Abstract: A time shifting signal acquisition probe system has a signal acquisition probe having a memory containing a time delay constant representative of the propagation time delay of an electrical signal passing through the signal acquisition probe. A measurement test instrument receives the electrical signal from the signal acquisition probe and generating digital samples of the electrical signal in an acquisition system in response to a trigger signal and producing a waveform record. A communications bus coupled between the signal acquisition probe and the measurement test instrument couples the signal acquisition probe time delay constant from the signal acquisition probe to the measurement test instrument wherein processing circuitry in the measurement test instrument time shifts the waveform record of the electrical signal relative to the trigger signal by the amount of the signal acquisition probe time delay constant.

Abstract: A time shifting signal acquisition probe system has a signal acquisition probe having a memory containing a time delay constant representative of the propagation time delay of an electrical signal passing through the signal acquisition probe. A measurement test instrument receives the electrical signal from the signal acquisition probe and generating digital samples of the electrical signal in an acquisition system in response to a trigger signal and producing a waveform record. A communications bus coupled between the signal acquisition probe and the measurement test instrument couples the signal acquisition probe time delay constant from the signal acquisition probe to the measurement test instrument wherein processing circuitry in the measurement test instrument time shifts the waveform record of the electrical signal relative to the trigger signal by the amount of the signal acquisition probe time delay constant.

Abstract: An input by-pass circuit for a current probe has first and second switches coupled between current probe inputs and current sensing circuit inputs. A switch control is coupled to the switching circuit for selectively coupling and decoupling the current probe inputs to the current sensing circuit such that the current signal continuously flows in the device under test.

Abstract: A current sensing circuit has a transformer where a current to be measured induces a magnetic flux into a magnetic core. The magnetic core has a magneto-electric converter for sensing DC to low frequency current signals and a secondary winding for sensing higher frequency current signals. The magneto-electric converter generates an output that is coupled via an amplifier to a non-inverting input of a transimpedance amplifier. The inverting input of the transimpedance amplifier is coupled to the secondary winding of the transformer. A current signal path having a transimpedance resistor couples the inverting input to the output of the transimpedance amplifier. The transimpedance amplifier functions as a power amplifier for coupling a nulling current to the transformer for DC to low frequency current signals and functions as a transimpedance gain amplifier for higher frequency signals.

Abstract: A communications bus management circuit for a current probe system detects the connection of the current probe system to an instrument and the connection of a current probe to a current probe amplifier of the system. A controller generates a probe enable signal in the presence of the detected connection to the instrument that is coupled to a switching circuit. Switch elements couple the communications bus of the instrument to the communications bus of the current probe amplifier in the presence of the probe enable signal. The controller further generates a current probe present signal in the presence of the detected current probe that is also coupled to the switching element. A further switch element couples the data line of the instrument to ground via a resistive element in the presence of the current probe present signal and floats the data line when the current probe present signal is absent.

Abstract: A current probing system has a current probe and a detachable adapter. The current probe has a probe body with electrically conductive contacts that mate with electrically conductive contacts on the adapter. Leads extend from the adapter for coupling to a current carrying conductor. The leads can connect to a plug that is coupled to a current diverting device for coupling a current signal to the current probe. The adapter may also include a switch that selectively couples the current signal to the current probe when the adapter is mated with the current probe. The contacts of the current probe are coupled to a current sensing circuit which generates a voltage output representative of the current signal. The voltage output is coupled to an oscilloscope via an electrical cable.

Abstract: An output termination auto detection circuit includes a reference resistance having one side coupled to a known input voltage and selectively coupled into a signal line of an input device. The other side of the reference resistance is coupled to an output terminal of the input device which is coupled to the input of a host instrument. The host instrument has an input resistance termination that functions as the output termination of the input device. A detection device is coupled to a common mode between the reference resistance and the input resistance of the host instrument for measuring the voltage at the node. Knowing the reference resistance, the input voltage and the output voltage at the node, the output termination of the input device (i.e. the input termination of the host instrument) can be determined and a indication of an improperly terminated input device may be provided to a user.

Abstract: A constant input impedance AC coupling circuit for a current probe measurement system has a resistive-capacitive network that includes a capacitor for coupling the current output signal of a current measurement probe to the low input impedance measurement instrument and the resistive terminating element disposed in the measurement instrument. The resistive-inductive network includes a resistor and a synthesized inductor having a high inductive value, large current carrying capacity and an L/R time constant equal to the RC time constant of the resistive capacitive network. The resistive-inductive network is coupled to the resistive-capacitive network and receives the current output signal from the current measurement probe for terminating DC and low frequency signal components of the current output signal below the low frequency cutoff of the resistive-capacitive network in the same low input impedance of the measurement instrument.

Abstract: A current probe transformer temperature monitoring method determines an initial transformer temperature of the current probe as a function of the winding resistance of the transformer. A relative temperature of the Hall Effect device is also determined as a function of resistance change of the Hall Effect device. The initial transformer temperature and the relative Hall Effect device temperature are combined to produce a continuous transformer temperature indicative of the temperature of the transformer. The current signal to the multi-turn winding is removed when the continuous transformer temperature exceeds a threshold temperature value and a visual indication may be provided.

Abstract: A communications bus management circuit for a current probe system detects the connection of the current probe system to an instrument and the connection of a current probe to a current probe amplifier of the system. A controller generates a probe enable signal in the presence of the detected connection to the instrument that is coupled to a switching circuit. Switch elements couple the communications bus of the instrument to the communications bus of the current probe amplifier in the presence of the probe enable signal. The controller further generates a current probe present signal in the presence of the detected current probe that is also coupled to the switching element. A further switch element couples the data line of the instrument to ground via a resistive element in the presence of the current probe present signal and floats the data line when the current probe present signal is absent.

Abstract: A current probe transformer temperature monitoring method determines an initial transformer temperature of the current probe as a function of the winding resistance of the transformer. A relative temperature of the Hall Effect device is also determined as a function of resistance change of the Hall Effect device. The initial transformer temperature and the relative Hall Effect device temperature are combined to produce a continuous transformer temperature indicative of the temperature of the transformer. The current signal to the multi-turn winding is removed when the continuous transformer temperature exceeds a threshold temperature value and a visual indication may be provided.

Abstract: A constant input impedance AC coupling circuit for a current probe measurement system has a resistive-capacitive network that includes a capacitor for coupling the current output signal of a current measurement probe to the low input impedance measurement instrument and the resistive terminating element disposed in the measurement instrument. The resistive-inductive network includes a resistor and a synthesized inductor having a high inductive value, large current carrying capacity and an L/R time constant equal to the RC time constant of the resistive capacitive network. The resistive-inductive network is coupled to the resistive-capacitive network and receives the current output signal from the current measurement probe for terminating DC and low frequency signal components of the current output signal below the low frequency cutoff of the resistive-capacitive network in the same low input impedance of the measurement instrument.

Abstract: An output termination auto detection circuit includes a reference resistance having one side coupled to a known input voltage and selectively coupled into a signal line of an input device. The other side of the reference resistance is coupled to an output terminal of the input device which is coupled to the input of a host instrument. The host instrument has an input resistance termination that functions as the output termination of the input device. A detection device is coupled to a common mode between the reference resistance and the input resistance of the host instrument for measuring the voltage at the node. Knowing the reference resistance, the input voltage and the output voltage at the node, the output termination of the input device (i.e. the input termination of the host instrument) can be determined and a indication of an improperly terminated input device may be provided to a user.