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NBSIR 79-1726 (ERA)

Electromagnetic Pest Control

Devices

Charles C. Gordon

Kenneth W. Yee

National Engineering Laboratory

Center for Consumer Product Technology

Product Performance Engineering Division

National Bureau of Standards

Washington, DC 20234

February 1979

Final Report

Issued March 1979

spared for r C~ 1 ~ wironmental Protection Agency

200 fice °f Enforcement, Pesticides, and Toxic

qr Substances Enforcement Division

,U b ashington, DC 20460

79-1726

C.2

National Bureau of Standard* MAY 1 5 1979 —

Mt ro

NBSIR 79-1726 (EPA)

ELECTROMAGNETIC PEST CONTROL

DEVICES

Charles C. Gordon

Kenneth W. Yee

National Engineering Laboratory

Center for Consumer Product Technology

Product Performance Engineering Division

National Bureau of Standards

Washington, DC 20234

February 1 979

Final Report

Issued March 1 979

Prepared for Environmental Protection Agency

Office of Enforcement, Pesticides, and Toxic

Substances Enforcement Division

Washington, DC 20460

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director

Table of Contents

page

1.0 Executive Summary 1

2.0 Introduction 1

3.0 Units Evaluated 2 4.0 Evaluation Procedure 3

4.1 X-Ray and Visual Examination . 8

4.2 Electromagnetic Measurements 8

5.0 Results of Evaluation 9

5.1 Results of X-Ray and Visual Examination . . 9

5.2 Results of Electromagnetic Measurements . . 10

6.0 Fields From Other Electrical Equipment 12

7.0 Conclusions 17

8.0 Appendix 19

1.0 Details of Evaluation by Unit 19

2.0 X-Ray Photographs 43

Table 1. Electromagnetic Pest Controllers 3

Table 2. EMF . Versus Distance. . 13

Table 3. Earth’s Magnetic Field ........... 14

Table 4. EMF From Electrical . Equipment 15

Table 5. Op erat ing , Vo It ag es and Currents 26

Figure 1. Sample Al 4 Figure 2. Sample B2 4

Figure 3. Sample Cl 5 Figure 4. Sample D 5 Figure 5. Sample Fl ......... , 6

Figure 6. Sample G1 6

Figure 7. Sample H 7 Figure 8. Comparison of Electromagnetic Field Strength 16

with Distance From C2 Unit

Figure 9. Electromagnetic Fields of Pest Controllers 16

and Common 115 V 60 Hz Equipment

Curve 1. Unit B1 27

Curve 2. Unit B2 28

Curve 3. Unit Al 29

Curve 4. Unit A2 30

Curve 5. Sketch of Output of Unit HI 31
page

Chart 1. Unit B1 32

Chart 2 Unit B2 33

Chart 3. Unit Cl 34

Chart 4. Unit C2 35

Chart 5. Unit C2 36

Chart 6. UnitD . . 37

Chart 7. Unit El 38

Chart 8. Unit E2 39

Chart 9. Unit Fl 40

Chart 10 Unit Fl 41

Chart 11 Unit Gl 42
ELECTROMAGNETIC PEST CONTROL DEVICES

1 . 0 Executive Summary

At the request of the Environmental Protection Agency

(EPA), the National Bureau of Standards, Center for Consumer

Product Technology, evaluated eight models of

electromagnetic pest controllers provided by EPA. The units

were evaluated to characterize any detectable

electromagnetic output but no judgment of the effectiveness

of the devices as pest controllers was made.

Visual and X-ray inspection and electromagnetic

measurements showed the units can be grouped into two

categories based on characteristics of the output signal--

the principal characteristics being either a pulse output or

a 60 Hz AC output. For the pulse output devices, no

significant external electromagnetic field was found. The

60 Hz units were found to generate detectable magnetic

fields. For all units, the fields detected would be less

than the earth’s magnetic field at distances of three meters

or more. Some common electrical equipment was found to

generate electromagnetic fields of the same order of

magnitude as that produced by these pest controllers.

2 . C Introduction

The National Bureau of Standards (NBS) was requested by

the Environmental Protection Agency, Office of Enforcement,

Pesticides, and Toxic Substances Enforcement Division, to

perform a limited evaluation of eight models of

electromagnetic pest controllers provided by EPA. Two

samples of some models were provided. These controllers are

electrical or electronic devices intended to riu an area of

pests such as rodents, rabbits, roaches, termites, and fleas

depending on the particular unit. NBS was requested to 1)

characterize any measurable electromagnetic output, but was

to make no judgment of the effectiveness of the devices as

pest controllers; 2) determine if models have any

commonality of their outputs which would allow grouping or

classifying of similar units for biological testing; ana 3)

determine the feasibility of developing a standard test

method for measuring and classifying units based on the

nature of the output. Due to the time and resources

available, the work was primarily directed to characterize

and provide comparative measurements of the outputs, and to

1
identify commonality between outputs. To the extent

practical, quantitative measurements were made and operating

principles or circuit components identified.

Nondestructive evaluation techniques were requested by

EPA since limited samples were obtained and several were

subsequently used by EPA for biological experiments to

determine the effects on animals or insects. The units were

to remain operable should further measurements be requested.

The measurements were to use readily available equipment,

where possible, so that further measurements could be made

by independent laboratories if necessary.

The EPA was responsible for obtaining test samples and

contacts with manufacturers. The EPA requestea technical

information and circuit diagrams but received only catalog

or advertising type literature. It was assumed that the

manufacturers did not choose to reveal this information.

Many units were either potted or assembled with rivets,

adhesive, or by other methods making nondestructive

disassembly difficult. This construction limited the

information obtained on circuits and components. Some units

are battery-operated and their cases were opened to perform

tests and inspect the battery supplies since batteries would

be replaced in the field.

A review of literature at the beginning of the

evaluation did not identify any published quantitative data

on the electromagnetic fields from, these devices. A

subsequent paper by Wagner (1978; ^ reports data on several

units.

3.0 Units Evaluated

The EPA furnished to NBS eight different types of

electromagnetic pest controllers for evaluation. Two

samples each of six of the types were furnished. A list of

these electromagnetic pest controllers with an NbS assigned

code for reference in data reporting and the EFA assigned

sample number is given in Table 1. The letter refers to

the type while the number designates the sample of that

type. The NBS code is also used to identify the X-ray

photographs in Appendix 2 and photographs of the outside of

each unit in Figures 1 through 7- Units El and E2 were

returned to EPA before photographs were obtained.

2
Taole 1 Electromagnetic Pest Controllers

NBSCode EPA No.

A1 Sampl

131918 (03213)

A2 Sample 131918 (03199)

B1 Sample 131978A

B2 Sampl

131978B

Cl Sampl

168054

C2 Sample 168054

D Sample 131901

El Sampl

131902

E2 Sample 131903

FI Sampl

131905A

F2 Sample 131905B

G1 Sample 131906A

G2 Sample 131906B

H Sample 123831

The units A1 , A2, and B1 , B2 are batter y-oper a tea

These units were received with batteries installed and the

units operating. They have no on-off switch and operation

is mdicatea by the periodic flashing of a small red light

emitting diode (LtD) in the center of the top of each case.

Instructional material supplied with these units indicates

that they snould run for approximately six months at which

time the batteries are to be replaced.

The other six types all operate from a 115 volt, 60 Hz,

AC power supply. These likewise do not have an on-off

switch but start immediately when plugged in. Units C, D,

and E have a circuit fuse. Units F and G have both a circuit fuse and a small light to indicate when they are

connected to the power supply. Unit H has an LED which

perioaically flashes to indicate when it is on.

4.0 Evaluation Procedure

Each unit was visually examined to the extent possible

without destruction. One sample of each type was X-rayed to

reveal hidden components, and each sample was subsequently
•• ^

FIGURE 1 SAMPLE A1

FIGURE 2 SAMPLE B2 ' '

4
FIGURE 4 SAMPLE 5
FIGURE 5 SAMPLE FI

FIGURE 6 SAMPLE G1

6
FIGURE 7 SAflPLE H

7

'
measured to characterize and, when possible, quantity any

measurable electromagnetic field emitted.

4.1 X-Ray and Visual Examination

X-ray photographs (Appendix 2) were maoe of one

sample of each of the types received. In most cases

when a unit was X-rayed, three different photographs

90° apart were made to reveal all possible internal

parts. The photographs at different angles (1) assist

in revealing hidden parts, (2) reveal internal

construction and parts location, (3) expose encapsulated

(potted) integrated circuits, etc., and (4) assist in

determining principles of operation. X-raying the units

was considered to be nondestructive. Each unit was

tested before and after X-raying arid for six types, the

X-rayed unit was compared to the non-X-rayed unit to

verify that no change had occurred.

The visual examination was limited to outside

inspection of the sealed units except for unit C2.

Since A1 , A2, bl , and B2 were battery-operated and tire

batteries had a finite life expectancy, the case screws

were removed to inspect the battery packs and measure

the operating current. It was also determined that it

was necessary to open these units and make internal

connections to the metal case and the battery to detect

any signal. Unit 02 was opened for visual inspection.

Its operation was found to be the same after opening as

before opening.

4.2 Electromagnetic Measurements

Electromagnetic measurements for DC fields were

made using a Schonstedt Model HSM-11 Station

Magnetometer. This instrument can ueteet a fiela of 0.5

nanotesla and ambient fields can be neutralized to

within 0.5 nanotesla (nT). The earth’s field is

approximately 50,000 nT or 0.5 gauss (10*5 nanotesla = 1

gauss) . AC magnetic field measurements were made using

a search coil as a detector. The coil consists of 250

turns of ho. 34 insulated wire wound with close spacing

in a single layer on a nonmagnetic form (phenolic) of 2-

inch diameter. The overall length is approx ima tel y 2

inches. For sinusoidal steady state magnetic fields,

the magnitude of the field can be calculated from the

voltage output of tne coil and the period of the

waveform. Two of these search coils were used at times

8
to make simultaneous measurements at different locations

around tne AC operated units. A aual-trace oscilloscope

was usee to display, measure amplitude, and analyze the

AC or pulse type signals. With this equipment the

outputs from two search coils to the unit under test

could be examined and analyzed simultaneously. A dual

channel DC amplifier-recorder was used in conjunction

with the oscilloscope to make permanent records of the

magnitude and frequency of the random or programmed onoff operation of certain units. The recorder input was

from a search coil.

For magnetic fields at 60 Hz, this equipment can

resolve less than 100 microtesla (1 gauss) peak-to-peak

.

The sensitivity increases in proportion to frequency.

This coil is useable up to about 100 kHz which is in

excess of any frequency measured or anticipated based on

tne size of the coils in the units which are visible in

the X-rays. For the search coil used, the peak-to-peak

magnetic field in microtesla is equal to 0.31 times the

peak-to-peak voltage (V) in millivolts times the period

(T) of' the waveform in milliseconds, 16.7 ms for 60 Hz.

[magnetic field (vT) = 0.31 x V(mV) x T(tns)]

5 . 0 Results of Evaluatio n General results on each unit examined are given in this

section. More detailed results are given in Appendix 1.

5 . 1 Results of X-Ray and Visual Examination

Visual inspection and examination of the X-ray

photographs and the electromagnetic measurements show

similarities between different units. Units A1 , A2, B1

,

B2, and H are similar except that the A's and B’s are

each powered by four 12-volt lantern-type batteries in

parallel and H operates from 115 volts AC. The X-rays

show that each has three coils and nine integrated

circuits on a printed circuit board. The electronics

all are encapsulated preventing further nondestructive

circuit determination. In the A and B units, the coils

and electronics are contained within sheet metal cubes:

in the A units totally enclosed, in the B units with one

side open which faces the ground when normally

installed. The metal cube in A appears to be aluminum,

the metal in B is magnetic. The cube in the A units is

9
contained aion^ with the batteries in a totaily closed

aluminum case. The ruetal in these units would act as an electrostatic shield. Only low frequency magnetic

fields of any magnitude would be expected to penetrate

the metal, particularly from the A unit's total ly-ciosed

case. Unit H does not have any ruetal shield.

The C, D, E , F, and G units appear similar. Each

has multiple coils, from 2 to 6 , which appear to be

mounted on a magnetic core. The two coils in E are side

by side, the others are all axial. Unit FI appears to

have three thryristor semiconductor switches which

control the coil currents and Unit G2 appears to have a thermal switch mounted against each coil. Fuses and

pilot lights are the only other significant components

identifiable.

b . 2 Results oi Electromagnet i c Measurem ent

DC Magnetic Field . The DC magnetic field

measurements made using the magnetometer were confined

to units B1 and B2. At any position of the probe

relative to the unit, and before any data was taken, the

ambient external fields were neutralized to about 1/2

nT. Then the unit was placed next to the probe anu

lined up as indicated by the instructions with the n (north) mark pointing north. A continuous chart

recording was made of the change in the magnetic field

due to the operation of the unit. The magnetometer

probe was positioned in several locations around the

unit to obtain the distribution profile of the field

generated by the unit. Chart 1 shows a portion of a recording for unit B1 and chart 2 shows a recording for

unit B2. The detectable change in the magnetic field is

approximately 5-12 nT. During the testing, the opening

of a laboratory door produced more field change than was

recorded due to unit El. There is a periodic shifting

of the magnetic field that most likely is caused by the

different internal digital type integrated circuits

operating to produce pulses. The higher frequency

components are discussed in a later paragraph. The

magnitude of the detected changes of DC magnetic field

are about 1/500U of the earth's magnetic field.

The magnetometer recordings of the output of units

D1 and B2 showed no significant differences between

these units. Since the X-ray and visual examination

showed that units A1 and A2 and H were very similar in

10
construction, in parts and layout to Bl and b2, these

were not cuecked using the nia 5 n etonie ter . They are

covered in the following section, where higher frequency

measurements are described.

AC Magnetic Field. The A, B, and H units were

ex ami n ed witn the search coil ana oscilloscope. No

detectable output was found from any of these units.

Therefore, other techniques were used to examine these

units . d 1

The covers were removed from units Bl and L2. The

oscilloscope high input lead was connected to the metal

can and the ground lead connected to the negative

battery terminal. Curves 1 and 2 are photographs of the

oscilloscope patterns for units Bl and B2 respectively.

These outputs appear to be digitally generated because

of the low frequency and exact pattern repetition.

Similar patterns were measured in units A1 and A2

between the metal box and the battery negative terminal.

These are shown in curves 3 and 4 respectively. No

metal can or box is used in unit K, as in A and B.

The oscilloscope was connected between one of the coil

leads and the negative side of the internal power

sup F ly. A similar pattern, shown in curve 5, was

measured. Any external fields resulting from these

internally measured signals was not determined by

analysis and none were measured.

The other five units, C, D, E, F, and G, all

produce 60 Hz magnetic fields measurable with the search

coil. All units switch the fields on and off in a generally random pattern. The various coils may be

energized at different times resulting in several levels

of field strength depending on the number of coils

energized. The coils are energized from several seconds

up to several minutes depending on the particular unit.

The long intervals and random patterns indicate some

type of thermal sensor determines the switching. The

outputs from these units are shown in charts 3 through

11 .

The maximum fields were measured at various

distances from each unit. The search coil voltage and

the calculated magnetic fields are given in Table 2 for

each unit. The largest fields were from unit C2 mounted

on a 2.4 meter iron pipe.

11
Examination of the cata in Table 2 allows a very

rapid decrease in field strength as the search coil is

moved away from each ^est controller under test. At

distances which are large compared to the diameter cl

the coil, the magnetic field from a current carrying,

coil decreases as the third power of the distance. ^ That is at 10 meters the field will be 1/1000 of the

field at one meter. The measurements at the 0.1b and

0.3 meter distances are not far enough from the coils to

follow this inverse cube relationship. Doubling tne

distance of the search coil from 0.13 rn to 0.3 m from

the unit reduces this detected field strength over a range of 3 to 13 times. These units are claimed to be

effective over an area of 2 to 12 hectares^ ' (5 to 30

acres). From the measurements at 0.3 m in Table 2, it

can be calculated that at 3 m the fields from various

units will be from 1/3 to 1/500 of the earth’s field.

The data in Table 3 shows the earth's magnetic field

strength throughout the United States for a comparison.

Figure 3 is a plot of the decrease in the

electromagnetic field strength with distance from the 02

unit. The points at 0.3 m and 0.6 rn (1 and 2 ft) are

laboratory measurements. From 3 meters to 12 meters (10

to 40 feet) are calculations based upon the field

decreasing as the third power of the distance. That is

at 12 in the field will be (1/4)-* times that at 3 m or

approximately 0.3 microtesla ( 0.003 gauss).

6 . 0 Fields From Other Electrical E quipment

As a comparison between the 60 Hz fields generated by

the pest controllers anc those encountered from everyday 115

volt 60 Hz equipment, the field from several common items

was measured and is shown in Table 4. A comparison between

data in Table 2 with that in Table 4 indicates some common

shop and household electrical equipment produce 60 Hz fields

in the same order of magnitude as those generated by the

pest controllers. The principal difference between those of

the same magnitude is that the pest controllers are turned

on and off in a fixed pattern or in a random pattern while

the shop and household units usually operate tor longer

periods. These motor units can be random in their on-off

operation. Some of tiie 115 volt 60 Hz motors showed pulses

with larger magnitudes. Figure 9 is a bar graph of data

from Table 4 showing a comparison of the electromagnetic

fields of pest controllers and common 113 volt 60 Hz

equipment when examined at a distance of 0.3 m (1 ft) to the

12
Table 2 EMF Versus Distance

Coil

(1)

Code Distance

Signal

mV (V)

Period

ms (T)

Constant

.31

Peak-to-Peak

Microtesla

.31 VT Gauss Comments

C2 closest 15 000 16.7 .31 77 700 777 top' 3 ) 0.15 m (6 in) 500 16.7 .31 2 600 26

0.3 m (12 in) 60 16.7 .31 300 3

C2 closest 18 000 16.7 .31 93 000 930 end (4)

0.15 m (6 in) 6 800 16.7 .31 35 000 350 8 ft pipe

0.3 m (12 in) 2 300 16.7 .31 12 000 120 on unit

0.6 m (24 in) 200 16.7 • 31 1 000 10

D closest 150 16.7 .31 780 8

0,15 m (6 in) 30 16.7 .31 160 2 0.3 m (12 in) 10 16.7 .31 50 .5

E2 closest 2 750 16.7 .31 14 000 140

0.15 m (6 in) 110 16.7 .31 600 6

0.3 m (12 in) 10 16.7 .31 50 .5

FI closest 1 250 16.7 .31 6 000 60

0.15 m (6 in) 200 16.7 .31 1 ooo 10

0.3 m (12 in) 60 16.7 .31 300 3

G2 closest 3 500 16.7 .31 18 000 180

0.15 m (6 in) 360 16.7 .31 1 900 19

0.3 m (12 in) 20 16.7 .31 100 1

(1) Search Coil; 250 turn, #34 insulated wire, 2-inch diameter, 2-inch length.

(2) Closest; search coil in contact with case of unit under test.

(3) Top; search coil located on top of unit.

(4) End; search coil located on end of unit

100 yT = 1 gauss

13
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15

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search coil detector. The kitchen blender showed a GO Hz

envelope of high frequency pulses from the motor brushes and

commutator in addition to a 60 Hz sine wave field.

7.C Conclusions

The eight types of electromagnetic pest controllers

furnished by EPA were examined. The NBS evaluation

indicates these can be separated into two categories based

on characteristics of the output signal: group 1, pulse

output; group 2, 60 Hz sine wave output. Of the units

evaluated, three (A, B, ana H) are in group 1 and five (C

through G) are in group 2.

Group 1 characteristics: 1) the units generate a low

level, repetitive pulse pattern which was measurable by

direct connection to the internal circuitry with an

oscilloscope; 2) low power drain; 3) digital integrated

circuits used to generate pulse pattern output. Evaluation

of group 1 units resulted in no significant detectable

external electromagnetic field with either a magnetometer or

a search coil used as a detector with an oscilloscope. The

only measurable signal from these units was found by direct

connection to the metal case of two of the units and to the

coil lead of the otner unit with an oscilloscope. The short

duration of both the positive and negative pulses for the

units would prouuce very low average power radiated signals.

Group 2 characteristics: 1) output is a 60 Hz

electromagnetic field; 2) operates from 115 volt, 60 Hz AC

power; 3) have a random or repetitive on-off pattern; 4)

appear to operate by driving various numbers of coils with

60 Hz AC.

The field generated by group 2 units was readily

detectable by the search coil and oscilloscope. The

electromagnetic fields from the 60 Hz units decrease very

rapidly with distance from the unit as shown in Table 2.

These fields will be less than the earth's magnetic field at

three meters from any of the units. Figure 8 illustrates

the rapid decrease of the electromagnetic field strength

with distance. For a circular area of 2 to 12 hectares (5

acres and 30 acres) for which various units are claimed to

be effective, the radius is approximately 76 meters and 200

meters (250 and 650 feet) respectively. For all units, the

magnetic field emitted will decrease with the third power oi

the distance from the unit. For distances larger than 3 m,

17
the earth’s field would significantly exceed these emitted

fields. These units transmit alternating fields which may

vary in amplitude and "on” time. Figure 9 shows that some

common 119 volt 60 Hz equipment generates electromagnetic

fields in the same order of magnitude as produced by these

pest controllers.

The NBS evaluation of this group of electromagnetic pest

controllers indicates a standard test procedure can be

developed for the group 2 devices to characterize their

output. This would utilize standard laboratory equipment

such as the vol t-ohmmeter , osc ii loscope , magnetometer, and

chart recorders. For group 1 devices, a standard test

procedure can be developed to determine if any significant

external electromagnetic field is emitted.

The biological effects of the electromagnetic fields on

rodents, insects, and other animals were not evaluated by

NBS.

NOTES

^

Wagner, R.E., "Outputs of Electromagnetic Devices, Their

Effects on Drywood Termites," Pest Control, September 1978.

p. 20. ’

fhe TEM cell at NBS, Boulder, CO, was considered for

additional measurements but was unavailable at the required

time.

^

Robert Plonsey and Robert E. Collin, Principles and

Applications of Electromagnetic Fields, p. 242, McGraw-Hill

Book Co . , 1961

( 4 ) 2 hectares are contained within a circle of 80 meters in

radius.

18
8 . 0 Appendix

1. Details of Evaluation by Unit

At least one type of each unit was measured for maximum

cur-rent consumption during operation. These results are

summarized in Table 5.

Unit A: Visual inspection was made of units A1 and A2.

Since these were battery-operated, their cases were opened.

Four 12-volt lantern type batteries in parallel supply power

to the electronics which is contained in a metal cube in the

center of a spun aluminum case. The case separates into two

halves of upper and lower approximately equal sections. Xray photographs of A1 show nine integrated circuits in the

potting compound (tiiree 16 pin and six 14 pin), several

resistors and capacitors, and three coils mounted in a delta

layout on top of the potting block. The coil's axes are

parallel to the ground when the unit is installed as

recommended. Laboratory testing and these photographs

indicate that this unit uses digital circuitry to generate a pulse pattern output. The top portion of the case was

removed to attach the oscilloscope probe to the metal box

housing the electronics with the scope ground probe being

connectea to the negative terminal of the unit's battery

power supply. The top of the metal box was placed back on

the unit, but not screwed into place, being careful not to

snort out the oscilloscope connections to the case. This

proceaure reduced the 60 Hz pickup present and produced a noise-free pattern on the oscilloscope for analysis and the

photographs, curve 3 (unit Al) and curve 4 (unit A 2). Both

units show a definite pattern repetition rate of

approximately 6.4 seconds. This repetition rate coincides

with the flashing of the LED indicator on top of the metal

housing cover. The units are obviously operated from

digital circuitry due to the exactly repeated output

pattern. The units are supposed to be identical in output

out there is significant variation between units Al and A2

in the amplitude of the positive pulses within a pattern.

Ttiis could be due to quality control problems or one unit

not operating within design specifications.

Unit B : The X-ray photographs of unit B2 show that it

also contains integrated circuits (six 14 pin and three 16

pin packages). Four 12-volt lantern batteries in parallel

supply power for the unit. A metal cube with one side open

houses the integrated circuits which are potted in an opaque

material. Three coils in a delta form extend through the

19
surface of this material. The coil's axes are parallel to

the ground when the unit in its installed position.

Likewise laboratory tests and these photographs indicate

this unit uses digital circuitry to generate a pulse pattern

output. This unit is housed in a plastic case with an LLD

mounted in trie top to indicate the unit is operating. This

LLD flashes about every nine seconds.

The covers were removed from units bl and 32 . The

oscilloscope was connected to the internal metal box for the

high input lead and ground lead was connected to the

negative battery terminal. Curves 1 and 2 are photographs

of the oscilloscope pattern for units bl and B2

respectively. This type of output is obviously digitallygenerated because of the low frequency and exact pattern

repetition. Units Bl and B2 have an equal number of

positive pulses (24). Unit Bl has 26 negative pulses. Unit

B2 shows two extra negative pulses of small amplitude

between the normal spacing for the other negative pulses.

These are probably due to a defective integrated circuit

(IC) and not due to variation in the design since according

to the manufacturer both units are supposed to be the same.

The pulse pattern repeats approximately every 17.5 seconds.

The small LLD light on the top to indicate the unit is

operating flashes approximately every nine seconds or twice

for each pattern of pulses.

The two battery operated units, A2 and B2, were tested

for output when installed in the ground. These were buried

to 1/2 of their height (thickness) in the earth as

recommended by the manufacturer. The oscilloscope was

connected to the internal metal can and battery common

terminal as in the laboratory tests. Unit A2 showed

approximately a 40% decrease in output signal when the unit

was in the earth relative to when it was tested in the

laboratory.

For the other battery-operated unit, B2, installed in

the earth, there was no change in the output signal relative

to that measured in the laboratory.

Unit C : The unit C2 was X-rayed in two pieces because

of its length. Both the top and base ends were photographed

with approximately 45° rotation to reveal hidden parts. Tne

photographs indicate six coils along a center rod with

associated modular type circuitry printed circuit boards.

There are three printed circuit boards. This unit was

opened and inspection showed the six coils are connected as

parallel pairs. Each pair is driven by one of the potted

modules. There is some end-play between the coil retainers

on the bottom and top of rod so the coils can slide along

the rod when driven by opposing magnetic fields. From the

chart recordings, photographs, and visual inspection of this

unit, it is not possible to identify the type of components

used to produce the output pattern shown in charts 3, 4, and
Chart 3 is of unit Cl with a search coil located

around the top rod and one located around the bottom rod

which was connected to a 2.4 meter iron pipe. From these

the top search coil indicates a large amplitude 60 Hz (max.

15 V peak-to-peak) magnetic field of about four seconds

duration that repeats every one minute and fifty seconds ana

a corresponding small field detected by the bottom search

coil. Within this pattern, but not at uniform times, the

top search coil indicated several reduced amplitude, foursecona duration fields and the lower coil detected, at

corresponding times, a larger amplitude field of

approximately four seconds duration. Also in addition to

these maximum fields in the bottom search coil, reducec

fields were detected of approximately four seconds duration

corresponding to similar detections in the top coil.

Similar recordings of unit Cl were made of unit C2.

These are shown in charts 4 and 5. Chart 4 shows the

calculations of the relative amplitudes from each coil for

each approximately four second "on" time of the unit (max.

15.5 V peak-to-peak).

Chart 5 shows the output from the top search coil only

for the period between 11 and 15 minutes after turn on. The

top pair of coils is designed No. 3, middle pair No. 2, and

lower pair No. 1. The pattern repeats every one minute and

50 seconds, but the operation of pairs 1 and 2 are not

consistent in order of operation within the pattern. The

difference in amplitude between the 1, 2, and 3 pairs of

coils is due to the difference in each coil-pair distance

from the search coil on the stub. The coil is closest to

the No. 3 pair. The reason for the random on-off time of

coil pairs 1 and 2 within the time pattern cannot be

identified without more circuitry information or destructive

examination of the encapsulated modules.

The search coil described was used to examine the

characteristics of each unit for oscilloscope analysis and

paper chart recording. Charts 3 through 11 are typical

records of the outputs from the 115 volt 60 Hz units when

detected by a search coil or coils. The chart speed in ail

recordings is 1 sec/mm with the smallest chart division

equal to 1 mm. The minute marks are indicated down the

center of the chart. The oscilloscope was used to determine

that these units had 60 Hz outputs. The maximum amplitude

detected by the search coil was determined from the

oscilloscope calibration and indicated on each channel of

recoruing. This reduced the time and confusion of adjusting

the pen recorder to a specific level. All charts are a portion of a recording taken after each unit was turned on

and run for some time. Recordings lasted from 15 minutes to

nearly one hour to analyze the characteristics of each

output

.

21
'when the unit C2 is initially turned on, all three coil

are energized and the upper No. 3 pairs separate from the

No. 2 and No. 1 pairs by the amount of travel possible for

the coils along the rod, about 12 mm. This is accompanied

by an audible vibration during the "on" time of about four

seconds. This audible vibration also occurs when the 1 and

2 pairs are "on" simultaneously. Smaller auaible vibrations

were noticed when a single pair of coils was driven or for

other combinations of pairs.

The driving signal to each pair of coils from its

associated encapsulated module was measured as 115 volts 60

Hz during the four seconds period. When a pair of coils is

being driven, they induced 60 Hz signal into the adjacent

undriven pairs.

U nit D : Two X-ray photographs were made of unit D

because of its length. This unit has a clear plastic center

section. Visual inspection shows three coils mounted on a metal rod with some space between the coils so they can

slide on the rod. A retainer on each end limits the travel.

The X-ray photographs of unit D reveal very little

additional identifiable circuitry. The random output

pattern could be controlled by a thermostatic type switch

which turns different coils on.

A paper chart recording was made of unit D (chart 6).

The search coil was placed as near as possible along the

clear plastic side, parallel to the center coil of the three

coils mounted on the center rod. After initial startup,

the unit turns off, but then operates in a random mode as shown in the chart. The output is low (0.26 volts peak-topeak) as detected by the search coil. The duration of "on"

time is variable. This unit appears to be controlled by a thermostatic type switch that is sensitive to the

temperature of the unit which would also be affected by the

amoient environment. This could produce the variation in

time of operation and duration. The radiated field is

always b0 Hz and can be less than one second in duration and

up to several seconds after the initial startup. The lower

amplituue signals are due to the random operation of the

other coils which are not coupled as closely to the search

coil as the center coil. This type of variable operation of

different coils in a multi-coil unit was observed when

testing units Cl and C2.

U nit E : The X-rays of unit El show two coils mounted

adjacent to each other with their center axis spaced 75 min

22
apart. The coil centers are such that two units could be

bolted together to increase the output fields. Each unit

has a fuse. Other circuitry appears limited. The unit is

also possibly controlled by a thermostatic switch.

The units El and E2 are also 115 volts 60 Hz powered

pest controllers. Both are supposed to be identical and

they operated essentially the same after the initial

startup. Each was examined with two search coils placed on

top with their axes on line with the axes of the internal

coils as revealed by the X-rays. Vvhen unit 1 was turned on,

a 60 Hz field was present from one coil for 15 minutes and

then went off for 12 minutes. The other coil was on tor 12

minutes and then off for 15 minutes. After the "off" time,

the unit El produced a 60 Hz, 2.6 volt peak-to-peak sine

wave. Duration of each transmission varied from less than

one second to several seconds. Both of the coils would

frequently be on simultaneously but would not necessarily

start or stop at the same time. Examination of chart 7

reveals the random nature of the operation after warm-up

between the time of 2? minutes and 31 minutes after turn-on.

A very sensitive heat element that detects the temperature

of each coil could produce this pattern. The ambient

temperature would be a factor affecting the operating

pattern

.

Unit E2 exhibited similar characteristics as unit El

except on startup each coil operated for approximately 3-1/2

and 2-1/2 minutes respectively, then both were off for 8-1/2

minutes. After this the random pattern shown in chart 8

began. All detected signals are 60 Hz sine waves and from

2.6 to 2.8 volts peak-to-peak at the search coils. This is

the same amplitude as unit El.

Unit F : The unit FI consists of a metal box with an

attached pipe. The X-rays show the box most likely contains

three thyristor semiconductor switches and the pipe section

contains several coils. The pipe and unit heat up with

extended time of operation. Thermostats could be used to

activate the thyristors to produce the pattern recorded in

charts 9 and 10.

The output of units FI and F2 were examined around the

case with a search coil and the oscilloscope. Both are 115

volts 60 Hz powered units and radiate 60 Hz sine waves of

varying amplitudes with time. Two search coils were used

for charts 9 and 10, one located at the end of the unit and

the other at the base of the case where the extension pipe

23
exits. The coils were located for maximum output in these

positions. The unit operated for approximately seven

minutes at a constant amplitude, then the output dropped to

a lower but constant amplitude (see chart 9). After

approximately 11 minutes the unit went off. The detected

amplitude at the higher level was 1.3 volts peak-to-peak at

the base search coil and only 0.4 V p-p at the end search

coil. Chart 10 shows the pattern of detected output after

several minutes of operation (21 to 2b minutes) . Other

portions of the recording show reversal of low and high

amplitudes but starting, stopping, and magnitude changes

occur simultaneously with the two search coils in these

positions. X-rays of the upper extension indicated

circuitry in the upper sections and coils in the pipe. Even

though the output is 60 Hz sine wave, this unit has a different on-off characteristic than the previous units

which were on for much shorter times and more frequently.

Unit G: The G1 and G2 type units are designed to be

clamped to a water pipe. They also are 115 volt 60 Hz

powered. The unit G2 X-rays show two coils around a common

center rod. They are spaced about 30 mm apart. The X-rays

indicate a thermal activated switch is mounted against each

coil. After initial turn on the temperature reaches the

switching level of the heat sensor which turns off the

associated coil. Thereafter, when the coil cools down, each

coil is activated when its switch closes and runs until the

switch opens.

Two search coils were also used to analyze unit G1 , one

located on top and the other on the side. Its output is a 60 Hz sine wave of 4.3 volts peak-to-peak from the top

search coil and 2.5 volts peak-to-peak from the side search

coil. After initial turn on the unit operated for nearly 25

minutes at its maximum peak amplitude at the side coil.

After that the operation becomes random with various

amplitudes and off times. Each amplitude change or off time

was simultaneously reflected by the two search coils. Like

the unit FI, all G1 "on" operations were longer than the

other 115 V 60 Hz units (see chart 11).

Unit H ; The unit H is enclosed in a plastic case

consisting of a base section containing all of the

electronic circuitry either molded in place or bonued by

other means. A top plastic piece is bonded to the base

flange. On top of this cover is mounted an LED. The case

is open along one side permitting inspection of the unit.

The encapsulated electronics, transformer, and three coils
are visible here. This opening was used to make electrical

connections for the laboratory testing and measurements.

The X-ray photographs of the H unit shows a power

supply, three coils coupled to the encapsulated module, and

the module of six 14 pin and three 16-pin integrated

circuits and other components.

The H unit is 116 volt 60 Hz powered. It contains a power supply to convert to 12 volts DC. The small light

emitting diode on the case flashes about every six seconds

(similar to Type A units) to indicate the unit is operating.

The X-ray photographs revealed that the unit H contains

electronic components similar to those in the A and B units

except for the DC power supply. Therefore, it was tested

for pulse output. No output was detectable using the search

coil. The oscilloscope common lead was connected to the

negative of the 12 volt supply. No metal case or box is

used in the H unit as in A or B units. The oscilloscope

probe was connected to one of the coil leads from the

encapsulted electronic components to investigate any pulse

output. The output is shown in the sketch, curve 5. The

pulse pattern is repeated approximately every 12 seconds.

This type of output is also obviously digitally generateu

because of the low frequency, exact pulse pattern

repetition, and the integrated circuits used as shown by Xray photographs. The maximum positive pulse output is over

twice that of the B units but the intermediate low amplitude

pulses are significantly less. The average power radiatea

is very low due to the short pulse duration and small

amplitudes which likewise is characteristic of the A and B

pulse units.

25
Table 5 Operating Voltages and Currents

Operating Max . Code Volts Current

Al 12 V DC 6 . 2 mA

A2 12 V DC 2.2mA

B11 V DC 2 . 3 mA

B 2 11 . 2 V DC 3 . 1 mA

C 2 115 V AC 3.1 A

D 115 V AC 9.4 A

El 115 V AC 3.1 A

FI 115 V AC 2 . 6 A

G2 115 V AC 5.3 A

26
UNIT B 1 : 6/8/78

Maximum Positive Pulse 2.3 V

Negative Pulse .675 V

Sweep Rate 5 SEC/CM

Pulse Rate .35 sec

Pattern Rep. Rate 17.5 sec

Gain .675 V/cm

CURVE 1

27
UNIT B 2: 6/8/78

Maximum Positive Pulse 2.25 V

Negative Pulse .825 V

Sweep Rate 5 SEC/CM

Pulse Rate .35 sec

Pattern Rep. Rate 17.5 sec

Gain .75 V/ cm

CUEVL2

28
UNIT A 1 : 6/7/78

Maximum Positive Pulse: .51 V

Negative Pulse : .09 V

Sweep Rate : 1 SEC/CM

Pulse Rate : .18 SEC

Pattern Rep, Rate : 6,4 SEC

Gain : ,183 V/cm

0120

29
UNIT A 2: 6/8/78

Maximum Positive Pulse .64V

Negative Pulse . I2V

Sweep Rate 2 SEC/CM

Pulse Rate . 18 SEC

Pattern Rep. Rate 6. A sec

Gain .183 V/CM

CURVE A

30
Volts

Curve 5: 10/23/78

Sketch of Output of Unit H 1 as shown on the Oscilloscope Display

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1 1 1 1 u 123456789 10 11 12

Time, S econd s Pattern Repeats ~ Every 12 Seconds

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8.0 APPENDIX

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U.S. DC PT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. 3* Jfecluteifs AcC«ssioi> No.

4. TITLE AND SUBTITLE 5. Publication Date

Electromagnetic Pest Control Devices I. Performlng Organization Code

7. AUTHOR(S)

Charles C. Gordon, Kenneth W, Yee

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, DC 20234

19. Prpject/Task/Work Unit No. 7620421

11. Contract/Grant No.

12. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City, state, ZIP) Environmental Protection Agency, Office of Enforcement,

Pesticides, and Toxic Substances Enforcement Division

401 M St., SW, Washington, D.C, 20460

13. Type of Report & Period Covered

Code

15. SUPPLEMENTARY NOTES

_ Document describes a computer program; SF-185, FIPS Software Summary, is attached.

16. ABSTRACT (A 200-word or ieex —' - —- * .iamfirant information. If document includes a s: At the request of the Environmental Protection Agency

(EPA), the National Bureau of Standards evaluated eight

models of electromagnetic pest controllers provided by EPA.

This evaluation was performed by the Center for Consumer

Froduct Technology. The units were evaluated to

characterize any detectable electromagnetic output but no

judgment of the effectiveness of the devices as pest

controllers was made.

Visual and X-ray inspection and electromagnetic

me a sur emen t s showed the units can be grouped into two

categories based on characteristics of the output signal

the principal characteristics being either a pulse output or

a 60* Hz AC output. For the pulse output devices, no

significant external electromagnetic field was found . The

60 Hz units were found to generate detectaDle magnetic

fields. For all units, the fields detected would be less

than the earth’s magnetic field at distances of three

or more . Some common electrical equipment was found

generate electromagnetic fields of the same order of

magnitude as that produced by these pest controllers.

17. KEY WORDS (s ix to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name;

separated by semicolons)

meters

to

Electromagnetic Pest Control Deivces

Electromagnetic Field Strength of Pest Control Devices

Pulse Type Pest Control Devices

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