In the design and debugging of switching power supplies, power electronics and high-speed digital systems, engineers have always faced a core challenge:How to accurately and reliably measure high-frequency, high-intensity current signals without affecting the circuit under test? Traditional current probes often have compromises in bandwidth, accuracy or usability.The TCP312A current probe paired with the TCPA300 amplifier forms a measurement system that features 300 MHz bandwidth, a wide dynamic range from 5 mA to 30 A, and excellent DC accuracy, it delivers impeccable current measurement performance and has become the industry benchmark for high-frequency power measurement.

1. Core Principle: Perfect Integration of Hall Effect and Transformer Technology

The TCP312A is not a simple current transformer. It adopts Hybrid Technology, which combines the advantages of AC Transformer and DC Hall-Effect Sensor, enabling accurate measurement from DC to high frequency.

1. AC Path (Transformer):

• High-frequency alternating current passes through the magnetic core and generates a signal based on the electromagnetic induction principle.

• Advantages: Provides extremely high bandwidth (up to 300 MHz) and excellent high-frequency response.

2. DC Path (Hall Effect):

• The Hall sensor detects the static (DC) magnetic field strength in the core to measure DC or extremely low-frequency current.

• Advantages: Solves the fundamental problem that traditional transformers cannot measure DC current.

3. Signal Combination (TCPA300 Amplifier):

• The TCPA300 amplifier accurately conditions and combines AC and DC signals, and finally outputs a composite voltage signal that truly reflects the DC and AC components of the current (unit: 1 V/A or 0.1 V/A) to the oscilloscope.

II. Detailed Features and Specifications (Defining Professional-level Performance)

TCP312A Probe Head Specifications

TCPA300 Amplifier Unit Specifications

3. Key Notes (To ensure measurement accuracy and equipment safety)

1. Degauss is the premise of measurement accuracy:

• Reason: Residual magnetism in the core will introduce serious DC measurement error.

• Requirement: Before each measurement, after changing the range, or when you suspect incorrect accuracy, degaussing must be performed. Close the probe jaws (do NOT clamp any conductor), press the  DEGAUSS button on the TCPA300 until the process is completed.

• Taboo: Degaussing with the conductor clamped or with high current passing through will damage the probe.

2. Avoid Core Saturation:

• Cause: Exceeding the rated current of the probe will saturate the core, leading to clipped waveform distortion and permanent degradation of accuracy.

• Operation: Always refer to the derating curve. For DC or low-frequency current, never exceed the continuous current limit of ±30 A DC or 15 ARMS.

3. Correct Connection and Matching:

• Use a high-quality coaxial cable (such as the provided RG-174) to connect the amplifier to the oscilloscope.

• Set the oscilloscope channel impedance to 50 Ω to match the output impedance of TCPA300, otherwise amplitude error and ringing will occur.

4. Environmental Interference Management:

• Current probes are sensitive to external magnetic fields. Keep away from interference sources such as power transformers and fans as much as possible.

• Keep the probe jaw clean and prevent metal debris from affecting core closure.

5. Calibration and Maintenance:

• Regular calibration (annual) is recommended to ensure measurement accuracy.

• Open and close the jaw gently to avoid mechanical shock.

IV. Core Application Fields

1. Switching Mode Power Supply (SMPS) Testing:

• Application Scenario: Measure switching current waveform of MOSFET/IGBT, diode reverse recovery current, inductor current ripple, and transformer magnetizing current.

• Value: Analyze switching losses, verify loop stability, evaluate magnetic component saturation, and diagnose overcurrent events.

2. Power Device Characteristic Analysis:

• Application Scenario: Cooperate with curve tracers or oscilloscopes to measure dynamic switching characteristics (such as Id-Vds curves) of SiC/GaN devices.

• Value: Accurately evaluate the turn-on/turn-off time, Miller plateau and short-circuit withstand capability of devices.

3. Power Integrity for High-Speed Digital Systems:

• Application: Measure transient operating current, power consumption curve and simultaneous switching noise (SSN) of CPU, FPGA and ASIC.

• Value: Optimize decoupling capacitor design, verify power rail dynamic response and conduct power consumption analysis.

4. Inverter and Motor Drive:

• Application: Measure three-phase output current and IGBT arm current.

• Value: Analyze modulation waveform quality, calculate output power and diagnose shoot-through fault of upper and lower tubes.

5. Circuit Protection and Fault Analysis:

• Application: Capture large transient current when fuse blows, circuit breaker trips, or surge suppressor activates.

• Value: Analyze fault current amplitude and duration to optimize protection circuit design.

V. Standard Operation Procedure (Four Steps for Accurate Measurement)

Step 1: System Connection and Setup

1. Connect TCP312A to the interface of TCPA300.

2. Connect the OUTPUT port of TCPA300 to a channel of the oscilloscope with a 50 Ω BNC cable.

3. Power on the TCPA300.

4. Set the impedance of the corresponding oscilloscope channel to 50 Ω, and set the vertical unit to Ampere (A) (depending on the selected sensitivity, 1V = 1A or 0.1V = 1A).

Step 2: Degaussing and Zeroing

1. Ensure the probe jaws are completely closed and no conductor is inside.

2. Press and hold the DEGAUSS button on the front of the TCPA300 until the progress bar completes or the indicator light goes out.

3. Observe the baseline on the oscilloscope screen, fine-tune the DC OFFSET knob on the amplifier to accurately adjust the baseline to zero position.

Step 3: Connect the circuit under test and perform measurement

1. Press the trigger on the back of the probe to open the magnetic core clamp.

2. Clamp the probe onto the wire that carries the current to be measured (clamp only one wire at a time to avoid magnetic field cancellation).

3. Based on the magnitude and frequency of the current under test, select the appropriate sensitivity on the TCPA300 (1 V/A for low current, 0.1 V/A for high current).

4. Set appropriate time base and vertical scale on the oscilloscope, and trigger to capture the waveform.

Step 4: Reading and Analysis

1. Read parameters including amplitude, rise time, frequency of the waveform directly.

2. Use the mathematical operation function of the oscilloscope to perform multiplication of current and voltage (P = V * I) to directly measure power.

3. Use the integration function to calculate the charge quantity (Q = ∫Idt).

Why choose the TCP312A + TCPA300 system?

• Unmatched Bandwidth: 300 MHz bandwidth is sufficient to handle the most demanding high-speed switching measurements.

• True DC Accuracy: Hall effect technology guarantees measurement accuracy for DC and low-frequency signals, which cannot be achieved by AC current transformers.

• Wide Dynamic Range: From 5 mA to 30 A, it can capture faint current ripples and withstand large operating currents.

• Excellent Usability: One-button demagnetization, DC bias adjustment, dual-range sensitivity make high-precision measurement simple and reliable.

• Tektronix Quality and Reliability: Industrial-grade design for long-lasting durability, measurement results are trustworthy.