Calibration-Peine Final written test

What does HART stand for?

Hiway Addressable Remote Transducer

What is a major advantage of HART?

it allows you to keep the existing 4-20 ma signal while superimposing a digital signal on the device without interfering with the 4-20 ma analog signal

What frequencies act as 1 and 0 in HART protocol?

1=1200 Hz

0=2200 Hz

How does FSK work?

Frequency shift keying is a digital communication method where data is transmitted by switching between two frequencies: 1200 Hz and 2200 Hz that represent 1 and 0

How does HART use FSK?

By superimposing its digital signal on a 4-20 mA analog signal allowing digital device information and diagnostics to be transmitted without interfering with analog process measurement.

Draw how to connect a HART 475 transmitter (NOT NEWER TREX)

ok

How does multidrop work in HART?

multidrop is used when there are multiple devices on one loop that share a 4-20 mA signal. Each device has a unique address recognized by HART.

How does point to point work in HART?

point to point mode is when a HART communicator is hooked directly to one device in a loop only. In this mode, frequency shift keying is used to superimpose a digital signal on top of the 4-20 ma signal that carries the process variable.

What is the minimum and maximum resistance needed when using 475 HART communicator?

max=43.5(Power supply voltage-10.5)

minimum =250 ohms

What is the OSI model

The open systems interconnection shows framework that defines how computer systems work.

Describe the steps necessary to rerange a transmitter

write down and then refer to question 11 in notes

Describe sensor trim and when to use it

Sensor trim calibrates the internal sensing element of the transmitter, which is responsible for converting physical variables into a digital signal. You would often need to do a sensor trim after reranging, or if the transmitters measure value does not match what a gauge is reading.

Describe analog trim and when to use it

Analog trim corrects error in the digital to analog conversion circuit within the transmitter. Should be done if the transmitters reading does not match the multimeter reading

Describe URV and LRV

The upper and lower range values tell an instrument what the lowest and highest values correspond to in an output signal. The URV and LRV also creates a range for the instrument to stay within.

What is a huge benefit of smart transmitters as compared to analog transmitters?

They allow simultaneous analog and digital communication.

When would you use Square root extraction?

When working with a flow process

What is baud?

the number of pulses per second in a communication channel

What are the two forms of transmission in HART protocol?

1. Poll/Response mode

2. burst(broadcast mode)

Can burst mode be used for multidrop systems?

No

In point to point mode, what is the smart device polling address?

0

What is 5-point calibration?

5-point calibration is when you divide a range into 5 equally spaced numbers, two of those numbers acting as 0 and 100% with the other three equally spaced in between

What is the data transfer rate for FSK in HART?

1200 baud

When using square root extraction, what values do you square root?

outputs only; analog(mA) and flow rate values.

Who developed the HART protocol?

rosemount

What digital signal modulation method does HART use?

Frequency shift keying (FSK)

What is the max number of devices in multidrop mode?

15 devices

What OSI layers does HART use?

Layer 1 (Physical), Layer 2 (Data Link), Layer 7 (Application)

What are the types of manifolds mentioned?

3-valve, 5-valve, and coplanar manifold

How do you isolate a transmitter from a process?

close low side iso, open equalizer, close high side iso, crack both vents ,bleed off pressure, fully open vents, blow air through vents

How do you get transmitter ready for calibration once it is isolated? (for class only)

close desired side vent, leave opposite vent open, close equalizer, open desired side iso valve

What is the significance of average AC signal in HART?

It does not affect the 4-20 mA analog signal

What is frequency shift keying?

Digital modulation technique where the frequency of a signal is shifted between discrete values

What is URL and LRL

The maximum and minimum values a device or process is designed to operate within

What processes is the transmitter with only 1 input on the high side used for? (inline)

open tank processes only, no differential pressure processes

What numbers are used for the addresses in multidrop mode?

0 is used for the starting transmitter, and the rest go in numerical order starting from 1. (1 2 3 4 5 etc)

What is the equation for beta ratio and what is the beta ratio symbol?

B=O/P

What is the equation to find inside pipe diameter?

P=O/B

What is the equation to find orifice plate diameter?

O= B x P

What are the steps to valving a transmitter back into service after it has been isolated or calibrated?

make sure equalizer is open, close both vents, crack high side iso, crack low side iso, close equalizer, burp vent valves(crack and then close again quickly), fully open both iso valves

What are the three process types we have discussed?

Level, flow, and pressure

When working with TREX communicator make sure that meter is…

connected in series with the TREX and transmitter