Rockwell Automation 1756-CFM ControlLogix Configurable Flowmeter Module - Manual (Page 48)

48 Rockwell Automation Publication 1756-UM010B-EN-P - December 2011
48 Configurable Flowmeter Module Features and Operational Modes
Gross Rate
Use Gross Rate to convert total counts to rate units. The module employs a
user-defined K-factor in the conversion. The K-factor is a divisor, and the time
interval is divided by this number, as shown below.
 If the input frequency is below 100Hz, the K-factor used is always 10.0
for frequencies interpolated between 0-100Hz.
 If the input frequency is between 100Hz and 200Hz, the K-factor is
interpolated as follows:
 If the input frequency is between 200Hz and 300Hz, the K-factor is
interpolated as follows:
 If the input frequency is greater than 300Hz, the K-factor used
is always 100.0. There is no K-factor calculation over 300Hz.
To use Gross Rate, you must set the K-factor values in Module Tags, as shown
below.
Gross Rate =
Total Counts in Meter Sample
K-factor
x Meter Factor
K-factor = (f
in
- 100.0) x
(71.0 - 25.0)
(200.0 - 100.0)
x 25.0
K-factor = (f
in
- 200.0) x
(111.0 - 71.0)
(300.0 - 200.0)
x 71.0
Name Style Data type Value Change during
operation
C.Operations[0].kFactStruct.kFactorForChan[0] Float REAL
25.0 (1) Yes
C.Operations[0].kFactStruct.kFactorForChan[1] Float REAL
25.0 (1) Yes
C.Operations[0].kFactStruct.kFactorForChan[2] Float REAL 71.0 Yes
C.Operations[0].kFactStruct.kFactorForChan[3] Float REAL 111.0 Yes
C.Operations[0].kFactStruct.kFactorForChan[4]-
C.Operations[0].kFactStruct.kFactorForChan[12]
Float REAL 0 Yes
C.Operations[0].kFactStruct.FreqAtKFactor[0] Float REAL 0.0 Yes
C.Operations[0].kFactStruct.FreqAtKFactor[1] Float REAL 100.0 Yes
C.Operations[0].kFactStruct.FreqAtKFactor[2] Float REAL 200.0 Yes
C.Operations[0].kFactStruct.FreqAtKFactor[3] Float REAL 300.0 Yes
C.Operations[0].kFactStruct.FreqAtKFactor[4]-
C.Operations[0].kFactStruct.FreqAtKFactor[12]
Float REAL 0 Yes
(1)
To avoid discontinuity when interpolating Gross Rate, make sure the values in C.Operations[0].kFactStruct.kFactorForChan[0] and C.Operations[0].kFactStruct.kFactorForChan[1] match.