37
6.6.2 Scaling Digital Counter Cards
1. Scaling is not normally required for digital counter cards because most digital systems are sup-
plied as scaled systems. (Refer to the earlier Subsection 6.4.1, page 18 for a discussion of scaling.)
2. Scaling is required for systems supplied as “unscaled” systems, or if the counter card is not
matched to the transducer serial number. Scaled systems will have a discrete scale factor, such
as 0.001 inches per count, and do not require scale factor determination.
To determine the scale factor (or to check system performance), move the magnet to a known
measured position on the transducer near full stroke. Observe the output and record it.
The scale factor is determined by dividing the measurement by the observed number of counts
or the observed output in BCD. As an example,
Measurement = 36.000 inches
Reading = 35,420 counts (or 35.420 in BCD)
Scale Factor = 36 = 0.0010163 inches per count
(35,420 counts per inch in BCD)
3. For systems that will be used for only one or more discrete positions, move the magnet to the
known measured positions that will be repeated during system operation. Observe and record
each reading.
Compare each observed reading to the measured reading and record results. Use the observed
readings in software programming as the set point or control points.
For greater system accuracy, repeat this step and average the readings.
4. For systems that are used for continuous readings or variable set points, apply the scale factor
in Step 2 to software programming so that each reading is multiplied by the scale factor (con-
sult receiver device manual). Continue to Step 5.
5. Move the magnet to a known, measured position at or near half of stroke. Observe the read-
ing and compare to the measurement. If the reading varies by more than ±0.05% full stroke,
repeat Step 2 using a different measurement near full stroke. Check the new scale factor by
performing Step 5 again.
6. If the readings do not relate to the stroke position, or appear erratic, refer to Appendix D for
troubleshooting information.
NOTE:
To obtain maximum system accuracy,
several scale factors should be calculated
using different measurements and the
factors should be averaged. Readings
should be taken at or near actual system
operation conditions.
NOTE:
To obtain maximum system accuracy
perform the above procedures at or near
the actual system operating conditions.
To Next Page
Loading...
Need help?
General