Input Parameter Module (1- In) P48 models
The controller has several input set-up parameters that must be programmed prior to setting any other controller parameters.
Input Type (tYPE)
Select the signal input type: Voltage (VOLt), or Current (Curr). The signal input terminal for voltage is #9 and for current is #10. Common is #8.
Decimal Point Position (dCPt)
Select the desired decimal point position for the scaled display. The selected decimal point position appears in the following parameters; rnd, dSP1, dSP2, SPLO, SPHI, SP, AL1, AL2, db-2, AHYS, and CHYS.
0
0.0
0.00
0.000
Rounding Increment ( rnd)
Rounding values other than “1” causes the scaled number to ‘round’ to the nearest rounding increment selected (i.e.. rounding of ‘5’ causes ‘122’ to round to ‘120’ and ‘123’ to round to ‘125’). If the process is inherently jittery, the display value may be rounded to a higher value than “1”. If the range of the process exceeds the required resolution, (ex. 0-1000 PSI, but only 10 PSI resolution required), a rounding increment of 10 will effectively make the display more stable.
This programming step is usually used in conjunction with programmable digital filtering to help stabilize display readings. (If display stability appears to be a problem and the sacrifice in display resolution is unacceptable, program higher levels of digital filtering or increase the level of process dampening.) Rounding increments of 10, 20, 50, and 100 may also be used to add “dummy zeroes” to the scaled readings, as desired.
1
2
5
10
20
50
100
The rounding increment is for the controller’s display only and does not affect (improve or degrade) the control accuracy of the unit.
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Digital Input Filtering and Display Update Rate (FLtr)
Select the relative degree of input signal filtering and display update rate.
The filter is an adaptive digital filter that discriminates between measurement noise and actual process changes. Therefore, the influence on step response time is minimal. If the signal is varying too greatly due to measurement noise, increase the filter value. Additionally, with large derivative times, control action may be too unstable for accurate control.
Increase the filter value. Conversely, if the fastest controller response is desired, decrease the filter value.
The Auto-tune procedure sets the filter value appropriate to the process characteristics. See Output Power Dampening parameter (OPdP), page 36, for filtering the output.
Fltr- 0 to 4
0 = least input filtering
3 = most input filtering
4 = most input filtering and slower (2/sec) display update rate
(outputs update at 10/sec rate)
Scaling Points
Prior to installing and operating the controller, it may be necessary to change the scaling to suit the display units particular to the application.
Although the unit has been programmed at the factory, the scaling will generally have to be changed.
The controller is unique in that two different scaling methods are available.
The two scaling procedures are similar in that the operator keys in the display values and either keys in or applies a signal value that corresponds to those scaling points. The location of the scaling points should be near the process end limits, for the best possible accuracy.
Once these values are programmed (coordinates on a graph), the indicator calculates the slope and intercept of the signal/display graph automatically.
No span/zero interaction occurs, making scaling a one-pass exercise.
Figure 14, Scaling Points
