Frequency Outputs Of
Commercial Electroacupuncture Stimulators Accurate? (Pilot Project)
Richard C. Niemtzow, MD
Debra Clydesdale, BScEE
Zang-Hee Cho, PhD
Terry Oleson, PhD
Young-Don Son, MSc
Peter A. S. Johnstone, MD
We investigated six commercial electroacupuncture stimulators for frequency
accuracy and waveform characteristics, and found that these devices
did not completely comply with the manufacturers stated specifications.
Frequency errors ranged from 0.10% to over 50.1%. Better-designed circuits
and quality components may ameliorate this deficiency. We recommend
that all electroacupuncture stimulators meet the
precision and calibration requirements of the National Institute of
Standards and Technology (NIST).
PENS, Stimulators, Frequency, Precision, Electroacu-puncture, Waveforms
Electroacupuncture (or, PENS [percutaneous electrical nerve stimulation])
is frequently employed as a therapeutic modality in the acupuncture
clinic, and it has been part of Traditional Chinese Medicine since the
early 1800s. Even though electroacupuncture seems to be quite modern,
it has the longest history of any electrical therapy. Renewed interest
in acupuncture in France during the 1800s coincided with the period
of research and exploration of electrical phenomemon. Sarlaniere le
Chevalier (1825) of France and da Camino (1834, 1837) of Italy were
the first to apply percutaneous electrical nerve stimulation. By 1900,
electrotherapy fell into disuse, but was revived in the 1970s when it
was discovered that electroacupuncture (PENS) was being used in lieu
of anesthesia for surgery in China.1
These parameters vary considerably from model to model because
a paucity of clinical research has not determined optimum values.
1) Pulse width
2) Rise time
3) Fall time
5) Pulse distortion
6) Pulse amplitude
7) Pulse offset voltage
8) Pulse repetition rate
9) Output impedances for both positive and negative polarity
10) Each component of pulse wave complex recorded on oscilloscopic
There are many different models of electronic stimulators available
to the clinician. These stimulators are capable of producing various
frequencies, waveforms, current and voltage outputs for therapeutic
benefit. While one may assume that the manufacturers specifications
are accurate and reliable, this premise may not be correct.
Procuring an electroacupuncture stimulator should be based on the intentions
of its clinical usage: output specifications. Careful consideration
to manufacturer reliability and safety should be paramount.2 The accuracy
and stability of these parameters is influenced by circuit design, electronic
component tolerances, power source, ergonomic design, and operator error.
All equipment procured from the manufacturer should be within its stated
specifications. A prescribed frequency of 5 Hz should output at 5 Hz,
and not 2 or 10 Hz. This deviation becomes more critical at higher frequencies
where safety becomes an issue. The frequency range of the stimulator
should progress smoothly and accurately if an analog dial is employed.
The waveform should be electronically free from distortion. If the device
produces a biphasic (negative and positive) wave, it should be balanced
with a net direct current (DC) of zero to avoid burning of the skin,
electroplating of the metal needle into the tissues, and electrolysis
of water producing hydrogen and oxygen bubbles into the interstitial
spaces where the stimulation is occurring. A low-voltage battery indicator
or warning system should be employed to prevent further degradation
of the electronic circuit and signal output so that the operator can
replace the battery in a timely fashion.
The purpose of this article was to survey 6 popular electronic stimulators
that are most likely used by the clinician, and compare the actual frequency
and waveform characteristics to the manufacturers specifications.
We do not believe at this time that it would be appropriate to identify
the manufacturer or model of the stimulators tested because the specimen-to-specimen
variation was not determined, as only 1 specimen of each type was investigated.
Omura states that there are approximately 10 basic electrical parameters
that can be measured from acupuncture stimulators (Table 1).3
Frequency is one of the primary variable output parameters that is commonly
utilized by the clinician. Thus, it is important and fundamental that
we look at this output, i.e., accuracy, fluctuation, and its associated
|Table 2. RESULTS: STIMULATOR 1
|Table 3. RESULTS: STIMULATOR 2
|% of error
|Table 4. RESULTS: STIMULATOR 3
|% of error
|Table 5. RESULTS: STIMULATOR 4
|% of error
|Table 6. RESULTS: STIMULATOR 5
|% of error
|Table 7. RESULTS: STIMULATOR 6
|% of error
MATERIALS AND METHODS
Pulse frequency and waveform were measured using 2 test instruments.
These were the Fluke 123S (Fluke Corp, Everett, WA [www.fluke.com]),
and the Newport P6000A digital frequency meter (Newport Electronics
Inc, Santa Ana, CA [www.newport.co.uk/]).
The waveform and frequencies above 5 Hz were measured using the Fluke
123 Industrial ScopeMeter test tool. This is a portable, hand-held digital
oscilloscope which incorporates many capabilities for research testing,
including recording functions for full hard copy archival capability.
Frequencies at 5 Hz and below were measured, but the waveforms were
not recorded, using the Newport P6000A digital frequency meter. This
is a microprocessor based, 6-digit frequency meter that allows high
accuracy/low-frequency measurements from .000001 Hz to 7 MHz.
Measurements taken with the Fluke 123S meter were recorded by linking
to a personal computer (PC). The ScopeMeter was connected to the PC
via optically isolated RS-232 interface. Measurements were recorded
on PC and stored on CD disc using FlukeView ScopeMeter software for
Windows (SW90W). Thus, all measurements of frequency above 5 Hz were
recorded on computer with hardcopy archiving for data storage and analysis.
Multiple readings were taken to ensure accuracy of recording, and to
confirm redundancy and consistency of measurement and output of stimulator
|Figure 1. Circuit diagram used for the measurement
of the frequency counting. Note it is the circuit used for the measurement
||Figure3. Stimulatore 4 had elcotronic noise onn
the top of its square wave.
|Figure 4. Stimulator 5 had a strange waveform pattern
that is neither symmetrical nor had equal direct current flow.
||Figure 5. Stimulator 1 had a waveform that met
the manufacturers specifications.
The 2 test instruments were calibrated for accuracy prior to this study.
(The calibration was carried out by ANMAR Metrology, Inc, San Diego,
CA [www.anmar.com]). This calibration
is traceable to the National Institute of Standards and Technology (NIST)
specifications4 or other nationally recognized measurement systems,
or have been devised from accepted values of natural physical constants
or ratio type of self-calibration techniques. Calibrations were performed
in accordance with ISO 9002, ISO 1012-1, ANSI/NCSL Z540-1, and other
national systems guidelines and meet a minimum of a 4:1 accuracy ratio
unless noted. All equipment receiving this certification is considered
within specifications of accuracy and standardization for a period of
1 year. Testing and measurements in this report were completed within
1 week after our test instruments received a certificate of calibration.
The testing environment for both instruments was at normal room temperature,
normal atmospheric pressure of sea level, normal humidity, with no known
exceptional electromagnetic interference levels. The power supply for
the equipment was commercial 110 V, 60-cycle alternating current (AC),
in order to rule out battery fluctuation variables.
All electroacupuncture stimulators tested were brand new or recently
reconditioned from the factory. All received new, fresh batteries prior
to testing. Warm-up periods were not controlled closely. Devices were
turned on and tested for approximately 30 minutes. This closely parallels
the normal clinical usage. Five measurements of each device were completed
to determine frequency and waveform aberrations.
Signal inputs to the Fluke 123S from electroacupuncture units being
tested were routed through commercially supplied electroacupuncture
alligator clips, directly into the 1:1 test probe of the meter. Each
electro-stimulator was tested at normal operating voltage levels, i.e.,
the amplitude of the output signal was one-half the full dial capability
(stimulators were turned up half-way). The red positive lead of the
alligator clip assembly was connected to the positive input of the Fluke
test probe. The black, negative lead was connected to the short, common
ground connector of the test probe. All readings were taken using the
Signal inputs, to the Newport P6000A meter, were routed through the
same type of alligator clip assemblies. The signals were conditioned
with a simple diode and resistor divider providing less than 10 V of
positive DC pulse to the meter, as required by the specifications of
this meter (Figure 1).
Stimulators tested were first turned to their lowest frequency settings.
As all electroacupuncture stimulator models do not share the same frequency
outputs, the lowest frequency on each stimulator was the starting point.
Measurements were taken and recorded either manually (P6000A) or via
computer (Fluke 123S above 5 Hz). After each reading, the next higher
frequency was selected and recorded. After the highest frequency was
selected and recorded, the process of selection and recording was repeated,
beginning with the original low frequency. The entire process was repeated
5 times for each stimulator being tested.
|Figure 2. Comparison of stimulators
Percent error variations and their fluctuations.
The vertical line on each bar represents the range of fluctuation
of the given frequency for each stimulator.
Stimulators that had pre-set, click-stop dials for frequency knobs enabled
us to test each device at the exact settings.
The following procedure was used with stimulators that had continuously
turning, analog dials with approximate labeling: the dials were turned
to the closest approximation of the indicated dial setting that was
possible with a careful and deliberate attempt to be exact. The dials
were viewed from directly above to eliminate, as much as possible, any
visual error or parallax, and the dials were turned to the most exact
position using visual acuity that represented the respective labeled
frequency. (This is a more exacting process than is typically used in
clinical practice, but was necessary for these measurements.)
Error percentage was calculated by taking the average of the 5 trial
measurements for each frequency and subtracting from it from the stated
by the manufacturer. That result was then divided by the manufacturers
stated frequency and multiplied by 100. For example, Stimulator 1 had
an average frequency of 4.971 Hz. The manufacturer stated that the frequency
should be 5.0 Hz. Therefore, 5.000Hz - 4.971= 0.029 (0.029/5.00) x 100=
0.58% error or rounding off to 0.60%.
Tables 2-7 depict results from the stimulator testing.
Frequency errors for all of the stimulators are summarized in Figure
2. Stimulators 1, 4, and 5 had click-stop dials. Stimulators 2 and 3
had analog dials, and stimulator 6 had an analog dial and a digital
meter to read the frequency output. Stimulators 1 and 6 most likely
had a higher quality circuit design. Stimulators 4 and 5, despite their
click-stop dials, suffered from frequency inaccuracies.
Frequency variation from click-stop dials appeared the most accurate
and easy to use. Accuracy from outputs that had either a marked scale
or number, and requiring the operator to line-up, were problematic.
Frequency error ranged from 0.1% to over 50.1%. Comparing all 6 stimulators
frequencies (Figure 2), the vertical line on the top of each bar graph
represents the deviation or how the data is scattered from its average
value. In Figure 2, we delineate that stimulator 2 has a wide
range of frequency deviation. However, the frequency errors for stimulator
4 did not change markedly, even though it has the highest error among
the stimulators and thus, its deviation is small.
Certainly, we reached error thresholds that are not acceptable for either
clinical or research utilization. Besides frequency, waveform influences
the safety and efficacy of clinical outcomes. Waveforms that are distorted
with noise or display bizarre stimulation patterns impact on the quality
and safety of electroacupuncture stimulation, and are not acceptable
in clinical or research practice (e.g., see Figures 35).
Further clinical research is needed to recommend optimal electrical
stimulation parameters to produce desired therapeutic electroacupuncture
effects. However, this research revealed that electroacupuncture stimulators
in current use may be fraught with poor frequency and waveform outputs
that do not represent the manufacturers specifications.
Our recommendation is that an annual review of stimulator quality be
sponsored, published, and thus made available to practitioners. We recommend
that all electroacupuncture stimulators meet the precision and calibration
requirements of the National Institute of Standards and Technology.
Further discussion should be undertaken to standardize frequency reporting
parameters and to agree on optimal calibration specifications.
The acupuncture profession must demand that the manufacturing of electro-stimulators
meet specified outputs and safety configurations.
- Kendall DE.
The Dao of Chinese Medicine. New York, NY: Oxford University Press;
- Lytle CD,
Thomas BM, Gordon EA, Krauthamer V. Electrostimulators for acupuncture:
safety issues. J Altern Complement Med. 2000;6:37-44.
- Omura Y. Electrical
parameters for safe and effective electro-acupuncture and transcutaneous
electrical stimulation: threshold potentials for tingling, muscle
contraction and pain; and how to prevent adverse effects of electro-therapy.
Int J Acupuncture Electrotherapeutics Res. 1985;10:335-337.
Institute of Standards and Technology. Available at http://www.nist.
gov. Link verified July 11, 2002.
Dr Richard C. Niemtzow is a Colonel in the United States Air Force and
a Radiation Oncologist. He practices medical acupuncture full-time with
oncology and general patients, and is also involved in research. Effective
July 31, 2002, Dr Niemtzow was transferred to Malcolm Grow Medical Center,
Andrews AFB, Maryland to continue his full-time acupuncture endeavors,
and as a Consultant to the Air Force Surgeon General.
Dr Niemtzow is President of the Medical Acupuncture Research Foundation
Richard C. Niemtzow, MD, PhD, MPH*
9800 Cherry Hill Rd
College Park, MD 20740
Phone: 301-937-7424 Fax: 301-937-3205
Colonel (Dr) Richard C. Niemtzow
89 Medical Group (AMC)
Malcolm Grow Medical Center
Andrews AFB, MD 20762
Debra Clydesdale, BScEE, completed acupuncture training at the Emperors
College of Traditional Oriental Medicine in Santa Monica, California,
and practices at Center for Health Enhancement at Saint Johns
Health Center, Santa Monica. She has an Electrical Engineering background,
and has been in private practice as a Structural Bodywork Practitioner.
Debra Clydesdale, BScEE, MTOM
Emperors College of Traditional
1807 Wilshire Blvd
Santa Monica, CA 90403
Zang-Hee Cho, PhD, is Professor of Radiological Sciences at the University
of California at Irvine, and Director of Functional Brain Imaging Laboratory
for Acupuncture Research. Dr Cho pioneered the first Acupuncture-fMRI
in 1997, and since then, has developed a number of acupuncture and fMRI
related techniques. Previous to acupuncture-fMRI research, he pioneered
the first Circular Ring PET scanner and BGO in the mid-70s. He has been
engaged in various aspects of medical imaging, especially
functional MRI imaging since the early 90s. Dr Cho is a member of US
National Academy of Sciences-Institute of Medicine for his contribution
to the development of the PET scanner and related BGO detector.
Zang-Hee Cho, PhD
Professor, Radiological Sciences, Psychiatry
and Human Behavior, and Ophthalmology
Department of Radiological Sciences
University of California at Irvine
Irvine, CA 92697
Phone: 949- 824-5905 E-mail: firstname.lastname@example.org
Terry Oleson, PhD, is an internationally-known lecturer in the field
of auriculotherapy, and conducted pioneering research on auricular diagnosis
and auricular acupuncture at the UCLA Pain Manage-
ment Center in Los Angeles. He is on the faculty and Board of the American
University of Complementary Medicine, and Chair of the Department of
Psychology at the California Graduate Institute.
Dr Oleson has published over 20 scientific articles and 2 books on auricular
acupuncture, including Auriculotherapy Manual: Chinese and Western Systems
of Ear Acupuncture and International Handbook of Ear Reflex Points.
Dr Oleson received the Auricular Acupuncture of the Year Award from
the International Congress of Chinese Medicine, and was co-chair of
the International Consensus Conference on Acupuncture, Auriculotherapy,
and Auricular Medicine in 1999.
Terry Oleson, PhD
PMB 2657, 8033 Sunset Blvd
Los Angeles, CA 90046
Phone: 323-656-2084 Fax: 323-656-2085
Young-Don Son, MSc is a graduate student working toward a PhD in Biomedical
Engineering at University of California-Irvine under Dr Cho.
Young-Don Son, MSc
Dept of Radiological Sciences
University of California-Irvine
Irvine, CA 92697
Dr Peter A.S. Johnstone is a Captain (Select) in the United States Navy,
Radiation Oncologist, and an acupuncturist at the Naval Medical Center
(NMC) in San Diego, California. He is the Director of Ancillary Services
at the Naval Medical Center. Dr Johnstone has contributed many articles
to acupuncture and radiation oncology research.
Captain (Sel) Peter A.S. Johnstone, MC USN**
Naval Medical Center San Diego
Radiation Oncology Division
34800 Bob Wilson Dr, Suite 14
San Diego, CA 92134-1014
Phone: 619-532-7274 Fax 619-532-8178