Detectors, Secondary Elements, Transducers, and Transmitters (12205-16)

In instrument and process control channels, the output signal from the detector typically serves as the

input signal to the transducer

an instrument channel block diagram does not include an amplifier block, it is most likely because

amplification is being performed elsewhere in the channel

Accuracy is the measure of

How close a result is to the standard accepted value

Reproducibility is the degree of closeness with which the same value can be measured

at different times

The characteristic of an instrument that a designer chooses based on the smallest change needed to be measured in the given process is known as

sensitivity

Measurements of variables such as pressure, temperature, and flow are typically made using

inferred measurement

known Testing the validity of an instrument's measurements during normal operation by comparing those measurements to known values is part of

Calibration

According to the ISA wiring convention for thermocouples, the color red designates

The negative wire

The Bourdon tube measures pressure by sensing the

deformation of the device itself

A metallic diaphragm gauge measures pressure by relying on

the distortion of the diaphragm under pressure

Pressure capsules are commonly used to

measure low pressure

The ion chamber detector and the scintillation detector are both

nuclear level detectors

Orifice plates are the most widely used primary flow elements because

they are inexpensive and easy to install

The venturi tube senses the difference between a high-pressure tap located upstream of the inlet cone and a low-pressure tap located

At the center of the throat

In an I/P transducer, a DC current input signal is received by a coil positioned in the electric field of a(n)

permanent magnet

P/I transducers are generally used in

chemical areas

Strain gauges are commonly used to measure

mechanical force

The action of generating a voltage by applying force or pressure to a crystal is the operating principle of

piezoelectric transducers

While the elastic deformation of a sensitive measuring element can be produced directly by an external force, it may also be a function of

acceleration

The part of a pneumatic DP cell that consists of a transmitter body and a diaphragm capsule is the

process measuring section

In a force-balance differential pressure pneumatic transmitter, the top of the force bar is connected to a

pneumatic flapper-nozzle

In a pneumatic force-balance temperature transmitter, the effects of ambient temperature are eliminated with the use of a(n)

Compensation bellows unit

Under some process conditions, the low leg of a DP cell used to measure level in a closed, pressurized ve can fill with

process fluid or condensation

How does the output from an analog transmitter relate to the input it receives?

It is proportional and continuous

The HART® protocol has a significant advantage over other similar protocols in that it

can send and receive signals over 4-20mA analog wiring