Flowserve 3400IQ Digital Positioner - Manual (Page 141)

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Logix 3400IQ Digital Positioner FCD LGENIM3402-00 – 0/07
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Glossary
A/D: Also called ADC or analog-to-digital converter. An A/D converts an analog signal into an
integer count. This integer count is then used by the micro controller to process information such as
position, pressure and temperature.
D/A: Also called DAC or digital-to-analog converter. A D/A converts an integer count into an analog
output signal. The D/A is used to take a number from the micro controller and command an external
device such as a pressure modulator.
EEPROM: Electrically Erasable Programmable Read Only Memory. A device which retains data
even when power is lost. Electrically erasable means that data can be changed. EEPROM have a
limited number of times data can be re written.
Micro controller: In addition to an integral CPU (microprocessor), the micro controller has built in
memory and I/O functions such as A/D and D/A.
Microprocessor: Semiconductor device capable of performing calculations, data transfer, and logic
decisions. Also referred to as CPU (Central Processing Unit).
Protocol: A set of rules governing how communications messages are sent and received.
PV: Primary Variable or Process Variable.
Resolution: Resolution is a number which indicates the smallest measurement which can be
made. You will often see Analog-to-Digital (A/D) converters referred to as a 10-bit A/D or a 12-bit
A/D. 10-bit and 12-bit are terms which indicate the total number of integer counts which can be used
to measure a sensor or other input. To determine the total integer count, raise 2 to the power of the
number of bits.
Example: 12-bit A/D
Total integer number = 2Number of Bits = 212= 4096
Resolution is the measurement range divided by the maximum integer number.
Example: A valve has a 2-inch stroke and a 12-bit A/D is used to measure position.
Resolution = Stroke/(maximum integer for 12-bit) = 2 inch/4096= 0.000488 inches
Sampling: Taking readings at periodic time intervals.
Serial Transmission: Serial transmission is a method of sending information from one device to
another. One bit is sent after another in a single stream.