Download Measurement methods

Measurement methods
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Atos 2 - Measurement methods
1
Introduction
The Slides in this Presentation
are representation of the Measurement Theories
rather than the actual model and instruments behavior
in the SPEA Systems.
For further detailed information on the models
and the instruments setup for each measurement
type please refer to the document titled
“Leonardo YA: Passive devices test methods “
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Resistor - Voltage measurement method
Two wires measurement
1
• The generator “G” forces a programmed current (Io) through Rx.
I0
• The voltage meter “M” measures the voltage drop on Rx (VRx).
Tp
• Applying the Ohm law the expected voltage will be:
VRx = Io • Rx
G
M
Rx
VRx
(V = 0.25V when I = 0.25ma and R = 1K ohm)
Tp
Typical application range: 100W ÷ 100KW
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Resistor - Voltage measurement method
Two wires measurement: wiring and contact resistance effect
1
I0
• The generator “G” forces a programmed current (Io) through Rx
Rh
Tp
• The voltage meter “M” measures the voltage drop on Rx (VM)
• If the forced current is relatively “high” (> 2.5mA) the wiring and
the contact resistance (Rh and Rc) will influence the measure
VRh
G
M
VM
Rx
VRc
Tp
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VRx
• The measured value (VM) will be influenced by the voltage drop
on these resistances:
VM = VRh + VRx + VRc
• The smaller the resistance value of Rx the bigger the
wiring and the contact resistance influence
Rc
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Resistor - Voltage measurement method
Four wires measurement (Kelvin measure)
1
I0
Rh
• The generator “G” forces a programmed current (Io) through Rx.
Tp
Tp
• The voltage meter “M” measures the voltage drop on Rx (VRx).
• If the forced current is relatively “high”(> 2.5mA) the wiring and
the contact resistance (Rh and Rc) will influence the
measure.
VRh
Rx
G
VRx
M
VM
VRc
Rc
Tp
• Two additional test points are used to connect the voltage
meter “M” to the circuit. Due to its high impedance the
measured voltage drop (VRx) will be equal to the voltage drop on
the tested resistor.
Tp
Typical application range: 100W
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Resistor - Voltage measurement method
Guard measurement
1
• The generator “G” forces a programmed current (Io) through Rx.
G
I0
Is
• The voltage meter “M” measures the voltage drop on Rx (VRx).
• Due to the circuit configuration the measured voltage drop will
be equal to:
Rs
B
A
VRx = Io • (Rx // Rs + Rp)
Ix
G
M
Rx
Rp
VM
• To measure Rx without the influence of Rs and Rp it is necessary
to have a Is current equal to 0; this is possible if the point “B”
is at the same voltage of point “A”
• The Guard is a “voltage follower” and is used to isolate the tested
component from the rest of the circuit.
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Resistor - Voltage measurement method
Parallel capacitance effect
1
• The resistor measurement forces a current pulse, the
measured value will be a voltage pulse.
I0
• The parallel capacitor present in the circuit will absorb the
current pulse until the Ton is long enough to charge the
capacitor.
G
M
Rx
VRx
Cp
I
I
t
t
V
V
t
Code:
R1.6
Measurement methods
t
7
Resistor – Current measurement method
Two wires measurement
1
• The generator “G” generates a programmed voltage (Vo) on Rx.
• The voltage meter “A” measures the current flow through Rx
(IRx).
G
V0
Rx
• Applying the Ohm law the expected current will be:
Vo
IRx = -------Rx
A
IRx
Typical application range:  50KW
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Resistor - Current measurement method
Current compensated measurement
1
• The generator “G” generates a programmed voltage (Vo) on Rx.
• The voltage meter “A” measures the current flow through Rx
(IRx).
G
V0
Rx
• If the resistor value is relatively “high” (> 100KW) the measured
current could be near the generator leakage current
A
IRx
Typical application range:  100KW
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• Applying Ohm’s law the expected current will be:
Vo
IRx = -------Rx
• To avoid this leakage current influence the leakage current is
measured in a HLD (hold) test
• The actual device under test current is measured next and the
leakage current value is subtracted from the actual value.
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Capacitor - Voltage measurement method
Two wires measurement
1
• The generator “G” forces a programmed current (Io) through Cx.
I0
• The voltage meter “M” measures the voltage Cx (VCx).
VCx
G
M
CX
• The measured value is related to the capacitor charge by the
following formula:
I
Io • T
I0
VCx = --------Cx
t
V
VCx
t
Typical application range: 100nF ÷ 1µF
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10
Capacitor - Voltage measurement method
Two wires measurement: wiring and contact resistance effect
1
• The generator “G” forces a programmed current (Io) through Cx
I0
G
M
Rh
• The voltage meter “M” measures the voltage drop on Cx (VCx)
VRh
• If the forced current is relatively “high”, the wiring and the contact
resistance (Rh and Rc) will influence the measure
VM
CX
VCx
• The measured value (VM) will be influenced by the voltage drop
on these resistances, adding an “offset” calculated as follow:
VM = VCx + VRh + VRc
I
VRc
VRh = Io • Rh
I0
VRc= Io • Rc
Rc
t
V
VM
VCx
DV
t
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Capacitor - Voltage measurement method
Four wires measurement (Kelvin measure)
1
• The generator “G” forces a programmed current (Io) through Cx.
I0
Rh
Tp
• The voltage meter “M” measures the voltage drop on Cx (VCx).
Tp
• If the forced current is relatively “high”, the wiring and the
contact resistance will influence the measurement.
VRh
CX
G
VCx
M
VRc
Rc
Tp
• Two additional test points are used to connect the voltage
meter “M” at the circuit. Due to its high impedance the measured
voltage drop (VCx) will be equal to the voltage drop on the tested
resistor.
Tp
Typical application range:  10µF
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Capacitor - Time measurement method
Two wires measurement
1
• The generator “G” forces a programmed current (Io) through Cx.
I0
• The timer “C” measures the time elapsed between the
programmed thresholds (V1 and V2).
G
C
CX
VCx
• The measured value is related to the capacitor charge by the
following formula:
Cx • (V2 – V1)
T = -------------------Io
I
I0
VCx
Typical application range: 1nF ÷ 100nF
t
V2
V1
t
T
Code:
R1.6
Measurement methods
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Capacitor – AC Current measurement method
Two wires measurement
1
• The generator “G” generates a sinus waveform on the Cx
capacitor pins.
I0
• The current meter “A” measures the current flow in the capacitor
at the zero crossing of the Voltage.
• The measured current value is directly converted to the relative
capacitive current value, by the system CPU.
G
CX
VM
V
A
I
Typical application range: 5pF ÷ 100nF
Code:
R1.6
Measurement methods
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Inductor - Current measurement method
1
• The generator “G1” generates a continuous voltage (V1)
• The generator “G2” generates a negative pulse voltage (V2)
• The inductor reaction to the negative pulse is a reverse current
flow measured by “G2”
LX
G1
V1
V2
G2
• The reverse current can be used to calculate the inductance by
the following formula:
I0
T • (V1)
I = -------------------Lx
A
Typical application range:  10mH
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Inductor - Time measurement method
Two wires measurement
• The test generator “G” charges the internal 10µF
capacitor
1
G
VRx
C
• During the test execution the capacitor is discharged by the
inductor
• This generates an oscillation (ring) of a frequency value related to
the inductor value.
Internal
Circuitery
• The counter “C” measures the time interval (TM) elapsed between
two defined thresholds, it can be measured applying the following
formula:
V
G
TM = p · LC
VTH
t
Typical application range: 1mH ÷ 10mH
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TM
16
Diode & LED – Vf measurement method
Two wires measurement
1
• The generator “G” forces a programmed current (If) through the
junction.
• The voltage meter “M” measures the voltage drop (Vf) on the
junction
G
M
Vf
If
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Diode & LED – Vf measurement method
Four wires measurement (Kelvin measure)
1
Rc
Tp
Tp
• The voltage meter “M” measures the voltage drop (Vf) on the
junction
VRc
G
Vf
If
• The generator “G” forces a programmed current (If) through the
junction.
M
• If the forced current is relatively “high” the wiring and the contact
resistance will influence the measurement.
• Two additional test points are used to connect the voltage
meter “M” to the circuit. Due to its high impedance the measured
voltage drop (Vf) will be equal to the voltage drop on the junction
Rh
Tp
Tp
VRh
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Zener Diode – Vf measurement method
Two wires measurement
1
• The generator “G” forces a programmed current (If) through the
junction.
• The voltage meter “M” measures the voltage drop (Vf) on the
junction
G
M
Vf
If
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Zener Diode – Vz measurement method
Two wires measurement
1
• The generator “G” forces a programmed current (If) through the
junction.
If
• The voltage meter “M” measures the voltage drop (Vz) on the
junction
G
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M
Vz
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Bipolar Transistor
1
• All the typical bipolar transistor parameters can be tested.
• Orientation tests can be performed (VBE and VBC)
C
• Working tests can be performed (VCE0 and VCE sat)
• Parametric tests are possible (ß gain, …)
B
E
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Bipolar Transistor – VBE measurement method
Two wires measurement
1
• The generator “G” forces a current between Base and Emitter
• The voltage meter “M” measures the voltage drop between the
junction Base and Collector (VBE).
If
• VBE junction measurement should be near 0.7V
B
E
VBE
G
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M
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Bipolar Transistor – VBC measurement method
Two wires measurement
1
If
• The generator “G” forces a current between Base and Collector
• The voltage meter “M” measures the voltage drop between the
junction Base and Collector (VBC).
• VBC junction measurement should be near 0.7V
G
M
VBC
C
B
E
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Bipolar Transistor – VCE0 measurement method
1
• The generator “G” generates a voltage drop between transistor
Collector and Emitter (VCE0)
• The transistor Base is shorted to Emitter (for NPN transistor)
• The transistor Base is shorted to Collector (for PNP transistor)
C
B
VCE0
• The current meter “A” measures the current flow between
transistor pins Collector and Emitter (ICE0).
E
ICE0
A
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G
• With this test configuration the transistor is in “interdiction” mode
(off = zero current)
• ICE0 = 0mA
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Bipolar Transistor – VCEsat
measurement method
Two wires measurement
1
• The generator “G1” forces a current between the Base-Emitter
junction in order to bias the transistor “ON” 1
• The generator “G2” forces a current between the transistor pins
Collector and Emitter 1
C
• With this test configuration the transistor is in saturation mode
B
G1
VCE
E
VBE
M
G2
• The voltage meter “M” measures the voltage drop between
transistor pins Collector and Emitter (VCEsat).
• VCEsat = 0V
Typical application range: signal transistor
1 = The current is forced in accord to the transistor technology (NPN or PNP)
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Bipolar Transistor – VCEsat
measurement method
Four wires measurement (Kelvin measure)
1
• If the forced current is relatively “high” (>10mA) the wiring and
the contact resistance (Rh and Rc) will influence the measured
voltage drop between the Collector-Emitter junction
Rh
C
B
G2
VCE
E
G1
VBE
• The generator “G1” generates a voltage to bias the
Base-Emitter junction “ON”.
• The generator “G2” provides a voltage bias between the
Collector and Emitter
Rh
M
• With this test configuration the transistor is in saturation mode
2
• Due to this the wiring and the contact resistances (Rh and Rc)
the transistor test is performed in two steps
Rh
C
B
VCE
E
G1
VBE
Rh
M
G2
• During the first test the voltage drop caused by the wiring and the
contact resistance is measured by the voltage meter “M” and
stored in a register. This stored value will modify the CE voltage
measurement.
• During the second test the voltage drop between the
Collector-Emitter junction is measured by the voltage meter “M”
Typical application range: medium/power transistor
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Mos-Fet Transistor
1
• All the typical Mos-Fet transistor parameters can be tested.
• Orientation test can be performed (Vf of the protection diode)
• Operating tests can be performed (VDS off and VDS on)
D
• Parametric tests are possible (RDS on, …)
G
S
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Mos-Fet Transistor – Orientation test method
Two wires measurement
1
• A diode test can be used to measure the
protection diode present between pins Drain and Source
• The generator “G” forces a current (If) between the
Drain and Source
D
Vf
G
S
If
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M
G
• The voltage meter “M” measures the voltage drop between
the Drain and Source
• If the protection diode is present and the part mounted correctly
the voltage meter should measure a forward biased diode voltage
near 0.7V
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Mos-Fet Transistor – Vds off measurement method
Two wires measurement
1
• The generator “G1” generates a voltage equal to 0 between
transistor pins Gate and Source (for N-channel)
• The generator “G2” tries to force a current between transistor pins
Drain and Source
D
G2
G
G1
• The current meter “A” measures the current flow between
transistor pins Drain and Source.
S
Im
A
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• In these conditions the Mos-Fet transistor is “OFF”
• Measured Current should be near “0mA”.
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Mos-Fet Transistor – Vds on measurement method
Two wires measurement
1
• The generator “G1” generates a voltage drop between transistor
Gate and Source (for N-channel)
• The generator “G2” forces a current between transistor Drain
and Source
D
G2
G
G1
• The current meter “A” measures the current flow between
transistor pins Drain and Source.
S
Im
A
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• In these conditions the Mos-Fet transistor works in “ON” condition
• Measured current should be about 10ma (normal test).
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Transformer
1
• Typical transistor parameters can be tested.
• The transformer phase can be verified
• The transformer ratio can be measured
• The impedance values of the transformer coils can be measured
Rel. 1.20 - 01.03.01
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Transformer – Impedance measurement method (Resistance)
Four wires measurement (Kelvin measure)
1
Tp
Tp
• Resistance value for a transformer winding can be measured.
Low Ohm values may require a Kelvin measurement
• The generator “G” forces a programmed current (Io) through
transformer winding.
G
M
VRx
• The voltage meter “M” measure the voltage drop on the winding
• Because the coil resistance value is usually small the wiring
and the contact resistance will influence the measure
Tp
Tp
• Two additional test points are used to connect the voltage
meter “M” across the coil. Due to DVM high impedance the
measured voltage drop (VRx) will be equal to the voltage drop
on the tested resistor/coil.
Resistor measurement
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Transformer – Phase measurement method
Two wires measurement
1
• The generator “G” forces a pulse on the transformer primary coil
• The voltage meter “M” measures a voltage value and phase as
as produced by the transformer secondary coil.
G
Rel. 1.20 - 01.03.01
M
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Transformer –
Ratio measurement method
Two wires measurement
1
• The generator “G” forces a pulse on the transformer primary coil
G
• The voltage meter “M” measures and stores the voltage drop
across the transformer primary winding
M
• The generator “G” forces a pulse on the transformer primary coil
• The voltage meter “M” measures the voltage drop on the
transformer secondary winding
2
G
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• The voltage meter “M” performs a percent ratio calculation
between the measured secondary voltage value and the previously
stored primary voltage value
M
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Optocoupler
1
• Typical opto-coupler parameters can be tested.
• The led orientation is usually the first measurement
• The voltage drop on the output during both the operating modes
(“On” and “Off”) can be measured.
Rel. 1.20 - 01.03.01
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Optocoupler – LED Vf measurement method
1
• The generator “G” forces a programmed current (If) through the
LED
• The voltage meter “M” measures the voltage drop (Vf) on the LED
• This verifies that the LED is present, working and correctly oriented
G
M
Vf
If
Rel. 1.20 - 01.03.01
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Optocoupler – Vce sat measurement method
1
• The generator “G1” forces a programmed current (If) through the
LED.
• The output transistor is biased into “saturation” mode
G1
If
Rel. 1.20 - 01.03.01
• The generator “G2” forces a current between the Collector-Emitter
junction
VM
M
G2
• The voltage meter “M” measures the voltage drop on the Collector
Emitter junction (VCE sat) (near zero volts)
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Optocoupler – Vce 0 measurement method
1
• The generator “G1” generates a voltage equal to 0V through the
LED.
• The output transistor is in “interdiction” “OFF” mode
If
G1
VM
M
G2
• The generator “G2” tries to force a current between the CollectorEmitter junction on the output transistor.
• The voltage meter “M” will measure the voltage limit of “G2” (VCE0)
because the transistor is “OFF” and no Emitter-Collector current
flows.
Rel. 1.20 - 01.03.01
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Relay
1
• All the typical relay parameters can be tested.
• Coil resistance value can be tested
• Contact verification (open and close) can be done
• Coil minimum operating voltage can be done
• Release voltage can be done
• Attraction time can be done
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Relay – Coil resistance measurement method
Four wires measurement (Kelvin measure)
1
I0
• The generator “G” forces a programmed current (Io) through the
relay coil
Rc
• The voltage meter “M” measures the voltage drop across the
coil
VRc
VM
G
M
• If the forced current is relatively “high” the wiring and the contact
resistance (RC and RH) will influence the measure
• Two additional test points are used to connect the voltage
meter “M” at the circuit. Due to its high impedance the
measured voltage drop (VM) will be equal to the voltage drop
on the coil.
Rh
VRh
Rel. 1.20 - 01.03.01
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Relay – Contact verification method
Two wires measurement – Cold method
1
I0
• The generator “G” tries to force a programmed current (Io)
through the normally open contact (or normally closed)
• The voltage meter “M” measures the voltage drop on it
VM
Rel. 1.20 - 01.03.01
M
G
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Relay – Contact verification method
Two wires measurement – Hot method
1
I0
• The generator “G1” generates the required voltage on the relay
coil to energize the contact.
• The generator “G2” tries to force a current (I0) between the
contact pins
G1
VM
M
G2
• The voltage meter “M” measures the voltage drop (VM) on the
contact pins.
• Measured voltage will be near be 0 across closed contacts and
near the programmed voltage of “G2” across open contacts
Rel. 1.20 - 01.03.01
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Relay – Working verification method
Coil minimum operating voltage
1
I0
• The generator “G1” generates the minimum operating voltage
(generally equal to 2/3 of nominal voltage) on the relay
coil.
• The generator “G2” forces a current (I0) between the contact
pins
G1
Rel. 1.20 - 01.03.01
VM
M
G2
• The voltage meter “M” measures the voltage drop (VM) on the
contact pin, it must be near be 0 with normally open contact and
near to the programmed voltage of “G2” with normally closed
contact
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Relay – Working verification method
Coil Release voltage
1
I0
• The generator “G1” generates the release voltage (generally
equal to 1/10 of nominal voltage) on the relay coil.
• The generator “G2” forces a current (I0) between the contact
pins
G1
Rel. 1.20 - 01.03.01
VM
M
G2
• The voltage meter “M” measures the voltage limit of “G2” with
normally open contact
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Relay – Working verification method
Attraction time
1
• The generator “G1” generates the required voltage on the relay
coil to cause the contacts to close
I0
• The generator “G2” forces a current (I0) between the contact pins
• The counter “C” measures the time (TM) elapsed between the
two programmed thresholds on the contact pin voltage (VM)
G1
VC
VM
C
G2
VC
t
VM
V1
V2
t
TM
Rel. 1.20 - 01.03.01
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Special Test; Analog Functional IC test
1
Driver2 supplies VCC to the board
Driver1 supplies logic high voltage to input of IC
Measurement Unit measures logic low voltage on IC output
Duplicate test and invert voltage settings for opposite logic level test
Use same setup to power up and measure regulator output voltage
46
ATOS 2 Programming Training Course
Open pin – Electroscan
FUNCTIONAL SCHEME
Mux
Conditioning circuit
~
+
~
-
Active Probe
A
A
M
Electroscan Box
Sensor plate
Integrated circuit
Printed circuit
GND
• The generator “G1” generates a sinus waveform that is injected through the pin of the IC.
Nail
Nail
• The sensor plate picks-up the electromagnetic field and the active probe amplifies the
signal. The Electroscan Box selects, by using the Multiplexer Stage, the relevant input and
converts the alternating signal to a continuous one.
• The voltage meter “M” measures the Electroscan Box continuous signal output.
G1
• If the pin is soldered, the current pass through the IC and generates a changing
electromagnetic field. So we can appreciate an output of the Electroscan Box of 2-10V. If
the pin is not soldered, the Electroscan Box output signal would normally be significantly
lower than 2 V.
• In the 3030 system, “ Electroscan Box ” and “G1” are integrated within a internal system
board named “YA32ESCAN”.
Code:
R1.6
Measurement methods
47
Open pin – Clamp diodes
Vcc
• Each pin of an integrated circuit is usually connected to two diodes
how it is shown in the schematics. Such diodes are normally within the
IC.
Internal diode A
• Measuring one of the internal diodes, it is possible to assure that the
pin is soldered.
Pin
• If the pin is not soldered, you will measure an open circuit, otherwise
you will measure a diode junction. In order to detect if the pin is
soldered, it is enough to measure one of the two internal diodes.
Internal diode B
Integrated circuit
GND
Code:
R1.6
• If a similar pin (or a diode or something electrically similar) is
connected in parallel to the pin under test, a problem rises: it’s not
possible to discriminate if the pin under test is soldered. In such
configuration you can’t use the “Clamp diode” measure method.
Measurement methods
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Open pin – Clamp diodes
Vcc Device
Test Pin-Vcc diode
Internal diode A
G
M
Vf
• The generator “G” forces a programmed current (If) through the
junction.
• The voltage meter “M” measures the voltage drop (Vf) on the junction
Pin device
If
Test Gnd-Pin diode
Pin device
Internal diode B
G
• The generator “G” forces a programmed current (If) through the
junction.
• The voltage meter “M” measures the voltage drop (Vf) on the junction
M
Vf
GND device
If
Code:
R1.6
Measurement methods
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