Report of Tests on Joseph Newman's Device
Because this device was tested as a unique device, one element of the experimental approach was to assure the validity of the results by providing at least two independent, or nearly independent, measurements of both the input and the output power. To select the appropriate instrumentation, it was necessary to carry out preliminary investigations of the input and output waveforms. For both the input and the output, the waveform consisted of a series of twenty-four pulses, with the series repeating at approximately one-to two-second intervals. In addition, the crest factor (i.e. the ratio of the peak pulse amplitude to the root-mean-square value of the waveform) was found to be as large as about ten. Many types of instrumentation do not respond correctly over the observed frequency range and crest factor range, so the
|Photograph of Joseph Newman's device which was delivered to the National Bureau of Standards|
|Photographs of two examples [(a) and (b)] of output waveform of device under test as measured using an oscilloscope|
selection of the measurement equipment was especially important. The measurement approaches which were used at the National Bureau of Standards to acquire the data reported were appropriate for the waveforms measured.
A further consideration is that the waveforms changed with time, both in terms of the shapes of the individual pulses and in terms of the repetition interval. This variation results, at least in part, from the erosion of the tape (see section 2.2) on the commutator.
2.2 Brief Description of the Device under Test
The system which was evaluated consists of three primary components: the power source, a battery pack; the commutator, which is mechanically connected to a magnet which rotates during normal operation of the device; and the coil. The battery pack consists of 116 nine-volt batteries arranged in five sets of twenty batteries and one set of sixteen batteries. The batteries in each set are connected in series and external wiring is used to connect these various sets in series. The battery pack was provided by Mr. Newman.
During the testing, it was determined that one of the batteries in one of the sets was defective. After this battery was removed, the battery pack operated reliably.
Testing was performed at two different voltage levels. One of these levels was a nominal open circuit voltage of 1000 volts (the maximum available from the battery pack) and the other was a nominal open circuit voltage of 800 volts. These voltage levels decreased by about 50 to 150 volts when the battery pack was connected to the device.
A drawing of the commutator is shown in figure 3. The body of the commutator wheel is constructed from a plastic material. The outer edge of the wheel is covered by a metallic strip. This strip is split into two semicircles which are separated by small plastic spacers. Twelve pieces of tape are attached to one of the semicircles. These pieces of tape are arranged so that alternate, approximately equal, segments of the semicircle are covered and exposed. Two brushes contact the wheel about 180* apart. Each of these brushes is connected electrically to one of the two leads of the coil. There is a small slip ring on each side of the wheel. The sliding contact on one of the slip rings is connected to the grounded side of the battery. This slip ring is connected to the semicircle which does not have tape on it. The sliding contact on the other slip ring is connected to the positive terminal of the battery pack. This slip ring is connected to the semicircle which does have tape on it.
This commutator operates so that during one half of a revolution one side of the coil is connected to the anode (positive terminal) of the battery pack while the other side is connected to the grounded cathode (negative terminal) of the battery. During the other half of the revolution, the side of the coil which had been connected to the cathode is now connected to the anode and the side which had been connected to the anode is now connected to the grounded cathode. During each half cycle, the twelve pieces of tape alternately cause the battery anode to be connected to and disconnected from the coil.
|Schematic drawing of commutator|
2.3 Input Power Measurements
The input power measurement system, as shown in figure 4, consists of a voltage divider (R1 and R2), a current shunt (Rcs) and appropriate instrumentation to obtain the product of the voltage and current waveforms. The voltage divider has a high impedance network which consists of a 5-megohm resistor and a parallel capacitance of 6 picofarads. The low impedance arm of the divider is a 50-kilohm resistor. The load on the divider is approximately 6 meters of coaxial cable to a low-pass filter and to two measuring instruments, each having an input impedance of 1 megohm. The resistance of the high impedance element was selected to minimize the power dissipated in the divider. The parallel capacitance was then chosen to obtain a uniform frequency response, to within +/-2%, for frequencies up to 5000 hertz.
A current shunt having a resistance of 100.1 ohms was selected to provide appropriate signal levels. Measurements showed that for both direct current and 50-hertz alternating current signals, the shunt maintained its nominal value to within a few tenths of a percent for currents in the range from 1 to 50 milliamperes.
The output signals from the divider and shunt were measured using both a sampling wattmeter and an analog-multiplier wattmeter. The sampling wattmeter was a wideband precision meter developed by the National Bureau of Standards . A block diagram of the wattmeter is shown in figure 5. The instrument has two voltage input channels, and it can calculate and display the average of the product of the two input voltages. One of these input voltages, V2, is derived from the current shunt and the other, V1 is derived from the voltage
|Schematic drawing of Newman device and input and output power measurement circuits|
|Block diagram of sampling wattmeter|
divider. The displayed value, with proper scaling, shows the amount of power drawn from the battery. Using appropriate software, the sampling wattmeter can also be used to measure either the average or the root mean square (rms) value of a signal applied to either channel.
Each input channel consists of the three circuit elements shown schematically in figure 5. First, the input-amplitude-conditioner circuit scales the input signal to a level which is appropriate for the remaining circuitry. Second, the track-and-hold circuit samples an instantaneous value from the input circuit and holds that value at its output. Third, the analog-to-digital converter transforms the value of the analog signal to an appropriate digital signal. As soon as the digital signal is determined and transmitted to the following circuitry, the track-and-hold circuit takes a new sample of the input signal which is transformed into the next digital value. Thus, a sequence of digital signals flows from each channel and the value of a specific digital signal is proportional to an instantaneous sample of an input signal.
The digital signals from each channel are applied to the inputs of a digital multiplier. The multiplier calculates the product of the two signals. These product values are transmitted to a digital averager which determines the average value of a large number of these inputs. The average values, which are proportional to the power drawn from a source or delivered to a load, are displayed on the front panel.
The analog-multiplier wattmeter is a commercial instrument which was modified so that it could accommodate an external current shunt. Originally, the instrument had a voltage-input channel and a current input channel. The input current was passed through an internal current shunt to generate a voltage signal of the proper amplitude. The signal on the input voltage channel was scaled using a voltage divider.
As shown in the schematic diagram of this instrument in figure 6, these two signals are applied to the input terminals of an analog multiplier circuit. The output of the multiplier is proportional to the product of the two input signals. This signal is filtered using a low-pass filter and applied to the input of an analog-to-digital converter. The. digital output is simultaneously directed to both a front panel digital display and to a digital interface circuit. For most of the data taken during this investigation, the digital output was recorded using a computer to "read" the signal at the digital interface connector. This digital signal is proportional to the power drawn from a source or delivered to a load.
As figure 6 shows, the instrument was modified for this application by disconnecting the voltage signal from the internal current shunt to the multiplier circuit. In place of the signal from the internal shunt, the signal from a new voltage attenuator is applied to the multiplier circuit. This attenuator receives its input V2 from the external current shunt Rcs. Thus, with proper scaling, the value of the display shows the power drawn from the battery.
Because of some very large spikes in the current waveform, a low-pass filter was used on the current signal to both the sampling wattmeter and the analog-multiplier wattmeter. The filter prevented the spikes from producing a
|Block diagram of analog-multiplier wattmeter|
significant measurement error. The use of the filter results in the determination of the input power which is lower than the true value. To determine the signal loss due to this circuit, matching sets of high-pass and low-pass filters were constructed. The results of measurements using these filters are given in section 4.2. Figure 7 is a schematic diagram of the high-pass and the low-pass filters. The filters were constructed using a resistance of 1000 ohms and a capacitance of 20 nanofarads.
2.4 Output Power Measurements
The output power was the power dissipated in a resistive load RL connected in parallel with the coil of the device under test, as shown in figure 4. Two values of resistive load were constructed: nominally 50,000 ohms, and 200,000 ohms. By using series and parallel combinations of resistors of these values tests were run at nominal loads of 400,000 ohms, 200,000 ohms, 150,000 ohms, 100,000 ohms, and 50,000 ohms. Most of the data, however, were taken at 200,000 ohms or 50,000 ohms. The 200,000-ohm level was selected because at this point the power dissipated in the load and the power dissipated in the device under test were approximately equal. The 50,000-ohm level was selected as the smallest value of the resistance that could be used routinely without potentially damaging the device; one of the goals of the test program was to perform only nondestructive measurements. A significant source of potential damage was the vibration of the device, which increased as the value of the load resistance decreased.
To determine the power dissipated in the load resistor RL, three different approaches were used. The first was the differential active attenuator diagrammed in figure 8. This attenuator, which was constructed at the National Bureau of Standards, produced a signal at its output which was proportional to the voltage difference across the resistive load. This output voltage was measured using a commercially available digital voltmeter. This voltmeter incorporated a thermal element. A thermal element  is among the basic tools used in the determination of the rms (root-mean-square) value of a voltage waveform. The thermal element consists of two primary components: a heater which changes' temperature with changes in the current being passed through the element and a thermocouple to produce a voltage which is proportional to the temperature. The power dissipated in the load is the square of the rms voltage across the load resistor divided by the resistance value of the resistor.
The second approach uses a thermal element which is not a part of a commercial instrument. In this case, a shunt resistor RTS, nominally 100 ohms for a 50,000-ohm load, is placed in parallel with the thermal element. This combination is then connected in series with the load. In this configuration, the thermal element is "floating", i.e. depending on the instantaneous position of the commutator, the thermal element may be near ground potential or it may be near the maximum voltage of the battery. The output from the thermocouple in the thermal element was passed through a low-pass filter and was measured using a digital voltmeter. This thermal element is calibrated by applying a known voltage signal across the thermal element and its associated resistor and recording the output voltage from the thermocouple. The voltage across the load resistor is calculated by recording the output from the thermocouple, computing the voltage across the thermal element and the associated resistor from the calibration data, and calculating the voltage
|Low-pass (a) and high-pass (b) filters|
|Block diagram of differential active attenuator|
across the load resistor by multiplying the thermal element voltage by the resistance ratio of the load resistor to the parallel combination of the shunt resistor and the resistance of the thermal element. The power is then obtained by squaring this voltage and dividing it by the value of the load resistance.
The third measurement technique used is shown in figure 9. This resistance configuration had the advantage of being convenient to use and conceptually simple. Because one side of the coil was nearly always connected to ground, significant current would flow only through the 200,000-ohm resistor which was connected to the side of the coil which was not connected to ground. Thus, as the commutator reversed the connections to the coil, the two resistors would alternately carry current. But, as is discussed in section 5.3, because the switching sequence of the commutator disconnected the coil from ground once each rotation, this measurement technique always produced a value of the output power which was too large so that the measured value of the efficiency was always greater than the true value. This configuration was called the BI-200 because it was composed of two load resistors RL1 and RL2 each having a resistance of 200,000 ohms.