Transcript Chapter 18,19

Chapter 18
Electrosurgery Generators
徐國恩
2016/4/6
18-3 Electrosurgery Machines
• RF generator：300 ~ 3000 kHz
• Active electrode：截面積很小(a few mm2)，
形成一probe供外科醫生操作
• Passive electrode(patient plate)：大面積
(>100 cm2))，放置在病患臀部或大腿下
• Operating principle：
相同的電流流經不
同截面積的電極，
造成電流密度不同
而產生不同的加熱
效果
• Application：切除
不良組織以及燒結
出血的血管
18-4 Electrosurgery Circuits
• Spard Gap Machine
• T1：昇壓變壓器，使之足以使空氣離子化，
一般為2000 ~ 3000 V
• C1/L1：Tank circuit
• L1/L2：Coupler
• RFC1,RFC2：To prevent RF energy from
getting into the power supply.
• Cut
• 一般不加 60 Hz
filter 的 cut wave
• Coagulation
18-4-1 Solid-state electrosurgery
generator circuit
18-5 Electrosurgery Safety
• Inappropriate points on the body：patient
plate 放置處遇到凸骨、凹痕、皺紋，或
是 patient plate 本身的彎曲不規則，都會
產生「熱點」而引起燒傷
• Inadvertent ground path ：另外在病患身
上形成接地迴路，使得電流不經由
patient plate 流出，造成燒傷 18-3
• Microscopic holes in the surgeon’s gloves
• Lipuids spilled into the machine
18-6 Testing Electrosurgery Units
使用thermocouple RF ammeter：
• 優點：
• 本身是一 rms-reading meter，可直接反應出
output level
• 不需要像 peak-reading meter 要針對輸出波形
作校正
• 缺點：
• 較其他儀表昂貴
• 其輸出是非線性，小功率部份判讀失準，所
以甚至需要不同範圍的兩個thermocouple
ammeter
使用 peak-reading meter：
• Voltage divider
• Toroid current transformer
• 普遍應用在低功率電療儀器的測試，如微燒
結及眼部或內視鏡電療
Chapter 19
Care and Feeding of BatteryOperated Medical Equipment
19-3 Introduction
Batteries are used for ：
• Protability
• Defibrillator
• Patient monitors
• ECG & blood pressure
• Patient safety
• Cardiac output computer
19-4 Cell or Batteries？
• The cell is the most basic element in a
battery and sets the minimum voltage for
that sort of device
• Additional voltage is gained by connecting
the cells in series, and extra current is
available by connecting them in parallel
• We would refer to multiple-cell entities as
batteries
• But in common usage, all cells and batteries
are called batterise
19-5 NiCd Cells and Batteries
• Most commonly used
• 1.2 V terminal voltage
• Sustain a charge-discharge cycle life of
1000 times before becoming unusable(the
battery drops below 80% of its oribinal
specified value
19-6 Battery Capacity
• The capacity of a battery is measured in
ampere-hours (A-H) (i.e., the product of
current load , in amperes, and the time
required to reach the designated discharge
state)
• NiCd batteries can deliver short-duration
currents of 50A or more, that is why they are
used in medical defibrillators and some
medium-powered portable radio transmitters
19-7 Battery-charging Protocols
• The general charging rule is：Charge at
1/10 ampere-hour rating for 14 hours
• Fast charging should not be done unless the
battery maker recommends it and be a little
cautious
Problems ：
• Sitting：The
solution for this
type of problem is a
trickle charge at a
rate between AH/30 and A-H/50
• Temperature effect
19-8 NiCd Battery Memory
• Memory means that a battery will not allow
deep discharge after repeated shallow
discharges (premature failure)
• A NiCd battery with memory problems can
some times be reformed by repeatedly fully
charging it and them immediately deep
discharging it
19-9 Battery Maintenance
• For most equipment the manufacturer
recommends that the batteries be
periodically discharged and then
recharged：
• 1.Fully charge the battery or cell
• 2.Discharge it fully with a current of A-H/10
for 8~9 hours for multicell batteries and 10
hours for single cells (because of polarity
reversal)
• 3.Recharge the battery at the A-H/10 rate for
14 to 16 hours
• Do not leave the battery in a discharged
condition for a long period, it may develop
interelement shorts
• Revitalization
• Revitalized batteries and cells should not be
regarded as reliable and should only be used
for shout terms, under emergency
conditions. Good engineering practice
requires replacement with a new cell rather
than salvaging the defective cell
19-10 Charging NiCd Batteries
There are two basic forms of charger for NiCd
batteries：
• Constant current (CI)
• The transformer secondary voltage hsould be
2.5 times (or more) the battery voltage
• A resistor limits the output current under shortcircuit conditions to A-H/10 charging rate
• Electronic constant current charger based on
three-terminal voltage regulator
• Constant voltage (CV)
19-12 Other Batteries
19-12-1 Lead-acid batteries
• 優點：reliable and easily available
• 缺點：very heavy and dangerous
• 用途：high-power portable applications
(automobile battery is often preferred)
• 保養：
• Water level in each of the cells must be checked
periodically (weekly)
• Clean the cap or replace it
• Warning：Lead-acid batteries produce
hydrogen as a normal byproduct
19-12-2 Carbon-zinc and alkaline dry cells
• 一般的用途(閃光燈、收音機、……)
• 缺點：
• 不可充電，用完就丟
• 端電壓在使用時下降很快
19-12-3 Mercury dry cells
• 優點：在電池壽命結束前，端電壓幾乎維
持定值
• 用途：儀器校正用
• 保養：如同NiCd batteries、carbon-zinc,
alkaline，水銀電池在不使用的時候最好
放在冷的環境中(ex.冰箱)，增加電池存放
時間
19-12-4 Gel-cell batteries
19-12-5 Lithium cells
• 優點：壽命長
• 用途：電腦、手錶、數位儲存記憶單元
• Warning：
• 注意過充或過熱的問題
• 不可攜帶到大氣壓力較小之處，如國際航線
班機