*20*10^-6 and use the fill down command.
5) Column E is now our energy contained in each sampling period, to obtain the total power we
must sum the column. We can do this using SUM(E1:EXXX) where XXX is the row number
of the last used row in the spreadsheet.
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