Hello PIC.ers,         (longish post)

After years of dealing with quad. optical rotary encoders and the counting
circuitry associated with them, I have only come across very few makers
of the linear variety.

HP make the HEDS9200 encoder, and you use their matching code strip to get
resolution as fine as 360 counts/inch.
USDigital offer the same device & it is easier to obtain their's
than HP's.
(HP is represented heavily in SA, USDigital isn't...   go figure..  )
Also, USD have been promptly very helpful to me but I'll still be left with
an incomplete answer - has anyone out there in PICland ever put one of
these devices into a 'plunger - type' housing, or seen it done?
I need to end up with an assembly with a spring-loaded (or maybe gravity)
plunger sticking out the bottom as mechanical dial gauges have.

The HEDS parts usually do duty in apps. where the opto. and code strip
are mounted on separate mechanical components which are themselves
confined to move in very restricted ranges, e.g. milling machine slides,
printer carriages, etc. with good lateral stability.

The sensor WILL be used in a PIC app. (16f877 or 16c74) for measurement
and control of a hydraulic press doing tests on granular load-bearing
material, to derive stress-strain relationships.
The closed loop controller (16c74 based, made in this shop) for the machine
already exists, but an appropriate displacement sensor doesn't.
If a HEDS-based sensor can be made to work, it will be massively cheaper
(ratio 1:5 or so) than the other established displacement transducers
like LVDTs, capacitive plungers or non-contact optics.
These have generally better resolution, but that's overkill in these jobs.
Afterwards, I'll have a bunch of other related apps. which have been crying
out for this for many years.

Comments anyone? Suppliers? Alternatives?
If JS Controls started _making_  these as a new business line,
would folks out there like to buy them from me?


TIA & bestos,   John


e-mail from the desk of John Sanderson, JS Controls.
Snailmail:          PO Box 1887, Boksburg 1460, Rep. of South Africa.
Tel/fax:            Johannesburg  893 4154
Cellphone no:   082 469 0446
email:                jsand@pixie.co.za
Manufacturer & purveyor of laboratory force testing apparatus, and related
products and services.