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Zero Lockdown
Zero Lockdown will drive the displayed flow and velocity, as well as the
associated outputs to zero when the velocity is below the set point. As
very low air velocities tend to be noisy and unstable, it may be best for
control purposes to raise the zero lockdown velocity to an appropriate
threshold above that which the velocity is steady and reliable.
Alarm/Alert Configuration
The Alarm/Alert Configuration menu provides access to select and
configure the transmitter alarm and alerts. Alarm type can be either
flow or temperature with Upper and Lower limits. The transmitter alarm
controls an onboard relay. Alerts are messages possibly indicating
issues with sensors or the transmitter.
Alarm Operation: If the process value (Type) exceeds the Upper or
Lower Limit, the relay will change state from the default of NO or NC
and the Type will change to red. When the process value recovers to
be within the Upper and Lower Limits, the relay will return to the default
state and the Type will return to black. The Limits Units are shown in
parentheses. These units are controlled by the System of Units and the
Units of Measure. If the units are US and the flow is CFH, CFH will be
the units used in Limits.
Alert Operation: Enable Reg. Alerts will turn ON / OFF
Enable Global Alerts will turn ON / OFF
Field Characterization
Field characterization (K-factoring) of a flow element is the adjustment
of the flow measurement system to match a known reference
measurement, (most commonly airflow traverse testing.) Field
characterization is typically done when there is insufficient straight duct
run or another issue that creates questionable output from the installed
measurement system.
A Field Characterization can be developed from one, two or three
reference flow rates – more could be used, but are not necessary. One
traverse test is required for each flow rate. It is recommended that a
minimum of a low and a high flow rate are used to determine a Field
Characterization. If there is little to no variance in the normal flow rate, it
is feasible to use a Field Characterization developed from a single flow
rate test. If a high and low flow rate test are performed and it is found
that these readings are substantially different, then a medium flow rate
should be considered to ensure a more accurate Field Characterization.
For any questions or concerns regarding Field Characterization
implementation, please contact Greenheck.
Field Characterization
On enables the Field Characterization and the selection of Calculate
or Manual. The Calculate selection will display the on-board calculator
that will determine the K-factor (device and reference data must be in-
hand and ready to input). Manual displays the Exponent and Gain value
forms for inputting externally determined Exponent and Gain values.
®
Zero Lockdown
Lockdown
ON
Velocity (FPM):
30
ENT - Accept ESC - Leave UP/DN - Change
Alarm/Alert Configuration
Type:
Flow
Upper Limit (CFM):
750
Lower Limit (CFM):
100
Enable Reg. Alerts:
OFF
Enable Global Alerts:
ON
ENT - Accept ESC - Leave UP/DN - Change
Field Characterization
On
Calculate
Manual
ENT - Accept ESC - Leave UP/DN - Change
Vari-Green® Transmitter
7
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