(this change in resistance becomes a measure of flow rate).ĭue to this, the galvanometer which was initially at zero position deflects and this deflection of the galvanometer becomes a measure of flow rate of the gas when calibrated. That is, the voltage across the bridge circuit is kept constant, that is, not varied.ĭue to the gas flow, heat transfer takes place from the sensing wire to the flowing gas and hence the temperature of the sensing wire reduces causing a change in the resistance of the sensing wire. Hot Wire Anemometer GM8903 Hot Wire Anemometer possesses the following features: 1.Measurement of wind velocity, temperature and flow 2.

This thesis presents a hot-wire anemometer suitable. It is shown that this instrument is inherently. Hot-wire anemometry has been routinely employed for laboratory measurements of turbulence for decades. As the electrical resistance of most metals is dependent upon the temperature of the metal ( tungsten is a popular choice for hot-wires), a relationship can be obtained.

Air flowing past the wire cools the wire. The anemometer is kept in the flowing gas stream to measure flow rate.Ī constant current is passed through the sensing wire. The performance of a constant-temperature normal hotwire in a supersonic flow is critically examined. Hot wire anemometers use a fine wire (on the order of several micrometres) electrically heated to some temperature above the ambient. The bridge arrangement along with the anemometer has been shown in diagram. There are two methods of measuring flow rate using a anemometer bridge combination namely:Ĭonstant current method Hot wire Anemometer In addition, they are fragile and can be easily damaged. Hot-wire anemometers are very accurate, but they can be affected by the temperature of the air. They work by heating a wire and measuring the change in temperature of the air as it flows past the wire. Leads are taken from the conducting wires and they are connected to one of the limbs of the wheat stone bridge to enable the measurement of change in resistance of the wire. Hot-wire Hot-wire anemometers are the most common type.

Conducting wires placed in a ceramic body.The main parts of the arrangement are as follows: This change in resistance of the wire becomes a measure of flow rate. 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. 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.

Anemometer hot wire