Dynamometer

The wattmeter is an electrodynamic instrument for meter the electric military unit or the put up rate of electric energy of either(prenominal) given roofy. The device consists of a brace of fixed spin arounds, cognize as present-day(prenominal) bowls, and a movable roll known as the potential loop. The authorized spin arounds ar connected in serial with the rope, dapple the potential coil is connected in parallel. Also, on analog wattmeters, the potential coil carries a needle that moves over a scale to indicate the measurement.A catamenia f paltrying with the accepted coil generates an electro attractivenessic field around the coil. The speciality of this field is proportionate to the line live and in phase with it. The potential coil has, as a general rule, a high-value resistor connected in series with it to reduce the current that flows through it. The pass on of this arrangement is that on a dc circuit, the deflection of the needle is comparative to twain the current and the potency, thus conforming to the compare W=VA or P=EI.On an ac circuit the deflection is proportional to the average instantaneous product of voltage and current, thus amount true power, and mayhap (dep quiting on shipment characteristics) showing a different reading to that obtained by scarce multiplying the readings showing on a stand-alone voltmeter and a stand-alone ammeter in the akin circuit. The two circuits of a wattmeter are believably to be damaged by uppity current.The ammeter and voltmeter are both(prenominal) vulnerable to heat in case of an overload, their pointers will be driven off scale still in the wattmeter, either or point both the current and potential circuits open fire overheat without the pointer approaching the end of the scale This is because the position of the pointer depends on the power compute, voltage and current. Thus, a circuit with a low power factor will give a low reading on the wattmeter, even when both o f its circuits are loaded to the maximum prophylactic limit.Therefore, a wattmeter is rated not only in watts, but also in volts and amperes. Retrieved from http//en. wikipedia. org/wiki/Wattmeter (A ergometer consists of an denseness (or absorber/driver) unit, and usually includes a agency for metre torsion and rotational velocity. An tightness unit consists of some type of rotor coil in a caparison. The rotor is twin to the engine or other equipment to a lower place test and is free to rotate at whatever speed is required for the test.some(a) means is provided to develop a braking tortuousness between dynamometers rotor and ho development. The means for develop tortuosity support be frictional, hydraulic, electromagnetic etc. according to the type of absorption/driver unit. One means for measuring crookedness is to mount the dynamometer caparison so that is free to turn buy food that it is restrained by a tortuousness arm. The housing butt joint be make free to rotate by using trunnions connected to each end of the housing to support the dyno in pedestal mount trunnion bearings.The crookedness arm is connected to the dyno housing and a weighing scales is positioned so that it measures the push back exerted by the dyno housing in attempting to rotate. The torque is the force indicated by the scales multiplied by the length of the torque arm mensural from the center of the dynamometer. A load mobile phone transducer hatful be substituted for the scales in lay out to provide an galvanizing signal that is proportional to torque. Another means for measuring torque is to connect the engine to the dynamometer through a torque sensing unification or torque transducer.A torque transducer provides an electrical signal that is proportional to torque. With electrical absorption units, it is possible to determine torque by measuring the current careworn (or generated) by the absorber/driver. This is in general a little accurate method, but i t may be adequate for some purposes. A broad variety of tachometers are available for measuring speed. Some types can provide an electrical signal that is proportional to speed. When torque and speed signals are available, test info can be transmitted to a data acquisition system rather than cosmos recorded manually.Speed and torque signals can also be recorded by a chart recorder or plotter. ) Power in an electric circuit is the product (multiplication) of voltage and current, so any meter intentional to measure power must account for both of these variables. A special meter accomplishment designed especially for power measurement is called the dynamometer movement, and is similar to a DArsonval or Weston movement in that a lightweight coil of electrify is attached to the pointer mechanism.However, distant the DArsonval or Weston movement, another (stationary) coil is employ instead of a permanent magnet to provide the magnetic field for the despicable coil to react agains t. The woful coil is generally energized by the voltage in the circuit, while the stationary coil is generally energized by the current in the circuit. A dynamometer movement connected in a circuit looks something like this pic The overtake (horizontal) coil of wire measures load current while the bottom (vertical) coil measures load voltage.Just like the lightweight moving coils of voltmeter movements, the (moving) voltage coil of a dynamometer is typically connected in series with a range resistor so that full load voltage is not applied to it. Likewise, the (stationary) current coil of a dynamometer may have preciseness bypass resistors to divide the load current around it. With custom-built dynamometer movements, shunt resistors are less likely to be needed because the stationary coil can be constructed with as heavy of wire as needed without impacting meter response, impertinent the moving coil which must be constructed of lightweight wire for minimum inertia.