Table of Contents
How does hot wire ammeter work?
A hot-wire ammeter can measure the alternating current in a circuit by allowing a fraction of this current to flow along a platinum-iridium alloy wire. Attached to this wire is a silk thread which passes over a pulley, which is then attached to a spring which keeps it under tension.
What is hot wire instrument?
An electrical measuring instrument (basically an ammeter) in which the current to be measured is passed through a thin wire and causes its temperature to rise. The temperature rise, which is proportional to the square of the current, is measured by the expansion of the wire.
What is measured by hot wire ammeter?
Hint: Hot wire ammeter, as the name suggests, measures the value of current in a device based on the amount of heating it does. The heat it produces is measured with the help of a wire; more the heat, more the current.
What is the scale of hot wire instrument?
Exercise :: Measurements and Instrumentation – Section 3
| 14. | The scale of hot wire ammeter is |
|---|---|
| A. linear B. non-linear C. cramped D. absolute linear Answer: Option B Explanation: Since deflecting torque ∞ I2, scale is non-linear. Workspace Report errors Name : Email: View Answer Discuss |
Why are hot wire instruments used to measure AC?
The hot wire instrument is used for both the AC and DC current. Hotwire instrument works on the principle of the thermal effect, that the length of the wire increases because of the heating effect of the current flow through it.
Which of the following is measured with the help of hot wire anemometer?
A hot-wire anemometer is a thermal transducer which has been widely used to measure instantaneous flow velocity. The use of the hot-wire anemometer permits instantaneous flow velocity to be calculated from electric voltage measurements.
Why calibration of instrument is important?
Calibrating a device ensures that the instrument will properly measure within the desired range for your application. This is important because a properly calibrated measurement device will help the user to maintain his or her system.
Why the hot wire instruments are not used as a standard meter?
The following are the disadvantages of the hot-wire instrument. The Hot Wire instrument gives the slow response. The instability occurs in the instruments because of the stretching of the wire. The instrument consumes more power.
How does a hot wire anemometer measure flow?
Hot Wire Anemometer works When an electrically heated wire is placed in a flowing gas stream, heat is transferred from the wire to the gas and hence the temperature of the wire reduces, and due to this, the resistance of the wire also changes. This change in resistance of the wire becomes a measure of flow rate.
How accurate is a hot wire anemometer?
They provide ±2% of reading accuracy which is essential for applications such as cleanroom certifications, laminar flow measurements, and R & D product development.
What factors would be considered to change calibration?
Components, such as electronics, used in an instrument may be affected by changes in operating temperature. If an instrument is calibrated at one temperature and then operated at a significantly different temperature, the temperature-induced error can also degrade the results’ accuracy.
Why is it important to be able to properly calibrate and measure objects viewed through a microscope?
Microscope Calibration can help ensure that the same sample, when assessed with different microscopes, will yield the same results. Even two identical microscopes can have slightly different magnification factors when not calibrated.
How does a hot wire ammeter measure an alternating current?
In a.c. the heat produced in wire through which the current flows depends only on the magnitude and not on the direction of the current flowing. This is the reason that a hot wire ammeter measured are a.c.
Can we use hot wire instruments in DC?
Ac and dc both can be measured by hot-wire instruments. Hotwire instrument uses the heating effect of current for measuring the magnitude.
Which of the following can be measured by hot wire anemometer?
This change in resistance of the wire becomes a measure of flow rate. ∴ Hotwire anemometer is used to measure the velocity of the fluid.
What is the principle of hot wire anemometer?
Thermal (or “hot wire”) anemometers use the principle that the amount of heat removed from a heated temperature sensor by a flowing fluid can be related to that fluid’s velocity. These sensors typically use a second, unheated temperature sensor to compensate for variations in the air temperature.
What are the factors that affect the accuracy of instrument?
Factors affecting the accuracy of the Measuring System
- The basic components of an accuracy evaluation are the five elements of a measuring system such as:
- -Coefficient of thermal expansion.
- -Calibration interval.
- -Stability with time.
- -Elastic properties.
- -Geometric compatibility.
What factors could affect the accuracy of an instrument?
Variables such as temperature, humidity, pressure, gravity, elevation, vibration, stress, strain, lighting, etc. can impact the measurement result. Some tests and calibrations are more sensitive to certain environmental factors than others.
What does the deflection of hot-wire instrument depend on?
The deflection of hot-wire instrument depends on (a) rms value of the ac current. (b) rms value of the ac voltage. (c) average value of the ac current. (d) average value of the ac voltage. Answer: (a) rms value of the ac current. 55. Consider the following statements about hot-wire instruments: They read equally well on dc and/or ac circuits.
What is the principle of hot wire instrument?
It works on the principle that the length of the wire increases because of the heating effect of the current flow through it. The hot wire instrument is used for both the AC and DC current. The construction of the hot-wire instruments is shown in the figure below.
What are the disadvantages of a hot wire instrument?
The Hot Wire instrument gives the slow response. The instability occurs in the instruments because of the stretching of the wire. The instrument consumes more power. The instrument is not able to withstand under overload and mechanical shock. Because of the above mention disadvantage, the instruments are replaced by the Thermo-electric instruments.
How many wires are used in a hot wire instrument?
The hot wire instrument uses two-wire. The one wire is bonded between the two terminals. And the second terminal is bound between the first wire and the third terminal shown in the figure above.