Set Electrical Offset to 0 and Electrical Slope to 1 to restore factory calibration.
Filter Time Constant
Filtering smoothes an input signal by applying a
Adjust the filter time interval with Filter Time [`FiL] (Setup Page, Analog Input Menu).
Example: With a filter value of 0.5 seconds, if the process input value instantly changes from 0 to 100 and remained at 100, the display will indicate 100 after five time constants of the filter value or 2.5 seconds.
Unfiltered Input Signal
Temperature
Time
Filtered Input Signal
Temperature
Time
Sensor Selection
You need to configure the controller to match the input device, which is normally a thermocouple, RTD or process transmitter.
Select the sensor type with Sensor Type [`Sen] (Setup Page, Analog Input Menu).
Sensor Backup
Sensor backup maintains
The sensor backup feature is only available in an
Turn sensor backup on or off with Sensor Backup Enable [`S;bA] (Setup Page, Analog Input 1).
Set Point Low Limit and High Limit
The controller constrains the set point to a value between a set point low limit and a set point high limit.
Set the set point limits with Low Set Point [`L;SP] and High Set Point [`h;SP] (Setup Page, Loop Menu).
There are two sets of set point low and high lim- its: one for a
High Limit of selected functional range
Range High Range (between High Limit of Sensor and Range Low)
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Scale High and Scale Low
When an analog input is selected as process voltage or process current input, you must choose the value of voltage or current to be the low and high ends. For example, when using a 4 to 20 mA input, the scale low value would be 4.00 mA and the scale high value would be 20.00 mA. Commonly used scale ranges are: 0 to 20 mA, 4 to 20 mA, 0 to 5V, 1 to 5V and 0 to 10V.
You can create a scale range representing other units for special applications. You can reverse scales from high values to low values for analog input signals that have a reversed action. For example, if 50 psi causes a 4 mA signal and 10 psi causes a 20 mA signal.
Scale low and high low values do not have to match the bounds of the measurement range. These along with range low and high provide for process scaling and can include values not measureable by the control- ler. Regardless of scaling values, the measured value will be constrained by the electrical measurements of the hardware.
Select the low and high values with Scale Low [`S;Lo] and Scale High [`S;hi]. Select the displayed range with Range Low [`r;Lo] and Range High [`r;hi] (Setup Page, Analog Input Menu).
Range High and Range Low
With a process input, you must choose a value to represent the low and high ends of the current or voltage range. Choosing these values allows the controller’s display to be scaled into the actual working units of measurement. For example, the analog input from a humidity transmitter could represent 0 to 100 percent relative humidity as a process signal of 4 to 20 mA. Low scale would be set to 0 to represent 4 mA and high scale set to 100 to represent 20 mA. The indication on the display would then represent percent humidity and range from 0 to 100 percent with an input of 4 to 20 mA.
Select the low and high values with Range Low [`r;Lo] and Range High [`r;hi] (Setup Page, Analog Input Menu).
Receiving a Remote Set Point
The remote set point feature allows the controller to use a thermocouple, RTD, 1 k potentiometer or process signal at input 2 to establish the set point,
Watlow | • 57 • | Chapter 9 Features |