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Welcome to our group Picotest Online Group! A space for us to connect and share with each other. Start by posting your thoughts, sharing media, or creating a poll.

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Injection transformer J2100A gain

Hello,

Could you please tell me why the gain of the transformer is near the -15dB ? what is the test setup for this measurement ?


Thanks for your help

36 Views
steve
steve
12 hours ago

Because with a 50 Ohm termination and a 50 Ohm source the signal level has to be 2 to get unity gain output (0dB=1)

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Tek MSO5B 2-port Impedance Calibration

I just got a Tek MSO58B scope with the PWR license and the Picotest PI Solution bundle to measure PDN impedance and capacitor parasitics out to 100 MHz. I have worked with VNAs in the past and understand the calibration / de-embedding process for RF systems and know that test fixtures and cables are going to introduce additional artifacts. However, the low frequency nature of this has me wanting to make sure I'm not missing something regarding the calibration. I have the J2102B in series to help minimize ground loop currents from impacting low frequency measurements, but want to make sure I'm not missing something else during the calibration process that would impact the measured data.

1. I'm assuming I should be taking SOL measurements to remove the effect of cables and test hardware? 2. I'm wondering if there is any integrated calibration incorporated into the Tek Power Integrity Software, like…

51 Views
steve
steve
12 hours ago

Great questions! I do imagine the calibration software will eventually be added to the scope, but as of now, there isn't any. You didn't say anything about the impedance magnitude, but this sounds like it is a 2-port shunt through measurement, so I'll assume it is low impedance. In that case the only impactful error is the SHORT. So you could measure a SHORT and then subtract that from your measurements. This will mostly remove the cable and probe coupling, which appears as increased inductance.


My rule is to ALWAYS measure something you know, and of similar magnitude, before measuring something you don't know. We keep low value resistors around for that purpose. We have them from about 250uOhms up to about 100 milliOhms.


My experience with the MSO6B has been really good for this measurement, and yes, calibration will improve it, and I expect that could come in time. The MSO5B is higher noise than the MSO6B, which impacts the minimum measurable impedance, but since we can go to about 100uOhms with the MSO6B, I imagine you can do 1 milliOhm or better with the MSO5B.

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PSRR Testing with the J2120A Line Injector

Dealing with Line Injection Issues (J2120A, J2123A)


Here is some information on the Power Supply Rejection Ratio (‘PSRR’) measurement setup using the J2120A line injector.


Depending on the load current and impedance you are trying to drive, the output of the injector may drop several volts.


In the vast majority of cases, the line injector is almost certainly working correctly. It is often the case that the test setup impacts the results and that a large voltage drop at its output is seen. We do get many questions about the J2120A and its operation.


After reading the following if you are still having issues, please let us know and we will be happy to have a call with you to discuss your particular measurement and test setup.


The J2120A is being asked to supply a certain amount of current (over frequency). If the impedance is too low, the J2120A runs…


1148 Views

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Probing question

Do you have a probe that can plug into a VNA and test/record the impedance of traces on a PCB? One with very small tips on one end and an “SMA” connector, “APC” connector, “N” connector, or even a “BNC” connector?

12 Views
Picotest
12 hours ago

A VNA is capable, but using 2 measurements, short and open. See this article:

https://www.edn.com/simple-trick-to-measure-plane-impedance-with-a-vna/


A TDR is a more direct measurement, using our J2154A and an oscilloscope:

https://www.signalintegrityjournal.com/articles/1852-the-goldilocks-tdr

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MS Excel add-in for M3510A is blocked

Has anyone been able to get the M35XX Excel add-in to work with recent 64-bit MS Excel version? I get a MS Forms dialog when opening Excel that an object couldn't be loaded, and then a compile error for WinApi. The Add-ins ribbon shows the Picotest M35XX PT-Link custom buttons, but can't run the add-in. This appears to be related to latest Excel being 64-bit, and the add-in being vintage 32-bit (DMMLINKM35XX.xla dated 2010).


Just wondering if there is a work-around to allow the add-in to function and import data. The MX35XXA_AP software (latest V2.02) works and nicely plots two parameters from my 3510A, but I'd really like to get the data to do some post-processing.

55 Views
tim
12 hours ago

Hi, just checking if this is still on someones 'to do' list?

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Measuring 1milliOhm 2 Port Shunt Thru

I am measuring Picotest Kit 1 milliohm resistor using 2 Port Shunt Thru method using Picotest Common Mode Isolator. As shown below above the low frequency range I am measuring a base of approx. 400uOhms instead of 1milliohms. Full 2 Port Calibration is performed. Noise floor was in the 10s of uOhms range. Mounting impedance is of course not accounted for but that should have increased the impedance rather than decrease? What am I doing wrong?


Noise Floor

44 Views
wasim739
12 hours ago

Better measurement results with the 2 Port Shunt State file provided. Able to see the difference Isolator makes in overcoming the ground loop error at low frequency. But the value is still ~400uOhms. Theoretically, I shouldn't be able to measure a lower resistance value than the real value? So not sure if this 1 milli ohm resistor from the PITK01 kit is actually only 400 uOhms in value.


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What's the difference between the P2104A 1-Port Probe and B-AMP 12 External Power Amplifier?


34 Views
Picotest
12 hours ago

The B-AMP 12 Amplifier (https://www.picotest.com/products_OL000168.html external power amplifier for the Bode 100) is used to amplify the Bode 100 output signal by 12 dB. It is primarily for PDN, and specifically for ultra-low impedance power rails. The P2102A/P2104A PDN probes work with, or without, the B-AMP, but all PDN measurements are mostly dependent on the cable resistance and the CMRR of the isolator (e.g., J2102B). In fact, in the University paper (https://www.picotest.com/measurements/download/UNIVERSITY_How_to_Measure_Ultra_Low_Impedance_(100uOhm_and_lower)_PDNsVersion17b.pdf ) we showed the impedance error can essentially be reduced to Rshield/CMRR. We also showed that a source power amp is the ONLY way to improve the SNR of the measurement, but has no impact at all on measurement accuracy, only on SNR (noise).


Ben Dannan (https://www.linkedin.com/in/benjamin-dannan/) showed the benefit of the B-AMP12 for measuring COT converters, which are typically noisy. That is where the SR issue comes from. Without VRM noise there is no need at all for a B-AMP12, but since the VRM noise raises the noise floor, the signal needs to be increased to maintain a given SNR. That is what the B-AMP12 does. The Bode 100 inputs can tolerate an absolute max voltage of 5Vrms but the recommended is below 3.3Vrms. The +13dBm source power is 1Vrms so at the output of the B-AMP12 the signal is 4V, not including the DC voltage of the rail being measured. It is VERY easy to damage the front end. Oscilloscopes typically have a maximum rating of 2.5Vrms, so even easier to blow out the front end. Having done it twice, in two different brand scopes, I can tell you that all channels are generally on a single board. Each scope repair cost more than $6K, so be careful.


I hope it is clear that the B-AMP12 is not a replacement for the PDN browser probes. So, comparing them as interchangeable does not make sense. The B-AMP can produce a cleaner plot for noisy power rails or ultra-low impedance (our record is 22uOhm, but Ben Dannan just demonstrated 4uOhms, using B-AMP12). This improvement would be the same with soldered cables or probes and accuracy would not be noticeably affected in either case. In most cases, an oscilloscope offers better noise performance for measuring PDN impedance and so doesn’t require an amplifier. On the E5061B ENA we demonstrated a 22uOhms measurement, without a power amp despite the instrument being limited to +5dBm. So, the only reason we could see for you to add a B-AMP12 is to overcome a noisy output, but beware that you can cause damage with it if you measure with too large a signal (as in impedance above a few Ohms).

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