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BSA Flow Software Installation and User's Guide - CSI

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6.7.8 Digital input specifications<br />

P2<br />

26<br />

27<br />

DSUB25<br />

13<br />

25<br />

12<br />

24<br />

11<br />

23<br />

10<br />

22<br />

9<br />

21<br />

8<br />

20<br />

7<br />

19<br />

6<br />

18<br />

5<br />

17<br />

4<br />

16<br />

3<br />

15<br />

2<br />

14<br />

1<br />

dig _inp0<br />

dig _inp1<br />

dig _inp2<br />

dig _inp3<br />

dig _inp4<br />

dig _inp5<br />

dig _inp6<br />

dig _inp7<br />

dig _inp8<br />

dig _inp9<br />

dig _inp10<br />

dig _inp11<br />

dig _inp12<br />

dig _inp13<br />

dig _inp14<br />

dig _inp15<br />

reserved<br />

+5V<br />

Figure 6-81 Digital input connections<br />

6.8 Analog Monitor Option<br />

Input 16 bit, TTL-level<br />

Nominal low-level: 0V ≤ VIL ≤ 0.8 V<br />

Nominal high-level: 2V ≤ VIH ≤ 5 V<br />

Input filtering Signals sampled at 10MHz; a change in<br />

pattern must be stable at two consecutive<br />

clocks to be accepted<br />

Input impedance 20 kΩ pull-down to ground<br />

Safe input range: ± 20V; higher levels may damage the unit<br />

Input protection Diodes to ground <strong>and</strong> +5V; 5 kΩ series<br />

protection resistors<br />

Connector D-sub, 25 way<br />

With this option, simultaneous acquisition of LDA or PDA data <strong>and</strong> up to<br />

four analog signals is possible.<br />

The inputs are sampled at 8 Hz, so this option is meant for monitoring<br />

signals which vary very slowly (less than 4 Hz), for example the free-stream<br />

velocity of a wind tunnel, the temperature or the barometric pressure.<br />

The sampling is independent of the burst arrivals, <strong>and</strong> the output is the mean<br />

value of the samples acquired.<br />

Anti-aliasing filter Please note that there is no low-pass filter on the analog monitor inputs. If<br />

the signal to be monitored contains frequencies above 4 Hz, a low-pass filter<br />

with a cut-off frequency of 4 Hz or less should be inserted between the signal<br />

<strong>and</strong> the analog monitor input, in order to avoid aliasing (to fulfill the<br />

Nyquist sampling theorem)<br />

A Moments object followed by a List object is required to see the output.<br />

6-92 <strong>BSA</strong> <strong>Flow</strong> <strong>Software</strong>: Options <strong>and</strong> Add-ons

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