Fluid Components International GF90_GF92 - Manual (Page 49)

Doc. No. 06EN003229 Rev. H 45 GF Series Flow Meter Models GF90/GF92
FLUID COMPONENTS INTERNATIONAL LLC http://www.fluidcomponents.com
Serial Communications
Make the electrical connections using the infomation from the last chapter. The wiring diagram is Figure 8.
The data stream is sent at a rate of 9600 baud with no parity, 8 bit characters and 1 stop bit. The baud rate is
fixed and cannot be changed. All operations accessible through the keypad are also available through the
serial port, JP3 located on the lower right corner of the upper circuit board. The serial port input/output
stream duplicates the actions of the keypad and the LCD display. Commands sent through the serial port to
manipulate the flowmeter are exactly equivalent to the keypad sequences. Data coming out of the serial port
is equivalent to the data sent to the display. Remote communication with the flowmeter consists of character
sequences that duplicate actions taken at the keypad. For example, the string H 2 4 2 5 produces the same
results as pressing HOME, 2, 4, 2, 5 from the keypad. Figure 31A is an example of code written in Quick Basic
that extracts the flow rate and the temperature through the serial port.
A common communication problem is over writing flowmeter serial buffer. If the buffer is overwritten the last
characters sent are lost. If the flowmeter does not respond as expected to a command, slow down the data
flow from the user PC or control device.
The approximate relationship between current input and the digital value displayed in menu level 2.4.3 is:
Digital Value = Current Input x 51.1
The digital value is used to manipulate the measured flow rate or the TCdR value. This digital value is used to
calculate a factor that is multiplied by the measured flow rate or TCdR. The factor is calculated using the
relationship:
K
A
= A
1
+ (A
2
x s) + (A
3
s 2 ) + (A
4
x s 3 )
where s = Digital Value
A
i
= Correction Factor Coefficients ( i = 1 through 4 )
K
A
= Correction Factor
NOTE: Ai is used for clarity in the manual. The flowmeter uses Fj as the Correction Factor Coefficient.
The Auxiliary Input Equation coefficients are determined by the factory from the data supplied at the time of
order entry.