The passage of
high frequency
electrical current
through tissue to
create a desired
clinical effect.
2/7/20091
Page 2
What tests should be done?
1.Output tests in each different mode;
cut, coagand bi-polar.
2.REM high and low trip points
3.RF Leakage test
2/7/20092
Page 3
Different loads for different modes.
Usually bi-polar mode is tested at 100 ohms load,
cut mode at 300 ohms and coagulation mode at
500 ohms. Measure the current, not the watts. RF
power output circuitry is 1 to 6 N channel
MOSFET’s in parallel. With age and thermal
damage, they begin to fail and the output voltage
drops. Circuitry compensates by increasing the
current thru the MOSFET’s. Current times voltage
equals wattage. Measuring wattage will not detect
2/7/2009
the drop in voltage, but measuring current will
detect the voltage drop. Valleylab specifically
states to test for current under specified load.
3
Page 4
ESU Math, not quite rocket science
√ Watt setting of ESU / Load setting of tester =
desired test result
Bi-Polar 10 Watts
√ 100 Ω
Coag30 W
√ 500 Ω
Cut 75W
√300 Ω
2/7/2009
= √.1= .316 amp = 316 mA
= √0.06 = .245 A = 245 mA
= √.25 = .5A = 500mA
4
Page 5
REM testing
•Testing must be done with the middle
pin of the r.e.m. connector present.
Without the pin, the e.s.u. switches to
non r.e.m. circuitry.
•If an e.s.u. is sent to mfr. for repair
with a r.e.m. fault, testing must be done
with the actual patient pad.
•Normal power output testing bypasses
r.e.m. circuitry.
2/7/2009
5
Page 6
ESU Vocabulary page one
1.Current
The number of electrons moving past a given point per second,
measured in amperes.
2.Current Density
The amount of current flow per unit of surface area; current
concentration directly proportional to the amount of heat generated.
3.Current Division
Electrical current leaving the intended electrosurgical circuit and
following an alternate path of least resistance to ground; typically the
cause of alternate site burns when using a grounded generator.
4.Cut
A low-voltage, continuous waveform optimized for electrosurgical
cutting.
5.Cutting
Use of the cut waveform to achieve an electrosurgical effect that
results from high current density in the tissue causing cellular fluid to
burst into steam and disrupt the structure. Voltage is low and current
flow is high.
2/7/20096
Page 7
ESU Vocabulary page two
1.Desiccation
The electrosurgical effect of tissue dehydration and protein
denaturation caused by direct contact between the
electrosurgical electrode and tissue. Lower current
density/concentration than cutting.
2.Diathermy
The healing of body tissue generated by resistance to the flow
of high-frequency electric current.
3.Direct Coupling
The condition that occurs when one electrical conductor (the
active electrode) comes into direct contact with another
secondary conductor (scopes, graspers). Electrical current
will flow from the first conductor into the secondary one and
energize it.
4.Direct Current
A flow of electrons in only one direction.
2/7/20097
Page 8
ESU Vocabulary page three
1.Fulguration: Using electrical arcs (sparks) to coagulate
tissue. The sparks jump from the electrode across an air gap
to the tissue.
2.Generator: The machine that coverts low-frequency
alternating current to high-frequency electrosurgical current.
3.Ground, Earth Ground: The universal conductor and
common return point for electric circuits.
4.Grounded Output: The output on a electrosurgical
generator referenced to ground.
2/7/20098
Page 9
ESU Vocabulary page four
•Impedance: A form of electrical resistance observed in an
alternating current that is analogous to the classic electrical
resistance that occurs in a direct current.
•Insulation Failure: The condition that occurs when the
insulation barrier around an electrical conductor is breached.
As a result, current will travel outside the intended circuit.
•Isolated Output: The output of an electrosurgical generator
that is not referenced to earth ground.
•Leakage Current: Current that flows along an undesired
path, usually to ground; in isolated electrosurgery, RF current
that regains its ground reference.
2/7/20099
Page 10
ESU Vocabulary page five
•Monopolar Output: A grounded or isolated output on an
electrosurgical generator that directs current through the patient
to a patient return electrode.
•Patient Return Electrode (PRE): A conductive plate or pad
(dispersive electrode) that recovers the therapeutic current from
the patient during electrosurgery, disperses it over a wide
surface area, and returns it to the electrosurgical generator.
•Power: The amount of heat energy produced per second,
measured in watts.
•Power Efficiency Rating (PER)
A measure of the ability of an electrosurgical generator to
accurately deliver the selected power into a wide range of tissue
types.
2/7/200910
Page 11
ESU Vocabulary page six
•Radio Frequency (RF): An electrical current that alternates the
poles in the radio frequency range (300 kHz–36 Hz); the highfrequency current used in electrosurgery.
•Resistance
The lack of conductivity or the opposition to the flow of electric
current, measured in ohms.
•Voltage
The force that pushes electric current through
impedance/resistance; electromotive force or potential
difference expressed in volts.
•Watt
The unit of measurement for power.
2/7/200911
Page 12
Test jigs used for preventative maintenance
•Calibrated ESU analyzer
•Return/dispersive/patient cable
•Active/output cable
•Variable 1 to 150 ohm resistor
2/7/200912
Page 13
Preventative Maintenance
Factory recommended schedule every 6 months refer to p 5-19, 5-24
Bipolar output test (page 5-18)
1.Set analyzer load resistance to 100
ohms.
2.Set bipolar power to 10.
3.Press footswitch and measure current in
all 3 modes. (Current delivered should
be 315 mA +/- 24 mA rms)
2/7/200913
Page 14
Cut mode output test (page 5-19)
1.Set the analyzer load resistance to 300
ohms.
2.Set CUT power to 75 watts.
3.Press CUT footswitch and measure current
in the Pure, Low & Blend modes. (Current
delivered should be 499 mA +/- 38 mA.)
4.Repeat this test on the MONOPOLAR 2
using a hand piece.
2/7/200914
Page 15
Coag output test ( page 5-20)
1.Set the analyzer load resistance to 500
ohms.
2.Set CUT power to 75 watts.
3.Press CUT footswitch and measure
current in the Pure, Low & Blend modes.
(Current delivered should be 245 mA +/19 mA.)
4.Repeat this test on the MONOPOLAR 2
using a hand piece.
Page 16
Comment to previous page:
According to the service manual the
settings should be: 80W (Low, Med,
High), 500ohms, 400mA +/-28mA.
Page 17
Return Electrode Monitoring testing
1.Set var. resistor to 120 ohms and
connect to REM jack.
2.Slowly increase resistance until led turns
RED and alarms sounds, record trip
point. (135 =/- 5 ohms)
3.Disconnect, set to 20 ohms, connect.
4.Slowly decrease resistance until red led
2/7/2009
and alarm, record trip point. (3-6 ohms)
16
Page 18
RF Leakage Testing
refer to page 5-23 “Checking monopolar High Frequency leakage current”
1.Set load to 200 ohms, set cut to 300
watts & pure mode, set coagto 120
watts and spray mode.
2.Activate footswitch in 4 different
settings: Open/Closed and
Active/Dispersive
2/7/2009
3.Record highest current, should not
exceed 150 mA
17
Page 19
If High Frequency leakage is high:
1.Check REM pad socket connector
2.P.N. S202701854, $160
3.Compare your result with past tests
and other similar units
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