AMETEK 957 SSI Brik - Manual (Page 9)

9 1080 N. Crooks Road • Clawson, MI 48017 • 800.635.0289 • Phone 248.435.0700 • Fax 248.435.8120 • www.ametekapt.com
FACTORY AUTOMATION
®
Startup
1. Verify connections
The 957SSI is reverse polarity protected; however, com-
ponents can be damaged from improper connections or
over voltage. Before applying power verify connections
are correct.
2. Turning on power
Note that the system may execute uncontrolled movement
when power is first applied when the 957SSI is part of a
closed loop system whose parameters have not yet been
configured.
Position Update
The position of the magnet on the extrusion is precisely
determined by a time of flight method. The 957SSI con-
verts this position value to a 24, 25, or 26 bit Binary or
Gray code data stream where it is transmitted to the host
controller via SSI. All displacement outputs are absolute
and do not lose their position after loss of power.
Position update frequencies are available up to 6500
measurements per second (Length dependant) in Asyn-
chronous mode, and are controller dependant in the Syn-
chronous mode. However, if the controller interrogates
the 957LDT quicker than the LDT can provide data, the
957SSI Brik™ LDT will automatically switch to the Asyn-
chronous mode and supply the host controller with the
most up to date positional information.
Synchronous Update Mode
A clock pulse train from the host controller is used to shift
out sensor data, one bit of positional data is transmitted
to the controller for each clock pulse received by the sen-
sor. The first clock pulse edge from the host controller
signals the LDT to make a measurement. The positional
data from this measurement will be used during the next
controller update cycle.
NOTE: The data in this mode will always be one update
cycle old.
Asynchronous Update Mode
The 957SSI Brik™ LDT takes measurements at its preset
internal interrogation rate (length dependant) and provides
information when requested from the host controller.
NOTE: If the controller or interface module does not spec-
ify Synchronous mode, we recommend using the LDT in
the Asynchronous mode.
Direction
The 957 can be configured increasing, decreasing, posi-
tion, or velocity. Option “F” (Measure Direction Forward)
will increase counts as the magnet moves from the head
of the LDT to the tip. Option “R” will be exactly opposite.
The zero position will be located at the end of the blue
housing. This is an area where it is physically impossible
to detect a magnetic signal. If the 957SSI is in the “Mea-
sure Direction Reverse” option, the zero point will be at the
far tip of the LDT, again a position that the magnet cannot
be detected. If the velocity option is selected, the unit will
output velocity and not displacement.
SSI Clock
Synchronous
Asynchronous
Controller
Update
Internal
Repitition
Update
Position
Update
Position
Update
Position
Update
Position
Update
Position
Update
Position
Update
Position
Resolution
The resolution of the positional output is selectable in the
part number and can be ordered in English (Imperial) or
metric units. Selections 1 thru B are valid options. Refer
to section 3.5 Part Numbering for further details.