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Installation Manual
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3.3: Features
Automatic Gain Control
The Automatic Gain Control feature will automatically search and find the magnet on power up and adjust the
signal strength to the optimum setting. If power is applied without a magnet on the LDT, the LDT will go into a fault
condition and transmit a voltage or current outside of the programmed range. See Chapter 1: 958A Overview, for
list of fault conditions and outputs. To correct this, turn power off and place magnet within the active stroke area,
re-apply power.
3.4: Setting Zero & Span Positions
As an option the 958A can be ordered with Programmable Zero & Span positions. See page 10 part numbering to
see if this option filed was selected.
Note: If option “P” was not selected in part number configuration, the unit is
non-programmable.
All units come fully programmed from the factory and do not require re-programming unless desired. The units
are 100% absolute and will not lose programmed parameters on power loss. The Zero and Span points can be
programmed in any order and anywhere within the LDT’s active sensor area.
NOTE 1:
Zero or Span can be adjusted individually without setting the other.
NOTE 2:
Zero = 0V on 0-10 VDC, 0V on 0-5 VDC, .25 on .25-4.75 VDC, .5 on .5-4.5 VDC units and 4mA on 4-20mA
units.
There is a timing sequence that is used to unlock the probe for programming. This is to insure that the Zero or Span
positions cannot be accidentally re-programmed by someone in the field.
Manual Setting of Zero & Span
To set the Zero and Span position, follow these steps:
1. Apply power to the LDT.
2. Place magnet assembly where Zero is to be located, but within the active region of the probe.
3. Short the Program Input pin to the Power Supply Common for 4 seconds. Remove the short for 1 second.
Within 5 seconds, short the Programming Input pin to the Power Supply Common. This completes the Zero
programming process.
4. Place magnet assembly where Span is to be located, but within the active region of the probe.
5. Short the Program Input pin to the Power Supply Common for 4 seconds. Remove the short for 1 second.
Within 5 seconds, short the Programming Input pin to the Power VDC.
This completes the programming process.
NOTE:
The LDT must be unlocked to program the Zero and unlocked again to program the Span. Once either the
Zero or Span is programmed the LDT will go back into the locked mode.
!
WARNING:
During normal operation, electrically insulate the Program wire to prevent accidental setting of
Span.
