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The National Defense Research Committee began a guided missile program in 1940, believing it might be useful to the armed forces later in the war. The program sought to develop a missile that would seek out and guide itself to a target. The assumption was correct, but the Germans developed similar technology first, using it to sink Allied ships while remaining out of range for return fire. Help from the Bureau was solicited in 1942 to solve the aerodynamic and servomechanism challenges that arose from the testing of the early prototype.

 

Initially, the guided missile used a television screen to transmit a live feed of its position back to an operator using a manual remote control to guide it. This option proved to be an utter failure and the Bureau turned to investigation of methods using radar. One possibility used a radar receiver tuned to the target’s transmitter for guidance while the other had both a transmitter and receiver and used echoes from the transmitter to identify the proximity of the target. The study of these two options encompassed over a hundred Bureau staff and the whole hydraulics laboratory.

 

The first missile ready for testing in 1942, the “Pelican,” was the type with only a receiver. The plane carrying the weapon would illuminate the target with its radio and the bomb would home in. In the rush to get the test missiles ready as quickly as possible, minor flaws were overlooked which later resulted in serious problems with the tests. Although easy to correct, by the time the problems were remediated, the second type of radar missile, the kind with both transmitter and receiver, had shown even greater promise and become the focus of the Bureau’s energies.

 

The “Bat” was a 1,000-pound flying bomb that sent out pulses of sound and used their echoes to guide the missile. Testing began on the bat in 1944 and by the fall of that year, both the Bat and Pelican had been declared successful in testing conducted on a battleship. Although the Bat had the advantage of being self-sufficient and not dependent on the drop plane to illuminate its target, the Pelican had the distinct advantage of a larger range (20 miles). Nevertheless, it was the Bat that was ultimately produced for use overseas.

 

Another important technology of the WWII era was the high-frequency direction finder or “Huff-Duff.” Built on technology developed at the Bureau in 1915, Huff-Duff stations were meant to target German U-boats that would attack Allied supply convoys crossing the Atlantic. The U-boats would hunt the convoys in packs, using their wireless to communicate. Having detected the enemy’s wireless signal at the Huff-Duff station, Allied planes would then deploy and use radar to find the U-boats. The existing technology did, however, have errors, which prompted the NDRC to request that the Bureau study high-frequency finders to identify ways of measuring the errors.

 

The two resulting papers, "High-frequency direction finder apparatus research by the NBS" and "The polarization of downcoming ionospheric radio waves" contained the basic research on which all future research on direction finders would be built. Even so, the Huff-Duff investigation was but a small part of a much larger Bureau project on the ionosphere.

 

It had already been known since 1925 that conditions within the ionosphere affected radio communications and research was leading to better and more accurate predictions of when and how radio communications would be affected. A month after the Japanese attack on Pearl Harbor, a Bureau letter circular on radio-weather predictions was withdrawn from circulation and all further open publication on the subject ceased.” Any information relating to radio communication became a military secret until the war was over.

 

Thanks to the war, the military had to be able to identify the best and safest transmission paths over which to communicate. Following an accident involving an airplane, the British, then Australians and finally the Americans sought to improve their propagation services. In this country, the NDRC asked the Bureau to educate the military through the compilation of a textbook detailing the basics of radio skywave propogation. The information the Bureau set forth in its Radio Transmission Handbook—Frequencies 1000 to 30,000 kc prompted the NDRC to ask the Bureau to continue the work and led to the establishment in 1942 of the Interservice Radio Propagation Laboratory (IRPL). The purpose of the IRPL was to centralize radio propagation data and disseminate the information to the military.

 

**The information presented here is drawn from “Measures For Progress: A History of The National Bureau of Standards” (Rexmond C. Cochrane)

 

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Dr. Briggs proceeded slowly and cautiously when it came to the atomic issue, but one week before the attack on Pearl Harbor, there was an official recommendation made to commit to the production of an atomic bomb. Less than 2 weeks after Pearl Harbor, a timeline was established that would result in the production of a finished bomb by January 1945. Five promising approaches to bomb production were identified and all were to be explored through the pilot plant stage. The Bureau’s role at this point became “the development of analytical procedures for controlling the purity of critical materials in the reactors and in the bomb.” In this capacity, the Bureau received almost 9,000 material samples on which they performed almost 30,000 analyses.

 

Work on the bomb progressed through research performed in the military, governmental and educational sectors to the point of the assemblage of a dream team of theoretical and experimental physicists, mathematicians, armament experts, specialists in radium chemistry and in metallurgy, specialists in explosives and in precision measurement at Los Alamos, New Mexico. The Bureau contributed a group from its proximity fuze program and a team dedicated to the purification of U235 scrap so it could be used again. Finally, in July 1945, the bomb was tested successfully. https://www.youtube.com/watch?v=Ru2PWmGIoB8

 

Though overshadowed by the immensity of the development of the atomic bomb, the WWII era yielded two other amazing advances – namely, the airburst proximity fuze and radar. The airburst proximity fuze allowed for bombs to be detonated in the air prior to impact with the ground which greatly enhanced their destructive power. Using this technology, detonation occurs when radio waves emitted are reflected back to the device with sufficient intensity to indicate close proximity to a large object triggering an electronic switch to initiate the detonation.

 

The Bureau became involved in work on this type of fuze after the NDRC (National Defense Research Committee) assigned the research to the Department of Terrestrial Magnetism at the Carnegie Institution of Washington in 1940. Within the Bureau, the work fell to the team that had previously constructed the radiosonde and radiotelemeter. Within 6 months, they determined that different types of radio would be necessary for rotating projectiles (used by the Navy in antiaircraft guns) and nonrotating (for the Army and Air Force to use with bombs, rockets and mortars). Only the work on the nonrotating element fell to the Bureau, which focused on the potentials of either an acoustic fuze or a photoelectric fuze. After eliminating acoustic and other methods, testing began using the Doppler effect of reflected radio waves. By early 1941 they had achieved proof of concept but it took almost 2 more years to develop to the point of being used by the military in combat operations.

 

Testing and development continued and the program outgrew its laboratory space at the Bureau in 1942. In December of that year, with requests for additional fuze types and other related projects, the Bureau consolidated the various projects into the ordnance development administration. Since the face of the war was constantly changing, the fuze projects were as well. A project established to meet one threat might have to be retooled as that threat gave way to another. Fuze designs had to be tweaked to accommodate different types of exploding weapons. For example, the differences presented by the dry battery used in the bomb fuze as opposed to the power source for the rocket fuze. The dry battery was far more temperature sensitive and had a very short shelf life. These limitations meant an alternate power source had to be found – ultimately resulting in a small generator being fitted to the spinning vane of the conventional bomb fuse. This solution all but eliminated the problems of shelf life and temperature sensitivity, and also made the bomb safer to handle, since it wouldn’t detonate unless sufficient wind passed the vane (as in a drop) to produce enough power to trip the fuze.

 

All of the advances in fuze and detonation technologies dramatically increased the destructive power of exploding weapons used by the U.S. during WWII. In fact, the technology was so powerful, that use of the fuzes was forbidden in circumstances where the enemy might be able to recover a fuze for later analysis or identify its nature simply by observation. For example, bombs incorporating the proximity fuze were not used for D-Day for fears that a fuze might be recovered from the beach at Normandy. As the war neared its end, fuze plants were “monopolizing 25 percent of the total facilities of the electronic industry and 75 percent of all molding plastics firms.”

 

**The information presented here is drawn from “Measures For Progress: A History of The National Bureau of Standards” (Rexmond C. Cochrane)

 

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Tuesday, 21 July 2015 00:00

Blog: A Perpetual Dilemma: Rent or Buy?

In this article by Robert Preville (Founder & CEO, Kwipped), the author discusses the potential benefits of renting lab equipment, as opposed to buying. Did you know that Cooper Instruments & Systems offers equipment rental options? The article expands on the following advantages renting can offer:

 

  • control cash flow
  • "try before you buy"
  • bring in job-specific equipment
  • more access to new technology

 

Click here to view the white paper.

 

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Based on work out of Germany, France and Finland, and at the request of the US Weather Bureau, two researchers of the Bureau’s electrical division began an endeavor to devise a practical system of radiometeorography for the weather service. A similar request was made by the aerological division of the Navy’s Bureau of Aeronautics, this one being researched by a team from the radio laboratory. This second team’s offering seemed better suited to both requests, so the duo from the electrical division fitted the device they had developed with Geiger counters and began launching them 20+ miles up to gather cosmic ray data. Their findings would impact thinking on radiation and the effect of cosmic rays on radio communication as well as the study of atomic structure. Using data gathered from 18 launches of their device, Leon Curtiss and Allen Astin confirmed international reports proposing that the greater part of cosmic-ray phenomena was caused by secondary effects within the Earth’s atmosphere.

 

The team from the radio division, meanwhile, successfully devised a unit that transmitted continuous data on cloud height and thickness, temperature, pressure, humidity, and light intensity in the upper atmosphere. Dubbed the “radiosonde”, the device was effective at 15+ miles up and at distances up to 200 miles. By 1940, it completely changed the US weather and meteorological services with 35,000 units being built and launched each year.

 

During the 1930s and 1940s, the Bureau was party to nearly every expedition sponsored by the National Geographic Society, including visits to the polar regions and balloon flights 14 miles into the stratosphere. The Society and the Bureau co-sponsored an expedition to the USSR to observe and photograph the 1936 solar eclipse, capturing the first-ever natural color photographs of an eclipse using a 14-foot camera conceived and constructed at the Bureau. Both the camera and the Bureau would participate in several other solar eclipse expeditions around the globe over the next few years. Dr. Briggs even organized an eclipse expedition to Brazil in 1947 that comprised 76 researchers from the Bureau, armed forces and National Geographic Society.

 

Concurrent with this atmospheric research, huge breakthroughs were made across the world in the fields of physics and atomic research. The Bureau’s first studies in this vein were into atomic chemistry, not physics. The existence of isotopes (atoms of the same chemical element with different atomic weights) had been discovered, but researchers were having difficulty finding a heavy isotope of hydrogen using the existing technology. The Bureau stepped in to suggest use of its cryogenic lab to study liquid hydrogen where experiments confirmed the existence of the proposed heavy hydrogen isotope.

 

In a series of discoveries by American and European scientists, the existence of neutrons was confirmed and the first nuclear reactions were performed. Enrico Fermi experimented using uranium with an atomic weight of 238 and bombarding the atoms with neutrons to split the nucleus, but his results were inconclusive. Later experiments by others confirmed that the same isotope of uranium could be split and finally that it could be split into two nuclei of roughly equal size but producing enormous quantities of energy in the process. These findings were relayed to Albert Einstein by Niels Bohr, who also informed him that Hitler had control of the only known source uranium ore and had placed an embargo on it.

 

This news and its significance were conveyed to President Roosevelt, who immediately sought the advice of Dr. Briggs at the Bureau. Within a week, Dr. Briggs was chairman of the newly formed Advisory Committee on Uranium. The Committee’s task was to investigate uranium fission (faster than Nazi scientists could). Less than a month from Einstein’s initial letter to the President, the Committee issued a report indicating the distinct theoretical possibility of a chain reaction that would produce enough energy for an explosive weapon or to power a submarine.

 

As the Second World War began in Europe, and recognizing the potential implications of researching nuclear fission, Dr. Briggs hesitated as to what he and the Bureau should do next. Was this a line of research he and his organization would or should pursue? The Committee was absorbed, renamed and absorbed again into a series of other national defense programs created as Nazi Germany continued its European conquests, before finally becoming inactive under the umbrella of the Manhattan District division of the Army Corps of Engineers in 1942.

 

 

**The information presented here is drawn from “Measures For Progress: A History of The National Bureau of Standards” (Rexmond C. Cochrane)

 

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Thursday, 28 May 2015 00:00

Q&A: Calibration Curve

Following is the transcript from a question and answer session conducted with a Cooper Instruments technical engineer.

 

Q:            What is a calibration curve?

A:            A calibration curve is the performance curve of the transducer; that is to say, its output in relationship to the range of applied loads from a no load condition to that of a full scale load.

If you were to measure the output of a 100 LBF load cell and record the output at 0, 25, 50, 75 and 100 LBF, theoretically you would have a curve much like the one in fig 1. As this is a perfect example, the performance curve is a straight line. In real world conditions however, there will always be a slight error that will prevent a straight line, but depending on the amount of error, the performance could possibly be accepted as straight. Whether the performance is good or not, the resulting performance representation is considered a “curve”.

 

 

Q:           How is it calculated?

A:           As shown above, the calibration curve is not calculated but rather it’s measured. Some calibrations are calculated if, during a calibration, the lab is unable to apply certain data points or force points. In cases like this, the laboratory can turn to statistical tools to calculate what the performance is most likely to be at these unmeasured points. It is; however, always best to stay away from extrapolating data unless absolutely necessary.

 

 

Q:           Most indicators offer a 2-point calibration: what does that mean?

A:           An indicator is a device that allows the user to equate a desired engineering unit to the output of the transducer. Most indicators allow for what is called a 2-point calibration, meaning you can define only 2 points on the calibration curve and the meter assumes a straight (linear) curve. So, if you follow the recommendations in the manual, you will use a no load condition of your transducer and define it as your zero load point. The second point is usually your full load point, and in the case found in Fig 1, the full scale would be defined as 100. Consequently, when the meter reads exactly half the value of the full scale point, the meter will report 50.

 

 

Q:           What are the limitations of a 2-point calibration?

A:           The limitation to a 2 point calibration is that it assumes your transducer is performing at a theoretical (perfect) level. You’ve heard the saying “nature abhors a straight line”? Well, this is a very true saying, and applies to transducer performance just as much as it does to rivers and streams. Now, the effect of the lack of linearity depends on the errors due to inaccuracies and on the user’s quality requirements.

Let’s assume that the 100 LBF transducer in our example performs with a nonlinearity specification of ±1% at half scale, and the 2 point indicator has been calibrated at 0 Lbf and 100 Lbf, when 50 Lbf is applied, the display will read 50, but the actual force is in the range of 49 to 51 Lbf. So due to the 2-point calibration, the inaccuracy of the performance curve is hidden.

So in short, the limitation of a 2 point calibration is the inability to compensate for nonlinear performing load cells, yielding inaccurate readings.

**It’s important to note that a load cell will always perform within OEM specification limits when new. However, after prolonged use and age the performance will begin to degrade, and a 2 point calibration may not be able to compensate for this change.

 

 

Q:           How does using a multi-point calibration linearize a load cell's

               performance?

A:           Now that we know there can be an amount of error between 2 points of a curve, it stands to reason that if we shorten the distance between the points, the smaller the errors will be had between those same points.

So, if we calibrate our meter with more than 2 points, we will begin to reduce the measured errors and improve the performance of the load cell system. In Fig-2 below you can see the same 2 point calibration curve in the blue dotted line. Compare this curve with that of the individual data points. You can see an error grows up to the halfway point and then reduces as it gets to the highest data point.

If we were to use a 5-point calibration method on this instance, you would get a performance more on the lines that the black line represents. Fig-3 demonstrates the new calibration curve with the red dotted line, when applying the multi-point calibration for 5 points.

 

 

Q:           How does a linearized performance prolong the useful life of a load cell?

A:           As the load cell ages with use, the linear performance will decay. With the use of a 2 point calibration, there will be a point where the load cell will not maintain the performance needed and may eventually get to a point where the errors cannot be compensated for.

With the use of an indicator with multi-point calibration functionality, the errors can be compensated for and performance can be maintained.

 

 

Q:           What solutions can Cooper Instruments offer when an indicator with 2-point calibration is not sufficient for the user's application?

A:           Cooper Instruments offers several products with multi-point calibration

               options:

The DFI INFINITY B, M3, M5 and 7i all allow for multi-point calibration. We also offer the DSC USB, which has software that allows for multi-point calibration. Our sales representatives would be happy to help you select the right product for your application.

 

As always, if you have any questions related to this material, our support staff at Cooper Instruments is available to help. Contact them by calling (800) 344-3921 or emailing This email address is being protected from spambots. You need JavaScript enabled to view it..

 

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With much of the US in denial, a group of foreign-born scientists led by Niels Bohr foresaw the country’s eventual involvement in WWII. Bohr, for example, urged a moratorium on publication in the Allied countries of research related to nuclear fission. It was almost a year before the scientific community truly headed Bohr’s warnings. Dr. Briggs, from his position on the Advisory Committee on Uranium, began to prepare himself and his agency for the possibility of war. Briggs prepared for the Department of Commerce and list of services the Bureau was prepared to offer “in the event of war.” Among these: to test all materials to be purchased under the Strategic Materials Act, to increase its output of optical glass, to certify US materials sent abroad (especially instruments, gages, metals and cement), and more. Dr. Briggs also included with his memorandum a copy of “The War Work of the Bureau of Standards” which detailed the Bureau’s contributions during WWI.

 

The country as a whole was totally unprepared for a new war – the armed forces had outdated equipment (and that in short supply) while much of the nation was still facing the high unemployment and sluggish manufacturing of the Great Depression. The general mood of the country was against involvement in the war (as evidenced by the 1940 Democratic Party Platform) and thus mobilization to prepare for war was slow. In taking on projects related to wartime preparation, the Bureau was forced to begin classifying much of its research. As a result, the annual reports from the Bureau became restricted to only nonconfidential research. By 1942, so much of the material was classified that there was no point in printing the annual report at all. The sensitive nature of the work being done at the Bureau also led Dr. Briggs to close the laboratories to visitors, fence in the property and close Van Ness Street, which ran through the site. By the beginning of 1942, 90 percent of Bureau staff were dedicated to war research and Military Police patrolled the “prohibited zone” that was the Bureau grounds.

 

That the Bureau would be tasked with testing the strength and properties of material like metals used for weapons, airplanes and the like or with finding materials that could be substituted for those in short supply as a result of the war would seem obvious. There were also more obscure aspects of war to be considered, however. One interesting example is the Bureau’s participation in a “joint Army-Navy program to determine the characteristics of sky glow from artificial sources and the extent to which sky glow and shore lights might aid hostile ships offshore.” Among other priority Bureau projects during the early part of the war were research on petroleum conservation (because oil tankers were great targets for enemy submarines) and the production of synthetic rubber. Gas was rationed (to save the rubber in car tires more than to save gas), resulting in numerous citizen inventions intended to save gas being submitted to the Bureau for testing.

 

Thanks to the war, the Bureau’s staff would increase by more than 238 percent from 1939 to 1945, including over 200 members of the armed forces. Even more dramatic, funding increased from $3 million just prior to US entrance into the war to $13.5 million by 1944. To accommodate the huge demand for testing and the now huge staff, all of the Bureau’s conference and lecture rooms were converted to laboratories and 2nd and 3rd shifts were introduced to make maximum use of the space and equipment. The standard work week was also lengthened from 39 hours before the war to 44 hours.

 

The Bureau continued to be involved in the development of the atomic bomb by testing the purity of uranium and other elements. While many at the Bureau suspected that a weapon using uranium might be under development, the secrecy ran so deep and the security was so tight that even researchers working directly on the project sometimes failed to realize what the end-game might be, thinking instead that the uranium would be used for power plants to power planes or submarines.

 

**The information presented here is drawn from “Measures For Progress: A History of The National Bureau of Standards” (Rexmond C. Cochrane)

 

As always, if you have any questions related to this material, our support staff at Cooper Instruments is available to help. Contact them by calling (800) 344-3921 or emailing This email address is being protected from spambots. You need JavaScript enabled to view it..

 

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