Digital Multimeters (Also Brymen BM869 repair)

[eccerr0r]

Re: Digital Multimeters

Actually my worry is that I measure lead acid batteries and use the voltage for state of charge... Inaccurate reading would make me believe the battery was in the wrong state. Yeah fortunately there's no safety problem here but it could cause me to think the battery was fully charged when it's not. Hundreds of millivolts matter!

I might have to go use my PSU and characterize my meters to tell which ones give me BS after (or before??!!) the battery annunciator comes on.

I guess this is a bonus of non FET analog meters.

[retiredcaps]

Re: Digital Multimeters

I would hope the Fluke would shut off before the battery becomes an accuracy issue?

Some of the newer Fluke models will display "batt" on the lcd and not let you take a measurement when the battery gets too low.

The older Fluke models just have a low battery icon and it is up to the user to change batteries ASAP.

Generally, I know what I'm measuring when I'm using the 70 series with the weak battery. If I'm measuring high voltage, then for sure, I'm grabbing a different meter with fresh batteries.

Well built quality meters protects users from an oops moment, but the biggest thing and best protection is still your brain and using it.

I know the cheap/free Harbor Freight DMM does have inaccuracy issues when the battery is run low.

Yes, you will get inaccurate readings before the low battery icon comes on with the cheaper meters.

[stj]

Re: Digital Multimeters

i couldnt give a damn about the battery life, i just wish they would give a "low battery" warning *before* they start giving bullshit readings!

[eccerr0r]

Re: Digital Multimeters

Once the Fluke 70 series low battery life indicator comes on, I use it until it gives inaccurate readings. Then, and only then, does it get recycled. I can usually squeeze another 100 to 150 hours out of the 9V when the low battery indicator comes on.

I'd be kind of worried about running them so low that there's inaccuracy... I would hope the Fluke would shut off before the battery becomes an accuracy issue?

I know the cheap/free Harbor Freight DMM does have inaccuracy issues when the battery is run low... If I need that meter I make sure I replace the battery just to make sure I don't get fooled by an incorrect reading.

200 hours is a long time as long as you don't leave the meter on when not being used... that probably is the biggest killer, I doubt I'd measure a 5 ohm resistor for minutes at a time, and probably would get annoyed at the beeper turned on 100% duty cycle for 10 minutes to test a connection for intermittent continuity

[retiredcaps]

Re: Digital Multimeters

Ah interesting, so I guess I will throw out the 9V when it dries up before all the zinc gets consumed?

I rotate my 9V batteries around. The new ones go into the smoke detectors on an annual basis. The used smoke detector 9V batteries go into other multimeters or devices around the home. The various devices that show low 9V battery then get put into the Fluke 70 series.

Once the Fluke 70 series low battery life indicator comes on, I use it until it gives inaccurate readings. Then, and only then, does it get recycled. I can usually squeeze another 100 to 150 hours out of the 9V when the low battery indicator comes on.

Also I wonder how much power the Fluke uses when using the beeper/in low ohms mode while actually measuring something.

The 77 II uses 0.60mA with probes shorted on resistance and 0.71mA with probes shorted on continuity/diode.

Then again I think 200 hours is good enough.

Depends. If I use a 9V battery, I want it to last more than 200 hours simply because I don't have an rechargeables. If the meter lasts 200 hours using AA or AAA, then I'm fine because I'm using eneloop ni-mh cells.

My Fluke 187 requires 4 AA and only lasts about 80 hours. So I use eneloops and just have another charged set/sets ready since they are LSD cells.

[eccerr0r]

Re: Digital Multimeters

Ah interesting, so I guess I will throw out the 9V when it dries up before all the zinc gets consumed? Also I wonder how much power the Fluke uses when using the beeper/in low ohms mode while actually measuring something. These situations I assume would truly use the most power. I guess I could sort of measure without removing the battery, just measure how much current flows through the test probes when the meter is measuring ohms. The beeper I'm not sure I have a choice.

Then again I think 200 hours is good enough. Most of the times that I'm forced to replace batteries is when I forget to turn the meter off. Usually I use a meter for a minute, take a few readings, and shut it off for hours. It should last a long time like that!

I think the worst battery consuming DMM I have uses an A23 battery... Too easy to leave on, and A23s are hard to find cheap.

[retiredcaps]

Re: Digital Multimeters

Regarding the BM869 and battery life. This recent thread at eevblog happened around the same time as this one. User over there might have had an oops moment at 300V or higher and it affected the battery consumption/draw of the BM869. However, he was able to troubleshoot and find the problem.

http://www.eevblog.com/forum/testgea...-9v-batteries/

I estimate BM869 battery life around 110 hours using a 9V battery.

[retiredcaps]

Re: Digital Multimeters

All of my other 9V meters quote only 200 hours or so, that's mind boggling with a 10:1 ratio, how could it be?

Ironically, the original Fluke 8020A which became so popular and historic had a 200 hour battery life. The next generation after the 8000 series was the 70 series that improved battery life by tenfold.

Imagine if all our products were designed to run 10x longer using the same battery source.

[retiredcaps]

Re: Digital Multimeters

I was kind of surprised at the Fluke meters, my 77 also has a quote of 2000 hours on a 9V.

Now that I saw your post, I realized I made a mistake with the Fluke 27 battery lifetime. It is 1000 hours, not 2000.

I did do a current draw test with my Fluke 77 II back in Oct 19, 2012. I posted the results at eevblog

http://www.eevblog.com/forum/blog/ee...131/#msg155131

AC - 305 ua
DC - 280 ua
300mv - 270 ua
ohms - 275 ua
diode - 280 ua
A AC - 305 ua
A DC - 275 ua

Assuming a 550 mAh 9V battery, you see how it gets close to 2000 hours. I have a Radio Shack meter that draws less than 1 mA, but uses two AA cells. Assuming the two AAs are 2500mAh, I get 2500 hours battery life.

[retiredcaps]

Re: Digital Multimeters

The 27 is a workhorse, lasts 2000 (two thousand) hours on a 9V battery

Doh, I meant 1000 (one thousdand) hours.

[retiredcaps]

Re: Digital Multimeters

AFAIK The Fluke 27 HV probe is not for use on line circuits.

You could be very well right. I don't know a lot about the HV probes and never did any research or documentation into it. Just something for the OP to investigate since we don't know what transformer he was measuring.

If I needed a HV probe myself, I would probably call in a professional to fix whatever is wrong or I would replace. Working occasionally on 400V DC is enough for me and that is with hands-free probes, eye protection, etc.

[eccerr0r]

Re: Digital Multimeters

I was kind of surprised at the Fluke meters, my 77 also has a quote of 2000 hours on a 9V. I still have the original 2 for $1 carbon zinc in there, and it's still going strong. All of my other 9V meters quote only 200 hours or so, that's mind boggling with a 10:1 ratio, how could it be? Anyone keep good track and verify 2000 hours (I sure didn't keep track...)

I was testing a TSC7116CPL 3.5 digit LCD panel meter IC, and by itself it's drawing enough current to hit only about 200 hours on a 9V. Not sure who made this clone of Intersil's design...

I think worst of all is my B+K LCD DMM (not counting my Viz...). It draws a good 6mA or so, and runs off of C (UM2) batteries. A 9V would drop out in less than 100 hours hence the 6xC cells, I suppose.

My Viz Voltohmyst 3.5 digit uses 4 C (UM2) batteries. It should last only 3 to 4 hours. It uses an LED display and uses NiCd cells.

[Per Hansson]

Re: Digital Multimeters

AFAIK The Fluke 27 HV probe is not for use on line circuits.

[retiredcaps]

Re: Digital Multimeters

Since the OP is in USA, there are frequent auctions on ebay for the Fluke 27 + HV probe. Sometime you can get it for $50 to $70 USD. I don't know the exact specifications of the HV probe, but you can probably find it easily on Fluke's website. I never measure more than 400V DC so I never bothered to investigate.

An example that sold for $39

http://www.ebay.com/itm/291717473735

The 27 is a workhorse, lasts 2000 (two thousand) hours on a 9V battery and built like a tank. It also has schematics and a bill of materials in the service manual. Most of it is through hole components which makes repair easier.

Fluke 27 review/teardown by Dave

https://www.youtube.com/watch?v=MKuvmoW0AZQ

And yes, I have a Fluke 27.

[Per Hansson]

Re: Digital Multimeters

Nice team work!
Now if you still want to measure that transformer might I suggest a HV probe?

https://www.badcaps.net/forum/showthread.php?t=53574

[stj]

Re: Digital Multimeters

lol triple sleeves on the ptc's - expecting a repeat?

[jasonbay13]

Re: Digital Multimeters

Alright. done patched it up and got some pics. and if you are wondering about the flux and soldering, i took that pic just after cutting the leads and later cleaned it up with some 91%.

ohms mode works, havent tested accuracy and all modes yet. but it should be fine as long as i dont do something stupid again :/

really surprised it didnt die completely.


Thanks all so much for the help.

[wraper]

Re: Digital Multimeters

As the reading approaches 500V, the PTC resistance should start to get higher. If the voltage goes past 500V, the PTC resistance should continue to go higher. The meter should continue to function, but your accuracy results could be affected.

The lower voltage rating on the PTC should not affect the accuracy of the meter for readings under 500V.

BTW, making an "oops" moment like having the meter on resistance while the probes are plugged into mains (120V) may affect the accuracy of the meter until the PTC cools down. See Dave's eevblog ohms overload video (10 minute video).

https://www.youtube.com/watch?v=UX7xmA7F5bc

PTC voltage rating has nothing to do with readings at all. It is protection device, it changes it's resistance ONLY when voltage is clamped with varistors, what does not happen at all unless input voltage exceeds 1.8 kV. That means with lower voltage PTC, meter will have worse overvoltage protection but no other negative effects.

[TechGeek]

Re: Digital Multimeters

^
Absolutely. I'd rather deal with melted plastic than a meter on fire.

[stj]

Re: Digital Multimeters

if you changed the order to regular resistors, 100% put heatshrink sleeving over them.