207
Also refer to: Cycle Time; Relay; SSR and Time Propor-
tioning Control.
USB Menu
A lock-code protected USB menu is offered from the
main menu for the USB option. This allows the user to
read or write files to a USB memory stick. The current
configuration of the instrument can be copied to the
stick, or the instrument can be reconfigured from a file
created using the PC software or copied from another
instrument. Profiles can also be copied from the instru-
ment to a USB stick or you can upload pre-stored files
created earlier from the PC software or copied from an-
other instrument. Data recordings can be copied to the
stick for later analysis on a PC.
Refer to the USB Menu information in the Configuration
& Use section.
Also refer to: Data Recorder; Lock Codes; Main Menu;
PC Software and Profiler
Valve Motor Drive Control (VMD)
This control mode is used when directly controlling
the motor of a modulating valve or damper. It uses a
3-point stepping Valve Motor Drive control algorithm
to open or close the valve. VMD mode is not suitable
if the modulating valve has its own positioning circuit
(use standard control with a continuous current pro-
portioned linear output) or solenoid valves (use stan-
dard control with a time proportioned output).
Also refer to: Continuous Control; Linear Output; Mod-
ulating Valve; Solenoid Valve; Three Point Stepping
Control and Time Proportioning Control.
Valve Position or Flow Indication
The valve motor drive control mode does not require
any kind of position feedback in order to correctly con-
trol the process. However, where potentiometer feed-
back or (mA or VDC) flow signals are available, they
can be connected to the 2nd input to indicate valve
position or flow level. The display is a percentage (0
to 100%) shown as a bar-graph in the main operator
mode screen. Even if position feedback is provided, it
is not used by the VMD control algorithm when posi-
tioning the valve, thus avoiding problems associated
with faulty feedback signals.
Also refer to Auxiliary Input; Bar-graph; Display Strat-
egy; Open Loop VMD; PID; Set Valve Closed Position;
Set Valve Open Position; Setpoint; and Valve Motor
Control.
Valve Open & Closed Limits
When valve position indication is used in VMD con-
trol mode, the valve limit parameters can be used to
“clamp” the maximum and minimum valve positions.
The controller will not attempt to drive the valve past
these points. The position indication input must cor-
rectly scaled using “set valve open” and “set valve
closed” before using the valve limits.
Also refer to Set Valve Closed Position; Set Valve Open
Position; Valve Motor Control and Valve Position Indi-
cation.
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