Ohmic instruments UPM-DT-1 User manual

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508 August St. Easton, MD 21601
Voice: [phone]
Fax: [phone]
www.ohmicinstruments.com
ULTRASOUND POWER METER
Models UPM-DT-1 & 10
OPERATOR’S MANUAL

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© Ohmic Instruments Company
2004
All rights reserved. This manual may not be reproduced in complete form without written permission of Ohmic Instruments
Company. Test forms may be copied as required by the original purchaser of the instrument. Information contained in this
manual is believed to be accurate and reliable; however, no responsibility is assumed by Ohmic Instruments Company for its
use. Ohmic reserves the right to supply its instruments with design changes and/or component substitutions that may not be
documented in this manual.
DT1-10_MANUAL.PUB Rev. 2 8/3/04 JN

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TABLE OF CONTENTS
Introduction.....................................................................................................................................................................5
Unpacking the Power Meter............................................................................................................................................5
Replacement Parts .........................................................................................................................................................5
Selecting a Location for Operation ..................................................................................................................................6
Panel Controls and Display Indicator...............................................................................................................................6
Overview of Display Indicators ........................................................................................................................................6
Operating Procedure ......................................................................................................................................................7
Transporting the UPM-DT...............................................................................................................................................7
General Operating Notes ................................................................................................................................................7
Calibration ......................................................................................................................................................................8
Programming Print Control..............................................................................................................................................8
Setting Date and Time ....................................................................................................................................................9
Serial Computer/Printer Interface..................................................................................................................................10
Shipping Instructions For UPM-DT Series Power Meters............................................................................................... 11
Specifications ...............................................................................................................................................................12
Maintenance................................................................................................................................................................. 12
Water, Tank Size, Transducer Placement & Temperature Considerations..................................................................... 13
Ultrasound Radiation Levels ......................................................................................................................................... 13
Theory of Measuring Ultrasound Power With the Radiation Force Method.....................................................................14
Sample Inspection Record............................................................................................................................................15
Warranty....................................................................................................................................................................... 17

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INTRODUCTION
Measurement of power output levels of diagnostic and
therapeutic ultrasound equipment has become increas-
ingly important to determine exact patient exposure lev-
els in case a potential risk exists to the patient. Since the
Radiation Control for Health & Safety Act of 1968 and the
1976 Medical Device Amendments to the FDA Act be-
came effective, all manufacturers of diagnostic Doppler
ultrasound equipment are required to submit information
regarding their maximum peak and average exposure
level, beam patterns, and other pertinent information.
Hospitals are responsible for regularly scheduled testing
(every six months) of output power and safety to main-
tain their accreditation.
The Ultrasound Power Meter, Model UPM-DT series, is
designed to measure the ultrasound power output of di-
agnostic or therapeutic transducers up to 30 watts. The
principle of measurement is the radiant force method.
The UPM-DT-1 and UPM-DT-10 are mechanically identi-
cal, each having a positioning clamp to hold the trans-
ducer in de-gassed water above a conical target. The
ultrasonic energy passes through the water to reflect off
the target and is then absorbed by the rubber lining. The
radiant power is directly proportional to the total down-
ward force (weight) on the target. This weight is then
transferred through the target support assembly to the
electro-mechanical load cell inside the scale. The cell is
in a computer-controlled feedback loop and produces a
digital readout in watts of power (custom units) or grams
of force. The choice of units (grams or watts) is selected
by front panel pushbuttons. The units are supplied with a
plug-in 120 VAC to 24 VAC 50/60Hz adapter. A me-
chanical shock mounting in the carrying case protects
the electronic balance mechanism. Model UPM-DT-1
has a display resolution of ±2 milliwatts and Model UPM-
DT-10 has a display resolution of ±10 milliwatts.
UNPACKING THE UPM-DT POWER METER
The power meter comes complete with all accessories in
a sturdy carrying case. To make ultrasonic measure-
ments, the water tank requires only one pint of de-
gassed water. If de-gassed water is not available, use
distilled water, NOT tap water.
The following replacement parts can be ordered if neces-
sary from Ohmic :
The picture above shows the cone
target assembly and transducer
positioner (Tank not shown).
The rear panel of the UPM-DT Series
provides power and RS-232 computer /
printer connections. Adjustments to level
the unit are made by rotating the rear
stands.
Front view of UPM-DT-1 & 10. Shown is the
electronic balance, base assembly, test tank
& transducer positioner.
 Test Tank with Rubber
 Positioning Clamp Assembly
 Cone Assembly
 Calibration Weight Standard [specify Ohmic #53001]
 Detachable Line Cord / 120 VAC Adapter
 Instruction Manual [specify “DT1-10_MANUAL.PUB”;
available in PDF format]
 Carrying Case

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The UPM-DT-1 & 10 Power Meters should always be
used in environments free from excessive air currents,
corrosives, vibration and temperature or humidity ex-
tremes. These factors will affect the displayed readings.
DO NOT operate the Power Meters:
 Next to open windows or doors causing drafts or
rapid temperature changes
 Near air conditioning or heat ducts
 Near vibrating, rotating or reciprocating equipment
 Near magnetic fields or equipment that generate
magnetic fields
 On an unlevel work surface
Allow sufficient space around the instrument for ease of
operation and keep away from radiant heat sources.
Never set any material on the Power Meter or place your
hands or fingers on it while taking readings.
1. Power On/Off button
2. Mode button; selects standard weighing and animal
weighing modes
3. Units button; selects grams-P-C-N-Custom units
4. Setup button (service use only)
5. O/T button; when pressed, sets the unit to zero
6. when pressed, travels up through menus
7. when pressed, travels down through menus
8. when pressed, travels to the left through menus
9. when pressed, travels to the right through menus
10. Enter/Print button; when in menus, selects items on
display; otherwise prints data
11. Leveling Indicator; indicates leveling position of the
balance
Not shown:
 Leveling feet; used to level the balance (located at
rear)
 Hold-Down Clip; located under tank; secures tank to
unit (for transportation only)
OVERVIEW OF DISPLAY INDICATORS
 Use or key to change: Used to prompt the
user while navigating through the menu system.
 Stable: Indicates that the measured value has be-
come stable.
 Change: Is displayed together with Mode, Units or
Setup, signifying that a change to balance settings is
being performed.
 Mode: Is displayed when the Mode button is
pressed. Allows the user to know what area of the
balance menu is being addressed.
 Units: Is displayed when the Units button is
pressed. Allows the user to know what area of the
balance menu is being addressed.
 Setup: Is displayed when the Setup button is
pressed.
 Custom: Displays total power output in watts.
 Symbols for weighing units include:
DT-1 DT-10
g = grams x.xxx x.xx
p = custom watt units x.xxx x.xx
c = custom watt units x.xx x.x
n = custom watt units x.x x.
PANEL CONTROLS & DISPLAY INDICATOR
SELECTING A LOCATION FOR OPERATION

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OPERATING PROCEDURE
1. Remove the top of the carrying case by unlatching
the clamps located on each side. The Ultrasound
Power Meter is mounted on the base of the carrying
case. For all applications, the unit must be re-
moved from the carrying case base, by removing
the 4 thumbscrews at the sides of the unit.
2. Place the UPM-DT on a stable and level surface
(use the Leveling feet and indicator on the unit).
Avoid air currents and mechanical vibrations. Level
unit as much as possible.
3. Loosen the positioning clamp and remove target
from the test tank where it is normally stored.
4. Place the back of the tank against the target sleeve.
Lower the target rod into the concentric test sleeve
located behind the test tank, which simultaneously
place the cone target into the tank. If the cone can
swing in an arc, it is not down far enough. Tip the
rod back slightly to fully engage the rod.
5. Fill the test tank to ¼ inch below the top of the rubber
liner with recently de-gassed water at room tempera-
ture. (To obtain de-gassed water, boil distilled water
for 20 minutes, fill a jar completely, cover surface
with saran wrap, and allow to cool)
6. By means of the positioning clamp, attach the trans-
ducer head and place its radiating face 1/8” to 1/4”
inch below the water level, parallel to the water sur-
face, and directly above the center of the cone.
Check transducer surface for uniform wetting (no air
pocket or bubbles should be on its surface).
7. Plug the line cord/adapter into a 120 VAC, 50/60Hz
power outlet and depress the ON/OFF button.
8. Allow 5 minutes for the scale to stabilize. With no
ultrasonic power applied to the transducer, press
either of the two O/T buttons to zero the unit.
9. Check response using the 1 gram weight. 1 gram is
equal to 14.65 watts.
10. Apply power to the Transducer Under Test (TUT).
Re-zero before each measurement and take your
power reading when the display has stabilized. De-
termine the maximum peak power with the maximum
duty cycle and pulsed output settings with the equa-
tion:
PAVE = Pp ÷ Rtpa
PAVE = calculated average power
Pp = Peak Pulsed Power Setting on unit under test
Rtpa = Ratio of Temporal Peak to Average Power (from
each manufacturer)
11. To calculate the watts/cm2 output, take the total watts
reading from the unit and divide by the area. The
area is d2÷ 4 (d is the diameter of the trans-
ducer) if the transducer is smaller than the cone.
Otherwise, use cone area.
12. After tests are completed, unplug the meter, empty
the tank, and place the dry target cone in the tank for
protection.
TRANSPORTING THE UPM-DT
Lift off the target cone assembly from the sleeve, empty
water into a sealable container, dry the tank and cone,
place cone in the tank and clamp the target rod into the
storage clips on the side of the target sleeve. Rotate the
transducer clamp arm over the top of the tank and
stretch the large rubber band between the two hooks of
the hold-down clip, over the clamp arm and tank. Place
unit on base of carrying case and secure it on posts us-
ing knobs provided (for shipping instructions see Page
11).
GENERAL OPERATING NOTES
Line Power / Voltage: UPM-DT Series meters are set to
operate on 12 VAC 50/60Hz. The unit is supplied with a
120 VAC adapter. Check for correct line voltage before
use. For voltages 220/240 VAC, an optional power
adapter and line cord are required.
Measurement Range, Watts & Grams: Model UPM-DT-
10 has four ranges. When Custom P is showing, the
UPM-DT-10 displays watts with a resolution of ± 20 milli-
watts or ± 0.02 watts. When the grams indicator gis on,
the resolution is 10 milligrams (± 0.01 gram). Each gram
equals 14.65 watts and 10 milligrams is equivalent to
146.5 milliwatts (rounded to 0.14 watt). Use Custom C
mode for most therapy equipment testing. If measure-
ment conditions are not stable, use Unit N or Grams
mode (when using the grams mode multiply the readings
by 14.65 to obtain watts).
Model UPM-DT-1 also has four ranges. When watts or
milliwatts are being measured, a Unit indicator below the
display will illuminate. Unit P appears for ±2 milliwatt
resolution; Unit C gives ±10 milliwatts, and Unit N dis-
plays to the nearest ±0.1 watt. Use Unit C and Nfor all
measurements except the lowest range requiring Unit P
mode. When the gram gsign appears, the display gives
readings to the nearest ±1 milligram. Each milligram cor-
responds to 14.65 milliwatts. Depressing the Units but-
ton, then or buttons will select the desired range.
Re-Zero / Tare: By depressing the O/T button, the
meter will zero at the present balance condition. During
re-zeroing, the display will be blank until the microproc-
essor senses a stable condition. If no ultrasound force is
applied, then the display will simply indicate true zero
reference; otherwise the applied ultrasound will become
the offset zero reference. This feature is convenient for
automatic zero setting before taking a reading, but also
to balance out a fixed ultrasonic power setting and to
measure incremental ± deviation from this mean setting.

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Set Up: If you accidentally get into the Setup menu,
push the button until exit is displayed, then push En-
ter. The UPM-DT Series Ultrasound Power Meters are
custom programmed balances with additional hardware
(cone target, tank, etc.) designed to provide ultrasound
power readings. Entry into the Setup menu enables a
user to modify certain setup parameters with respect to
custom units, calibration stability and linearity. Ohmic
Instruments Company assumes no responsibility for the
performance of these units if user changes to the internal
setup parameters or program are made. Any change to
the internal program parameters voids the warranty and
calibration certification. Should reprogramming to the
original parameters be required, the unit must be re-
turned to Ohmic’s facility in Easton, Maryland. An hourly
labor rate of $75 will be charged and recalibration fees
will be assessed.
CALIBRATION
A 1-gram calibration weight is suplied. With the trans-
ducer under test turned off, zero the unit by pressing the
O/Tbutton. Place the weight on the arm of the cone
target. Within 10 seconds the unit should read 14.65
watts (± 1%). A set of precision weights and a scale pan
assembly is needed to recalibrate the unit. Send the unit
to our service department for calibration. A calibration kit
is also available. If you accidentally get into CAL mode,
push the button until exit is displayed, then push En-
ter. It is recommended that these units be returned to
Ohmic Instruments Company on a yearly basis for recali-
bration and recertification.
PROGRAMMING PRINT CONTROL
The Print menu provides a number of options which can
be turned on or off. It contains eight submenus: Auto
Print, which includes selection of Off, Continuous, Inter-
val and Stability; Inter, which specifies the time interval
for automatic output of displayed data; Stable, a data-
only feature, Numeric only or full display data for output;
PrtDate, PrtTime, Reference, which prints reference
weight value, and Lock, which enables you to program
balance parameters and to lock the settings.
Procedure:
1. Press the Setup button; CAL is displayed.
2. Press or button until PRINT is displayed.
3. Press Enter button to save setting.
4. Press or button until either AUTOPRT, INTER,
STABLE, NUMERIC, PRTDATE, PRTTIME, REF-
EREN, LOCK, or EXIT is displayed.
5. Press Enter button to save setting.
6. Press or button and select either menu setting
or On or Off.
7. Press Enter button to save setting.
8. Press or button to continue to LOCK or EXIT.
9. Press Enter button to save setting.
Auto Print Feature: When enabled, the Auto Print fea-
ture causes the balance to automatically output display
data in one of three ways: continuously, at user-
specified time intervals, or upon stability. Default set-
tings are shown bold:
 OFF—when set on, turns off the Auto Print feature
 Cont—when set on, outputs printed data continu-
ously
 Inter—provides a user specified printing interval
 On Stb—provides printed data only when a stable
reading is achieved
Interval: Can be set to provide a specified printing inter-
val between 1 and 3600 seconds.
Print Stable Data Only: When set On, this feature per-
mits only stable display data to be output. OFF is the
default setting.
Print Numeric Data Only: When Numeric Data Only
function is turned ON, this allows the balance to output
only numeric data for the RS-232 output (see page 10).
OFF is the default setting.
Print Time: When the Time function is set ON, allows the
balance to output the current time to the printer. OFF is
the default setting. See Setting Date and Time below.
Print Date: When the Date function is set ON, allows the
balance to output the current date to the printer. OFF is
the default setting.
Reference: When the Reference function is ON, prints
the value of weight used as a reference in either Percent
or Parts Counting modes. OFF is the default setting.
Lock: Lock ON/OFF can be changed only when the
Hardware Lock switch is set OFF/disabled. A menu is
locked when the menu lock is set ON and the Lock
switch is ON. Lock, when selected and turned on, locks
all of the entries made under the Print menu. In the
locked condition, items may be looked at but not
changed in the menu. When set off, entries may be
changed. OFF is the default setting.

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The UPM-DT Series provides date and time data which
can be viewed on a computer or printed out on an exter-
nal printer. When you put your new instrument into op-
eration for the first time, you should enter the current
date and time. These settings are retained as long as
the balance remains connected to a power source.
Date is a feature which enables the balance to be set to
a U.S. date standard or European. U.S. standard has
the month, day and year each separated by a / in the
printout. The European date standard has the day,
month and year each separated by a period. The default
setting is U.S. standard.
Procedure:
1. Press the Setup button; CAL is displayed.
2. Press or button and select Date from the menu.
3. Press Enter button; TYPE is displayed.
4. Press Enter button; SET M d y, d M y, y M d, M y d,
y d M, or d y M is displayed.
5. Press or button and select type of date.
6. Press Enter button; SAVED is displayed, then SET is
displayed.
7. Press Enter button; first digit of date will flash.
8. Using or buttons, enter the correct date.
9. When the correct date is entered, press Enter but-
ton.
10. SAVED is displayed momentarily, and EXIT appears.
11. Press Enter button; balance returns to weighing
mode.
Time is a feature which enables the balance to be set to
the current time in either U.S. standards (12 hour peri-
ods) or European/military standards (24 hour periods).
The default setting is U.S. standards.
Procedure:
1. Press the Setup button; CAL is displayed.
2. Press or button and select Time from the menu.
3. Press Enter button; TYPE is displayed.
4. Press Enter button; TYPE 12 hr is displayed.
5. Press or button and select 12 hr or 24 hr.
6. Press Enter button; SAVED is displayed, then SET is
displayed.
7. Press Enter button; SET with time will flash.
8. Using or buttons, enter the correct time.
9. When the correct time is entered, press Enter button.
10. SAVED is displayed momentarily, and EXIT appears.
11. Press Enter button; balance returns to weighing
mode.
Adjustments up to ± 60 seconds a month can be made to
the balance’s internal clock. Repeat the first seven
steps, ADJUST is displayed. Using the arrow buttons,
enter time correction and press Enter button.
SETTING DATE AND TIME

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RS-232 INTERFACE: The UPM-DT-1 and UPM-DT-10
Ultrasound Power Meters are equipped with a bi-
directional RS-232 compatible interface for communica-
tion with printers and computers. When the balance is
connected directly to a printer, displayed data can be out-
put at any time by simply pressing PRINT or by using the
Auto Print feature. Connecting the balance to a computer
enables you to operate the balance from the computer, as
well as receive data such as displayed weight, weighing
mode, stability status, etc.
Hardware: On the rear of the balance, the right hand 9-
pin male subminiature “D” connector is provided for inter-
facing to other devices. The balance will not output any
data unless pin 5 (CTS) is held in an ON state (+3 to +15
VDC). Interfaces not utilizing the CTS handshake may tie
pin 5 to pin 6 to defeat it.
Output Formats: Data output can be initiated in one of
three ways: 1) by pressing PRINT; 2) using the Auto
Print feature or 3) sending a print command (“P”) from a
computer.
Default Settings: Baud-2400; Data bits-7; Parity-None;
Stop bits-2; Lock-Off.
RS-232 Commands: All communication is accomplished
by standard ASCII format. Characters shown in the fol-
lowing table are acknowledged by the balance. Invalid
command response “ES” error indicates the balance has
not recognized the command. Commands sent to the
power meter must be terminated with a carriage return-
line feed (CRFL).
SERIAL COMPUTER/PRINTER INTERFACE
1. N/C
2. Data Out (TXD)
3. Data In (RXD)
4. Tare (External Signal)*
5. Clear to Send (CTS)
6. Data Terminal Ready (DTR)
7. Ground
8. Request to Send (RTS)
9. Print (External Signal)*
* External PRINT and/or TARE switches may be installed as shown. Momen-
tary contact switches must be used.
IMPORTANT!
An Ohaus RS-232 cable is required to enable the balance to communicate with a com-
puter or printer; a standard RS-232 cable will not work. The cable can be ordered from
Ohmic or directly from Ohaus (www.ohaus.com). Cable part numbers are as follows:
25-pin: #AS017-02;
9-pin: #AS017-09.

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Command Character Description
? Prints current mode: Mode, Stability, CR, LF
nnnA Set Auto Print Feature: nnn = 0 Turns feature OFF
nnn = S Output on Stability
nnn = C Output is continuous
nnnn = 1-3600 Sets Auto Print interval in seconds
P Print Display Data
xD Set 1 second print delay: x = 0 for OFF
x = 1 for ON
T Tare (Same effect as pressing O/T button)
ON Turns balance on
OFF Turns balance off
TIME Prints current time
Mm/dd/yy SETDATE Set date
hh:mm:ss SETTIME Set time
The UPM-DT Series Ultrasound Power Meters are cus-
tom programmed balances with additional hardware
(cone target, tank, etc.) designed to provide ultrasound
power readings. When utilizing the RS-232 interface cer-
tain setup commands may be entered that enable
changes to the internal programming with respect to cus-
tom units, calibration stability and linearity. ONLY THE
COMMANDS ABOVE SHOULD BE USED.
Ohmic Instruments Company assumes no responsibility
for the performance of these units if user changes to the
internal setup parameters or program are made. Any
change to the internal program parameters voids the war-
ranty and calibration certification. Should reprogramming
to the original parameters be required, the unit must be
returned to Ohmic’s facility in Easton, Maryland. An
hourly labor rate of $75 will be charged and recalibration
fees will be assessed.
SHIPPING INSTRUCTIONS FOR UPM-DT SERIES
POWER METERS
To make certain that your Ultrasound Power Meter ar-
rives at our repair department unharmed during shipment,
please follow these instructions:
1. Empty water from tank and lock scale.
2. Wrap the target cone in a protective covering and
place in tank, do not put target support bracket in
the tabletop tube nor in the clips (if tank should
move during shipment, the bracket will be damaged).
3. Place the weight under the screw provided. Make
sure the transducer clamp asembly is screwed in
place tightly over the tank and pull the large rubber
band over the tank and clamp.
4. Secure unit in case using wing brackets and knobs.
5. Fasten the case lid onto the base, after making cer-
tain there is nothing loose inside.
6. The package used for shipping should be strong and
large enough to allow for adequate packing material
on all sides of unit.
7. Ship to:
Ohmic Instruments Company
508 August Street
Easton, Maryland USA 21601
8. Enclose paperwork (packing slip, purchase order
form, letterhead) which includes your return address,
contact name and telephone number. A description
of the work that needs to be done would be helpful.
By using the above instructions you will avoid additional
charges which can be incurred if the unit is not packaged
well enough to withstand rough handling during shipment.

12
SPECIFICATIONS
UPM-DT-1 UPM-DT-10
Power Range 0 to 30 Watts 0 to 30 Watts
Resolution ±2mW ±10mW
Minimum Detectable Power 1mW 10mW
Display Sensitivity 0.001 / 0.01 / 0.1 Watt 0.01 / 0.1 / 1 Watt
Accuracy ±3% + One Digit ±3% + One Digit
Zeroing Method Automatic Automatic
Averaging of Measured Values 100 100
Stabilization 2.5 Second Integration 2.5 Second Integration
Maximum Weight Capacity 210 Grams 600 Grams
Maximum Transducer Size 3” Diameter 3” Diameter
Transducer Operating Frequency 0.5 to 10MHz 0.5 to 10MHz
Test Media Degassed Water Degassed Water
Computer Interface RS-232, 300-9600 Baud RS-232, 300-9600 Baud
Default Baud Rate 2400 2400
Power 12 VAC, 1 Amp 12 VAC, 1 Amp
120 VAC Adapter Supplied
(Adapters for 240 VAC Available on
Special Order)
120 VAC to 12 VAC w/ 3-Prong Male
Plug and 6-Ft. Cord
120 VAC to 12 VAC w/ 3-Prong Male
Plug and 6-Ft. Cord
EMI Rating Conforms to CE & FCC Conforms to CE & FCC
Electrical Safety Conforms to UL & CSA Conforms to UL & CSA
Size 11” x 15” x 10” (H x L x W) 11” x 15” x 10” (H x L x W)
Weight 22 Lbs. Net 22 Lbs. Net
Carrying Case Black Anodized Aluminum Black Anodized Aluminum
Verification of Proper Scale Functioning: Small varia-
tions of water surface motion, air currents or mechanical
movements may cause uncertainties in power measure-
ments. To test scale accuracy at low levels, set up the
scale as in the Operating Procedure (Page 7). Place the
14.65 watt weight on the flat surface of the target arm.
Read meter three times; readings should be within ± 1%
(for example, 14.504 to 14.796 for UPM-DT-1 and 14.52
to 14.80 for UPM-DT-10). In case of doubt about lower
power resolution, repeat the same procedure using light
objects such as thin paper slices to produce readings of
5 to 10 counts; repeat readings. Average uncertainty
should be within ± 2 counts on the grams as well as on
the watts scale. Avoid mechanical and air movement or
variations in magnetic fields while making tests.
Out of Measurement Range Warnings: Model UPM-DT-
1 accommodates weight differential of ± 200 grams while
UPM-DT-10 accommodates ± 600 grams. When the
scale exceeds this range, “Error 8.3” will be displayed.
Something may be pressing hard on the target or sup-
port. “Error 8.4” indicates underweight condition. This
will occur if the target is out of place on the UPM-DT-1.
No Display: 1) Check power and line cord; 2) Verify that
the line voltage is set correctly.
If you need further assistance, please call our service
department.
MAINTENANCE

13
WATER, TANK SIZE, TRANSDUCER PLACEMENT &
TEMPERATURE CONSIDERATIONS
Water as a Measurement Medium: The measurements
are to be performed in de-gassed water because ultra-
sound propagation in water closely approximates that in
tissues (see UL-1-1981, AIUM/NEMA Standard Publica-
tion). The ultrasonic attenuation in water can be taken
as a lower limit on the attenuation which will be encoun-
tered in the body. Large areas in the body can consist of
low attenuating material such as urine and amniotic fluid.
The use of water prevents measurements in a more
highly attenuating material such as liver equivalent gels
from representing the highest possible intensities which
might be encountered in the body. A measurement tem-
perature of 24°C ± 3°C (75°F ± 5°) is chosen for conven-
ience.
De-Gassed Water: Ultrasound power measurement ac-
curacy is affected (by lowering the power reading) if the
water contains more than five parts per million of air. To
de-gas, boil distilled water for one half-hour, then pour
into a suitable container, seal tightly and place in refrig-
erator. This process will give the required quality. The
container should be heat resistant glass; or thick plastic
may be used after the water has been cooled. Before
testing, pour water into tilted test tank to minimize turbu-
lence. The test tank water surface will absorb oxygen
and a change of de-gassed water is recommended be-
fore each test. An alternative method of de-gassing wa-
ter is to heat the water to the boiling point, then put a
vacuum to it for five minutes.
Water temperature affects accuracy; use a testing tem-
perature of 21 to 27°C ambient. Sonic energy agitates
the water surface through heating and scattering. Test-
ing time should be limited to a few minutes; prolonged
testing, particularly at higher power levels, will drive out
dissolved air and air bubbles will be visible on surfaces in
the tank. These bubbles can be gently brushed off.
Transducer Wetting and Placement: After tilting the
transducer into the water at a 45° angle, verify that the
surface is uniformly wetted; if not, wipe the surface clean.
The transducer should be positioned above the cone
target. Small variations will occur due to placement. Try
various positions above target to obtain a maximum
power reading.
ULTRASOUND RADIATION LEVELS
There are no maximum limits in the U.S. for therapy
power, only the verification of the displayed setting accu-
racy to ± 20% of actual output is required. Exposure lev-
els for physical therapy applicator heads range from
100mW/cm2 to 3W/cm2. Total power requires multiplica-
tion by the radiated cross sectional area in cm2.
The power limits shown in the following table for diagnos-
tic ultrasound have been extracted from FDA Section
510(k) guidance to manufacturers on submissions and
clearance as of February 1993. Refer to the AIUM and
FDA publications for complete and up to date testing
standards and interpretations. Measurements are done
in all standard modes of operation. Power intensity is
rated as Spatial Peak Temporal Average (ISPTA) and Spa-
tial Peak Pulse Average (ISPPA). The values in mW/cm2
are derated for tissue and in parenthesis for the water
medium (use the chart below):
PRE-AMENDMENT ACOUSTIC OUTPUT LIMITS
Use ISPTA
Tissue
(mW/cm2)
Water
ISPPA
Tissue
(mW/cm2)
Water
Peripheral Vessel 720 1500 190 350
Fetal Imaging & Other * 430 730 190 350
Cardiac 94 180 190 350
Opthalmic 17 68 28 110
* Abdominal, intra-operative, pediatric, small organ (breast, thyroid, testes, etc.), neonatal cephalic, adult cephalic

14
THEORY OF MEASURING ULTRASOUND POWER WITH THE RADIATION FORCE METHOD
Sound is a form of energy that sets the particles in the isonated medium into vibrational motion. The particles then
possess a kinetic energy. If dPm is the rate of the flow of this energy about an area dA, then the mean acoustic energy
is:
Eq. 1 I = dPm/dA I= Acoustic intensity at a point in that area, Watts/cm2
When a plane sound wave propagates through a uniform non-absorbent medium, the intensity must be the same for
all points in the wave. Let Erepresent the energy density, i.e., the energy per unit volume. When the sound energy
passes through a unit cross-sectional area with a speed c, the intensity is:
Eq. 2 I = cE E= Energy density per unit volume, ergs/cm3
c= Ultrasound wave velocity, cm/sec
The radiation pressure effect can be explained by analogy to the application of an alternating electric voltage to a non-
linear load. With the non-linear load it appears that both AC and DC components are present. In ultrasonics the non-
linear element is the density of the fluid and hence acoustic impedance (load) varies in the same periodical manner as
the density. Therefore in ultrasound the two components of pressure, one alternating and the other direct are present.
The average AC pressure per cycle is zero, but the DC pressure of radiation is:
Eq. 3 P= I/C P= Pressure of Radiation, ergs/cm3
Therefore, from the above two equations, the pressure of radiation (P) is equal to the energy density (E).
Eq. 4 P= E
It is this DC pressure of radiation that can be measured. At low frequencies, below 100KHz, a standard high fre-
quency hydrophone can be used. For higher frequencies, generally used in medical applications, 1-15 MHz, hydro-
phones are not available. At these frequencies the force can be measured using a precision balance and a radiation
force target that is perfectly absorptive. The conversion from force to power can be accomplished using the equation:
Eq. 5 p = Wgc W= measured force, grams
g= acceleration, dynes
c= velocity of ultrasound, cm/sec
p= power, ergs/sec
By combining all constants together and converting from ergs/sec to watts, we obtain a simplified equation that is used
to calculate the ultrasonic power once the force is measured:
P = w(14.65) P= Ultrasonic power in watts
w= Ultrasonic force in grams
To determine the ultrasonic watt density (watts/cm2or watts/in2) of a given transducer the P is divided by the cross
sectional area of the transducer.

15

16
9. CONTINUOUS WAVE MODE CERTIFICATION (Average Power)
WATTS
SELECT POWER
ON OFF DIFF. WATTS ALLOWABLE
RANGE
3.7 - 6.3
SAT. UNSAT.
Average of 3 Readings
5
WATTS
SELECT POWER
ON OFF DIFF. WATTS ALLOWABLE
RANGE
7.4 - 12.6
SAT. UNSAT.
Average of 3 Readings
10
WATTS
SELECT POWER
ON OFF DIFF. WATTS ALLOWABLE
RANGE
11.1 - 18.9
SAT. UNSAT.
Average of 3 Readings
15
WATTS
SELECT POWER
ON OFF DIFF. WATTS ALLOWABLE
RANGE
14.8 - 25.2
SAT. UNSAT.
Average of 3 Readings
20
WATTS
SELECT POWER
ON OFF DIFF. WATTS ALLOWABLE
RANGE
SAT. UNSAT.
Average of 3 Readings
WATTS
SELECT POWER
ON OFF DIFF. WATTS ALLOWABLE
RANGE
SAT. UNSAT.
Average of 3 Readings
10. PULSED MODE CERTIFICATION (Amplitude Modulated Waveform)
MAX.
PULSE
MODE
SETTING
POWER
ON OFF DIFF. WATTS
CALCULATIONS
(Pp)
Average of 3 Readings = Measured Average Power (Av)
Pp RTPA
CALC.
AVERAGE
POWER
(Pp / RTPA)
Difference
Between
Measured AV
And
Calculated AV
Is Difference < ± 0.6% Of
(Pp / RTPA)
YES NO
REMARKS
11. SHORT TERM LIFE TEST COMPLETE? YES NO
12. ADDITIONAL TEST (Describe in Detail):

17
Not withstanding any provision of any agreement the fol-
lowing warranty is exclusive.
Ohmic Instruments Company warrants each instrument it
manufactures to be free from defects in material and work-
manship under normal use and service for the period of 1-
year from date of purchase. This warranty extends only to
the original purchaser. This warranty shall not apply to
fuses or any product or parts which have been subjected
to misuse, neglect, accident, or abnormal conditions of
operation.
In the event of failure of a product covered by this war-
ranty, Ohmic Instruments Co. will repair and recalibrate an
instrument returned within 1 year of the original purchase:
provided the warrantor's examination discloses to its satis-
faction that the product was defective. The warrantor may,
at its option, replace the product in lieu of repair. With re-
gard to any instrument returned within 1 year of the origi-
nal purchase, said repairs or replacement will be made
without charge. If the failure has been caused by misuse,
neglect, accident, or abnormal conditions of operations,
repairs will be billed at a nominal cost. In such case, an
estimate will be submitted before work is started, if re-
quested.
THE FOREGOING WARRANTY IS IN LIEU OF ALL
OTHER WARRANTIES, EXPRESSED OR IMPLIED, IN-
CLUDING BUT NOT LIMITED TO ANY IMPLIED WAR-
RANTY OF MERCHANTABILITY, FITNESS, OR ADE-
QUACY FOR ANY PARTICULAR PURPOSE OR USE.
OHMIC INSTRUMENTS COMPANY SHALL NOT BE LI-
ABLE FOR ANY SPECIAL, INCIDENTAL, OR CONSE-
QUENTIAL DAMAGES, WHETHER IN CONTRACT,
TORT, OR OTHERWISE.
If any failure occurs, the following steps should be
taken:
1. Notify Ohmic Instruments Co. giving full details of the
difficulty, and include the model, type, and serial
numbers (where applicable). On receipt of this infor-
mation, service data, or shipping instructions will be
forwarded to you.
2. On receipt of shipping instructions, forward the instru-
ment, transportation prepaid. Repairs will be made
and the instrument returned, transportation prepaid.
SHIPPING TO MANUFACTURER FOR REPAIR OR AD-
JUSTMENT
All shipments of Ohmic Instruments Co. instruments
should be made via United Parcel Service or "Best Way"
prepaid. The instrument should be shipped in the original
packing carton, or if it is not available, use any suitable
container that is rigid and of adequate size. If a substitute
container is used, the instrument should be wrapped in
paper and surrounded with at least four inches of excelsior
or similar shock absorbing material.
CLAIM FOR DAMAGE IN SHIPMENT TO ORIGINAL
PURCHASER
The instrument should be thoroughly inspected immedi-
ately upon delivery to purchaser. All material in the ship-
ping container should be checked against the enclosed
packing list. The manufacturer will not be responsible for
shortages against the packing sheet unless notified imme-
diately. If the instrument is damaged in any way, a claim
should be filed with the carrier immediately. (To obtain a
quotation to repair shipment damage, contact Ohmic In-
struments.) Final claim and negotiations with the carrier
must be completed by the customer.
Ohmic Instruments Company will be pleased to answer all
application or use questions, which will enhance your use
of this instrument. Please address your requests or corre-
spondence to: Ohmic Instruments Company, 508 August
St., Easton, Maryland 21601, ATTN: Technical Support.
Or call Ohmic Technical Support at 410-820-5111.
All rights reserved. This manual may not be reproduced in
complete form without written permission of Ohmic Instru-
ments Company. Test forms may be copied as required by
the original purchaser of the instrument. Information con-
tained within this manual is believed to be accurate and
reliable. However, Ohmic Instruments Company assumes
no liability for its use. Ohmic Instruments Company re-
serves the right to supply its instruments with design
changes and/or component substitutions that may not be
documented in this manual.
WARRANTY
508 August St. Easton, MD 21601
Voice: [phone]
Fax: [phone]
www.ohmicinstruments.com

18