It's a good question. There isn't a whole lot of info available because most manufacturers just insist that you use only their products, and they do not often publish specs that would let you mix/match. I chose the monitor that I bought because it specifically allowed current monitoring/adjustment. I searched for the part numbers for my Varian sensors, and finally found the heater is 165mA, and the output is about 14mV at full vacuum.
Yes, when reading the vacuum, the meter is connected directly to the thermocouple. It looked like there is a pot in-line for full-scale calibration. I wondered about ambient temperature compensation, but the cold-side junction of the thermocouple system is inside the metal envelope of the sensor. I think the idea is that since energy losses from the filament will be to the metal envelope via radiation and conduction, compensation happens automatically.
Ben, your explanation just gave me an idea of DIY vacuum gauge. First, temperature can be measured by heater's resistance itself. Thermocouple is not necessary. And, second, PTC resistor (or Polyfuse) should work very well as a heater/sensor due to strong exponential temperature dependence of its resistance.
I like how he makes the point of using analog electronics versus modern digital designs, noting how simple and cool the old analog designs can be, and how creative they had to get to even build stuff without the help of digital control. I think thermocouples are also very cool as a device. It is good to see a video on someone using one because it sparks the imagination.
Ben that was fascinating. Loved every second. Isn't amazing how much we have advanced in technology since wooden circuit boards. lol The next 50 years is going to be so cool...I hope I live long enough to see it all. Great work, thanks.
Depends on how much refrigerant has been adsorbed by the lining, they can outgas into a high vacuum for days. Warm up a set in warm water and you will see it outgassing the refrigerant.
Hello, Ben, thank you for the video! I never knew that such sensors exist. Is there an acoustic analogue of this sensor, while an acoustic circuit will attenuate when density lowers? Keep up with the videos. You're the most interesting contributor to my YT feed:) Regards form Bulgaria, Ivan
Somewhat interesting the way that toggle lever to check the filament current acts on the leaf switch behind it, rather than a molded toggle switch that we'd see as normal today...
i found a very similar dual thermocouple vacuum meter built in a very similar style and case that actually manages to be much much simpler then yours. all it has in it is a transformer, rotary switch and 2 trimpots one for each sensor. it also uses an "amperite ballast" tube to regulate the heater current. i had never seen this type of tube before but its use made this meter silly low parts count
Really interesting. Does everytything from your second schematic (for setting heater current) normally get switched out when reading TC temperature (vacuum)? Or is the TC connected with other parts to the meter? Is there some sort of calibration to adjust for various ambient temperatures? Keep up the great work!
Tnx Ben, very interesting. Couldn't a vacuum meter be crafted from a modified smoke detector? For this case, the gap between plates would be made much narrower also the ionization current circuit would need to be tweaked.
Thank you very much for nice description with demonstration. I want to purchase this thermocouple vaccum guage! Can you please guide me regarding this, where I should contact.??
Im surprised you use that Supco VG64. I bought one of those and thankfully I tested it before I tried pulling down my A/C and couldnt get below like 200Torr (yeah, not mTorr, Torr, absolute shit vacuum) with the pump hooked directly to the gauge with a short piece of hose. I looked around and found a lot of people complaining about the sealing of the units being really questionable. I threw it out and got a Yellow Jacket one, with just the bargraph in microns and was able to get down to 100 micron.
Ive got one of those cheap pumps for $150 When it was new and after using good quality pump oil instead on the crappy oil it came with it got down to 12 microns, right now its has around 5000h of use and still pulls down to 16 micron. I think you got a defective one. Instead of throwing it away you should have used it for some thing else and just play with it/fix it.
There are some thermocouple vacuum gauge tubes that have 7 or 8 pins, and they connect to controllers via 3 pin XLR (microphone) connector. Any idea what those extra pins do and why XLR?
Would a red bull can used in place of the "super sonic ping pong ball" accelerate fast enough under vacuum to make a viable experiment demonstrating how aluminum can slice through structural steel like a hot knife through butter? Shear failure.
If had the right stuff, I'd put a speaker and microphone in high/low pressure (and various gases) and observe the effects... If you are capable of this, well... go right ahead. Be my guest.
It's a good question. There isn't a whole lot of info available because most manufacturers just insist that you use only their products, and they do not often publish specs that would let you mix/match. I chose the monitor that I bought because it specifically allowed current monitoring/adjustment. I searched for the part numbers for my Varian sensors, and finally found the heater is 165mA, and the output is about 14mV at full vacuum.
Yes, when reading the vacuum, the meter is connected directly to the thermocouple. It looked like there is a pot in-line for full-scale calibration. I wondered about ambient temperature compensation, but the cold-side junction of the thermocouple system is inside the metal envelope of the sensor. I think the idea is that since energy losses from the filament will be to the metal envelope via radiation and conduction, compensation happens automatically.
Ben, your explanation just gave me an idea of DIY vacuum gauge. First, temperature can be measured by heater's resistance itself. Thermocouple is not necessary. And, second, PTC resistor (or Polyfuse) should work very well as a heater/sensor due to strong exponential temperature dependence of its resistance.
Congratulations, you have invented a Pirani gauge
I like how he makes the point of using analog electronics versus modern digital designs, noting how simple and cool the old analog designs can be, and how creative they had to get to even build stuff without the help of digital control. I think thermocouples are also very cool as a device. It is good to see a video on someone using one because it sparks the imagination.
Ben that was fascinating. Loved every second. Isn't amazing how much we have advanced in technology since wooden circuit boards. lol The next 50 years is going to be so cool...I hope I live long enough to see it all. Great work, thanks.
The smell of the old equipment. Not bad to remind folks of the PCB issue with those old gems.
Old electronics are always fun. I found an old radio with an air gap capacitor for tuning.
Depends on how much refrigerant has been adsorbed by the lining, they can outgas into a high vacuum for days. Warm up a set in warm water and you will see it outgassing the refrigerant.
Hello, Ben, thank you for the video! I never knew that such sensors exist. Is there an acoustic analogue of this sensor, while an acoustic circuit will attenuate when density lowers?
Keep up with the videos. You're the most interesting contributor to my YT feed:)
Regards form Bulgaria, Ivan
Very interesting, how to measure pressure indirectly with a simple setup.
Somewhat interesting the way that toggle lever to check the filament current acts on the leaf switch behind it, rather than a molded toggle switch that we'd see as normal today...
i found a very similar dual thermocouple vacuum meter built in a very similar style and case that actually manages to be much much simpler then yours. all it has in it is a transformer, rotary switch and 2 trimpots one for each sensor. it also uses an "amperite ballast" tube to regulate the heater current. i had never seen this type of tube before but its use made this meter silly low parts count
Makes me want to get one of those heads and make my own.
Great video. Now I know a lot more about these things, have a bunch of broken meters around I might be able to fix.
Really interesting. Does everytything from your second schematic (for setting heater current) normally get switched out when reading TC temperature (vacuum)? Or is the TC connected with other parts to the meter? Is there some sort of calibration to adjust for various ambient temperatures? Keep up the great work!
Tnx Ben, very interesting. Couldn't a vacuum meter be crafted from a modified smoke detector? For this case, the gap between plates would be made much narrower also the ionization current circuit would need to be tweaked.
Natural rubber like used in the hoses is actually pretty good for the low vacuum seen in forelines, You shouldn't see any appreciable outgassing.
I'm not sure that AC current is actually redundant, because the 2 instances of the word current are in slightly different contexts
Ya man, super interesting. It's awesome you can look at it and figure it all out. Cheers man!!
Simplicity, thanks for sharing!
Thank you very much for nice description with demonstration. I want to purchase this thermocouple vaccum guage! Can you please guide me regarding this, where I should contact.??
Excellent video. I have considered modifying one of these to use a digital read out. Can you post a more detailed schematic please.
I think it is 1/4" NPT.
That's a nice little gauge!
Thanks for sharing :)
What about putting a rubber washer below the ground nut so it does not tough the hot wire?
What use of two meters on pump , is it for positive and negative pressure ??
Im surprised you use that Supco VG64. I bought one of those and thankfully I tested it before I tried pulling down my A/C and couldnt get below like 200Torr (yeah, not mTorr, Torr, absolute shit vacuum) with the pump hooked directly to the gauge with a short piece of hose. I looked around and found a lot of people complaining about the sealing of the units being really questionable. I threw it out and got a Yellow Jacket one, with just the bargraph in microns and was able to get down to 100 micron.
Ive got one of those cheap pumps for $150 When it was new and after using good quality pump oil instead on the crappy oil it came with it got down to 12 microns, right now its has around 5000h of use and still pulls down to 16 micron. I think you got a defective one. Instead of throwing it away you should have used it for some thing else and just play with it/fix it.
Thanks!
There are some thermocouple vacuum gauge tubes that have 7 or 8 pins, and they connect to controllers via 3 pin XLR (microphone) connector. Any idea what those extra pins do and why XLR?
What's the threading on the inlet into the vacuum pump?
you plan to rewire that switch so you don't melt down your shop?
Do you have value vacuumgauge sensor
Would a red bull can used in place of the "super sonic ping pong ball" accelerate fast enough under vacuum to make a viable experiment demonstrating how aluminum can slice through structural steel like a hot knife through butter?
Shear failure.
I reacted to that too, it's more annoying to me than it probably should be.
applied science sputtering video brought me here:))
That cardboard capacitor probably need to replaced.
For sure
If had the right stuff, I'd put a speaker and microphone in high/low pressure (and various gases) and observe the effects... If you are capable of this, well... go right ahead. Be my guest.
hmm... meltdown would make a good video though...
ATM machine. :>
LCD display, meh
Baih. =]