RLC Bridge

I don't know about the 4192A, but many HP instruments from the 80s had a matg programming capacity. For instance, the DSA could compute group delay with a few math operation. So there may be a program to compute LCR equivalents for you network analyzer in an applications manual or note.

The impedance bridge for the 4195 had two or three standards. There was the official HP short, official HP open (er, I think), and the official HP 50 ohm load. They all went on that 7mm switchable sex connector. I'm a little fuzzy if there was something you actually had to attach that was an open.

I'm sure for the LCR, they simply looks at the slope over frequency to get the L and C values. I'd had to think about how they determined R. There were a few models, i.e. parallel and serial, and I think one with the R all in the L with the C in parallel.

Yes I must have a look about.

The 4195a is a 50 ohm system, but the 4192a is different, they get the L and R and C from the voltage and current measured at a single (selectable) frequency. AFAIK that is all you can do with one frequency, but by sweeping it should then be possible to derive more complicated networks.

Unfortunately I have so far managed to studiously avoid learning the maths to do this in practice.

Don't buy Tonghui.

I just got my second one (TH2821B) in yesterday and it had no battery installed. I installed the battery from my broken Tonghui (TH2821A) but it would not charge. Additionally, the battery indicator showed full charge when it died from lack of power.

I am now trying to communicate with all parties to get this resolved. I now think the Tonghui is trash. Although it makes measurement very well, the power system is obviously junk.

Looks like lots of meters around. Someone ought to compare them for accurac y on a hundred different parts. Not likely to happen. So what I would do is borrow or rent an expensive LCR and compare it with a handheld LCR on repr esentative parts to expect to test. Like do you want to check ceramic part s with DC bias for checking loss of value? or do you want to check ESR of e lectrolytics or test big transformers > 10 Henrys or Caps bigger than 10mF ( which is a limit on most) or check SMT mainly or THT mainly or both ?

I like my Model: 380193 Extech Instruments portable 4 digit LCR with all th e bells and whistles with Normalized readings, short/open calibration optio n, % bin sorting , export to excel, 120,1k,100kHz. Some users may want 1MHz .

Phil Hobbs wrote

Just looked them up.

An amazing product!

Not sure if they ship to the UK (many US firms don't, or want a silly price list $200) but I have asked.

Also they do not publish the accuracy.

Dave Jones did a teardown and review some while ago:

Cheers

Phil Hobbs

Phil Hobbs wrote

The most embarrassing review I've seen in ages :)

I've ordered the device before seeing it :)