Author Topic: Brymen BM-869S diode mode?  (Read 739 times)

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Offline kgavionics

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Brymen BM-869S diode mode?
« on: July 10, 2020, 03:18:09 pm »
Hello guys
I bought a Brymen BM-869S few months ago. I'm quite happy with the meter, but I have an issue which I find very frustrating which is the diode mode! I'm troubleshooting a defective TV power supply and when testing the diode  in reverse bias, the meter reading keeps increasing slowly without showing OL, as opposed to my old Fluke 8060A which display the OL within a few seconds! How do I know if a diode is blocked in reverse bias if the meter reading keeps increasing without displaying Overload! Is this a bug or what?

Thank you in advance
 

Offline bdunham7

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Re: Brymen BM-869S diode mode?
« Reply #1 on: July 10, 2020, 03:35:39 pm »
I would guess that you are testing in circuit, that there is a capacitance (and possibly resistance) parallel to the diode and that the test current on the Brymen is lower than the Fluke.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Offline kgavionics

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Re: Brymen BM-869S diode mode?
« Reply #2 on: July 10, 2020, 04:00:41 pm »
I would guess that you are testing in circuit, that there is a capacitance (and possibly resistance) parallel to the diode and that the test current on the Brymen is lower than the Fluke.
It's totally disappointing ! I'll keep using my old Fluke for dide testing!
 

Offline bdunham7

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Re: Brymen BM-869S diode mode?
« Reply #3 on: July 10, 2020, 04:17:33 pm »
It shouldn't be disappointing, it is just a characteristic.  You have to know the characteristics of your test instruments in order to use and understand them properly.  This is what RTFM means!

Some meters have selectable test currents for the diode ranges, but if not, 1mA is somewhat standard.  It appears the Brymen uses less for some reason. There is no 'correct' answer and in most applications, the lower test current would be fine.

b/t/w, your 8060A is one of the best handheld DMMs in the history of test equipment, so it will be tough for new ones to "measure up".
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 
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Offline HKJ

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Re: Brymen BM-869S diode mode?
« Reply #4 on: July 10, 2020, 05:24:06 pm »
Some meters have selectable test currents for the diode ranges, but if not, 1mA is somewhat standard.  It appears the Brymen uses less for some reason. There is no 'correct' answer and in most applications, the lower test current would be fine.

There is not standard for diode test current on hand held meters, on bench meters you may be able to select test current.
The problem is the protection, usually you need a few kohm between the internal circuit and the terminals, these kohms are made with PTC's that can switch to high impedance when you plug the test leds into mains while in the ohm range.
For most DMM designs a acceptable compromise is in the range of 0.2mA to 2.5mA diode test current.
 
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Offline kgavionics

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Re: Brymen BM-869S diode mode?
« Reply #5 on: July 10, 2020, 06:05:11 pm »
It shouldn't be disappointing, it is just a characteristic.  You have to know the characteristics of your test instruments in order to use and understand them properly.  This is what RTFM means!

Some meters have selectable test currents for the diode ranges, but if not, 1mA is somewhat standard.  It appears the Brymen uses less for some reason. There is no 'correct' answer and in most applications, the lower test current would be fine.

b/t/w, your 8060A is one of the best handheld DMMs in the history of test equipment, so it will be tough for new ones to "measure up".
Sorry for not  RTFM before, i checked the manual and it says that is uses 0.4 mA!
Your right too about the 8060A which is indeed one of the best DMMs ever build!
 


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