Smart Instruments Flashcards
What are the 3 characteristics of smart transmitters?
1) Programmable
2) Have memory
3) Can report faults, run self-diagnostics, and perform calculations
Communication with smart transmitters is accomplished from a _________________
using _______________ or __________________.
Remote source, field communications, computer workstations
What is the function of a reversed polarity protection diode?
1) Allows a meter to be connected into the loop without breaking a circuit
2) Protects the transmitter if it’s improperly connected
What is the function of the zener regulator?
Provide required power to operate the internal circuit
What is the function of the Analog to Digital Converter?
Takes analog input from the sensor and converts it into a digital value that is required by the microprocessor
Why do smart transmitters have an isolation circuit?
Provides electrical isolation between the ADC and the microprocessor using light
What 4 factors do flow computers need?
1) Static pressure
2) Temperature/density
3) Differential pressure
4) Viscosity
What is stored in the configuration memory of a smart transmitter?
Things like LRV,URV, sensor type, unit selection, transmitter identification number
What is stored in the characterization memory of a smart transmitter?
Things that are specific to a transmitter for example T/C tables, RTD tables
What is the function of DAC in the smart transmitter?
Convert digital input from the microprocessor into a 4-20 mA signal
How do smart transmitters improve accuracy compared to analog transmitters?
Sensor linearization which is stored in the characterization memory
What type of modulation do smart transmitters use?
FSK
Upon calibration you notice that the DMM mA reading does not match with the communicator display. What type of trim is required and what does it adjust?
Output trim which adjusts the DAC.
Upon calibration you notice that the PV on your communicator display does not match with an inline pressure gauge. What type of trim is required and what does it adjust?
Sensor trim that adjusts the ADC.
