Today is an age of electronics.When we thinkabout measurements, electronics help us build systems which are highly sensitive, accurate and precise.We cant imagine our measurements without electronics.But electronics has been around since last 55-60 years since theinvention of first Transister at Bell Labs.
What were the measurement techniques before that?

Same way, today Microcomputer forms the heart of any Industrial Automation systems.Before that, in first generation computers (were of room size ) used vaccume tubes to implement digital logic.That would not be a feasible solution to implemet industrial automation.

What were the automation techniques before the semiconductor age since process industrias such as cement, copper, steal, textiles, power, chemicals and fertilisers are around for more that 100 years !!!!!!

 

Factories used to control things with relays and drum controllers. Today, PLCs emulate these in software as ladder logic and "drum sequencers". Process industries used a lot of air logic. Remote control and communications was based on teletype technology. And in a lot of cases, they just had an operator standing there watching a dial and turning a knob.

Instrumentation did run on tubes (valves). A lot of gauging was also done using custom made gauge blocks.

Before micro-computers, they used mini-computers. Some of DEC's early models were intended for process control applications. The DEC PDP-8 supposedly originated from discussions with Fisher. The very first microcomputer was built in France as a low cost replacement for process control mini-computers.

Early PLCs were not based on minicomputer bit-slice technology, not microprocessors. Microprocessors existed at the time, but they were too slow.

Punch cards and paper tape were invented to control automatic weaving looms, with the earliest ones dating back nearly 300 years. You will find that change was evolutionary, not revolutionary. Semiconductors and microprocessors have mainly served to reduce costs and increase reliability.

 

The first of what you might call industrial measurements were things like steam engine speed, and James Watt for instance developed a self-contained measurement and control device which he called a governor.

It operated from the centrifugal force developed by the rotation of a set of weights. Pneumatic systems do a lot of quite complex calculations using the pressure of air - which can be generated by effects such as level, flow, temperature as well as pressure.

The original PID controller was a pneumatic device and even modern digital systems still use pneumatics to deliver the final grunt to a control valve. Pneumatics can also be used to carry out logic operations. There are pneumatics based control systems and also automation systems currently in operation (with some still being installed).

The third format is hydraulic. This can deliver a lot more force and react a lot faster than pneumatics.

And don't get hung up on digital - the development of the Saturn space hardware was based on computations using analogue computers. Operational amplifiers using thermionic valves have been used where pneumatics couldn't cut it.

In short- don't blinker yourself into thinking that just because us oldies didn't have all the gee whiz stuff you young shavers take for granted that somehow the world stopped turning. A lot of the old techniques are the basis for the modern systems and a lot of current practice is based on historical developments.

 

I have a book called "Industrial Electronics" by Guilliksen and Vedder. It covers all sorts of different electronic industrial control and sensing applications that were in common use at the time it was written. It was published in 1935. There's a lot of tube circuits in there. So, yes tubes were considered quite feasible for use in industry.

 

We still sell a ton of pneumatic thermostats. After a hundred years of development, they're extremely reliable and durable. They run off of 18 to 25 psig and generate a 3 psig to 15 psig signal to call for more or less heating, a deadband, or more or less cooling. They do PID loops.

Best,
B.O. Sept. 15, 2008
--
Robert Old
Siemens Building Technologies, Inc., HVAC Products
1000 Deerfield Pkwy., Buffalo Grove, IL 60089-4513 USA
Phone: +1(847)941-5623, Skype: bobold2
bob.old at siemens com

 

Yes, and for some purposes tubes would still be a better choice if they were widely available. I have an old electricians handbook and it has chapters on some of the old stuff. I had to laugh recently when we had a problem with a UV polymerization unit (dryer) where they used a saturable reactor to control the lamp current. No one had any idea how that part worked and were amazed when I hooked up a DC power supply to get the lamps running until the parts came in. Not seen much today, but SR was an excellent fit for the application. SRs, MagAmps, Mercury Pool rectifiers, Thyratrons, tubes. They got the job done just fine. Some would be still be simpler and more reliable than the ways that replaced them. Once upon a time I designed a couple VT exciters for sputtering gold. I still haven't seen any 50,000 watt transistors.

Regards

cww