Battery impedance testing with your J2111A Current Injector
I have a glance to the Bode 100 application note about battery impedance testing with your current injector:
and I was wondering whether you see any impairment in doing the same with Tektronix MSO5.
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The MSO6B with the latest power software is capable of both 2 port (VNA) and three port (FRA) frequency domain measurements, though the FRA doesn’t provide impedance units (yet).
You don’t say what your battery voltage is, but for low voltage batteries, the 2-port shunt through is more accurate, though requires an attenuation resistor, attenuating probe, such as P2102A or DC Blocks. The measurement also requires the J2162A active splitter and either J2102B coaxial transformer or J2113A active splitter to measure low impedance at frequency below about 1MHz, depending on the cables.
The FRA method requires the J2111A, which includes a 1Ohm current monitor, and with a low noise scope probe, can also measure impedance. While we don’t usually discuss it, there is also a similar ground loop in this measurement, and in fact, in most measurements. Since this measurement is a current sink, it’s a floating measurement.
Either of these measurement techniques can measure 1mOhm or lower with care. I attached a verification of the J2111A impedance measurement, performed by Keysight, using their E5061B VNA. This VNA has an advantage in this it has a differential input for the voltage measurement, eliminating the ground loop. A standard differential probe is generally pretty noisy, so not quite as good for low impedance measurement. Using a J2113A or J2102B with one of our P2104A or P2105A probes or will yield the best results if the impedance is very low.
We have most of these in the demo pool, if you would like to borrow one. We can use the measurements to create an application note for the MSO6B.
Email info@picotest.com for any demo equipment requests.