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821-A: Difference between revisions
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The {{Title|General Radio 821-A Twin-T Impedance Measuring Circuit}} were introduced in {{Catalog K2}} and remained available through {{Catalog O}}. | The {{Title|General Radio 821-A Twin-T Impedance Measuring Circuit}} were introduced in {{Catalog K2}} and remained available through {{Catalog O}}. | ||
The Type 821-A is an impedance measuring device operating between 460 kHz and 40 Mhz. Measurements are made using the Parallel-T null circuit and the parallel substitution method. Its calibrated in capacitance and conductance. Just some of the applications are the measurement of capacitance and dissipation factor of capacitors, and the inductance and Q of coils. The 821-A requires a generator and detector to accomplish a null. An oscillator of sufficient output at the frequency of interest, the Type [[1330-A]] Bridge Oscillator is the recommended generator. A communications type radio receiver equipped with a BFO and RF gain control makes a suitable detector. A well shielded cable with a coaxial connection to the receiver is highly recommended. | The Type 821-A is an impedance measuring device operating between 460 kHz and 40 Mhz. Measurements are made using the Parallel-T null circuit and the parallel substitution method. Its calibrated in capacitance and conductance. Just some of the applications are the measurement of capacitance and dissipation factor of capacitors, and the inductance and Q of coils. It is best suited for measuring high impedances in contrast to its contemporary the [[916-A]] RF bridge more suited for lower impedance measurements. The 821-A requires a generator and detector to accomplish a null. An oscillator of sufficient output at the frequency of interest, the Type [[1330-A]] Bridge Oscillator is the recommended generator. A communications type radio receiver equipped with a BFO and RF gain control makes a suitable detector. A well shielded cable with a coaxial connection to the receiver is highly recommended. | ||
The Type 821-A is direct reading instrument for capacitance and conductance, some math is required to obtain other impedances. | The Type 821-A is direct reading instrument for capacitance and conductance, some math is required to obtain other impedances. | ||