CT1/CT2 Current Probes

The CT1 and CT2 Current Probes are designed for permanent or semi-permanent in-circuit installation. Each probe consists of a current transformer and an interconnecting cable. The current transformers have a small hole through which a current carrying conductor is passed during circuit assembly.

The P6041 Probe Cable provides the connection between the CT1 and CT2 Current Transformers and a BNC oscilloscope input. A 50 Ω termination is required to terminate the cable when connected to a high-impedance (1 MΩ) oscilloscope input. One probe cable can be used to monitor several current transformers that have been wired into a circuit.

Miniature Construction

The CT1 and CT2 detachable cable design enables one or more probes to be located on circuit boards or in other limited space areas.

The CT6 offers the smallest form factor available, for measurement on ever-shrinking circuit boards and components. It is designed for temporary installation and does not incorporate removable cables, as the CT1 and CT2 do.

Extendible Probe Length

Specified rise time and bandwidth are obtained when using the probe cables provided: The P6041 cable used with the CT1 and CT2 is 42 inches nominal. If additional length is required, the cables can be extended by using high-quality 50 Ω cable and suitable interface connectors. (Also see Special Probe Cables, Optional Accessories.) Long cables may degrade high-frequency response.

High Sensitivity

The CT1 and CT6 provide an output of 5 mV for each milliamp of input current when terminated in 50 Ω. The CT2 provides 1 mV per milliamp when terminated in 50 Ω.

Typical Systems

The CT1, CT2, and CT6 high-frequency current transformers are dynamic (i.e., non-DC) current measuring devices. They are typically used in conjunction with compatible high-bandwidth oscilloscopes and other instruments to observe and/or record high-frequency current waveforms. The CT1, CT2, and CT6 normally operate directly into 50 Ω scopes and other measuring device inputs.

The CT1 or CT2 can be used with 1 MΩ input systems; use the P6041 probe cable and terminate the output with a 50 Ω feed-through termination (see Optional Accessories).

In all cases, the CT1, CT2, and CT6 must work into 50 Ωs to obtain specified performance and sensitivity.

Typical Measurement Applications

Differential Current Measurements

Most true-differential voltage amplifiers have a maximum bandwidth of about 100 MHz. The CT1 or CT6 can make differential current measurements to 1 GHz and 2 GHz, respectively, by passing two wires carrying opposing currents through the same core. The displayed result is the difference current. The CT2 can perform the same function to 200 MHz.

In all cases, Derating with Frequency and Amp-second Product (Current-time Product) guidelines should not be exceeded. (See Characteristics.)

Single-shot and Low Rep-rate Pulse Measurements

These common measurements are easy to make with the CT1, CT2, or CT6 provided that your signal fits within the Max Pulse Current and Amp-second Product (Current-time Product) guidelines for the specific current probe characteristics.

For example, the CT2 is rated at 36 A peak, with an Amp-second Product of 50 × 10^-6 seconds (50 Amp-microseconds), therefore the CT2 can safely handle a 36 A peak pulse with a maximum width of 1.39 microseconds or lower amplitude pulses for longer pulse widths. The CT1, CT2, and CT6 all have low-frequency roll-off characteristics. Low-frequency "droop" will exhibit itself when the pulse width approaches the L/R time constant of the specific transformer.

Propagation Delay Measurements

Two CT1 or CT2 Current Transformers with matching probe cables can be used to measure propagation delay (transit time) between the input and output currents of high-frequency devices. The probe outputs are connected to the inputs of dual-channel real-time or sampling scopes.

Verification of any Probe/Cable/Scope System mismatch can be obtained by passing the same signal current through both probes and observing total system delay difference, if any.