ND Series

Industrial Middle Pressure Sensors

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12

10.6.2 Rate Control Register

Default Value: 0x1C

The Rate Control Register controls the rate at which the DAV

pin is asserted indicating new data is available. This register

is primarily used to throttle down the actual data transfer

rate (when using the DAV as the trigger to sample) since the

general industrial requirement is less than the internal 444

Hz update rate.

The function of this register is that it is the reload value of a

data rate counter. The value of the Rate Control Register is

the divisor of the 444 Hz internal data rate. Since a divisor of

zero is not possible, a zero value will select the auto-select

rate mode. In this mode, the rate is selected based on the

selected bandwidth limit. The auto rate value is roughly 3x

the corner frequency of the selected bandwidth limit in all

auto selected rates (where possible).

Note: Start-up time for the sensor is approximately 80ms for

the first sample to be settled. Requesting data during this

time will result in invalid information. However, this start-up

time can be used for configuring the Mode and Rate

registers by performing a transfer with the desired Mode

and Rate register values and discarding the received

pressure data. After waiting the required start-up time, the

sensor will respond with desired data since the Mode and

Rate registers have been pre-established.

10.7 Computing Pressure

The pressure data is in the form of 16 bit signed integer sent in high byte then low byte order. This is a differential output by

definition and the data range is ±215. There is a 10% margin in the output scaling and the selected full scale will reside in the 90%

band of the total available output data range. Refer to Equation 1 (below) for the general model for computing the output pressure.

As an example, if the sensor output is 3,647 counts and the selected pressure range is 1.0 inH2O, then the output pressure is 0.124

inH2O. Conversely, for a -3,647 count with the selected pressure range of 1.0 inH2O, the computed output pressure is -0.124 inH2O.

Refer to Example 1 (below) for the specific example computation.

������������������������1:������������������������������������������������2������������=������������������������������������������������������������������������������������������������������������������������

90%∗215

∗������������������������������������������������������������������������������������������������������������������������������������������������������������ ������������������������������������������������������������������������������������1:������������������������������������������������2������������= 3,64790%∗215∗1������������������������������������2������������=0.124������������������������������������2������������

b7

b6

b5

b4

b3

b2

b1

b0

Rate Control Register

0

0

0

0

0

1

0

1

0

0

1

1

1

1

0

1

1

1

Auto Select

444 Hz

222 Hz

148 Hz

1.75 Hz

1.74 Hz

1.0 Hz

2.0 Hz

5.0 Hz

10 Hz

20 Hz

50 Hz

100 Hz

Selected BW Limit

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

1

1

1

1

1

1

1

1

1

444 Hz

148 Hz

63.4 Hz

31.7 Hz

15.3 Hz

6.0 Hz

3.0 Hz

Auto Select Rate

Rate Control Register Detail

200 Hz

444 Hz