Hi 6A3sUMMER,
Familiar with all of them. Infinite was correct, no potential difference, no current flow = open circuit. It was really an early lab standard and the method was still used long past that meter. I had a Fluke 8200A to start (not the same concept), and early DVM that was accurate beyond the display indication.
Still use some HP power head type meters. Thermistor based bridge design. They also used the ingenious "flux gate" type for current measurements. Brilliant. I still use those.
Familiar with all of them. Infinite was correct, no potential difference, no current flow = open circuit. It was really an early lab standard and the method was still used long past that meter. I had a Fluke 8200A to start (not the same concept), and early DVM that was accurate beyond the display indication.
Still use some HP power head type meters. Thermistor based bridge design. They also used the ingenious "flux gate" type for current measurements. Brilliant. I still use those.
Hewlett Packard did build a very good VTVM. There models include 10 megaohms volt , 11 megaohms volt and the lab grade 110 megaohms volt. It is standard we live with today.
The most built and used for all brands is 11 megaohms volt.
They found the 11 megaohms volt work best and anything higher was pointless.
Today with the DMM they have 1 megaohms volt to 10 megaohms.
FYI oscilloscopes are mostly 1 megaohms volt.
I can not tell why the DMM do have the probes like VTVMs have.
The DMM has computer and calibration is simple by software.
So putting a different type probe is simple compared to VTVM.
They one different in VTVM to a DMM is a VTVM that was built in 1935 will still work today. If DMM try that trick the battery keeping the memory up it need to be reprogrammed before working.
Dave
Spiffy DIY...
Always cool when you do it yourself-
I, on the other hand, purchased a Radio Shack 22-220 FET VOM off ebay for $30. Good exterior condition.
Needed lil HCL on the selector switch- then came around nicely
DISCLAIMER
When using Hydrochloric Acid for cleaning contacts... Be advised not to inhale the vapors, allow contact w/ skin... drink or bathe in it
However meter movement is too slow for my liking. My refurb'd Eico 232 needle snaps up to a reading post haste... I like that when probing close proximity nodes in P to P wirings... less chance of a wandering hand creating a short circuit wtg for reading.
Jim
Attachments
I just stay with industrial standard witch is Vacuum Tube Voltmeter.
They more with how mush power was need to take the volt reading.
Here is a comparison on VTVM, Oscilloscope, DMM and VOM
VTVM 11 meg ohm volt uses @ 1.0 volts 0.000,000,09 amps
High end VTVM 110 meg ohm volt @ 1.0 volt use 0.000,000,009 amps
Oscilloscope and DMM 1 meg ohm volt uses @ 1.0 volts 0.000,001 amps
High end DMM 10 meg ohm volt @ 1.0 volt 0.000,000,1 amps.
VOM 20,000 ohm volt uses @ 1.0 volt 0.000,05
That good for low frequencies.
You find problems.
For higher frequencies you start looking at shielding .
But can built probes that work on this equipment.
I do not know why they do not build DMM with correct probes.
If read history of the VTVM you could see why.
You hand without shielding your hand can change the voltage
Just try a Theremin you see how just hand can change what you working on
Dave
Or electrostatic meters if you want to get pricey!
https://www.tek.com/en/products/kei...4810&msclkid=89acb88af31017ba2355dc659b647f3f
It looks great at 200T ohms. .
Now where would use this for $8,300.00
They did nuts in the 1950's now we have a repeat. The 1960's the found 10 meg to 11 meg ohm volt work the best.
I will say there will be colleges that will equipment the classroom with this DMM.
Dave
Now where would use this for $8,300.00
They did nuts in the 1950's now we have a repeat. The 1960's the found 10 meg to 11 meg ohm volt work the best.
I will say there will be colleges that will equipment the classroom with this DMM.
Dave
Some vacuum tube amplifier schematics listed the voltmeter type that was used for the voltage measurements.
VTVM 10 Meg Ohm / 11 Meg Ohm; Or VOM 20,000 Ohms/Volt.
And technicians knew to use the higher voltage range of their VOM, to reduce the loading on the circuit.
Higher voltage ranges gave you less resolution of the voltage, you had to interpolate.
But the lighter loading on the circuit actually gave you a more accurate reading.
That helped to reduce the number of phone calls to the manufacturer.
Do you remember when companies actually would pick up the phone?
Do you remember how you ever livedwithout the internet and cell phones, etc.?
VTVM 10 Meg Ohm / 11 Meg Ohm; Or VOM 20,000 Ohms/Volt.
And technicians knew to use the higher voltage range of their VOM, to reduce the loading on the circuit.
Higher voltage ranges gave you less resolution of the voltage, you had to interpolate.
But the lighter loading on the circuit actually gave you a more accurate reading.
That helped to reduce the number of phone calls to the manufacturer.
Do you remember when companies actually would pick up the phone?
Do you remember how you ever livedwithout the internet and cell phones, etc.?
Yes ( Do you remember how you ever livedwithout the internet and cell phones, etc.?)
Back 1960's if no schematic on back you would write manufacturer and send a schematic with test voltages use a VTVM. Long distance was to costly. Later it was a fax machine.
I have Simpson 260 just chech Amazon for price today almost $600.00. I also have Transistor VTVM too.
Dave
Back 1960's if no schematic on back you would write manufacturer and send a schematic with test voltages use a VTVM. Long distance was to costly. Later it was a fax machine.
I have Simpson 260 just chech Amazon for price today almost $600.00. I also have Transistor VTVM too.
Dave
Hi 6A3sUMMER,
lol!
Do I ever remember those days! You were also on your own many times and some manufacturers made everything a secret. No internet (or bulletin boards)? That was normal life. Long distance was extremely expensive, and fax was years off. Teletypes were for well monied companies. Those rooms were loud!
Yes, they always picked up the phone, and a receptionist was highly efficient at directing calls. Service departments were generally polite and professional, a few had <big> attitudes.
The problem with using the higher range to reduce loading was the accuracy of the meter movement. Most companies measured using the standard VTVM on the appropriate range and published those voltages. Yes, some circuits didn't work properly. Remember "do not measure this point" on schematics? ANyway, common accuracy was 1.5% top of scale for a very good meter, 2% more common. This could devolve to almost 30% nearer the bottom of the scale. HP characterized each movement and had up to 5 scale spacing changes per scale. You cannot swap meter scales between HP movements without being very careful to measure the tracking.
I have a 260 6p on my bench. Sometimes you need an average reading meter for AC. Like for calibrating a tube tester for example.
lol!
Do I ever remember those days! You were also on your own many times and some manufacturers made everything a secret. No internet (or bulletin boards)? That was normal life. Long distance was extremely expensive, and fax was years off. Teletypes were for well monied companies. Those rooms were loud!
Yes, they always picked up the phone, and a receptionist was highly efficient at directing calls. Service departments were generally polite and professional, a few had <big> attitudes.
The problem with using the higher range to reduce loading was the accuracy of the meter movement. Most companies measured using the standard VTVM on the appropriate range and published those voltages. Yes, some circuits didn't work properly. Remember "do not measure this point" on schematics? ANyway, common accuracy was 1.5% top of scale for a very good meter, 2% more common. This could devolve to almost 30% nearer the bottom of the scale. HP characterized each movement and had up to 5 scale spacing changes per scale. You cannot swap meter scales between HP movements without being very careful to measure the tracking.
I have a 260 6p on my bench. Sometimes you need an average reading meter for AC. Like for calibrating a tube tester for example.
The D'Arsonval meter movements were very linear.
Quality was paramount, or the particular manufacturer who cheated would be out of business back then.
The Moving Vane meter movements were essentially a toy (you have some current, you do not have some current).
That is the non-linearity that is being talked about.
Quality was paramount, or the particular manufacturer who cheated would be out of business back then.
The Moving Vane meter movements were essentially a toy (you have some current, you do not have some current).
That is the non-linearity that is being talked about.
They are not as linear as you think, not for high accuracy measurements. It's all relative.
HP wrote an article on it's movements. I have talked to the guy that did our meter movements for the calibration lab I worked in. It is quite an art. That and balancing the movement. I won't touch one!
HP wrote an article on it's movements. I have talked to the guy that did our meter movements for the calibration lab I worked in. It is quite an art. That and balancing the movement. I won't touch one!
There are a lot of vintage tube amplifier manuals that specify the voltage and current tolerances are +/- 10%.
There were no DMMs back then, many amplifiers without regulated power supplies, the power mains voltage variations were a joke (peak voltages, crest factors, and true rms voltages).
Did you ever hear someone complain about the sound of his amplifier where the voltages and currents wire off by 10%?
Many repair centers did not have precision test equipment back then.
I worked for US Government laboratories and Test and Measurement companies. They were the exception, precision equipment was the order of the day.
I Interpolated my Post Versalog slide rule to 4 places, +/- 3 for the 4th position (like 3.165, interpolated as 3.162 to 3.168).
(admittedly, the Versalog numbers were etched with a precision machine).
Even that accuracy could not get a proper orbit around the moon without a mid-course correction, but it still was pretty accurate.
Guess what, the rocket motor burns and servo direction controls were not perfect, again, a reason for a mid course correction.
To get linearity out of the D'Arsonval movements required some well machined metals and well cut metals, as well as spring material that followed Hooke's Constant law. With linearity (point to point resolution and even increments) out of the way . . .
The sensitivity accuracy was determined by the accurate placement of the magnetic shunt.
Quality was required, if you wanted to compete with the leaders.
Anything less than that was either not called for back Then,
Or was Today's usual business practice to squeeze out the most profit.
There were no DMMs back then, many amplifiers without regulated power supplies, the power mains voltage variations were a joke (peak voltages, crest factors, and true rms voltages).
Did you ever hear someone complain about the sound of his amplifier where the voltages and currents wire off by 10%?
Many repair centers did not have precision test equipment back then.
I worked for US Government laboratories and Test and Measurement companies. They were the exception, precision equipment was the order of the day.
I Interpolated my Post Versalog slide rule to 4 places, +/- 3 for the 4th position (like 3.165, interpolated as 3.162 to 3.168).
(admittedly, the Versalog numbers were etched with a precision machine).
Even that accuracy could not get a proper orbit around the moon without a mid-course correction, but it still was pretty accurate.
Guess what, the rocket motor burns and servo direction controls were not perfect, again, a reason for a mid course correction.
To get linearity out of the D'Arsonval movements required some well machined metals and well cut metals, as well as spring material that followed Hooke's Constant law. With linearity (point to point resolution and even increments) out of the way . . .
The sensitivity accuracy was determined by the accurate placement of the magnetic shunt.
Quality was required, if you wanted to compete with the leaders.
Anything less than that was either not called for back Then,
Or was Today's usual business practice to squeeze out the most profit.
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Hi 6A3sUMMER,
You are absolutely correct on all counts.
Manufacturing tolerances (machining and metallurgy) caused variability in meter movements. I have some extremely accurate movements but they sold for ghastly prices!
My work in a cal lab exposed me to the practical side of what I learned in university. Eye opening to see theory in practice, and physical limitations of things. Temperature and temperature gradients were issues.
So many things might impact your measurements - and you know that especially if you worked at NIST in the primary artifact lab, or primary standard lab. Do you think they might throw you out if you bumped the Weston cells? lol!
Today, most repair facilities do not have equipment accurate enough to measure bias current with any certainty. I used 34401A's and now 34465A and 34461A, still use my 3457A meters too.
You are absolutely correct on all counts.
Manufacturing tolerances (machining and metallurgy) caused variability in meter movements. I have some extremely accurate movements but they sold for ghastly prices!
My work in a cal lab exposed me to the practical side of what I learned in university. Eye opening to see theory in practice, and physical limitations of things. Temperature and temperature gradients were issues.
So many things might impact your measurements - and you know that especially if you worked at NIST in the primary artifact lab, or primary standard lab. Do you think they might throw you out if you bumped the Weston cells? lol!
Today, most repair facilities do not have equipment accurate enough to measure bias current with any certainty. I used 34401A's and now 34465A and 34461A, still use my 3457A meters too.
The companies guarantee 2% or 3%. In technical they will be one range leesthan 1% but never till what range it was calibrated too.
When check my Simpson 260 in DC ranges (2.5, 10 & 50 volt range) it was so close it hard to see if off.
But have own it since new and no one has ever played with adjustments. My Fluke was same way.
The only thing I know that needs that accuracy is volt meters.
I do want accuracy on my voltmeters.
In radios you looking for peck voltage. I have run across voltages like 11.4 or 3.14 volt adjustments That was on industry equipment the Simpson 260 did the job.
Dave
Some measrurements called out a comparison to a standard.
Inexpensive standards had limited accuracy.
A new Carbon Zinc cell (not a battery; A battery technically defines 2 or more cells, check the dictionary) was about 1.56V open circuit
The dyna Stereo 70 had about a 1.56 Ohm sense resistor.
Read the battery with your VOM, note the needle position, then measure the voltage across the 1.56 Ohm resistor, and adjust the channel bias pot until the needle is at the same place as it was when you measured the battery.
That defined 100mA the EL34 pair's combined current for that channel.
Measurement setups are sometimes created out of a Genius moment, that is one of them.
I was measuring 500GHz signal from a waveguide, before NIST even had settled on the standards for Waveguide measurements.
I bet only a few remember the method for measuring the 3dB pulse bandwidth power measurement.
It required the the pulsed signal source (an accurate known attenuation power sample of the radar); a 3dB pad; a diode detector; an oscilloscope, and back then it required a grease pen (there were no scope cursors back then).
Try and be like the original Genius who figured that one out (figured out how to do it).
I am pretty sure there are some who read Tubes/Valves who remember this measurement.
Measurements are fun!
Inexpensive standards had limited accuracy.
A new Carbon Zinc cell (not a battery; A battery technically defines 2 or more cells, check the dictionary) was about 1.56V open circuit
The dyna Stereo 70 had about a 1.56 Ohm sense resistor.
Read the battery with your VOM, note the needle position, then measure the voltage across the 1.56 Ohm resistor, and adjust the channel bias pot until the needle is at the same place as it was when you measured the battery.
That defined 100mA the EL34 pair's combined current for that channel.
Measurement setups are sometimes created out of a Genius moment, that is one of them.
I was measuring 500GHz signal from a waveguide, before NIST even had settled on the standards for Waveguide measurements.
I bet only a few remember the method for measuring the 3dB pulse bandwidth power measurement.
It required the the pulsed signal source (an accurate known attenuation power sample of the radar); a 3dB pad; a diode detector; an oscilloscope, and back then it required a grease pen (there were no scope cursors back then).
Try and be like the original Genius who figured that one out (figured out how to do it).
I am pretty sure there are some who read Tubes/Valves who remember this measurement.
Measurements are fun!