# Questions about measuring Shottky diode...

Thread Starter

#### UnnamedUser159

Joined May 3, 2016
501
Hi there.

Because the written in one repair guide i have buyd analogue meter to have one. I have decided to not take the cheapest one and take one model which is one idea more expensive - ax-7003.

the 'problem' - in my tool there are X1K and X10 Modes about Resistance.

In guide they are using - x1 and x10K...

Should the reading be the same - for example low reading and high reading AND full scale and some leaking direction to zero

thanks in advance!

#### KeepItSimpleStupid

Joined Mar 4, 2014
5,088
Those kind of meters have a zero adjustment and it;s best to zero each range. As the "ohmmeter battery" dies, the low resistance scales won't zero.

The zero is performed with the test leads shorted together.

The resistance should be the same, but the precision suffers.

The resistance of a Shotkey diode would be different for each range because the current produced is different.

Thread Starter

#### UnnamedUser159

Joined May 3, 2016
501
As the "ohmmeter battery" dies, the low resistance scales won't zero.
i maybe will use it only for Shottky diodes testing and if i doubt in battery i will replace it with new.

...

i just want to do my job - check the diod which is desoldered from the board.
What tests to make and what values are good for me?

For example mbr20150fct and
SBLF10100CT

thanks

Last edited:

#### Janis59

Joined Aug 21, 2017
1,482
RE:""i just want to do my job - check the diod which is desoldered from the board.""

Why to destroy that pcb by desoldering. Use the device permitting the straight measurement on the pcb what is not disturbed by neighbour elements. Mainly it is the class of devices working on 60-300 mV what are not opening any p-n barrier. One of such excellent device is this, https://www.ebay.com/itm/Mega328-LC...654007&hash=item5d6054324a:g:aYAAAOSwTLxZgv5A
Only You ought then do is to attach a proper steel needle containing plugs to the wires plugged into those blue brick, and for larger safety to put the apparatus in small plastic box. I owned one few weeks ago and still I am very satisfacted.

Thread Starter

#### UnnamedUser159

Joined May 3, 2016
501
and lets get back on thread - how to use this new item to measure the shottky diodes. That which confuses me are the different range modes in guide and in my testing device.

#### be80be

Joined Jul 5, 2008
2,069
But from what your saying you better off with a cheap Dvm with diode check like even a $20 dollar one from harbor freight. They really not that bad just cheap. Thread Starter #### UnnamedUser159 Joined May 3, 2016 501 I have reread the thread right now. So ... my analogue meter is not good enough for measuring shottky, right ? can i use my dvm Mastech 830C for that and just searching for 150–450 mV in forward direction and infinity in the other one? #### be80be Joined Jul 5, 2008 2,069 It will test them the fluke diode checking link tells you how Thread Starter #### UnnamedUser159 Joined May 3, 2016 501 I have sblf10100ct the pins with + (the external ones) with + probe and on the center -/black probe/ 300/311 and in oposite direction i have 1 and 1. On MBR i have : 377 377 again and in oposite 1 and 1 again they seems to be okay, right ? #### be80be Joined Jul 5, 2008 2,069 Yes that about right Now set it to ohm and test to see if you get a 0 reading when the pov lead is on the negative side you'll get a 0 or it will like mine go from 0 and jump to M Ohms then back to 0 hooked the right way it will read 1 or so k Ohms If both readings are close your good to go. The range it .2xx to .4xx your .377 on both so your good there But I'd still test with ohm scale 0 and some meter will jump to high M Ohm then back to 0 The hooked the right way it be low K Ohms. Last edited: #### be80be Joined Jul 5, 2008 2,069 The big problem with the ax-7003 is the battery it's not big enough. The Simpson people though about that and made there's a whole lot better a simpson is a great meter. Back when radio shack was king they had some that where close to a simpson just not as rugged. Kind of funny I got my first job they gave me a Simpson and had me test tracs diodes and power transistors was a big part of getting the job. I was the only one that passed the test out of 50 guys and one woman I was the only one there that didn't have a EE I almost didn't get the job because of that. But the shop master said he could tell I wanted to learn and pulled for me. I had to drop out I got 2 years to go I had kids and money was needed to take care of them. Last edited: #### crutschow Joined Mar 14, 2008 30,753 That meter is +- 5% that means it can be off 10 % in real world use. What? ±5% means the measurement will be within +5% to -5% of the actual value. #### ian field Joined Oct 27, 2012 6,536 and lets get back on thread - how to use this new item to measure the shottky diodes. That which confuses me are the different range modes in guide and in my testing device. be80be answered you question - an analogue meter won't help much for what you want to do. Even the cheapest DMMs have a diode check function that does. #### be80be Joined Jul 5, 2008 2,069 What? ±5% means the measurement will be within +5% to -5% of the actual value. Have you ever really tested it out most time's there off more then 5% yes it should be 5% But most cheap meters that say +- 5 % are more like 10 % I think they sick that in for the meter leg. I have a Extech it about 1% and a Klein MM1000 .5% It's a nice meter my fluke got stolen out of my car with about$6000 in tools I had for testing wire network's and hand tools my Klein's are gone.
first time i ever forgot to lock the doors I get robbed.

I have about 8 only 2 are very good meters I've tested them there close enough for horseshoes

Last edited:

#### Reloadron

Joined Jan 15, 2015
6,951
Analog meters aside for a moment and with a focus on diode testing you may want to think about a very ancient simple method with a very low cost. Low cost makes the assumption you have access to an oscilloscope. Resistances aside when you test a diode be it any of several diode families think about what parameters you are interested in seeing. Using an everyday common transformer with a mains voltage primary and a 6.3 volt secondary (or close) you can build what we called an oscilloscope octopus. As can be seen in the link it amounts to a poor man's curve tracer. They can be as simple as a transformer with a few resistors or more complex. They afford you the opportunity to actually see what is going on with a diode.

Ron

Thread Starter

#### UnnamedUser159

Joined May 3, 2016
501
Yes that about right
Now set it to ohm and test to see if you get a 0 reading when the pov lead is on the negative side you'll get a 0 or it will like mine go from 0 and jump to M Ohms
then back to 0

hooked the right way it will read 1 or so k Ohms

If both readings are close your good to go.

The range it .2xx to .4xx your .377 on both so your good there
But I'd still test with ohm scale 0 and some meter will jump to high M Ohm then back to 0

The hooked the right way it be low K Ohms.
about the first check - what ohms range to use - 200 2k 20k 200k or 2M?

you talk about RED probe to cathode and black to anode?

thanks

#### ian field

Joined Oct 27, 2012
6,536
about the first check - what ohms range to use - 200 2k 20k 200k or 2M?

you talk about RED probe to cathode and black to anode?

thanks
Analogue meters are counter intuitive - DMMs push conventional flow out through the red lead.

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