It isn't digital, the TMR sensors produce a linear analog signal. Can you make a LVDT controller and trans/receiver for less than $7? how accurate would a home made version be? I've always thought LVDT is interesting but I've not yet tried to make one.
Having just admitted to a
serious mistake on another thread, I question my current ability to fabricate much of anything. I could build such a controller from parts I have on hand if my mind were up to it. The LVDT itself would be a handful on a good day. The term, LVDT, means a "Linear Variable Displacement Transformer". To wind such a device by hand would take considerable work. The finer the positioning measurement, the finer the wire necessary. The moving part is simply a magnetic slug on a non-magnetic rod. The transformer is the "bug-a-boo". To wind a "Tesla" coil would be simple compared to an LVDT. The electronics is simply a matter of measuring the difference between two signals. To make the electronics with purchased parts it would cost well over $20-25, at today's prices.
I had not intended to imply that an LVDT was "better", more a matter of questioning the "digital" solutions being the ultimate answer. Now you tell me that the measuring device is linear, only the numeric display is digital. I concede the point and will stand down.
As an "old school" electrician, I was involved in the early transition from purely magnetic control to "first generation" PLCs for industrial control. At the time, there were no "digital scales" in that environment. We built our own with hydraulics and home brew (in house built) electronics and a digital volt meter. When a salesman came along with a commercial version, he had to tune the instrument to fit the accuracy of what we already had. His scales couldn't stand up to a "2 shift" (20 hrs) production schedule.
In those days, a pressure transmitter was a modified guage with an LVDT attached where the needle was. The only true digital was in displays.
I hold that analog still has its' place with controls. It just takes less smarts and money to make everything digital. There is some loss of accuracy but in most cases is not that important. Only in highly precision instruments does that difference come into play.
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