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Another fnirsi fail
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flash2b:

--- Quote from: nctnico on September 02, 2024, 03:31:53 pm ---
--- Quote from: flash2b on September 02, 2024, 03:16:14 pm ---Why did this guy put his DSO in roll mode?

He could have captured the start-up in normal acquisition model assuming he has some memory in his DSO. On roll mode a DSO is very, very, very slow and frequency pulse will not be shown.

--- End quote ---
Unless you enable peak-detect (assuming this Fnirsi has this feature).

--- End quote ---

In the video he uses a Siglent DSO.....
ataradov:

--- Quote from: ebourg on September 02, 2024, 04:13:02 pm ---Besides the mismeasured ESR, is this product good for testing components?

--- End quote ---
Yeah, it works fine. It is just a nice GUI and package over the same firmware. If you need any component tester, I'd pick this one over the old one where the battery is flopping unless you come up with a case of your own.
ledtester:
The device on the right looks like a "LCR-TC4" which is an implementation of the open-source TransistorTester project:

https://www.eevblog.com/forum/testgear/%2420-lcr-esr-transistor-checker-project/

https://github.com/Mikrocontroller-net/transistortester

This project has a long history (10+ years) and many implementations have appeared on Aliexpress and Ebay. It is quite safe to say that any "LCR" meter that features a ZIF socket is based on this project. A recent list of implementations offered for sale may be found in this post:

https://www.eevblog.com/forum/testgear/%2420-lcr-esr-transistor-checker-project/msg4733444/#msg4733444

The design document for the project may be found here:

https://github.com/Mikrocontroller-net/transistortester/blob/master/Doku/trunk/pdftex/english/ttester.pdf

The explanation of how ESR is measured by these devices may be found starting on page 98. There are actually two proposed methods - the description of the second method starting on page 101.

Neither of these methods are the traditional way of measuring ESR and the document admits that.

Another thing to keep in mind is that the TT project was designed for the AVR microcontroller - in particular 5V operation. Recent implementations are starting to use alternative MCUs - like the LGT8F328 clone of the atmega328. A couple of years ago FNIRSI released the DSO-TC2 -- their first mash-up of a DSO138-like oscilloscope and a TransistorTester:

https://www.eevblog.com/forum/testgear/new-(toy)-dsolcr-meter-fnirsi-tc2-(june-2022)/

The DSO-TC2 they actually used two MCUs -- a MM32F103RET for the TransistorTester and a WCH CH32F103C8T6 presumably for the oscilloscope. According to the above EEVblog thread the DSO-TC2 didn't report ESR.

In any case, the TransistorTester on the right in the video is very likely using an AVR MCU -- like an atmega328 -- and the original TT code whereas the DSO-TC3 is using a different MCU and different code base.



aeg:

--- Quote from: nctnico on September 02, 2024, 02:42:44 pm ---Also, the 5.0 Ohms shown may be a limit of what the Fnirsi can measure. The number being exactly 5.0 is kind of a giveaway here. I don't think there are general purpose / commonly used capacitors with an ESR greater than 5 Ohms when they are new.

--- End quote ---

A new "low ESR" Nichicon UPW2E2R2MPD 2.2uF/250V capacitor measures 9.8 ohms on my Bob Parker meter.
Paul T:
The FNIRSI seems to be way out of line.  In general, these devices aren't very accurate testers, they are convenient component identifiers & basic function checkers.  Great for binning lots of components quickly, or the first step for determining what a poorly marked component might be.  Later, when I want to use one of those binned parts, I go directly to a "real" LCR meter or DMM to accurately check the performance before making use of it.

On use, it's best to press the transistor test button three times to see how repeatable the result is.  The results I get are usually not reassuring, I often document the median value.  Sometimes inductors are identified as diodes, etc. which goes into a "test on something else" bin.  Also try putting the component in the receptacles different orientation and see what you get.

When it's working correctly, give 10% lee-way on resistance (accuracy range 10Ω-10MΩ) and capacitance (range 100pF-20MF) and 20% error on inductance (range 20uH-20H).  This is based on two LCR-T7's I have that I've evaluated across an array of reference components I have collected.

On these units I've added a foot pedal switch connection option and also a recessed slider power switch.  The only purpose of that power switch is to disconnect the battery when it freezes on testing.  This happens from time to time testing mosfet-looking components that might stump the microprocessor.

I also have several different external termination adapters: hooks, grabbers, spring terminal board, SMD plate made from an old SIM card with the little bond wires cut. 

One final recommendation: Use these devices off of the battery, not plugged in.  Keep away from sources of EMF during use, including things like LED bulbs and fans.

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