 TUNE YOUR LOOP: Questions to keep you sharp. Tune Your Loop is a series of posts consisting of questions from ISA Training Courses.

1. To compute capacitive reactance the following formula is used. Xc = 1/ 2Πfc.
(“c” is expressed in farad and “f” is expressed in hertz.) What is the capacitive
reactance if the frequency is 60 Hz and the capacitor size is 5 micro farad.

[ordered_list style=”lower-alpha”]
1. .019Ω
2. 5.31Ω
3. 531Ω
4. 5310Ω[/ordered_list]

2. The temperature range of a transmitter is 100 -300°F. The output signal range is
3-15PSI. What would be the expected output signal for an input temperature of
175°F.

[ordered_list style=”lower-alpha”]
1. 4.5PSI
2. 6PSI
3. 7.5PSI
4. 13.5PSI[/ordered_list]

3. If the flow rate remains constant in a fluid line and the pipe diameter in one
section is 10 inch with a velocity of 2 feet per second what will be velocity
through the pipe be when the fluid passes through the pipe when it is reduced to
4 inches? (The formula is Flow rate = velocity times area of the pipe. [Q=VA]The
formula for area of the pipe is ΠR2.)

[ordered_list style=”lower-alpha”]
1. 6.25 ft/sec
2. 12.5 ft/sec
3. 5.0 ft/sec
4. 1.25 ft/sec[/ordered_list]

4. During calibration, the maximum error was 2.5 units over a span of 50 units.
What is the percent of span error?

[ordered_list style=”lower-alpha”]
1. 20%
2. 5%
3. .5%
4. 2.5%[/ordered_list]

1. c

2. c

3. b

4. b

From the ISA course Mathematics for Instrumentation Technicians (FG02) pre-instructional survey.

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