ADM-870C 07/14/0945
system to settle, then press the READ key to take the second (backpressure compensated) reading. If necessary, the
FlowHood may be removed from the outlet in order to close the flaps. Position the FlowHood as before, and wait three
seconds for the flow to stabilize before taking the second reading. The compensated reading will be displayed with a ‘c’ for
compensated, as CF c nn.
11.2.1 MEMORY DISPLAY IN FLOWHOOD MODE
Backpressure compensated and noncompensated readings are recorded separately in memory. Individual readings
displayed using the RCL keys will have a small ‘sc’ for stored, backpressure compensated readings or a small ‘su’ for stored,
nonbackpressure compensated readings.
The average function will display two different averages. The average of just the backpressure compensated readings will
be displayed as nnc nnnn. The average of just the nonbackpressure compensated readings will be displayed as nnu nnnn.
The sum function will display two different sums. The sum of just the backpressure compensated readings will be displayed
as
3c nnnn. The sum of the noncompensated readings will be displayed as 3u nnnn.
The maximum and minimum functions will each display two different maximums or minimums. The maximum backpressure
compensated reading will be displayed as xx
¸
c nnnn. The minimum of just the backpressure compensated readings will
be displayed as xx
ºc nnnn. The maximum nonbackpressure compensated reading will be displayed as xx
¸
u nnnn. The
minimum of just the nonbackpressure compensated readings will be displayed as xx
ºu nnnn.
11.2.2 RATIO ERR DISPLAY
The meter may display RATIO ERR following a backpressure compensated measurement in which the numerical ratio of
the two parts of the measurement sequence exceeds predetermined limits. Normally this indicates, either that the operator
has made a procedural error, or that a dynamic change (such as a changed damper setting) has occurred between the two
parts of the backpressure compensated measurement process.
RATIO ERR may also be displayed as the result of measurements taken at outlets with extremely low pressure drops (less
than .003 in wc @ 500 cfm). These outlets may not be suitable for the backpressure compensation method, and may require
other means of air flow measurement.
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