AMETEK 1746 LDT Interface Card - Manual (Page 6)

Chapter 1: Introduction & Overview
Installation & Programming Manual 2
The 8 words in the output image table are used to program parameters into the 1746L PLC LDT
Interface Module. The following describes all the parameters that need to be programmed.
LDT Type
This parameter will notify the 1746L what type of LDT is attached to the unit. The LDT type
could be: Start/Stop (SS), Control Pulse (CP), Variable Pulse (VP), Variable Pulse Internal
(VPI), or a liquid level LDT (STIK). There is no default value. The parameter must be pro-
grammed by the user.
Input Type
Each input can be configured as “movement detect” or a “position hold” input. There is no
default value. The parameter must be programmed by the user.
Wire Speed
The wire speed for each LDT needs to be programmed into the unit so that the inch value can be
calculated. The default value is 9.0µs/in.
Recirculations
The number of recirculations in the LDT needs to be programmed into the unit so that the inch
value can be calculated correctly. The default value is 1.
LDT Length
The LDT length must be programmed for a VPI mode. This is used for LDT fault detection.
The value is entered in inches to the tenth decimal place. The default value is 999.9 inches.
Home Position
This will electronically program an offset into the unit. The new position is programmed into the
1746L. For the two channel version of the module, there are two separate home positions. The
home position is sent in multiple words. The default value is zero.
Counts Direction
The counts direction indicates whether the counts should be increasing as the magnet moves
away from the LDT head or decreasing as the magnet moves away from the LDT head. The
default value is decreasing as the magnet moves away from the head.
1.2: Output Image Table
the output image table is a bit register. This bit register contains a programming bit used to initi-
ate the programming sequence. The second word is the command word and the other 6 words
are used for the command parameters. In order to program a parameter, the command is en-
tered into the command word and the parameter values are entered in the parameter words. The
programming bit in the bit register is set to a 1 to indicate there is new data in the output image
table. It is the 0 to 1 transition that will trigger the 1746L to read and process the data and then
either set the acknowledge bit or the data error bit.