Instrumentation Technician MCQ All valves cause some degree of flow loss due to friction even in the full-open position. Which type of valve causes the greatest reduction in flow even when the valve is open? a. globe b. gate c. plug valve d. swing check valve Ans. A (globe) Which one of the following is the correct instrument required to measure a low magnitude high frequency current? a. induction b. thermocouple c. moving iron d. dynamometer Ans. B (thermocouple) Which procedure will correct the occasional discharge from a reduced pressure principle backflow preventer when the water pressure fluctuates? a. Install a swing check valve downstream of the RP. b. Install a swing check valve upstream of the RP. c. Put in a stronger check valve spring upstream of the RP. d. Restrict the water flow to the RP by using a globe valve. Ans. B (Install a swing check valve upstream of the RP.) What will need to be done on a level control system using a capacitance probe as the sensor, if the proc

  Structure of measurement systems   The measurement system consists of several elements or blocks. It is possible to identify four types of element, although in a given system one type of element may be missing or may occur more than once. The four types are shown in Figure and can be defined as follows. General structure of measurement system Sensing element This is in contact with the process and gives an output which depends in some way on the variable to be measured. Examples are: Thermocouple where millivolt e.m.f. depends on temperature Strain gauge where resistance depends on mechanical strain Orifice plate where pressure drop depends on flow rate. If there is more than one sensing element in a system, the element in contact with the process is termed the primary sensing element, the others secondary sensing elements. Signal conditioning element This takes the output of the sensing element and converts it into a form more suitable for further processing, usually a d.c. voltage,

  Vortex Flow Meter Vortex flow meters utilize a bluff body or cylinder mounted in a pipe spool that creates alternating vortices behind the cylinder. The frequency of the alternating vortex is proportional to the fluid velocity. Vortex flow meters have no moving parts to maintain or repair, and the signal is read electronically and simply converted to a flow rate. Vortex meters work well with most clean fluids and have similar application ranges to DP flow meters. Working Principle of Vortex Flow Meter Vortex flow meters utilize a bluff body or cylinder mounted in a pipe spool that creates alternating vortices behind the cylinder. The frequency of the alternating vortex is proportional to the fluid velocity. Vortex flow meters have no moving parts to maintain or repair, and the signal is read electronically and simply converted to a flow rate. Vortex meters work well with most clean fluids and have similar application ranges to DP flow meters. Vortex flow meters are also referred to

  Humidity, Soil Moisture & Rain Sensor   Humidity Sensor A humidity sensor is an electronic device that measures the humidity in its environment and converts its findings into a corresponding electrical signal.Relative humidity is calculated by comparing the live humidity reading at a given temperature to the maximum amount of humidity for air at the same temperature.  Introduction  Humidity Sensors are the low cost-sensitive electronic devices used to measure the humidity of the air. These are also known as Hygrometers. Humidity can be measured as Relative humidity, Absolute humidity, and Specific humidity. Based on the type of humidity measured by sensor, these are classified as Relative Humidity sensor and Absolute Humidity sensor. Based on the parameters used to measure humidity, these sensors are also classified as Capacitive Humidity Sensor, Resistive Humidity Sensor, and Thermal Conductivity Humidity Sensor. Some of the parameters to consider while choosing these sensors a

  Rain Sensor What is a Rain Sensor? A rain sensor is one kind of switching device which is used to detect the rainfall. It works like a switch and the working principle of this sensor is, whenever there is rain, the switch will be normally closed. Rain Sensor Module The rain sensor module/board is shown below. Basically, this board includes nickel coated lines and it works on the resistance principle. This sensor module permits to gauge moisture through analog output pins & it gives a digital output while moisture threshold surpasses.  This module is similar to the LM393 IC because it includes the electronic module as well as a PCB. Here PCB is used to collect the raindrops. When the rain falls on the board, then it creates a parallel resistance path to calculate through the operational amplifier. This sensor is a resistive dipole, and based on the moisture only it shows the resistance. For example, it shows more resistance when it is dry and shows less resistance when it is wet.

  Soil Moisture Sensor What is a Soil Moisture Sensor? The soil moisture sensor is one kind of sensor used to gauge the volumetric content of water within the soil. As the straight gravimetric dimension of soil moisture needs eliminating, drying, as well as sample weighting. These sensors measure the volumetric water content not directly with the help of some other rules of soil like dielectric constant, electrical resistance, otherwise interaction with neutrons, and replacement of the moisture content. The relation among the calculated property as well as moisture of soil should be adjusted & may change based on ecological factors like temperature, type of soil, otherwise electric conductivity. The microwave emission which is reflected can be influenced by the moisture of soil as well as mainly used in agriculture and remote sensing within hydrology. These sensors normally used to check volumetric water content, and another group of sensors calculates a new property of moisture wi

  Humidity Sensor A humidity sensor is an electronic device that measures the humidity in its environment and converts its findings into a corresponding electrical signal.Relative humidity is calculated by comparing the live humidity reading at a given temperature to the maximum amount of humidity for air at the same temperature.  Introduction  Humidity Sensors are the low cost-sensitive electronic devices used to measure the humidity of the air. These are also known as Hygrometers. Humidity can be measured as Relative humidity, Absolute humidity, and Specific humidity. Based on the type of humidity measured by sensor, these are classified as Relative Humidity sensor and Absolute Humidity sensor. Based on the parameters used to measure humidity, these sensors are also classified as Capacitive Humidity Sensor, Resistive Humidity Sensor, and Thermal Conductivity Humidity Sensor. Some of the parameters to consider while choosing these sensors are the Accuracy, Linearity, Reliability, Repe

  MQ-135 Gas Sensor The MQ-135 gas sensor senses gases like ammonia nitrogen, oxygen, alcohols, aromatic compounds, sulfide, and smoke. The boost converter of the chip MQ-3 gas sensor is PT1301. The operating voltage of this gas sensor is from 2.5V to 5.0V. The MQ-3 gas sensor has a lower conductivity to clean the air as a gas sensing material. In the atmosphere, we can find polluting gases, but the conductivity of the gas sensor increases as the concentration of polluting gas increases. MQ-135 gas sensor can be implemented to detect the smoke, benzene, steam, and other harmful gases. It has the potential to detect different harmful gases. The MQ-135 gas sensor is a low cost to purchase. The basic image of the MQ-135 sensor is shown in the below figure. Basic Pin Configuration Of Alcohol Sensor The MQ-3 alcohol gas sensor consists of a total 6-pins including A, H, B, and the other three pins are A, H, B out of the total 6-pins we use only 4 pins. The two pins A, H are used for the heat

  Alcohol Sensor What is an Alcohol Sensor? An alcohol sensor detects the attentiveness of alcohol gas in the air and an analog voltage is an output reading. The sensor can activate at temperatures ranging from -10 to 50° C with a power supply is less than 150 Ma to 5V. The sensing range is from 0.04 mg/L to 4 mg/L, which is suitable for breathalyzers. MQ3 Alcohol Sensor MQ3 is one of the most commonly used sensors in the MQ sensor series. It is a Metal Oxide Semiconductor (MOS) type of sensor. Metal oxide sensors are also known as Chemiresistors, because sensing is based on the change of resistance of the sensing material when exposed to alcohol. So by placing it in a simple voltage divider network, alcohol concentrations can be detected. MQ3 alcohol sensor works on 5V DC and draws around 800mW. It can detect Alcohol concentrations anywhere from 25 to 500 ppm. Complete Specifications Operating voltage : 5V Load resistance : 200 KΩ  Heater resistance : 33Ω ± 5% Heating consumption : &l

  Smoke Detector A smoke detector is a device that senses smoke, typically as an indicator of fire. Smoke detector consists of two parts: A sensor to sense the smoke Electronic horn to horn the people Two basic types of smoke detectors are used today: ionization and photoelectric. The sensing chambers of these detectors use different principles of operation to sense the visible or invisible particles of combustion given off in developing fires. Types Of Smoke Detector Ionization Smoke Detector Photoelectric Smoke Detector Ionization Smoke Detector The ionization smoke detector is widely used. Its capability to detect smoke originating from fire is best utilized for clean-burning fires that produce small particles during combustion. The ionization smoke detector consists of an alpha particle producing a radioactive source (americium-241), a smoke chamber, and charged detector plates. The alpha source causes the air within the smoke chamber to become ionized and conductive As smoke parti