Buying a new multimeter: how important is hFE?

rsjsouza

Joined Apr 21, 2014
383
I've noticed the adaptor with the transistor socket, but I thought it's same adaptor for other meters that actually have hFE (based on this review: youtu.be/Bz6CYDRl1M8 ). Do you have a reference for this info?
I couldn't find the adaptor I have to try out a few things, but the user's manual agrees with you: the UT61A is the only one that has a hfe range selector position. Regardless, I don't think this detracts from the meter itself.
 

DarthVolta

Joined Jan 27, 2015
521
I like to check gain of BJT sometimes, but I don't have anything that can to it well. I saw a cool circuit to try making using a Wheatstone bridge type circuit. I of a dozen things I want to make, after my DMM repair obsession is over.
 

dl324

Joined Mar 30, 2015
16,846
I like to check gain of BJT sometimes, but I don't have anything that can to it well.
You can buy or build a curve tracer. They're going for $200+ (used, but working) on eBay these days. I picked up a non-functioning BK501 10-15 years ago on eBay and it cost about a dime to fix it (bad gate in a 7402).

There are also some DIY designs on the internet. I can't remember the name of the guy who designed one that I wanted to make. He also made a resistor substitution box and was involved in making PCBs with the toner transfer method. The latter was how I became aware of him.
 

DarthVolta

Joined Jan 27, 2015
521
Well I started to plan/build 1 at 1 point, off an internet design that worked. I even have a big 1960/70's TV transformer that had lots of windings. His used a 30V and some 100V Vcc, switched with releys I want to try using too. Now I know a lot more about op-amps so that's up there on my list of stuff to make.

I tried making 1 like David Hess (the Tektronix guy? with great videos) I'll have to try that again too and with better op-amps, mine didn't work very well.

But using the cheap tester type sure beats looking at a data sheet that says 100-500, IMO and guessing.
 

Papabravo

Joined Feb 24, 2006
21,159
Actually for design purposes the value of hFE should be unimportant. In production it is difficult to test SMT parts packaged tape and reel. You put the part on the board and it either works or it doesnt. what you do with it when it doesn't work reflects economic reality. As a hobbyist, all you really care about is: "does the part behave as a transistor well enough for my purposes".
 

sparky 1

Joined Nov 3, 2018
756
That is true. There are cheap curve tracers for $20 will be showing up soon.
Well I started to plan/build 1 at 1 point, off an internet design that worked. I even have a big 1960/70's TV transformer that had lots of windings. His used a 30V and some 100V Vcc, switched with releys I want to try using too. Now I know a lot more about op-amps so that's up there on my list of stuff to make.

I tried making 1 like David Hess (the Tektronix guy? with great videos) I'll have to try that again too and with better op-amps, mine didn't work very well.

But using the cheap tester type sure beats looking at a data sheet that says 100-500, IMO and guessing.
I think the cheap curve tracers will come out seen a few already. The DIY interesting.
The small display screens but enough precision to get reasonably close uA .
I think a ramp generator might be a good start on simulator.

 
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sparky 1

Joined Nov 3, 2018
756
Already I have seen one curve tracers sold as an accessory to to a hand held oscilloscope. That is digital.

The DIY kits usually designed to use the XY input mode. Found mostly on older analog oscilloscopes. A DIY curve trace for XY. David Hess design and what is in the video is more for a seasoned builder. Some op amps are good at triangle. The smooth control of the ramp. The rate and slope, that sub-circuit makes nice curve tracers and a sloppy ramp or having unwanted artifacts leaves much to be desired.
 
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sparky 1

Joined Nov 3, 2018
756
Already I have seen one curve tracers sold as an accessory to to a hand held oscilloscope. That is digital.

The DIY kits usually designed to use the XY input mode. Found mostly on older analog oscilloscopes. A DIY curve trace for XY. David Hess design and what is in the video is more for a seasoned builder. Some op amps are good at triangle. The smooth control of the ramp. The rate and slope, that sub-circuit makes nice curve tracers and a sloppy ramp or having unwanted artifacts leaves much to be desired.
The new digital display curve trace are sold as an accessory to a digital scope. The credit here given to the u-core company in Turkey. The testing method has a working board side by side the DUT
https://www.ucore-electronics.com/product/uce-ct212/
 
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