Computer controlled vacuum pro/cons?

What are people using for controlling vacuum levels? I’ve been thinking about moving beyond the manual needle valve to a computer controlled version to automatically track historical levels and for automation. I’m running Edwards E2M28 (can go to 10^-3 mbar)

Do you get much value out of them?
Brands/models you like/dislike?
Is it OK to go with one that doesn’t go quite as low as the pump (0.1 vs 0.001 mbar)?


I run an Edwards EM-28.

There is no control on mine other than an electronic vent. It is a digital display based on a Pirani sensor and it has recording capabilities. Without at least a Pirani based sensor you cannot measure accurately the vacuum levels down to your pumps rated blank off value. I paid $388 from my Amazon order history because they had a smoking hot sale going. Be prepared for sticker shock when you see what Amazon sells the identical one for now… WOW did the price go up from the sale…

However in order to control the vacuum level and not just monitor it you need a Step motor driving a bleeder valve. The step motor would be driven by a controller like an Arduino that would open and close the valve to maintain a precise reading. This of course means always being at a lower pressure than blank off.

This is one way to control vacuum. The unit has an RS 232 port. It will send the pressure. The arduino or controller reads it and then adjusts the needle valve. Since vacuum does not typically fluctuate much it can be done presicely and really without any sort of PID loop. I have studied the idea extensively. I also have several years of experience designing controls for machines and have dealt with hundreds of variable frequency drives (also called inverter speed controls) that function to control the speed of electric motors like the one on an EM-28.

The motor speed could also be varied continuously to adjust system vacuum. Those drives typically operate on 230VAC and often on three phase power. Without three phase power most units can be tricked in a way to “see” the third phase and run fine but at slightly reduced horsepower rating. This would be another potential way to control vacuum levels albeit on a gross scale.

I am very happy with my pressure gauge and thought originally the sale I took advantage of was just B.S. and that they weren’t really as expensive as the slashed price…

I have not gone on to implement control of the vacuum level because frankly it has no utility outside of pure research. When I run I monitor the vacuum. When the vacuum levels are higher than about ten microns or so there are still terpenes in my system and I set my stir bar and temps accordingly. Once the vacuum pulls down to less than ten or twenty microns I know I need to switch the extract into the sublimation apparatus to then pull the cannabinoid up to the cold finger at usually ¾ of one micron. There is no practical or useful reason to attempt distillation of this stuff at any but the deepest vacuum I can pull. There is great usefulness in knowing with certainty what your pressure is down to the micron and the electronic vent valve on my unit is priceless (and another $350). That vent valve allows me to swing the pressure repeatedly hundreds of microns and I can honestly say that without that capability my entire process is seriously hobbled. It would take a post on its own to explain just how the rapid pressure swings solved one of the most serious problems I encountered but suffice it to say it is golden.

I like the idea of control in machinery second only to simplicity of design. I realized that both the frequency drive and the stepper controller needle valve would add complexity with nearly zero return because the reality is that everything else needs to be set to max vacuum obtainable. Moreover if a computer was adjusting the vacuum it would be impossible then to interpret manually the readings to tell you what is going on with terpenes and a few other items. There are four critical items the gauge keeps me alerted to this way; leaks, terpene content in the boil, wax or joint grease contamination in the compound, and vacuum pump oil contamination level. All of these can be detected and reacted to by knowing how to read the values on a fine tuned sensor that can read down to the blank off value of your pump. It would be easy enough to program my observations into a computer and have it react but the utility of that for me is also about zero lolz because it takes human hands to correct these things for my stuff.

Good luck and watch for sales! I got my EM 28 off craigslist for $1000 used and it just plugs away! Bargain.


The BR spinning band uses a dual sensor controller. One is 100 micron and the other is 1 micron to avoid having to use too fancy of a sensor for the full range.

Thanks for you detailed response. Sounds like you got the sale of sales on your Amazon deal! I’ve already got the sticker shot from a quote for CVC3000 + VSP3000 last week which basically is the same as yours except the control part and list price is literally 10x the price of your $350 price. I’ve got a handheld vac meter already but it go to the depths that vac can goto. Seeing that prices for those vac gauges being so pricey got me interested in going further (gonna spend $1200-$1500 on one that goes to those depths, why not one that can regulate as well)

I’ve got 25+ years in IT so automation is always on my mind, and was thinking with enough testing, etc I could possibly write a program that could provide highly repeatable, consistent results with low deviation (probably being way, way too optimistic). Being able to react immediately to temps, vacuum depth, stir, duration, chiller, etc via computer just seems right way to go but man is it a lot to drop on something that might just turn into an overpriced toy. I’m still on the fence but your statement on reality of how limited value computer control might be is swinging me a bit the other way.

I’ll probably just troll for random bargains on used equipment, I love going to the local universities disposition warehouse this time of year trying to find old equipment to play with as they are normally switching out equipment. I got a used Neslab M33 chiller for $250 that the manufacturer had come out and certified in November on a random walk through earlier this week. If I knew enough about it they have a Trace GC Ultra at auction that if I knew it was what I think it is and not missing any bits/pieces I’d throw down as being able to test in house would be really great.

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