August 2007, Vol. 19, No.8
Test Your Knowledge of Instrumentation
True or False Questions:
- Moisture contributes to instrument problems in three ways: short-circuiting, corrosion, and swelling.
- Electrostatic discharge can cause spikes of 2000 volts and damage instruments, even without physical contact or a visible spark.
- Sonic and ultrasonic level sensors compare the frequency of the transmitted signal to the frequency of the signal bounced back by the surface of the level being measured.
- Resistance temperature detectors operate on the principle that the resistivity of a metal changes with its temperatur
- Oxidation–reduction probes used to measure chlorine residual in chlorinated water need daily cleaning.
Multiple Choice Questions:
Which flows are transmissive (also known as through-beam or transit-time) ultrasonic flowmeters best suited to measure?
A. Nitrification return activated sludge.
B. Primary sludge.
C. Thickened sludge.
D. Primary effluent
Bubbler level measurement instruments for closed, vented tanks use differential pressure transmitters. Where are the high- and low-pressure ports connected, respectively?
A. High pressure to bubbler tube, low pressure to atmosphere outside of the tank.
B. High pressure to bubbler tube, low pressure to tank headspace.
C. High pressure to tank headspace, low pressure to bubbler tube.
D. High pressure to atmosphere outside of tank, low pressure to bubbler tube.
Which of the following is a typical maintenance concern with magnetic flowmeters?
A. Electrode blinding by high solids content.
B. Erratic signals from corroded pipe headspace.
C. Rock-damaged electrodes in unscreened wastewater.
D. Electrode corrosion in chlorinated water.
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Questions were developed by Steve Spicer and reviewed by the Association of Boards of Certification (Ames, Iowa) Validation and Examination Committee.
Water Environment Federation (2006). Automation of Wastewater Treatment Facilities, Third Edition; Manual of Practice No. 21. Alexandria, Va.: Water Environment Federation.