April is always an exciting time of year. It's a time for renewal
and growth . . . doing some spring cleaning . . . attending professional
trade shows . . . building your business. If all this gets to
be overwhelming and you need help solving tricky feedback control
problems, BEI is ready to lend a hand.
In the meantime, enjoy this month's newsletter. A
special thanks to all of you that have taken the time to
write back. We appreciate all of your comments.
Built for the Long Haul
Many of you already know that we produce a multi-turn
absolute encoder. With a capability of 12 bits by 12
bits of turns, our HMT25 yields a total of 16,777,216
positions. The mechanically-geared unit ensures
reliability over a long lifetime without concern about
back-up battery life (used in electronic multi-turn
For those that need the capability of a multi-turn
absolute, we've just made the data communication
portion a whole lot easier. Now the HMT25 can give
you data in an SSI format. This data set consists of 25
bits of serial information, which includes the 24 data
plus a parity bit for error checking.
With a system-supplied clock you can now
send/receive data synchronously with as few as six
conductors (two differential data pairs, two differential
clock pairs, plus power and ground). For a complete
specification along with an SSI timing diagram download
the PDF, below.
HMT25 With SSI Output, PDF . . .
||Words of Wisdom
"When nothing seems to help, I go and look at a
stonecutter hammering away at his rock perhaps a
hundred times without as much as a crack showing in
it. Yet at the hundred and first blow it will split in two,
and I know it was not that blow that did it - but all
that had gone before." Jacob Riis
Jacob Riis was a turn-of-the century immigrant who
sought to document and thereby help alleviate the
blight of New York City slums. He often wandered
these areas with the head of the New York Police Board
of Commissioners, then pre-presidential Theodore
To read more about his work as an investigative
reporter and his accomplishments, click on the link,
More about Jacob Riis ... »
||Can You Solve This?
Company ZYX had a high resolution encoder mounted
on a conveyor motor. The cable run was about 30 feet
and the customer called complaining of "noise". Even
when the conveyor was stopped, their counter would
The BEI applications specialist recommended that he
try using the receiver in differential mode, since it is a
very sound practice and usually eliminates most noise
problems, but the problem persisted. What was going
Answer: It turns out that the customer was
experiencing a problem called dither. If the conveyor
was "stopped" at the transition point of one of the
encoder square waves, any mechanical vibration in the
motor system could be interpreted by the counter as
This was especially evident since he was using a high
resolution encoder. The applications specialist
recommended he use the BEI Anti-Dither Module. This
module creates 1/4 cycle of hysteresis - enough to
stop the false counts. Problem solved. To learn a little
more about the Anti-Dither module, click the link below.
Anti Dither Module PDF . . . »
||The Last Laugh
An engineer died and reported to the pearly gates. An
intern angel, filling in for St. Peter, checked his dossier
and grimly said, "Ah, you're an engineer; you're in the
wrong place." So the engineer was cast down to the
underworld and was let in. Pretty soon he became
dissatisfied with the level of comfort and began
designing and building improvements. After a while,
they had air conditioning, flush toilets, and escalators.
The engineer was becoming a pretty popular guy among
One day, the Lord called Satan up on the telephone
and asked, "So, how's it going down there?" Satan
laughed and replied, "Hey, things are great! We've got
air conditioning, flush toilets and escalators. There's no
telling what this engineer is going to come up with
The Lord exploded, "What? You've got an engineer?
That's a mistake; he should never have gotten down
there; send him back up here immediately or I'll sue."
Satan laughed uproariously, "Yeah, sure. And just
where are YOU going to get a lawyer?"
||Your Opinion Matters
Hope this was a fun and informative newsletter. Feel
free to pass it along to your friends by clicking
the "Forward email" link at the bottom of the page. You
can also send me your comments and suggestions by
clicking the "email" link in the newsletter footer.
Thanks for reading and remember when you need
products or engineering help with your control system -