Pressure Reading Control - Honeywell HPB User Manual

HPB/HPA User Manual

4.3 PRESSURE READING CONTROL

The HPB commands allow considerable flexibility in tailoring pressure acquisition times, sample windows,
thresholds, and output rates. These are controlled by 7 commands: Deadband and Sensitivity (DS), Integration
(I=), Speed shift (S2), Speed shift at 50msec intervals (S5), Idle Count (IC), Reading Rate (RR), and OPerating
mode (OP). Figure 4.2 illustrates how the user may control these attributes in three ways:
First, the internal analog-to-digital converter integration time may be controlled over a range of 1 sample every 12
seconds up to 120 samples per second. This is controlled using the ‗Integration' (I=) command. The integration
time is used to control the A/D integration cycle that allow noisy pressure inputs to be filtered, or averaged, over a
selected period of time. See Figures 4.5 and 4.6. The integration time can be set within a range of 1 to 120
samples/sec using the I=Rn form or a range of 100msec to 12 sec/sample using the I=Mn form. The values for ‗n'
1 to 120 for both the rate (Rn) form and the millisecond (Mn) form.
The speed shift commands can only be enabled when the integration time is set using the I=Mn form. When
enabled, the thresholds for pressure change can be set that cause the output rate to double (S2) or update at 50
msec intervals (S5). When the change of input pressure reaches or exceeds the threshold, the sample rate shifts
to the higher rate.
Second, the integration cycles may be spaced with idle periods that cause pressure reading times to increase to
as often as one every 51 minutes. The Idle Count (IC) command will insert, or skip, from 0 to 255 idle periods
equal to the integration time. If the integration time is set to the maximum, 12 sec/sample, and an idle count of
255 is selected, then the time between samples = 12 sec. x 256 = 51.2 minutes.
Third, the reading rate may be controlled so pressure readings are obtained only when pressure changes occur.
The Reading Rate (RR) command can be set to only output changed readings, or to skip from 100 to 1000
identical readings. The Operating Mode command (OP) can be set to output every reading or to only output
readings when a
the pressure reading to vary as long as it remains within the deadband limits. This controls the
not allowing
sensitivity to change of the RR and OP command modes when the ‗output only when pressure changes' options
are selected. If the pressure signal is stable within the deadband limit, then the pressure reading time can be
increased up to 1000 times the integration time by using the RR command.
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pressure change occurs. The Deadband setting in the DS command can filter a small pressure change by
range from
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