Test instrument for determining apparent power consumption and ground faults in various portions of a distributed-load, constant voltage audio distribution system

Claim 2

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, comprising: a. a controlled output amplifier having an input for receiving an audio input signal of a frequency at which the apparent power consumption is to be tested, a control signal, input, and an output which controlled amplifier produces an output signal at the test frequency of a voltage dependent on the magnitude of the signal received at the control signal input; b. a resistance; c. means for connecting the resistance to the output of the controlled amplifier; d. means for connecting the resistance to that portion of the distributed-load, constant-voltage audio distribution system to be tested so that a test signal is applied to the portion of the system to be tested and the current that passes through the resistance is substantially equivalent to that which passes through that portion of the system to be tested; e. means for supplying a reference voltage signal having a magnitude corresponding to the voltage at which the apparent power consumption is to be determined; f. means, having inputs connected to the reference voltage supply means and the audio distribution system connection means and an output which is connected to the control signal input of the controlled amplifier, for producing an error signal at the output so that a test signal of a voltage corresponding to the voltage at which the apparent power consumption is to be determined is applied to the circuit under test at the audio distribution system connection means; g. means connectable across the resistance for producing a signal having a magnitude indicative of the amount of current passing through the resistance; and h. means connected to the current magnitude signal means for indicating the magnitude of the current passing through the resistance which indication is indicative of the apparent power consumed by the tested system.

Claim 3

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 1, wherein the reference voltage supply means comprises a resistance connectable to a power supply, having a plurality of taps which are proportional to different voltages at which the apparent power consumption is to be determined and a means for selectively connecting the taps to the error signal means so that the power consumption may be determined by using a single test instrument on systems and components of systems which operate at different voltage levels.

Claim 4

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 2, wherein the indicating means has a plurality of scales calibrated in ohms corresponding to the different voltage taps of the reference voltage supply means so that the impedance of the circuit being tested is indicated directly without the need for mathematical computations.

Claim 5

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 3, wherein the error signal means comprises a connection to the input of the controlled amplifier having an integrator to increase the sensitivity of voltage level control.

Claim 6

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 4, wherein the error signal means comprises a connection to the audio distribution connection means including an AC to DC converter.

Claim 7

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 5, wherein error signal means connection to the audio distribution connection means includes a buffer having a high input impedance to minimize the effect on the signal applied to the circuit under test.

Claim 8

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 1, wherein the current magnitude signal means comprises an AC to DC converter.

Claim 9

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 7, wherein the current magnitude signal means comprises, in addition, a buffer connected between the AC to DC converter and the resistance having a high input resistance to minimize the effect on the signal applied to the circuit under test.

Claim 10

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 8, wherein the current magnitude signal means is connected to the indication means through a summing amplifier having a first input connected to the output of the AC to DC converter, a second input for connection to a variable DC voltage supply to provide a zero signal level adjustment and comprising, in addition, a switch for selectively shorting the input to the current magnitude signal means to permit a zero signal level adjustment to be made.

Claim 11

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 9, wherein the summing amplifier has a third input for connection to a variable DC voltage supply to permit the nulling of a fixed load in the system under test so that the indication means will not include an indication of the apparent power consumed in a portion of the circuit under test which is not of interest but cannot be separated from the portion of interest.

Claim 12

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 1, wherein the controlled amplifier comprises a voltage controlled amplifier in series with a power amplifier.

Claim 13

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 11, wherein the output of the controlled amplifier is connected to the resistance through an isolation transformer.

Claim 14

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 1, comprising in addition an internal oscillator connectable to the controlled amplifier for supplying an audio frequency test signal input.

Claim 15

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 13, comprising in addition a means for connecting an external oscillator to the controlled amplifier to supply an audio frequency signal and disconnecting the internal oscillator.

Claim 16

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, as claimed in claim 1, comprising in addition a means, connected to the input of the controlled amplifier for varying the magnitude of the audio frequency input to the controlled amplifier, a monitoring circuit connected to the input of the controlled amplifier including an indicating meter to facilitate adjustment of the audio frequency input signal to a range best suited for the test instrument.

Claim 17

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, and for detecting ground faults in distributed-load constant-voltage systems as claimed in claim 15, comprising in addition a means for applying a potential between ground and the conductors of the distributed-load, constant-voltage system, including a means for connecting the indicating meter in series to indicate any leakage current which would indicate a ground fault.

Claim 18

A test instrument for determining the apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, comprising: a. a controlled output amplifier having a voltage controlled amplifier having an input for receiving an audio input signal of a frequency at which the apparent power consumption is to be tested and a control signal input; a power amplifier having its input connected to the output of the voltage controlled amplifier; and an isolation transformer having its primary connection to the output of the power amplifier so that an isolated audio frequency signal is produced at its secondary with a voltage magnitude that is dependent on the magnitude of a signal received at the control input of the voltage controlled amplifier. b. a plurality of resistances corresponding to different levels of apparent power consumption; c. means for selectively connecting the resistances between that portion of the distributed-load, constant-voltage distribution system to be tested and the secondary of the isolation transformer so that a test signal is applied to that portion under test and the current that passes through the resistance is substantially equivalent to that which passes through that portion of the system being tested; d. means for supplying a reference voltage signal having a magnitude corresponding to the voltage at which the apparent power consumption is to be determined including a resistance having a plurality of taps proportional to different voltage levels utilized in such systems to form a voltage divider; e. an error signal generator having a buffer having its input connected to the audio distribution system connection means to monitor the voltage level of the audio frequency test signal applied to that portion of the circuit being tested and to isolate it and minimize the effect of the monitoring; an RMS converter connected to the output of the buffer to generate a DC signal having a magnitude which corresponds to the magnitude of the test signal; a differential amplifier having one input connected to the output of the RMS converter and one input connected to the reference voltage supply means producing an output signal having a magnitude which corresponds to the amount by which the test signal varies from the desired voltage; and an integrator having its input connected to the output of the differential amplifier and its output connected to the control signal input of the voltage controlled amplifier to rapidly adjust the voltage level of the test signal to a desired level; f. a current signal generator having a buffer having its input connected to the connection means to monitor the current through the resistance to isolate the resistance and minimize the effect of monitoring; an RMS converter having its input connected to the output of the buffer; a first means for supplying a variable DC voltage; a second means for supplying a variable DC voltage; a summing amplifier having a first input connected to the output of the RMS-converter, a second input connected to the first DC supply means to provide a signal level adjustment, and a third input connected to the second DC supply means to provide a load nulling capability; g. an indicator connected to the output of the summing amplifier to indicate the apparent power consumed by the portion of the system under test which is directly related to the current through the resistance.

Claim 19

A test instrument for determining the apparent power consumption in various portions of a distributed-load, constant-voltage audio distribution system, comprising: a. a controlled output amplifier having a voltage controlled amplifier having an input for receiving an audio input signal of a frequency at which the apparent power consumption is to be tested and a control signal input; a power amplifier having its input connected to the output of the voltage controlled amplifier; and an isolation transformer having its primary connection to the output of the power amplifier so that an isolated audio frequency signal is produced at its secondary with a voltage magnitude that is dependent on the magnitude of a signal received at the control input of the voltage controlled amplifier. b. a plurality of resistances corresponding to different levels of apparent power consumption; c. means for selectively connecting the resistances between that portion of the distributed-load, constant-voltage distribution system to be tested and the secondary of the isolation transformer so that a test signal is applied to that portion under test and the current that passes through the resistance is substantially equivalent to that which passes through that portion of the system being tested; d. means for supplying a reference voltage signal having a magnitude corresponding to the voltage at which the apparent power consumption is to be determined including a resistance having a plurality of taps proportional to different voltage levels utilized in such systems to form a voltage divider; e. an error signal generator having a buffer having its input connected to the audio distribution system connection means to monitor the voltage level of the audio frequency test signal applied to that portion of the circuit being tested and to isolate it and minimize the effect of the monitoring; an RMS converter connected to the output of the buffer to generate a DC signal having a magnitude which corresponds to the magnitude of the test signal; a differential amplifier having one input connected to the output of the RMS converter and one input connected to the reference voltage supply means producing an output signal having a magnitude which corresponds to the amount by which the test signal varies from the desired voltage; and an integrator having its input connected to the output of the differential amplifier and its output connected to the control signal input of the voltage controlled amplifier to rapidly adjust the voltage level of the test signal to a desired level; f. a current signal generator having a buffer having its input connected to the connection means to monitor the current through the resistance to isolate the resistance and minimize the effect of monitoring; an RMS converter having its input connected to the output of the buffer; a first means for supplying a variable DC voltage; a second means for supplying a variable DC voltage; a summing amplifier having a first input connected to the output of the RMS-converter, a second input connected to the first DC supply means to provide a signal level adjustment, and a third input connected to the second DC supply means to provide a load nulling capability; g. an indicator connected to the output of the summing amplifier to indicate the apparent power consumed by the portion of the system under test which is directly related to the current through the resistance.

Claim 20

A test instrument for determining apparent power consumption in various portions of a distributed-load, constant-voltage distribution audio distribution system and for detecting ground faults in distributed-load, constant-voltage systems, as claimed in claim 17, comprising, in addition, an internal oscillator connectable to the controlled amplifier for supplying an audio frequency, means for connecting an external oscillator to the controlled amplifier and disconnecting the internal oscillator; a monitoring circuit connected to the input of the controlled amplifier including a meter to indicate the level of the oscillator signal; means for applying a potential between ground and the conductors of the distributed-load, constant-voltage system, including a switch for connecting the meter in series to indicate any leakage current which would indicate a ground fault.