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VELTRON DPT-
plus
Air Monitor Corporation
116-010-91.P65 (09/18/09)
VELTRON DPT-
plus
- IO&M Manual
3
SECTION 3 – FEATURES
3 – FEATURES
3.1 – USER SETUP MENU
The microprocessor program contains a User Setup menu system for setting user selectable parameters. Four
pushbuttons: , , , and allow the user access to the menu for setting configuration modes and values.
Refer to the Configuration Programming (Section 5.6) instructions for operation details. Also contained in the User
Setup menu is all input and output calibration. The calibration method is completely digital and contains no analog
potentiometer adjustments which are susceptible to drift. Non-volatile memory is used for storing all setup parameters
and calibration values, and will remain unchanged after set, even when power to the unit is off.
3.2 – AIR DENSITY CORRECTION
The VELTRON DPT-
plus
transmitter is capable of accepting a process temperature input to perform density correction
to volumetric or mass flow. Temperature input is a 4-20mA signal from a remote temperature transmitter; non-linear
temperature inputs can be linearized by the microprocessor.
3.3 – TRANSMITTER HOLD
Certain operations performed by the microprocessor place the unit into a
Hold
mode. This occurs when the User Setup
menu system is activated, when an AUTO-zero is performed, or when an AUTO-purge cycle is in progress. When in
Hold
, all
Normal
mode processing is halted and outputs are held at their last value prior to
Hold
.
Normal
operation is
indicated by the "CPU Activated"
(dot) in the upper right of the display blinking at a rate of four times per second. A
Hold
mode is indicated by the "CPU Activated"
(dot) blinking at a rate of once per second.
3.4 – AUTOMATIC ZEROING
At periodic intervals the microprocessor will automatically execute an AUTO-zero cycle consisting of the following
sequence: The transmitter output and display signals are put on
Hold
; a valve is activated which disconnects the
process high pressure from the high port of the transducer and connects the process static pressure to both sides of
the transducer, creating a true zero differential pressure; after a brief stabilization period, the transducer zero offset
signal is measured and stored in memory; the valve is deactivated and after a brief period for process signal stabilization,
the
Hold
is released and
Normal
process measurement resumes. will be displayed whenever AUTO-zero cycle
is in progress.
During
Normal
operation, the zero offset value stored in memory is subtracted from subsequent transducer readings
until the next AUTO-zero cycle occurs and repeats the process. For calibration purposes a switch is provided which
allows the user to manually activate the zeroing valve. AUTO-zero On/Off and Interval are available and configurable
using the User Setup menu.
X
zero