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6.6 System Calibration
There are no adjustments on the Digital Personality Module or on the transducer. Instead, the system is
calibrated at the Counter Card or by external means. The scaling (inches per count) is determined by a
fixed frequency crystal oscillator, while the zero point is determined by re-settable DIP switches on the
counter card. Generally, the system components do not show shift, age, or drift over time, and re-calibra-
tion is not necessary. However, calibration may be used to compensate for mechanical wear on external
mechanical parts connected to the magnet or the transducer.
6.6.1 Re-zeroing the Digital Counter Card
On the Counter Cards, the zero point is preset at the factory, using a pair of DIP switches, S1 and
S2. Zero is set at 2 inches from the hex flange of the transducer, or at a distance specified by the
customer. If reverse output is specified, the zero point is set at 2.5 inches from the tip of the
transducer rod.
There are three ways of changing the zero setting:
1. Mechanical Offset
The zero position can be adjusted by changing the mechanical offset of the magnet relative to the
transducer rod. This requires a coupler device which permits a screw adjustment of the magnet.
Fabricate a coupler device to hold the magnet. The coupler should include adjustment screws that
allow fine adjustments of the magnet along the transducer rod. Move the magnet to obtain a zero
reading.
If the coupler does not allow magnet position adjustment, it can sometimes be used to lock the
magnet in place, while shims or washers are used to move the transducer relative to the magnet.
(Do not attempt this if the unit is installed in a hydraulic cylinder).
2. Software Programming
In some applications it is possible (and preferable) to maintain a zero offset in software at the
receiver. This permits quick re-zeroing without adjusting the magnet or resetting the DIP switches.
For the detailed procedure, consult the manual for the receiver device. Move the magnet to the
desired zero position and set the receiver reading to zero.
In most cases, the zero offset is determined by adding the binary complement to the reading
observed with the magnet in the desired zero position.
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