Rockwell Automation 1771-CFM,D17716.5.99 CONFIGURABLE FLOWMET User Manual

Page 38

4–4

Configure the CFM Module

Publication 1771Ć6.5.99 - December 1995

Sampling Termination

if set, enables the input

sampling to be terminated

on either a time base only

(BTW 6) or a set number

of input pulses (BTW 7)

depending on which

condition arises first.

4 x High Hertz if set, the Highest Allowable

Frequency entry is multiplied by 4 to enable

entries > 32,767.
For example, to get a 100,000 peak allowable

frequency, you set this bit and enter 25,000 in the

word containing the Highest Allowable Frequency

(BTW 8, 18, 28 or 38).

Prover Type selects the type

of prover being used

(unidirectional or bidirectional):

0 = unidirectional (1 run, 2 switches)

1 = bidirectional (4 switch run)

Acceleration Calculation Time

calculates acceleration every Nth

frequency sample.

0 = acceleration rolling average over 5

samples

1Ć750 = number of frequency samples

(BTW 9 Acceleration Alarm Value must

0 0).
For example, if you place a value of 7

here, the CFM module:

a. stores the 1st frequency calculation

b. subtracts this calculation from the

8th frequency sample

c. divides this remainder by the time

between samples and places the

result in BTR 11, 20, 29 or 38

d. stores the 8th frequency sample

and waits for the 15th sample

all

T, NRT

all

Bandwidth Limit if set, limits the minimum

frequency the CFM module is capable of reading

to 1/Minimum Frequency Sampling Time.

When 1: the worst case response time of the

module is decreased to approximately

2 x Minimum Frequency Sampling Time.

When 0: frequency range = 1Hz Ć 100kHz

(worst case response time can be 2s at

extremely low frequencies)

0 = full frequency range (1Hz Ć 100kHz)

1 = minimum frequency (1/Minimum Frequency Sampling Time)

all

Frequency in 10ths allows you

to select the precision of the

frequency returned in the BTR.

If set, the frequency is returned

with the LSD being in tenths,

while if 0, the LSD is in ones.

0 = frequency returned as 100, 123

1 = frequency returned as 100, 123.2

Minimum Frequency Sampling Time specifies the minimum time the

CFM module spends to determine frequency (unless Number of Pulses to

Terminate Sampling is enabled in HighĆresolution Frequency mode, which may

allow the the input channel to end sampling earlier than the specified minimum).
Important: In Direction Sensor, this time is used to determine the maximum

sample time and the minimum frequency returned and does not

actually determine the time period for frequency sampling.

all

word 5 (channel 0)

word 15 (channel 1)

word 25 (channel 2)

word 35 (channel 3)

word 5 (channel 0)

word 15 (channel 1)

word 25 (channel 2)

word 35 (channel 3)

word 6 (channel 0)

word 16 (channel 1)

word 26 (channel 2)

word 36 (channel 3)

RANGE: 4ms Ć 1000ms (0 Ć 3 = DEFAULT)

DEFAULTS: HR, DS = 4ms / T, NRT = 100ms

Operating Mode for Channel 2

Operating Mode for Channel 0

Operating Mode for Channel 3

Operating Mode for Channel 1

0 = unused channel

1 = Totalizer

3 = HighĆresolution Frequency (channels 0 & 1 or 2 & 3)

➀

2 = Nonresettable Totalizer

4 = Direction Sensor (channels 0 & 1 or 2 & 3)

➀➁

word 4

Select a mode of operation on a per

channel basis by placing the shown

hex values in the proper bits:

➀

These modes are selected only via channel 0 or channel 2.

➁

If using both channels (0 & 1 and 2 & 3) for this mode, you cannot set sampling time for both = 4ms.

The maximum sampling time is:
< 2s Ċ if the Bandwidth Limit is not enabled and

a signal < 1 Hz is applied (sample time [

Minimum Frequency Sampling Time + 1/frequency input)
< 2 x the Minimum Frequency Sampling Time Ċ

if Bandwidth Limit is enabled and a very low input signal

frequency is applied (sample time [

Minimum Frequency Sampling Time + 1/frequency input)

Debounce Filtering

debounces the Gate

input for a period of 1s.

The first low to high transition

of the gate will cause the

CFM module to take

appropriate action (no other

transitions will be seen for 1s).

0 = OFF / 1 = ON

T, NRT