Description: Measuring a low value 2mOhm resistor The measurement of low impedances can be difficult due to the limitations of various measurement techniques. The two-port shunt-thru method allows the measurement of ultra-low (uohms to ohms) impedance values. Limitations introduced due to the resistances of the ground braids of the two cables being in parallel with each other and in series with the DUT can be remedied by using a J2102A common mode transformer or the J2113A Differential Amplifier. This is the test setup for the measurement of most types of passive components.

2m Ohm Resistor

Ferrite Bead

Description: Measuring Components Using the E5061B GP Ports (Low Frequency)

Connect the J2160A to the three GP Ports on the E5061B. This configures the ports for the 2-Port Shunt-Through measurement. Using cables and a shorting barrel, perform a THRU calibration as shown in the Calibration Test Setup page. Remove the barrel and connect the cables to your component.

J2102A/J2113A Sidebar Note:
The E5061B GP (LF) Ports are configured with a floating ground. Therefore, they do not need the J2102A/J2113A to break a ground loop as the ground loop does not exist.It DOES exist in the higher frequency Port 1 and Port 2 E5061B ports and either a J2102A or J2113A is needed in that case.

10 milli-ohm Resistor Measurement:

Description: Measuring the in-circuit output impedance
If the output of the device is loaded by the 50ohm connections, connect DC Blocks to one or both ports and perform the Calibration. You can make the connection to the circuit using soldered coax a cable, micro-coax connections, or most easily with the Picotest PDN probes. Shown below is the Picotest 2-Port Probe. With its forked tip and flexible ground lead browsing multiple board connections is easy. You can also setup use two Picotest 1-Port probes which give you a bit more flexibility with connection pitch.

2-Port Shunt-Through - Circuit Probing Using the 2-Port PDN Probe

Transient Load Step Measurement:
It should be noted that performing transient load step testing is particularly convenient with the Picotest 2-Port probe.One lead can go to a load stepper, like the Picotest J2111A (100mA) or J2112A (1A) and the other lead can connect directly to the 50 ohm port of your oscilloscope to measure the voltage response.You can then browse the regulators on your board, load stepping them at will.BOTH the load step stimulus and the voltage measurement occur at the same time through the one connection point. WOW!!

Description: Measuring the in-circuit output impedance – Two 1-Port PDN Probes
If the output of the device is loaded by the 50ohm connections, connect DC Blocks to one or both ports and perform the Calibration. You can make the connection to the circuit using soldered coax a cable, micro-coax connections, or most easily with the Picotest PDN probes. Shown below is the setup using two 1-Port Probes. Using two Picotest 1-Port probes gives you a bit more flexibility with connection pitch.

2-Port Shunt-Through - Circuit Probing Using the Two 1-Port PDN Probes

2-Port Shunt-Through - Circuit Probing Using two 1-Port PDN Probes

Description: Extending the Two-Port Shunt Thru Impedance Range
This variation of the 2-Port Shunt-Through measurement extends the impedance range that the measurement can support. This extension is useful for measuring impedances that vary widely such as those encountered with passive components, opamps, low power voltage references, and linear regulators that span the 1-port and 2-port measurement ranges.

The extension process is simple. Here, we add a 499 ohm resistor to each leg.

0.1uF COG Shunt Capacitor

1.8uH inductor

Note: The extended range measurement shifts the range up in this case so the minimum impedance that can be measured is in the 5-10mohm range. The benefit is the greatly extended high impedance measurement capability. The resolution at resonance is a function of the number of data points