Red Lion PAXT User Manual
Page 17
17
PAXT: ICE POINT SLOPE
PAXT: TEMPERATURE DISPLAY OFFSET*
17
DISPLAY ROUNDING*
Rounding selections other than one, cause the Input Display to ‘round’ to the
nearest rounding increment selected (ie. rounding of ‘5’ causes 122 to round to
120 and 123 to round to 125). Rounding starts at the least significant digit of
the Input Display. Remaining parameter entries (scaling point values, setpoint
values, etc.) are not automatically adjusted to this display rounding selection.
The temperature display can be corrected with an offset value. This can be
used to compensate for probe errors, errors due to variances in probe placement
or adjusting the readout to a reference thermometer. This value is automatically
updated after a Zero Display to show how far the display is offset. A value of
zero will remove the affects of offset.
to
FILTER SETTING*
The input filter setting is a time constant expressed in tenths of a second. The
filter settles to 99% of the final display value within approximately 3 time
constants. This is an Adaptive Digital Filter which is designed to steady the
Input Display reading. A value of ‘0’ disables filtering.
to
seconds
FILTER BAND*
The digital filter will adapt to variations in the input signal. When the
variation exceeds the input filter band value, the digital filter disengages. When
the variation becomes less than the band value, the filter engages again. This
allows for a stable readout, but permits the display to settle rapidly after a large
process change. The value of the band is in display units. A band setting of ‘0’
keeps the digital filter permanently engaged.
to
display units
*
Factory Setting can be used without affecting basic start-up.
This parameter sets the slope value for ice point compensation for the
Custom TC range (
) only. The fixed thermocouple ranges are
automatically compensated by the meter and do not require this setting. To
calculate this slope, use µV data obtained from thermocouple manufacturers’
tables for two points between 0°C and 50°C. Place this corresponding µV and
°
C information into the equation:
slope = (µV
2
- µV
1
)/(°C
2
- °C
1
).
Due to the nonlinear output of thermocouples, the compensation may show
a small offset error at room temperatures. This can be compensated by the offset
parameter. A value of 0 disables internal compensation when the thermocouple
is externally compensated.
to
µ
V/°C
For the PAXT, the following parameters only apply to Custom
Sensor Scaling.
SCALING POINTS*
Linear - Scaling Points (2)
For linear processes, only 2 scaling points are necessary. It is recommended
that the 2 scaling points be at opposite ends of the input signal being applied.
The points do not have to be the signal limits. Display scaling will be linear
between and continue past the entered points up to the limits of the Input Signal
Jumper position. Each scaling point has a coordinate-pair of Input Value (
)
and an associated desired Display Value (
).
Nonlinear - Scaling Points (Greater than 2)
For non-linear processes, up to 16 scaling points may be used to provide a
piece-wise linear approximation. (The greater the number of scaling points
used, the greater the conformity accuracy.) The Input Display will be linear
between scaling points that are sequential in program order. Each scaling point
has a coordinate-pair of Input Value (
) and an associated desired Display
Value (
). Data from tables or equations, or empirical data could be used to
derive the required number of segments and data values for the coordinate pairs.
In the SFPAX software, several linearization equations are available.
to
SCALING STYLE
If Input Values and corresponding Display Values are known, the Key-in
(
) scaling style can be used. This allows scaling without the presence or
changing of the input signal. If Input Values have to be derived from the actual
input signal source or simulator, the Apply (
) scaling style must be used.
After using the Apply (
) scaling style, this parameter will default back to
but the scaling values will be shown from the previous applied method.
This parameter does not apply for the PAXT. Scaling values for the
PAXT must be keyed-in.
INPUT VALUE FOR SCALING POINT 1
For Key-in (
), enter the known first Input Value by using the arrow keys.
The Input Range selection sets up the decimal location for the Input Value. With
0.02A Input Range, 4mA would be entered as 4.000. For Apply (
), apply
the input signal to the meter, adjust the signal source externally until the desired
Input Value appears. In either method, press the
PAR key to enter the value
being displayed.
to
DISPLAY VALUE FOR SCALING POINT 1
to
Enter the first coordinating Display Value by using the arrow keys. This is
the same for
and
scaling styles. The decimal point follows the
selection.
INPUT VALUE FOR SCALING POINT 2
to
For Key-in (
), enter the known second Input Value by using the arrow
keys. For Apply (
), adjust the signal source externally until the next
desired Input Value appears. (Follow the same procedure if using more than 2
scaling points.)
These bottom selections are not
available for the PAXT.
Note:
style - Pressing the RST key will advance the display to the next
scaling display point without storing the input value.
key-in data
apply signal