Sorry, but I find the idea that ANY modern digital multimeter can destroy ANY integrated circuit to be absolute nonsense.

While I agree in general, you know what they say about never say never.

I've worked with IC's that, because of the performance requirements, had zero input protection on the detector pins, were quite low impedance (they were current-mode inputs), and had circuitry that would be damaged by input currents exceeding 100 uA. They were a royal bitch to work with.

Even so, I'm pretty cavalier (more than I probably should be) about handling CMOS chips, including most of the ones I've designed, and don't think I've ever damaged any -- you never know how much life you've taken off one or how much you've affected it's performance by careless handling. We HAVE had chips that have gotten zapped and destroyed by ESD and I think some of those were due to careless handling during extremely dry conditions (and I'm pretty careful about strapping up when the humidity is low), but those events were rare.

 

Isn't .434V enough to forward bias this diode

I would have expected so, howbeit 434mV is 'borderline' for said device -- More to the point - your instrument's continuity mode mightn't 'like' the 'drop' --- What does the instrument read in 'junction check' mode? (remember that said reading is an EMF -- not a resistance) -- To the broader issue - I don't advise use of 'continuity mode' for inspection of populated circuit boards -- the resistance range offers more information and greater test-condition 'predictability'

Best regards
HP

 

What does the instrument read in 'junction check' mode?

In diode test mode I read 173mV.

Also, when in continuity mode, connected to forward bias the diode using the Extech meter, I measured the voltage across the diode using another meter and read 136mV. Why is it that the open voltage in continuity mode was measured at 434mV however when the diode was inserted the voltage is 136mV? I am assuming this has some bearing on why the diode is not being forward biased in continuity mode.

 

Why is it that the open voltage in continuity mode was measured at 434mV however when the diode was inserted the voltage is 136mV?

Because the instrument is current limited -- additionally the 'test signal' may be pulsed...

I am assuming this has some bearing on why the diode is not being forward biased in continuity mode.

Quite possibly -- The forward current at the junction in conjunction with the instrument's current limiting scheme may result in 'relaxation oscillator behaviour' - or merely 'ratcheting' of the current back to such a degree that the condition is inconsistent with 'continuity' -- In either case, the instrument would not indicate continuity despite slight or periodic forward bias -- Then too, all bets are off should the instrument indeed operate via 'sampling pulses' -- in any event, it's a mater of 'the right tool for the job' - and all that Please 'save' continuity mode for wiring, 'bare' boards, etc... -- But use resistance mode for examining populated boards/circuits...

Very best regards
HP

 

... -- But use resistance mode for examining populated boards/circuits...

I've watched in videos that demonstrate when troubleshooting shorts on populated boards one can use the resistance mode on their meter and as they get closer to the short there would be a decrease in resistance. The same videos make reference to using a meter with high resolution to be advantageous in this situation. My Fluke 8012A has a 2 ohm range with a resolution of 1 milli ohm. Attached are the specifications of this range.

According to the specs it mentions an open circuit voltage of 16V max on the low ohm range. It also mentions a full scale voltage of 0.02V and a max test current of 10.5mA.

Would you consider it generally safe to use this 2ohm low ohms mode to locate shorts as described above on a populated boards without having semiconductors being forward biased or components such as CMOS ICs being damaged?

What is the difference between the open circuit voltage and the full scale voltage listed in the specs? (I also tried to forward bias the 1N5817 in the 2ohm low ohms range and it read open).

 

The low ohms range of your meter does not supply enough current to forward bias the diode, use the diode range, for the most part I have found it rather pointless to test most semi conductor devices in circuit because of other components affecting the reading.
The odd diode may be the exception.
What ever reading you obtain is not definitive due to the possibility of other components affecting the reading.
Max.

 

Is the indication of damage analogous to ESD damage : For example they are those who say they do not follow proper ESD procedures and have never destroyed a component -- yet the component can become degraded but not destroyed.

Can it be said that those who use continuity mode on their DMM and never experienced a component being destroyed may have inadvertently degraded it?

That depends on the excitation voltage output of the DMM in continuity/ohms mode.

For example, if the allowed emitter-to-base voltage of a BJT, or the reverse voltage across an LED is exceeded by the DMM's output voltage, some degradation, or even complete destruction of the device being probed might occur.

 

Would you consider it generally safe to use this 2ohm low ohms mode to locate shorts as described above

Absolutely not!

Some devices (e.g. certain ICs, UHF through EHF schottky detector diodes, etc...) may be damaged by 16V -- Then too, 10mA is much too much current! -- Though I must say I'm surprised! - In my experience Fluke/Wavetek/Keithley are quality instruments! -- Are you certain you've correctly interpreted said specifications?

I also tried to forward bias the 1N5817 in the 2ohm low ohms range and it read open).

The current flow likely loads the EMF to equilibrium very near (i.e. just 'above') threshold (or, perhaps, 'sets up' an oscillatory condition) -- in any event, sensitive devices will be momentarily, perhaps repetitively, exposed to 'high' currents while zero-bias devices will carry the full 10.5mA throughout the test interval! --- If you are certain of the specifications another meter is advisable for the stated purpose!

Best regards and good luck!
HP

 

As I have learned from many experienced repair specialist I have found that only Analog Multimeter which uses 2 AA battery and one 9v battery are more dangerous for testing semiconductors. As their low ohms Scale probably Rx1 range has 50mA of Test Current which can easily destroy sensitive components. All Fluke DMM are safe to test components in any function Ohms, Continuity or Diode Scale are less than 1mA Current which is safest test Current range. That is why all professional repair engineer or technician use Fluke DMM for reliable and safe testing of components and equipments. I don’t believe that Fluke DMM’s any range could damage any component. Only static charge can damage or destroy sensitive component like MOSFET or IGBT and in some cases ICs.

 

All Fluke DMM are safe to test components in any function Ohms, Continuity or Diode Scale are less than 1mA Current which is safest test Current range. That is why all professional repair engineer or technician use Fluke DMM for reliable and safe testing of components and equipments. I don’t believe that Fluke DMM’s any range could damage any component. Only static charge can damage or destroy sensitive component like MOSFET or IGBT and in some cases ICs.

I found the following thread interesting where a member provided the following data below:

Fluke 87-1 1989 Ohms Test <1.3 volts
Fluke 87-1 1989 Diode Test <3.9 Volts
Fluke 87-2 ---- Ohms Test <1.3 volts
Fluke 87-2 ---- Diode Test <3.9 Volts
Fluke 87-3 1997 Ohms Test <1.3 volts
Fluke 87-3 1997 Diode Test <3.9 Volts
Fluke 87-4 1999 Ohms Test <5 Volts
Fluke 87-4 1999 Diode Test <5 Volts
Fluke 87-5 2004 Ohms Test <7.9 Volts
Fluke 87-5 2004 Diode Test <7.9 Volts

https://www.eevblog.com/forum/testgear/multimeter-with-low-continuity-test-voltage/25/

Also see:
Can a Multimeter's Continuity Mode damage circuits?

 

Yes to damage. Like small junction Jfets fwd biasing their Gate Source
junction.

Also reported is forward biasing super beta transistor inputs on OpAmps
with them resulting in noise degradation.

Regards, Dana.

 

All Fluke DMM are safe to test components in any function Ohms, Continuity or Diode Scale are less than 1mA Current which is safest test Current range. That is why all professional repair engineer or technician use Fluke DMM for reliable and safe testing of components and equipments. I don’t believe that Fluke DMM’s any range could damage any component. Only static charge can damage or destroy sensitive component like MOSFET or IGBT and in some cases ICs.

You shouldn't make a blanket statement like that. Like any engineering/design question the correct answer should be it depends on the application. In this case it depends on what you define as "destroyed". You have to remember that a resistance measurement is an active measurement that stimulates a circuit under test and as such that stimulation has the potential to exceed the Absolute Maximum Part specs for current or voltage (albeit at a very low power level).

In general, you're not likely to "destroy" an IC but you could potentially cause latent damage to the IC particularly if the VOC of the DMM is very high like a Fluke 87-V. While this is likely not a problem for most applications if you want to have a highly reliable product you need to reduce/control the potential of latent part damage especially if all you needed to do was to take a look at a parts spec sheet. The vendors provide those limits for a reason.

You shouldn't use a DMM or any measurement device on an IC/MOSFET/IGBT/etc. if you don't have a good understanding on the test currents & voltages used by the measurement device and the Absolute Maximum Part ratings of your part.

Disclaimer: I use Fluke 87-3's (Discontinued, unfortunately) almost exclusively when measuring sensitive components.

 

Hello,

I have a question with regards to measuring continuity using a DMM ohms setting on a non powered circuit board. I read the following here:

"Avoid: Any other kind of continuity tester for PCB work. Never use the Ohms, Diode or Beeper function on your DMM to measure continuity on a circuit board!" http://pdp-8.org/tools.html

The above site recommends to use a zero beeper such as this one:
http://www.jensentools.com/stanley-supply-services-zero-current-audible-continuity-tester/g/1214

The above linked tool indicates there is zero current through semiconductors and it is "CMOS SAFEST".

I also read here that "It is possible to damage semiconductors when using an ohmmeter to test them."

Am I correct to understand that if I use my DMM ohms setting to measure continuity on a circuit board (such as to check if a trace is broken), there is a possibility that components such as semiconductors (e.g. CMOS ICs) could get damaged? Would you consider it worth it to buy the above tool for measuring continuity on circuit boards (esp. those of 70s/80s vintage) instead of using a DMM?

Thank you

Advice will vary here, but honestly, if you want to be safe and do it right, never frying a component unnecessarily, the primary reason you don't use a Ohmeter to measure through components is because you don't know how much voltage and current the ohmeter is using to test with. This can exceed one or more components, in your circuit potentially. The thing is, if you apply power to your non-powered circuit-board with your ohmeter, you don't know where the power from the ohmeter will go- it is now powering some portion of your circuit, and polarity counts.

If you want to be safe, and don't have any options, always used the diode test option on your DMM or voltmeter if it has it. The diode test option is specifically limited in current and voltage to be safe to semiconductors, diodes, transistors, LEDs, etc.

Just my $0.02.

 

"if you apply power to your non-powered circuit-board with your ohmeter, you don't know where the power from the ohmeter will go- it is now powering some portion of your circuit, and polarity counts."

I, also, in 40+ years have never seen damage caused by using a V-O-M or DMM on anything I was testing. 40 years ago, when I was visiting a client to do a lengthy install, I knew an old guy who would use a 6-volt lantern battery with a buzzer on long leads, to ring out cables between two rooms and it would sometimes power up some of the gear he was working on, through its signal inputs! I had to troubleshoot and repair some of it after he blew it up.

 

"if you apply power to your non-powered circuit-board with your ohmeter, you don't know where the power from the ohmeter will go- it is now powering some portion of your circuit, and polarity counts."

I, also, in 40+ years have never seen damage caused by using a V-O-M or DMM on anything I was testing. 40 years ago, when I was visiting a client to do a lengthy install, I knew an old guy who would use a 6-volt lantern battery with a buzzer on long leads, to ring out cables between two rooms and it would sometimes power up some of the gear he was working on, through its signal inputs! I had to troubleshoot and repair some of it after he blew it up.

Not questioning your experiences, or anyone else's. The fact remains, damage is possible, and I've seen it happen.