hybridfree/eevblog-posts huggingface dataset:
multimeter doesn't zero - Page 1
Forum section: electronics / beginners

author: stevestk
author_rank: Newbie
timestamp: April 18, 2010, 02:41:13 am
content: I bought a meter at a yard sale today. The ac/dc voltage varies and does not zero when when the probes aren't touching anything (I've seen it 10 - over 100 mV) When the probes are crossed, the dc reads zero and the ac reads .7 mV. Is this abnormal? Is it broken or not properly calibrated?

author: Unknown
author_rank: Unknown
timestamp: April 18, 2010, 02:58:05 am
content: Probably the leads acting as antenna's. It doesn't take a lot of current through 10Mohm to generate a few mV, as long as it doesn't occur when actually connected to something, it should be fine. All meters with an 'infinite' (>10Gohm) input impedance have the same effect. As long as the output impedance of your test point isn't too high, this shouldn't matter. 100mV in DC mode is a bit high for 10Mohm I believe, my Fluke 189 is <1mV unless I'm moving the leads, in AC it's like 500mV with the leads close to power cords. The high reading in DC mode might indicate poor CMRR. Not a calibration issue in my opinion, possibly a design issue.If it's a true-RMS meter, it's perfectly normal that it doesn't read zero in AC mode with the leads shorted. The response of the True-RMS converter is not exactly linear close to 0V, so they adjust it so it's accurate in the linear part. The accuracy specs are usually not valid below 20% of full-scale or so. You should not subtract this from other readings. There's a note on the Keithley website somewhere that explains this. Not sure about non-true-RMS (false-RMS?) meters, I don't own any decent meter without true-RMS. I can't see any reason why it wouldn't read close to zero.

author: EEVblog
author_rank: Unknown
timestamp: April 18, 2010, 03:22:18 am
content: Some meters have a very high impedance (Gohms) mV mode, so it's normal for it to read all over the place with no source connected.Have you tried it with some known source voltages?Dave.

author: Simon
author_rank: Unknown
timestamp: April 18, 2010, 08:52:05 am
content: should be ok even my sparkling new amprobe AM220 does it but has 10 Mohm input and I think 100 Mohm for mV

author: Waifian
author_rank: Regular Contributor
timestamp: April 18, 2010, 02:12:47 pm
content: Yup, this is normal. Just goes to show you what is in he air.like others said if it is still crazy on a circuit measurement that you know is solid then I would be concerned. Enjoy your meter!

author: Simon
author_rank: Unknown
timestamp: April 18, 2010, 02:19:55 pm
content: try holding a scope probe in the air in a room and don't be surprised to see some volts of 50 Hz sinusoidal waveform: you mains power

author: Waifian
author_rank: Regular Contributor
timestamp: April 18, 2010, 02:33:43 pm
content: Oh yes! I can get 60 hz on my frequency display all the time here in the USA shen not connected to anything.

author: stevestk
author_rank: Newbie
timestamp: April 18, 2010, 04:06:23 pm
content: Thanks for the responses and info.
Multimeter error - Page 1
Forum section: electronics / beginners

author: tizi
author_rank: Contributor
timestamp: April 19, 2017, 07:52:47 am
content: Hi All,i have a major mt22 multimeter (FREEBEE), everything seems to work except in ohms mode in auto / manual does not display OL reads 4K.any tip i could trythanks in advance tizi

author: grifftech
author_rank: Frequent Contributor
timestamp: April 19, 2017, 09:00:41 pm
content: conductive gunk on PCB

author: tizi
author_rank: Contributor
timestamp: April 19, 2017, 09:09:48 pm
content: had a quick look at the board couldn't see anything that stood out, waiting on the new eevblog multimeter to arrive will do further teststizi

author: retiredcaps
author_rank: Super Contributor
timestamp: April 19, 2017, 11:28:50 pm
content: When you short the probes, does the meter read 0.1 ohms? If not, what does it show?

author: tizi
author_rank: Contributor
timestamp: April 20, 2017, 08:38:09 am
content: i forgot to mention that, indeed it displays 0.1 ohms when probes are shorted

author: jeroen79
author_rank: Frequent Contributor
timestamp: April 20, 2017, 10:09:08 am
content: Measure the resistance between the terminals with the meter off using another meter.

author: retiredcaps
author_rank: Super Contributor
timestamp: April 20, 2017, 05:10:53 pm
content: If shorting shows 0.1 ohms, what does it show for a 100, 1k, 10k and 100k ohm resistor?

author: tizi
author_rank: Contributor
timestamp: April 21, 2017, 12:26:15 am
content: eevblog meter has arrived will test it over the weekend

author: Cornerz
author_rank: Newbie
timestamp: September 21, 2017, 11:59:30 am
content: Hi @Tizi, did you ever get to the bottom of the error? I have exactly the same issue on my MT22...Thanks!
Multimeter innovation 3320 question - Page 1
Forum section: electronics / beginners

author: Atom_slayer
author_rank: Newbie
timestamp: December 15, 2024, 07:05:13 pm
content: I have an innova 3320 multimeter. It drives me nuts when I measure volts and there are phantom numbers on the display until I put the probes on the circuit. Can anyone tell me why this happens?

author: Aldo22
author_rank: Super Contributor
timestamp: December 15, 2024, 08:15:51 pm
content: That is normal.https://www.eevblog.com/forum/beginners/fluctuating-acdc-readings-on-my-new-digital-meter/

author: Atom_slayer
author_rank: Newbie
timestamp: December 16, 2024, 03:41:08 am
content: Thank you!!!
Multimeter input protection question - Page 1
Forum section: electronics / beginners

author: RossS
author_rank: Contributor
timestamp: September 04, 2016, 09:15:17 pm
content: After watching Dave's, I'm confused about the diode bridge used to clamp voltage across the shunts until the fuse blows.Dave says the diode bridge in the Fluke 27 uses standard 1n4007 diodes, and indeed theservice manualconfirms this. However, the 1n4007 diodes I've found can only handle a peek forward current of 30-45A for single digit milliseconds (example 1,example 2). Surely the current will be much higher than this if you plug your meter directly into mains? Until your mains breaker blows, you'd be limited just by the resistance of the fuse. I measured the 44/100A fuse in my Fluke 87 (same fuse as the 27) at ~800 mOhms. At 120V where I'm from, that's 150 amps.How can the diodes deal with this huge amount of current for the amount of time it takes for the fuse to blow? I must be missing something.

author: retiredcaps
author_rank: Super Contributor
timestamp: September 04, 2016, 09:23:22 pm
content: Did you watch the followup video?

author: Kleinstein
author_rank: Super Contributor
timestamp: September 04, 2016, 09:34:51 pm
content: Watching that 2nd video, a high current pulse should not be a problem - the fuse should be always faster than the 1N4007.However at a current just over 1 A, the fuse might actually be rather slow. So not much spare to take into account that the diodes are rather close to each other.

author: RossS
author_rank: Contributor
timestamp: September 04, 2016, 09:40:31 pm
content: Quote from: retiredcaps on September 04, 2016, 09:23:22 pmI completely missed that. Thanks for the pointer!The video nicely answers my question. As Kleinstein also mentions, the point I was missing is that the fuse is always going to blow before the diodes.
Multimeter: is it bad for the meter to have selected wrong range? - Page 1
Forum section: electronics / beginners

author: Nisei
author_rank: Regular Contributor
timestamp: August 19, 2015, 01:56:08 pm
content: My Uni-T UT61E (auto ranging) meter starts beeping like crazy when I have set it to manual range and go over the limit of that range (DC Voltage mode).My question: is it bad for the meter or is it just a warning that you've exceeded the maximum voltage of that range so the displayed value isn't correct?

author: McBryce
author_rank: Super Contributor
timestamp: August 19, 2015, 02:11:28 pm
content: No it shouldn't have any negative effect on any decent DMM as long as you haven't gone above the absolute maximum that the meter can measure. It's just letting you know that you're out of range.McBryce.

author: Nisei
author_rank: Regular Contributor
timestamp: August 19, 2015, 02:35:54 pm
content: Thanks for the quick response.Nice to know, I thought I might damage it when it happens but it seems to be alright then
Multimeter ports - Page 1
Forum section: electronics / beginners

author: JonPyro
author_rank: Regular Contributor
timestamp: February 19, 2019, 03:48:44 pm
content: Does anyone know what multimeter port sockets are called? I know they also accept banana plugs. I want to replace one on my metre but can't seem to find that type on RS or Farnell. Most are too fat so won't let me lead shield fit over them.

author: Nerull
author_rank: Frequent Contributor
timestamp: February 19, 2019, 03:51:19 pm
content: Sheathed banana jacks.

author: JonPyro
author_rank: Regular Contributor
timestamp: February 19, 2019, 04:14:21 pm
content: Thank You, shrouded was what I was after!!
Multimeter probes in your hands. - Page 1
Forum section: electronics / beginners

author: paulca
author_rank: Super Contributor
timestamp: July 24, 2020, 03:36:11 pm
content: I know this comes up a lot.If I hold my multimeter probes in my hands, I get a DC voltage. When I let go I get 0.000V. Holding the probes it ranged between -400mV and +250mV while I tested. It changes oddly too. It sits stable for a few seconds then climbs or drops for a few seconds and stabilises for a while before moving again.That's not the weird part. It seems not to matter where I put the probes. If I hold one in each hand or if I hold both on the same finger the voltage is around the same range. I event stuck both in my mouth and I got similar voltages.I tried touching different things around me and it didn't change the voltage, although I didn't try an actually electrical connection or earthed fixture.If you do this on a scope is it just noise? Does my body cause a DC offest to the normal electrical field around me that normally appears as noise on scopes, amplifiers, etc. etc. What determines that voltage offset? Does it tell me anything if it's high or low?Even then how can the voltage exist at any point across my body... is it just an artefact of body capacitance messing with the meter?BTW, when I google this I get crack pot bullshit about EMF and grounding yourself in bed. LOL

author: bdunham7
author_rank: Super Contributor
timestamp: July 24, 2020, 04:09:04 pm
content: When you use a meter (or any test instrument) it becomes part of the circuit. Never forget that.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 25, 2020, 12:56:50 pm
content: As a simple check to verify if my scope still works, and the probe is connected to the right channel, I often touch the tip of the probe.It usually picks up the local 50Hz, and with an amplitude can be multiple volts.A bit of diode operation can maybe be introduced by any contact of dis similar materials.Then there are thermocouples which generate a DC voltage (And can even deliver a significant current. Thermopiles have been built with multiple kilo watts ofoutput).Regular DMM's have an input impedance of 10MOhm, but it can be higher. With such impedances it's easy to pick up all kind of stray noise.
Multimeter reading 0ohms for all non open circuits - Page 1
Forum section: electronics / beginners

author: Roverfan
author_rank: Contributor
timestamp: March 11, 2023, 08:27:39 am
content: Hi guys, I've got a basic ms8221. It came with a blown fuse but also just realised the ohms/continuity reading is off as well. It measures all non open circuits as zero ohms, and in beep mode it beeps as if reading a short circuit. It does not do it if the circuit is completely open. In diode mode it reads 0.00 before the probes are even touching anything.Does this point to a particular component being defective?

author: Kleinstein
author_rank: Super Contributor
timestamp: March 11, 2023, 09:28:16 am
content: In some meters the test current for the ohm readings also goes through the fuse used for the current ranges. So it could be just the fuse.Usually there is a PTC to protect the current source in case there is a voltage source instead of the resistor. The PTC and a possibly an additional series resistor are somewhat prone to damage if one tries to measure the resistance of the mains supply. Ideally it would survive, but not for sure at the low cost end and definitely not a good idea.

author: Roverfan
author_rank: Contributor
timestamp: March 15, 2023, 12:42:55 pm
content: It turned out to be the spring contacts in the rotary switch. Noticed the selector switch had spaces for 8 springs contacts but only 7 were present. Moving one fixes the resistance measuring faults. May need to obtain another spring contact. I don't know if it needs all 8 contacts. Need to watch some teardown vids or study the board a bit more
Multimeter recoomendation with mixed volts/current and peak value measurement? - Page 1
Forum section: electronics / beginners

author: hirada
author_rank: Regular Contributor
timestamp: February 01, 2021, 01:40:20 pm
content: I am looking for a multimeter, that not only is capable of displaying DC, AC and AC+DC rms values, but also for AC and AC+DC the peak values. My current ones only do either. One does show peak values, even offset, but not the mixed rms values, the other one does measure (or calculate) AC+DC rms, but has no peak value measurement. That is a little annoying.Example, in case my wording is not clear: If I am having 2V DC and a 400mVpp sine AC on top, next to being able to read 141mV, 2V and 2,005V respectively, I also could get to see max: 200mV, min: -200mV for AC as well as max: 2,2V and min: 1,8V min for AC+DC.Same would of course hold true if the AC is greater than the offset. Like 1V DC offsetting 4Vpp AC. Ripple or offset, should not make any difference.I can happily live with frequencies below 10kHz, but high crest factors, I am not primarily interested in sinewaves. And rather for low voltages and currents.In a perfect world that new DMM would also feature a serial port. Or lxi, for linux connectivity.The AimTTi 1908P may tick all the boxes, but from the handbook it is not clear to me, wether its min-max function will work as desired.Is it capable of showing the actual peak values or does it just stores various min/max rms values? I suspect the latter, but hopefully someone can prove me wrong. My current both DMM behave differently in this regard. Or rather, one has peak as an added functionality, that is missing here.Any alternatives that may accomplish what I am looking for? Preferrably sub 1000ish? Other functions like resistance, diodes etc. are not of importance, as I already have those in sufficient quality.Edit: The HMC8012 does seem to have an AC+DC mode as well. It also talks about peak to peak, but for some reason this is listed as a mathematical function. It is therefore not clear, wether the peak values for offset voltages are also displayed correctly or limited only to the pure AC values. As those do not seem to be measured, but calculated. Again, we should keep the high crest factors in mind. So sqrt(2) may not be sufficient.
Multimeter showing difference in reading negative voltage. - Page 1
Forum section: electronics / beginners

author: bborisov567
author_rank: Regular Contributor
timestamp: December 28, 2021, 09:25:28 pm
content: I have an old BBC M2006 multimeter, recently i have noticed that when measuring negative voltage (black probe connected to +, red to -) i get around 0.3 V difference. I am using a 9v battery for testing. Specs say 0.25%+1 digit accurancy. I am having trouble identifying which part of the circuit is responsible for input voltage polaty. I was thinking about the V5 and V6 transistor pair. Probably aging has shifted their parameters?

author: bob91343
author_rank: Super Contributor
timestamp: December 29, 2021, 03:38:02 am
content: What does it read when the leads are shorted? It may just be a zeroing error.

author: bborisov567
author_rank: Regular Contributor
timestamp: December 29, 2021, 07:20:44 pm
content: It goes to zero when shorted so i decided to open it. After inspection i found some oxidation residue sround V9, just cleaned it and now the multimeter works perfectly. Anyways could somebody explain how a typical schematic for reversing polarity in a multimeter works?

author: Kleinstein
author_rank: Super Contributor
timestamp: December 29, 2021, 07:31:25 pm
content: With many DMMs the polarity reversal is handled as part of the ADC. So the ADC can work with positive and negative voltages as well.In some cases the zero is not special at all and just a point about in the center. The common ICL71xx dual slope ADCs us a capacitor to hold the reference voltage and than use CMOS switches (as part of the chip) to connect the capacitor with the reference voltage one way or the other.It is rare that the input voltage is actually reversed. That was more like a thing of the 1960s with analog meters and a few very early DMMs.

author: magic
author_rank: Super Contributor
timestamp: December 29, 2021, 08:16:31 pm
content: Look up ICL7106, it's the classic IC of this kind and the datasheet explains all of its operation with diagrams and everything.Your schematic shows MAX133, but pin names in the bottom right corner make me think it's a very similar device.These ADCs use external analog components so they can be sensitive to board contamination.
Multimeter Test Probe? - Page 1
Forum section: electronics / beginners

author: Gabriel
author_rank: Regular Contributor
timestamp: November 24, 2017, 11:51:21 am
content: Hi All,What do you think of these 10 in 1 multimeter probes? Are they any good?One of my main concerned is whether they will slip and the attachment will come off. Also what happens when the banana plugs wear out?I was looking athttps://www.ebay.com.au/itm/Universal-10-in-1-Electronic-Specialties-Test-Lead-Cable-Multimeter-Test-Probe/361848031698?hash=item543fd2c9d2:g:VWYAAOSw4GVYR~qkor something like that. I am not worked too much about the CAT rating as I only (usually) work with low voltage (<50V) max upto 240V mains. Also could I use these on a power supply? I couldn't see why not but maybe I missed something! Is there kit that you would recommend in particular for any reason?Thanks In Advance,Gabriel
Multimeter UNI-T UT60S how to activate MIN/MAX ? - Page 1
Forum section: electronics / beginners

author: Maximus Panin
author_rank: Contributor
timestamp: February 27, 2024, 09:51:12 pm
content: How to activate the MIN/MAX function on UNI-T UT60S ? I heard that on some multimeters some functions are not activated and can be activated by contacts. For example, like onRichmeters RM102Datasheet for controllerSD7502Looking at the block diagram, you need to close legs P12, P14 on the controller.I tried short-circuiting and short-circuiting for a long time, nothing happens. Is it a matter of firmware?

author: BeBuLamar
author_rank: Super Contributor
timestamp: February 27, 2024, 11:14:06 pm
content: I think it doesn't have the Min/Max function although the LCD does have those.

author: Maximus Panin
author_rank: Contributor
timestamp: February 28, 2024, 08:46:24 pm
content: BeBuLamar

author: BeBuLamar
author_rank: Super Contributor
timestamp: February 29, 2024, 02:15:02 am
content: You can ask Uni Trend. I am sure it doesn't have such function.
Multimeter vs ADC stability - Page 1
Forum section: electronics / beginners

author: MaggoT
author_rank: Newbie
timestamp: December 17, 2012, 10:13:21 am
content: Hello!This is something i have been wondering about, how do multimeters produce such stable readings compared to an ADC in a microcontroller, or an external ADC?For instance when i measure the voltage across a small DC motor (which is of course a very noisy load) the ADC jumps around all over the place. I have tried using an RC-filter to the ADC input, as well as taking 16 readings over 16mS and averaging the value out but the readings are still very unstable.Even a cheap multimeter produces a very stable reading when measuring the voltage across the motor.How is this done? Is it hardware design or is there some nifty way to average this out in software?best regardsMaggoT

author: SeanB
author_rank: Super Contributor
timestamp: December 17, 2012, 10:54:56 am
content: Most multimeters use an integrating technique to get the readings. This reduces the noise a lot at the expense of needing a longer sample time and a slower update rate. Have a look at the appnotes and data sheets for an ICL7106 chip for more details.
MULTIMETER WURTH - Page 1
Forum section: electronics / beginners

author: lionelkjh
author_rank: Frequent Contributor
timestamp: March 11, 2025, 07:44:55 am
content: Hello everyone! The integrated circuit of my WURTH multimeter is defective (DTM0660L); it only works in manual mode and no longer in automatic range, for all electrical quantities to be measured.....Looking more closely at the card; a 5-pin area must be used to read and reprogram....I plan to replace it, I have 2 programmers: the TL866 and the RT809H but I don't know how to read the content and put it back on the new circuit using these 2 programmers....I took a photo of the multimeter card with the circuit datasheet....Thank you in advance for your enlightened advice....Cdt

author: Kleinstein
author_rank: Super Contributor
timestamp: March 11, 2025, 08:21:09 am
content: The 5 pins on the side look like a programming header (e.g. JTAG or similar). However with very little information available on the DMM chip and likely some read protect active, there is not much one could ues it for.The PCB looks a bit dirty around to SO8 chip. Chances are it is just flux residue, but could be an issue. The picture is not that clear to really see details. I know it can be tricky to get a good close up picture.I am afaird there is not much that can be done to fix the meter. Maybe look for visible faults and check the battery voltage.

author: ahsrabrifat
author_rank: Regular Contributor
timestamp: March 11, 2025, 08:26:11 am
content: Maybe the firmware has been corrupted.

author: Simon
author_rank: Unknown
timestamp: March 11, 2025, 06:40:34 pm
content: WURTH ? as in wurth elektronik? (https://www.we-online.com/en)

author: 2N3055
author_rank: Super Contributor
timestamp: March 11, 2025, 07:14:02 pm
content: Quote from: Simon on March 11, 2025, 06:40:34 pmNo, the tool company :https://www.wuerth.de/

author: mwb1100
author_rank: Frequent Contributor
timestamp: March 12, 2025, 01:54:39 am
content: No idea if this will be any help, but Kerry Wong has translated the datasheet for the DTM0660 DMM chip:-http://www.kerrywong.com/blog/wp-content/uploads/2016/04/DTM0660DataSheet.pdfHe did the translation in support of an article that hacked communications support to a meter with the DTM0660L:-Hacking DTM0660L Based Multimeters
Multimeters for Hvac techs - Page 1
Forum section: electronics / beginners

author: slimm
author_rank: Newbie
timestamp: May 09, 2011, 09:50:56 pm
content: I am an electronics hobbyist who works as a commercial HVAC technician. I have seen the youtube $50.00 and $100.00 shootout and have learned a lot. Also I have suggested young technicians view the eevblog videos on our talk forumwww.hvactalk.com----Any chance Dave Jones could review a line of Multimeters by Fieldpiece? They make meters just for HVAC technicians. I mostly work with 480 volt 3 phase power so safety is a big issue for me.

author: PetrosA
author_rank: Frequent Contributor
timestamp: May 10, 2011, 03:22:33 am
content: I've seen Fluke and Extech DMMs and clamps (sometimes both, as a kit) marketed for HVAC techs. I'm not sure what you'd need that most decent clamps or DMMs wouldn't have. I'm guessing you need or would want a thermocouple, inrush current measurement and CAT III 1000V/CAT IV 600V, so I think most decent meters would work fine for you. Am I missing anything?That being said, I think for clamps you would be happy with clamps/DMMs from:AEMCAgilentAmprobeExtechFlukeGreenleeHiokiIdealet al.

author: BrickBoiler
author_rank: Contributor
timestamp: May 10, 2011, 12:40:55 pm
content: Slimm, I'm also a commercial HVAC tech. Same thing for me, its all about safety.I see a lot of the guys using the fieldpiece meters, but I think it's mostly because they are less expensive than fluke and available at the supply house. They all seem to like them though. I had one a long time ago. Manual ranging with only a weird 2A current range (glass fuse). Eventually the little plastic shrouds in the jacks popped out and one of the probes cracked in cold weather. It's in my junk box now, they don't even sell it anymore so the new ones might be better.Are you looking at getting a DMM / Clamp meter combo or just one of the all-in-one style clamp meters?

author: slimm
author_rank: Newbie
timestamp: May 10, 2011, 01:54:12 pm
content: Only recently has Fluke produced meters branded for hvac. Fieldpiece has been making hvac meters for over a decade. Also if I have an issue with a Fieldpiece product I can ask Russell Harju (big shot at fieldpiece) right on the hvactalk forum and get it resolved quickly. Fluke is owned by Danaher (huge corporation that makes Craftsman,Kobalt and dozens of other products) and My business is not that important to them. Micro amps (one millionth of an amp) is one feature a lot of meters do not have and 4-20 ma for control circuits also.

author: McPete
author_rank: Regular Contributor
timestamp: May 11, 2011, 08:09:13 am
content: Check out the Fluke 116. It's got a thermocouple (type K) input, plus a µA range for doing flame sensors, plus all the usual mod-cons for volts/ohms/diodes etc... No current ranges besides DC µA though. If you need to measure AC current, I'm sure you could pick up a basic clip-on current transformer quite cheaply that'd do AC current at least as well as cheap tong.If you can hang the expense, grab an 87V, or a Yokogawa TY530. Maybe check out Agilent too? I'm not so familiar with their range.
Multimeters reading bizarre ref. voltage output - Page 1
Forum section: electronics / beginners

author: mobius9
author_rank: Newbie
timestamp: October 21, 2021, 08:04:29 pm
content: Hi all,I am in manufacturing and have had an unexpected change in my test equipment readings. I have aMAX6029EUK21+Tthat I am probing as part of a quality check on pin 5, the voltage reference output (supposed to be 2.048v for our p/n). I've tried powering our board with the 3 power supplies over here - two BK Precision 1686A, and a Siglent SPD 3303C. All the power supplies have started behaving the same -the power supply output probes at the appropriate voltage (3.0v)the reference voltage chip appears to have a 3.0v reading across input and ground (intended)the output pin (expected 2.048v) is giving a low voltage reading, and appears to be slowly oscillating (see below video for more vivid explanation)If I bring the same equipment home, it returns to reading as expected (2.046-2.048v). If I use battery power, it reads as expected. We've been doing this for years at our current location without issue.I'm under the suspicion that our wall power is a little wonky and causing the issue. Our Fluke 115 is reading 120.8v and 60.00Hz. We are in a heavy industrial area, if that is helpful. Unfortunately, all I have are multimeters to diagnose this currently. What should I be looking into? The power conditioning area has been pretty hard to shop for with a lot of commentary for and against various equipment. Open to any suggestions.Video of the output on power supply, then battery.Cheers,Bobby

author: JustMeHere
author_rank: Frequent Contributor
timestamp: October 22, 2021, 01:32:27 am
content: Have you tried to turn off your lights at the office?

author: Psi
author_rank: Super Contributor
timestamp: October 22, 2021, 01:54:41 am
content: Quote from: JustMeHere on October 22, 2021, 01:32:27 am+1 for thisAlso try testing away from your blue anti static matt.They are great for static protection but terrible for coupling mains hum into nearby circuits or wires.
Multiple DC  output Power supply  - Page 1
Forum section: electronics / beginners

author: Md_Aslam
author_rank: Contributor
timestamp: October 25, 2022, 04:53:17 am
content: Can Anyone suggest me a DC power supply with multiple output options like 1.8v, 3.3v, 5v and 12v. I want an evaluation board kind of Device which will be embedded with all the different outputs in a single board.Waiting for quick reply...........

author: Faranight
author_rank: Unknown
timestamp: October 25, 2022, 10:03:37 am
content: I remember seeing this on kickstarter:https://www.kickstarter.com/projects/wissa/mini-power-station

author: Md_Aslam
author_rank: Contributor
timestamp: October 25, 2022, 11:23:37 am
content: Quote from: Faranight on October 25, 2022, 10:03:37 amThanks for suggestion, This product will be suitable for me But I need multiple values of 1.8v, 3.3v, 5v etc like 3 of each.
Multiple DC voltages and multiple grounds - Page 1
Forum section: electronics / beginners

author: rthorntn
author_rank: Frequent Contributor
timestamp: September 05, 2021, 01:14:08 am
content: Hi,Sorry for this question its probably silly.I have some ATX modular PSU's, the wiring of the cables can be different and I'm trying to figure out if I can use PATA cables that have "slightly" different wiring, I've been burned by this before.Standard PATA pinout:1Yellow12V2BlackGND3BlackGND4Red5VSupplied cable (checked with DMM in continuity), last column is pin on the 6-pin PSU connector:1Yellow12V42BlackGND13BlackGND34Red5V2Spares bin cable (checked with DMM in continuity), last column is pin on the 6-pin PSU connector:1Yellow12V42BlackGND33BlackGND14Red5V2So the Grounds are reversed, 12V and 5V are correct, so the (silly) question is does that matter, its DC right, so Ground is 0V?Another way of asking the question is does 12V (pin 1) have to use the Ground next to it in pin 2 or can it use pin 3?Are there seperate Grounds for each voltage rail, I don't think there are but I just want to be sure.Thanks.Richard

author: Bassman59
author_rank: Super Contributor
timestamp: September 05, 2021, 03:41:00 am
content: it's doubtful that the grounds are isolated. One ground wire per voltage rail is provided because each rail needs a return of the same ampacity. Also having separate ground wires is prudent for the case where the grounds actually are isolated.

author: james_s
author_rank: Super Contributor
timestamp: September 05, 2021, 06:03:15 am
content: The ground wires should ALL connect back at the same place in the power supply. That is certainly what the devices are expecting at least, the ground pins are normally tied together on the drives too. You can confirm with a continuity test. If they are not tied together something is wrong.

author: David Hess
author_rank: Super Contributor
timestamp: September 05, 2021, 07:49:37 am
content: The grounds all go to the same place so can be interchanged.
Multiple ground planes connected strangely?  - Page 1
Forum section: electronics / beginners

author: gmc
author_rank: Regular Contributor
timestamp: November 03, 2022, 10:13:12 pm
content: I"m busy looking at a SMPS from a old IBM computer and have a query on why they have done strange things with the ground plane. If you look at the attachment the red dot is connected to chassis earth.Folowing the PCB layout the 2 blue dots are also earth. Why did they not just join them together via the shortest path?I've also attached the top layout which shows some of the components.Is there some specific reason for this odd layout? Extra resistance maybe?

author: thm_w
author_rank: Super Contributor
timestamp: November 03, 2022, 10:24:42 pm
content: Usually its done on a voltage rail to have a current path pass through the area with filtering capacitance, to avoid noise exiting the area bypassing the filter.In this case I doubt it would make much difference, usually you are better with a flood fill and not trying to be fancy.https://incompliancemag.com/article/slots-in-gnd-planes/https://learnemc.com/not-so-good-emc-design-guidelines

author: gmc
author_rank: Regular Contributor
timestamp: November 03, 2022, 10:48:03 pm
content: Thanks, that's a interesting read.
Multiple i2c devices on single isolator? - Page 1
Forum section: electronics / beginners

author: mayor
author_rank: Regular Contributor
timestamp: May 30, 2021, 04:03:16 pm
content: Hi,I'm considering building a carrier board for Atlas Scientific amplifier boards (used to read ORP, pH and temperature), similar to their board:https://atlas-scientific.com/files/Wi-Fi-Pool-kit-setup-guide.pdf. I plan on using my own long-range microcontroller board instead of the Huzzah board.Apologies for the quality of the image, but this basically shows 3 isolated i2c boards and one non-isolated. They usehttps://www.analog.com/media/en/technical-documentation/data-sheets/ADM3260.pdffor isolation.Each is along these lines:Besides the fact that they use the enable/disable pin on the isolator to turn each of the sensors on and off, my question is:could you use a single isolator and tie the i2c bus of each sensor(they all have separate addresses) together instead of using 3 isolators?Thanks!
Multiple MOSFETs to share current load? - Page 1
Forum section: electronics / beginners

author: Student52
author_rank: Newbie
timestamp: September 25, 2018, 06:29:05 pm
content: Background:Hi!I'm designing a spot welding apparatus. I won't build it until I have more experience, and under supervision of an engineering student.Mostly doing it to challenge myself to learn more....QuestionThe spot welder will use 12 V capacitors and output around 1000 ampere for a very short time.Is it possible to use multiple MOSFETs to share the load?If so I can design that part of the circuit so that multiple MOSFETs are controlled by a single hi/low logic signal, and together they can handle the high current.If I want multiple MOSFETs to share the same load, do I just connect the gates from each MOSFET to the control signal lead, drains of all MOSFETs to the earth side of the load and the source of all MOSFETs to the 0 V from the power source?Of course I'll use pull down resistors and a number of other components, but do I need to isolate each MOSFET's gate or can I just connect all gates together and connect this common lead to the signal output?...Again, I won't build it until I have more experience, and have the supervision of an experienced engineering student.Would really appreciate your help, I'm eager to learn.This paint sketch illustrates what I mean.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 25, 2018, 07:20:57 pm
content: For a switching application one can parallel MOSFETs in parallel to share the load. However one should not directly wire the gates in parallel, as there is a chance the circuit could oscillate, due to a combination with parasitic inductance and drain-gate capacitance. The simple and possible way is to use individual gate resistors to isolate the MOSFETs from each other. Another point to watch for is parasitic resistance and also inductance as these can also effect the way the current is shared.Usuall first start smaller with something like 2 or 3 MOSFETs in parallel. For a lot of large MOSFETs the gate driver power might require to use separate drivers anyway, as the capacitance can get to large to use a single driver.
Multiple Network/WiFi Connections - Page 1
Forum section: electronics / beginners

author: metrologist
author_rank: Super Contributor
timestamp: September 15, 2017, 04:43:19 pm
content: I'm wondering what would be required if I wanted to use multiple wifi adapters and wired network all at the same time in Windows.For example, to connect to both a wifi AND Ethernet enabled instrument, and have Internet via a wifi hotspot or a USB broadband modem.

author: BroMarduk
author_rank: Unknown
timestamp: September 15, 2017, 06:51:10 pm
content: You will need to correctly configure your subnetting, and IP addresses for each of the networks, and will need a separate router for each Wi-Fi network (assuming you want them all separate). If you want to continue to have an internet connection, then you will need to make sure your primary network has a gateway.That said, you can probably still connect to all of them with a single hub if you set things up correctly. Are you going for isolation or just want to talk to multiple instruments?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: September 15, 2017, 09:02:13 pm
content: I cannot say much about the windows world; but sure you can run multiple network interface parallel. The question is more what for? Multihoming, so parallel use of two or more upstream internet connection is at least for IPv4 more than just unpractical; IPv6 at least brings the multihoming feature natively, so call source based routing. In the end, your OS mostly sets the limits how you can practically use multiple network connections

author: metrologist
author_rank: Super Contributor
timestamp: September 15, 2017, 09:06:12 pm
content: I am running a software application that communicates with several instruments that are on the network or are accessible through the Internet, and it also needs to access other Internet-based resources. There is no problem when using an internet connected computer and all instruments are on the same network and/or are available from the Internet (no firewall issues).The situation came up where the PC and at least one of the instruments had to be mobile. The instruments must communicate through an Ethernet port, so to be mobile we either use a x-over cable or use a wifi router configured as an AP connected to the instrument, and used the PC wifi connection to the AP. This worked fine when we had just one instrument, but the Internet requirement and use of multiple instruments in the field and online now presents.I read mixed things online about Win10 being able to support multiple wifi connections - it worked, MS broke it but stated it will be (is?) supported. Not sure about other Windows versions. I just don't have all the hardware here to set it all up (no wifi on my PC or mobile Internet myself), so I'm just guessing how it should work...
Multiple output linear regulator power supply - Page 1
Forum section: electronics / beginners

author: cpt.charlie
author_rank: Contributor
timestamp: June 10, 2014, 10:25:23 pm
content: Hi everyone!I'm working in a personal project that needs a few output voltages, therefore i have decided to repurpose an old laptop AC adapter (19V 3.42A) and designed a PCB with three lm317T (for variable outputs that feed some fans and dc motors) and a LM7805CV for my MCU, digital stuff and other low power parts of the project, the design of each regulator is pretty basic (just as shown at the datasheet) however my device has some unexpected misbehavior.Unfortunately i don't have an oscilloscope to check the noise on the power rails, i guess that the problem is a mixture caused by noise being injected (I know, the MCU should have it's own power supply) and a low output capacitance, should i increase the capacity of the caps in order to avoid this kind of problems? recommended values? can anyone recommend an effective method of filtering the power rails considering that I can't measure it with an oscilloscope? other recommendations /upgrades?I'm attaching the schematic and a photo fo the device.Thanks in advance.

author: mariush
author_rank: Super Contributor
timestamp: June 11, 2014, 01:51:09 am
content: Depending on who made those LM317 regulators, the minimum load required to make the regulator stable can be as high as 10mA.Most of the time, the minimum load is insured by the current going into the adjust pin. Try and lower the resistor from 240 ohm to 120 ohm or 100 ohm (and adjust the ratio to get your voltage).You can use more capacitance on the output for each regulator. You don't have to limit yourself to exactly 0.1uF just because the datasheet says so. Add a 100uF electrolytic for example at the outputs for example..other notes... always keep in mind that linear regulators work by dissipating the voltage difference as heat.With 5v out and 19v in, even at 50mA you're going to have (19v-5v) x 0.05a = 14 x 0.05 = 0.7 watts which is acceptable.. but if you're going to use the other outputs for up to 1-1.5A they heatsinks are going to be very hot.

author: cpt.charlie
author_rank: Contributor
timestamp: June 11, 2014, 05:19:43 pm
content: Thanks for the answer mariush, finally i have found the problem, it's a very basic issue with my design, there was no input capacitor at all, after adding a 25V 100Uf cap everything works as expected.
Multiple pads with the same function? - Page 1
Forum section: electronics / beginners

author: lutkeveld
author_rank: Regular Contributor
timestamp: December 30, 2014, 04:19:39 pm
content: Just curious. I'm currently designing a PCB with a chip with multiple (P)VDD's and P(GND)'s.Why can't they connect it internally, instead of letting us connect it via the PCB?That would make the pad count (and thus the package that can be used) a lot smaller, or am I missing something?

author: Bassman59
author_rank: Super Contributor
timestamp: December 30, 2014, 04:29:50 pm
content: Quote from: lutkeveld on December 30, 2014, 04:19:39 pmMultiple VCC and GND pins reduce the lead inductance of the package and improve thermal performance.

author: lutkeveld
author_rank: Regular Contributor
timestamp: December 30, 2014, 04:37:55 pm
content: What problems would increased lead inductance cause and why? Why is it a problem inside the package but not outside?Thermals as in the wires heating up because high current flow? So they want you to do it via the PCB because it can dissipate heat better?The chip is a Class-D (so highspeed) 12v amp if it matters.

author: Simon
author_rank: Unknown
timestamp: December 30, 2014, 06:10:13 pm
content: Increased inductance slows down fast responses for example a chip leading to be able to draw a lot of current very quickly would stall if the inductance of its power pins prevented the current flowing when needed. For example voltage regulator chips quite often have multiple pins. The other reason as stated is to help dissipate heat. Your common surface mount regulator with eight pains will usually have for ground pins, these also act as a way of getting rid of heat into the PCB. When you are talking about very powerful packages you need the extra pains to carry the total amount of current required and to keep the inductance down so that they can draw power quickly. For example a computer processor has quite a few power pins so that they can take in the total amount of current required. The pin is not connected directly to the chip inside the IC there is a bonding wire which goes from the chip to the pin. Many people use the word chip and IC interchangeably but in actual fact they are two different things. The IC is the complete package and is made up of the chip, the bonding wires, the pins, and the plastic moulding which holds it all together. The bonding wires will also have an inductance and a current limit so as you do with wires outside you do with wires inside the IC you parallel them to increase the capacity in the same way you would use a larger PCB trace to carry more current or to reduce the inductance of the trace and make it work better at higher frequency.
multiple potentiometers changing together - Page 1
Forum section: electronics / beginners

author: legrady
author_rank: Contributor
timestamp: January 22, 2025, 06:57:52 pm
content: I would like to have multiple potentiometers changing together, but two-deck pots are expensive, 3 deck pots are for Elon Musk and more are unobtainiun.I could use multiple digipots, but I need 1M pots, which are expensive and have a limited voltage range.Would JFETS be a suitable solution? Any suggestions?ThanksTom

author: Zero999
author_rank: Super Contributor
timestamp: January 22, 2025, 07:02:52 pm
content: J-FETs have a very poor tolerance and the ohmic region is very limited.What's the application? Can you avoid the potentiometers altogether?

author: legrady
author_rank: Contributor
timestamp: January 22, 2025, 09:29:18 pm
content: I want multiple eurorack ADSR envelopes to share attack rates.

author: BrianHG
author_rank: Super Contributor
timestamp: January 22, 2025, 09:42:39 pm
content: Expensive, how do you mean?4 channel pots for 2$6 channel for 4$6 channel for 2.50$Need I go on?What's too expensive?8 Channel for 2.42$All you had to do was search:# Link Adjustable Potentiometerin Aliexpress and see what you get.Even gang-able ones exist if you need 12 or 16 channels.

author: mikerj
author_rank: Super Contributor
timestamp: January 23, 2025, 12:22:19 pm
content: Check out Bourns PTD90 series, up to 8 gangs and very reasonably priced. They go up to 1 Megohm in linear and log tapers, though the the 1 Meg variants don't seem to be as easy to find as lower resistance parts.https://www.bourns.com/docs/product-datasheets/PTD90.pdfMay be worth trying this place:https://www.potentiometers.com/ptd90.cfm
Multiple Questions On Oscillators And Amplifiers. - Page 1
Forum section: electronics / beginners

author: XMA
author_rank: Contributor
timestamp: March 31, 2018, 10:52:41 pm
content: Hello, I am getting into oscillators and amplifiers, and I see that circuits and some amplifiers require a +9v and -9v and a ground. so could someone show me a simple schematic of how would I got around making it, or at least explain to me? I saw a pic showing that if you got two batteries and put them in series, the top is +v and the bottom is -v and the middle would be the ground. but im aiming towards using a single 9v battery.also on amplifiers im wondering what kind of amplifiers are there, especially audio amplifiers. I know there's op-amps based and there are transistor-based amplifiers, what more are there.also with oscillators from transistors and op-amps, how does it make it oscillate. arent the op-amps and transistors only able to gain current.now on something I don't ever seem to understand is, how the hell does a transistor go around amping the current/voltage. also with that when I take a look at circuit diagrams they always have a resistor, or two, and with that, I don't understand why would u need a resistor for a transistor to amplify. doesn't the resistor drop the voltage/current?very sorry, noob.

author: Cliff Matthews
author_rank: Unknown
timestamp: March 31, 2018, 11:04:03 pm
content: Hello and welcome. I would suggest you read through a while on DC and AC circuit fundamentals. We have a help area here:*https://www.eevblog.com/forum/beginners/electronics-primers-course-material-and-books/https://en.wikipedia.org/wiki/Electronic_oscillator

author: rstofer
author_rank: Super Contributor
timestamp: April 01, 2018, 01:54:31 am
content: Google for 'single supply op amp circuits'.Sure, you can use a single supply but you have to bias your AC signal up to Vcc/2 in order to get the output to swing between gnd and the positive rail.https://www.ti.com/lit/an/sloa030a/sloa030a.pdfThere are lots of videos on this topic.