Auto / Manual Control; Ramp-To-Setpoint Limit - Extech Instruments 48VTR User Manual

Automatic and Manual Control Modes
Automatic Control
Automatic Control is the normal mode of controller operation. In automatic mode the
controller automatically adjusts the control output as needed so that the PV = SV.
Manual Control
Manual control allows the user to manually raise and lower the control output. The user
can adjust the output percentage from 0.0 to 100.0%.
Relays and DC trigger outputs have only two states (ON & OFF), 100% is ON and 0%
output is OFF. A 4-20mA output is a continuous output, therefore 100% output is 20mA,
0% output is 4mA, 50% output is 12mA, and so on.
Follow the steps below to use Manual Control:
1. From the main display mode, press the RETURN key momentarily.
2. The 'H' for heating or the 'C' for cooling should appear on the lower LED digits
depending on which control action is selected. The control action parameter 'act'
can be found in the 3
3. Next to the 'H' or the 'C' is a numerical value; this is the output percentage. Use the
arrow keys to drive the output higher or lower.
4. Note that some older units had a lock-out feature for manual control. If the above
steps do not allow manual control, unlock the feature by pressing and holding the
DOWN Arrow and RETURN keys until the display blinks. To re-lock the feature,
press and hold the UP Arrow and RETURN keys until the display blinks.
5. To return to normal operation, press the RETURN key so that the SV and PV
displays appear.

Ramp-to-Setpoint Limit

To limit the rate that the PV changes as it moves toward the setpoint (SV) use the 'rAmP'
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parameter found in the 1 Menu Level. The setting range is 0.0 to 100.0 degrees per
minute.
For example, if a setting of 20.0 is entered, the controller will not allow the process to rise
more than 20 degrees (or other units) per minute.
A setting of '0.0' disables the feature. Use the UP and DOWN arrow keys to set the desired
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'rAmP' limit in the 1 Menu Level. Note that the 'rAmP' parameter will not appear in the 1
Menu Level if "Parameter Lock" (P-L) is set to '0' or an even number.
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Menu Level.
22 Model 48VTR - Version 5.0 – January 2006
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