Wheatstone Bridge: A (Not So) Honorable History
video description
Date: 2022-12-27
Related videos
Comments and reviews: 20
Robert
This is the first mention of the Wheatstone Bridge I've heard since I left Ma Bell many years ago.
Years ago telephone central offices had a test desk. In most cases it looked like one of the old corded switchboards operators worked from. The test desk took trouble reports from customers, tested them, dispatched a technician if necessary and then closed the ticket after noting what had been done to clear the problem. Most of them have disappeared if not because most testing is now done in the field by the technicians and the whole process has become computerized.
Every test desk had a Wheatstone Bridge mounted in a drawer. The test deskman (old terminology) used it to measure resistances on cable troubles using a Murray Test Or a Varley Test. A technician would call in and the testdesk using the cable plats send him to the farthest end of the cable and short circuit the pair of wires in trouble. The pair of wires would be connected to the bridge. If one side of the pair was grounded he would measure the resistance through the short circuit to ground. Then he'd reverse the bridge and look thought short in the other direction. Using a math formula and consulting the cable plats showed the overall resistance and capacitance the cable he could put the technician within a few feet of the problem location. I the cable was running in the air the outside temperature was factored in. Buried cable was consistent in temperature. Mixed buried and aerial cable caused a fluctuation in the math but a good test desk man could still get you very close.
At the time which was before the 1970s all the test deskmen were cable repairmen and a few equipment technicians tired of working outside in the weather. Some of the equipment technicians would transfer into the central office as Switchmen. That all changed in 1970 when the company women in these technical position to satisfy the Equal Employment Opportunity Commission. Without the field experience most of the women did the testing poorly. for the women it was all about money. The technical positions were filled with men and they paid better than the mostly clerical positions women were in. Almost immediately the company developed computerized testing. Once it had saturated the system almost all the testdesk personnel were downgraded to a clerical position that paid less and required less skill. The line cards were removed and the records were computerized. In an entire region there were one or two testdesk technicians and his testdesk used trunks to test in any troubles for the entire region. The Wheatstone Bridges. Eventually the Wheatstone Bridges disappeared. So did almost all of the technicians. The system is so computerized that people with those skills are no longer needed. That and the reduction of telephone lines on copper. Computers now compress thousands of telephones on what once could only carry one. Now you can get your telephone on a coax cable carrying your television signal and Internet service. Or you can just use a cellphone with a satellite dish for television. The installers now using technician as a title are installers. They have so little knowledge of equipment and electronics they are not technicians in reality
The Wheatstone Bridge left with the technicians and they aren't coming back.
reply
This is the first mention of the Wheatstone Bridge I've heard since I left Ma Bell many years ago.
Years ago telephone central offices had a test desk. In most cases it looked like one of the old corded switchboards operators worked from. The test desk took trouble reports from customers, tested them, dispatched a technician if necessary and then closed the ticket after noting what had been done to clear the problem. Most of them have disappeared if not because most testing is now done in the field by the technicians and the whole process has become computerized.
Every test desk had a Wheatstone Bridge mounted in a drawer. The test deskman (old terminology) used it to measure resistances on cable troubles using a Murray Test Or a Varley Test. A technician would call in and the testdesk using the cable plats send him to the farthest end of the cable and short circuit the pair of wires in trouble. The pair of wires would be connected to the bridge. If one side of the pair was grounded he would measure the resistance through the short circuit to ground. Then he'd reverse the bridge and look thought short in the other direction. Using a math formula and consulting the cable plats showed the overall resistance and capacitance the cable he could put the technician within a few feet of the problem location. I the cable was running in the air the outside temperature was factored in. Buried cable was consistent in temperature. Mixed buried and aerial cable caused a fluctuation in the math but a good test desk man could still get you very close.
At the time which was before the 1970s all the test deskmen were cable repairmen and a few equipment technicians tired of working outside in the weather. Some of the equipment technicians would transfer into the central office as Switchmen. That all changed in 1970 when the company women in these technical position to satisfy the Equal Employment Opportunity Commission. Without the field experience most of the women did the testing poorly. for the women it was all about money. The technical positions were filled with men and they paid better than the mostly clerical positions women were in. Almost immediately the company developed computerized testing. Once it had saturated the system almost all the testdesk personnel were downgraded to a clerical position that paid less and required less skill. The line cards were removed and the records were computerized. In an entire region there were one or two testdesk technicians and his testdesk used trunks to test in any troubles for the entire region. The Wheatstone Bridges. Eventually the Wheatstone Bridges disappeared. So did almost all of the technicians. The system is so computerized that people with those skills are no longer needed. That and the reduction of telephone lines on copper. Computers now compress thousands of telephones on what once could only carry one. Now you can get your telephone on a coax cable carrying your television signal and Internet service. Or you can just use a cellphone with a satellite dish for television. The installers now using technician as a title are installers. They have so little knowledge of equipment and electronics they are not technicians in reality
The Wheatstone Bridge left with the technicians and they aren't coming back.
reply
Dale
I worked as a Technician for a resistor company back in the 70's & 80's. We used our own factory built high speed testers and these testers were built with the wheatstone principles, but were far more complex. We had a decade resistor network that was set to the nominal value, two tolerance dials which set the plus and minus tolerance of the resistor under test. And finally a compensation pot that nullified internal resistance. Instead of two coaxial cables going to the test resistor, there were four and a compensation network was also applied to these cables. Then it really got complicated in that we had to test on the 60 cycle crossover. This was to keep any outside interference from the test. That crossover detection went to the logic circuit where it fed an and gate along with the bridge sample and the result good 1 or bad 0 went to a shift register. That's about it except that I did not mention that the sample signal is developed by a bi-latteral switch which is running at 60Hertz.
reply
I worked as a Technician for a resistor company back in the 70's & 80's. We used our own factory built high speed testers and these testers were built with the wheatstone principles, but were far more complex. We had a decade resistor network that was set to the nominal value, two tolerance dials which set the plus and minus tolerance of the resistor under test. And finally a compensation pot that nullified internal resistance. Instead of two coaxial cables going to the test resistor, there were four and a compensation network was also applied to these cables. Then it really got complicated in that we had to test on the 60 cycle crossover. This was to keep any outside interference from the test. That crossover detection went to the logic circuit where it fed an and gate along with the bridge sample and the result good 1 or bad 0 went to a shift register. That's about it except that I did not mention that the sample signal is developed by a bi-latteral switch which is running at 60Hertz.
reply
Michael
Jacobis voltagometer (an improved rheostat markedly better than that by Poggendorf) worked by suspending platinum wires in separate mercury containers. The mercury containers are connected by a platinum wire that can be raised or lowered to increase or decrease the length of platinum generated by the current, and hence the resistance.
Got this from a Dutch book from 1860:
Over het meten van den galvanischen geleidingsweerstand inzonderheid bij metalen
By Hendrik W. Schroeder van der Kolk
Incidentally, I like to find references in Dutch scientific literature, because traditionally, any educated Dutch person would have spoken German, English and French (and know Latin, so they were usually aware of more international publications than most.
reply
Jacobis voltagometer (an improved rheostat markedly better than that by Poggendorf) worked by suspending platinum wires in separate mercury containers. The mercury containers are connected by a platinum wire that can be raised or lowered to increase or decrease the length of platinum generated by the current, and hence the resistance.
Got this from a Dutch book from 1860:
Over het meten van den galvanischen geleidingsweerstand inzonderheid bij metalen
By Hendrik W. Schroeder van der Kolk
Incidentally, I like to find references in Dutch scientific literature, because traditionally, any educated Dutch person would have spoken German, English and French (and know Latin, so they were usually aware of more international publications than most.
reply
wrightmf
I remember college classes that had Wheatstone bridge circuits, my impression is professors use this bridge for circuit analysis problems for homework and exams. But other than that, nobody uses it. Then out into the real world becoming involved with jobs that have strain gages, that's where I saw the value of the Wheatstone bridge. There is very very little change in resistance in the strain gage itself, probably not enough to reliably measure without the Wheatstone bridge. With the bridge, it becomes easy to measure (of course need reliable low level volt meter and stable excitation.
Strain gages can be fascinating considering they accurately measure stress in structures whether it be building I-beams, car frames, or force-moment balances.
reply
I remember college classes that had Wheatstone bridge circuits, my impression is professors use this bridge for circuit analysis problems for homework and exams. But other than that, nobody uses it. Then out into the real world becoming involved with jobs that have strain gages, that's where I saw the value of the Wheatstone bridge. There is very very little change in resistance in the strain gage itself, probably not enough to reliably measure without the Wheatstone bridge. With the bridge, it becomes easy to measure (of course need reliable low level volt meter and stable excitation.
Strain gages can be fascinating considering they accurately measure stress in structures whether it be building I-beams, car frames, or force-moment balances.
reply
John
As a child of the late 20th Century, I am often humbled by science history. I was taught about electrical voltage, current and the relationship between them (resistance, capacitance and inductance) almost as if Ohm's Law always been understood and accepted since the beginning of time. It is fascinating to learn how this was not the case and that even among the best and brightest minds of their time, they was much uncertainty, disagreement and debate. It is remarkable that the idle thoughts of a handful of curious minds over 150 years ago led to the splitting of atoms, spacecraft that travel the Universe and supercomputers that we can carry around in our pockets.
reply
As a child of the late 20th Century, I am often humbled by science history. I was taught about electrical voltage, current and the relationship between them (resistance, capacitance and inductance) almost as if Ohm's Law always been understood and accepted since the beginning of time. It is fascinating to learn how this was not the case and that even among the best and brightest minds of their time, they was much uncertainty, disagreement and debate. It is remarkable that the idle thoughts of a handful of curious minds over 150 years ago led to the splitting of atoms, spacecraft that travel the Universe and supercomputers that we can carry around in our pockets.
reply
skidancin
Talk about a body electric: A wheatstone bridge is a major component of a lie detector. It is also the basis of the E-meter used by scientologists to guide their Dianetic auditing sessions. I once got my hands on an E-meter and soon learned that I could control it with my thoughts. As an actor might do, if I thought happy contented peaceful confident thoughts, the meter needle would move up to 4, And if I thought to put angry disturbed violent fearful thoughts into my brain, the needle would go down towards 1. At any rate, this is just to say that the connection between electrical resistance and human thoughts is fascinating.
reply
Talk about a body electric: A wheatstone bridge is a major component of a lie detector. It is also the basis of the E-meter used by scientologists to guide their Dianetic auditing sessions. I once got my hands on an E-meter and soon learned that I could control it with my thoughts. As an actor might do, if I thought happy contented peaceful confident thoughts, the meter needle would move up to 4, And if I thought to put angry disturbed violent fearful thoughts into my brain, the needle would go down towards 1. At any rate, this is just to say that the connection between electrical resistance and human thoughts is fascinating.
reply
Izhar
It is more important to correct the record now as, it could be the battle of same idea as it is today to take the credit of someone else's efforts and claim greatness which never is there because one who does it knows the truth therefore the fruits of greatness are never be there, it is clear that wheatstone was an influential very clever person who took advantage of the simplicity of creative minds. But the records must be straightened now.
reply
It is more important to correct the record now as, it could be the battle of same idea as it is today to take the credit of someone else's efforts and claim greatness which never is there because one who does it knows the truth therefore the fruits of greatness are never be there, it is clear that wheatstone was an influential very clever person who took advantage of the simplicity of creative minds. But the records must be straightened now.
reply
Barry
As a graduate electronic engineer with many years experience I wholeheartedly enjoy learning more regarding the history of how electricity has been understood from your videos. So thank you sincerely. I appreciate a more accurate timeline of who achieved what and when it was achieved.
As regards attribution I think employees outside of Academia today are almost certain that specific and personal revelations shall not carry their names.
reply
As a graduate electronic engineer with many years experience I wholeheartedly enjoy learning more regarding the history of how electricity has been understood from your videos. So thank you sincerely. I appreciate a more accurate timeline of who achieved what and when it was achieved.
As regards attribution I think employees outside of Academia today are almost certain that specific and personal revelations shall not carry their names.
reply
David
I wonder if it is true that many inventors and scientists of the 1800s and even later were dishonorable like Wheatstone? I'm thinking of the many stories about people like Alexander Graham Bell (telephone) and David Sarnoff (television) who took credit for discoveries or inventions actually first made by others. Have the ethical standards of society changed since then, or is there a different reason why this no longer seems to happen?
reply
I wonder if it is true that many inventors and scientists of the 1800s and even later were dishonorable like Wheatstone? I'm thinking of the many stories about people like Alexander Graham Bell (telephone) and David Sarnoff (television) who took credit for discoveries or inventions actually first made by others. Have the ethical standards of society changed since then, or is there a different reason why this no longer seems to happen?
reply
Mona
Thanks for taking the time to share. Such a simple circuit but very important for the first precision or matched resistors. It all seems so simple and obvious now but in 1839 sourcing an electric charge, copper wire or other metal conductive wire took some scrounging as well as quantifying the electric charge s intensity and flow. The Wheatstone and Galv-meter led to the first calibration of tools to measure Volts Amperes and Ohms.
reply
Thanks for taking the time to share. Such a simple circuit but very important for the first precision or matched resistors. It all seems so simple and obvious now but in 1839 sourcing an electric charge, copper wire or other metal conductive wire took some scrounging as well as quantifying the electric charge s intensity and flow. The Wheatstone and Galv-meter led to the first calibration of tools to measure Volts Amperes and Ohms.
reply
David
When studying electrical engineering, students barely have time to learn about the Wheatstone bridge and it's applications; hardly have time to learn about this history. However, now that Kathy has done all this legwork, EE students should watch this. In physics classes, much more history is provided in general physical principles like what are electrons doing, and who and how they figured this out.
reply
When studying electrical engineering, students barely have time to learn about the Wheatstone bridge and it's applications; hardly have time to learn about this history. However, now that Kathy has done all this legwork, EE students should watch this. In physics classes, much more history is provided in general physical principles like what are electrons doing, and who and how they figured this out.
reply
George
The basic bridge arrangement can also be used with two inductors or two capacitors as the top or bottom two elements, and that makes a very sensitive way to compare capacitors or inductors. The circuit can also be used with a gain element like a tube or transistor to make a very accurate oscillator or filter. Hewlett-Packard's first product was an audio oscillator that used such a bridge.
reply
The basic bridge arrangement can also be used with two inductors or two capacitors as the top or bottom two elements, and that makes a very sensitive way to compare capacitors or inductors. The circuit can also be used with a gain element like a tube or transistor to make a very accurate oscillator or filter. Hewlett-Packard's first product was an audio oscillator that used such a bridge.
reply
Kimball
Evil those unsolvable questions!
Invention and more inventions is balancing inventors on the point of a pin only one gets stuck and hoisted by his own petard only inventions no one else can understand are real invention. Then fools cannot fool anybody else. But only the French really invented anything of value and those claiming other wise are well truly pieds noirs.
reply
Evil those unsolvable questions!
Invention and more inventions is balancing inventors on the point of a pin only one gets stuck and hoisted by his own petard only inventions no one else can understand are real invention. Then fools cannot fool anybody else. But only the French really invented anything of value and those claiming other wise are well truly pieds noirs.
reply
tom
Thank you for this marvelously detailed video, I had time only for 5 or 6 minutes before skipping to the end. On mentioning using Wheatstone bridge circuit for use with strain guages to a Gloucester Engineering Manager years ago, It was mentioned he was associated with Gloucester and worked for Marconi.
reply
Thank you for this marvelously detailed video, I had time only for 5 or 6 minutes before skipping to the end. On mentioning using Wheatstone bridge circuit for use with strain guages to a Gloucester Engineering Manager years ago, It was mentioned he was associated with Gloucester and worked for Marconi.
reply
dein
isn't the telegraph much older than Wheatstone? and Cooke also copied the idea of compass needles - the arrangement of multiple needles to indicate letters may be original though.
here in Germany Wilhelm Weber is the known inventor of the telegraph, which is also not too much closer to the truth
reply
isn't the telegraph much older than Wheatstone? and Cooke also copied the idea of compass needles - the arrangement of multiple needles to indicate letters may be original though.
here in Germany Wilhelm Weber is the known inventor of the telegraph, which is also not too much closer to the truth
reply
Dwain
Practical uses of the Wheatstone Bridge include load cells and strain gages. Force and dimension change are able to be computed after gluing resistors to materials that will undergo stress. Being able to solve the Wheatstone bridge means you can make your own load cells on the cheap.
reply
Practical uses of the Wheatstone Bridge include load cells and strain gages. Force and dimension change are able to be computed after gluing resistors to materials that will undergo stress. Being able to solve the Wheatstone bridge means you can make your own load cells on the cheap.
reply
TheEvertw
If you give credit where credit is due, it is more likely that they will give you more exciting inventions you can make use of, making life better for all.
Taking someone's invention without giving credit is a bit like taking the golden egg but forgetting to feed the goose.
reply
If you give credit where credit is due, it is more likely that they will give you more exciting inventions you can make use of, making life better for all.
Taking someone's invention without giving credit is a bit like taking the golden egg but forgetting to feed the goose.
reply
nik
WOW, never knew any of this. Have a Wheatstone bridge in my collection that I got from a deceased estate for measuring resistors precisely, but the first Im hearing of these other people ie: as Jacobi and Christie. Once again much thanks for these stories.
reply
WOW, never knew any of this. Have a Wheatstone bridge in my collection that I got from a deceased estate for measuring resistors precisely, but the first Im hearing of these other people ie: as Jacobi and Christie. Once again much thanks for these stories.
reply
education
As a former EE student, these names, these people are the Hallowed saints of electronics (Voltaire, Ohm, Wheatstone, etc. Thank you so much for bringing them to life, and for showing them to be human; warts, misrepresentations and all.
reply
As a former EE student, these names, these people are the Hallowed saints of electronics (Voltaire, Ohm, Wheatstone, etc. Thank you so much for bringing them to life, and for showing them to be human; warts, misrepresentations and all.
reply
Diarmuid
Not so many people know that Wheatstone has a patent on the concertina, which is a 'squeezebox' musical instrument, a button accordion. These instruments depend on metallurgy to work, but it is not clear how much prior work was done
reply
Not so many people know that Wheatstone has a patent on the concertina, which is a 'squeezebox' musical instrument, a button accordion. These instruments depend on metallurgy to work, but it is not clear how much prior work was done
reply
Add a review, comment
Other channel videos
