Trying to solder with a cheapo hot air gun. - Page 1
Forum section: electronics / beginners

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 21, 2018, 06:48:55 am
content: So, I'm going for it. I decided to do my first soldering using the hot air and solder paste method.I was thinking of using type 5 solder paste ? with the flux already in it as I think a video was recommending it.I don't want to buy a completely new air gun, but I have a harbor fright type low and high setting hot air gun.I've used it before, and it can un-solder easy, but I wound up burning the board due to leaving it on one spot for too long.Now, I just got brand new ucurrent boards fresh from the pcb maker, and ordered the parts.(thank you sooo much Dave, I wish I could have simply bought them from you, unfortunately, none were available)I don't normally do air soldering at all so far because I use through hole components.I would like to use this low/high solder gun to save money because I don't see a reason to actually buy a 150 dollar airgun to use 1 time.The problem that I'm facing is that the air flow covers too much area which caused me to burn a cheap board last time, so I'm thinking that I need to get a nozzle to better direct the air flow.The question is, are the nozzles that fit the rework stations the same diameter as those cheap air guns, and if not, is there a way to modify them, like an adapter, to allow them to be used?

author: Nusa
author_rank: Super Contributor
timestamp: July 21, 2018, 09:17:45 am
content: I don't know that consumer heat guns have any sort of standard but it's way larger than rework stations as a rule. The nozzle adapter I'm using on mine reduces 23mm down to 8mm. Those are OD measurements on the adapter as I didn't remove it to measure.My advice, unless you have plenty of parts to ruin, is don't do it with that tool. You're more likely to have success with the frying pan method. The paste solder setup for either is about the same. Practice on some junk board first. of course.Hand-soldering is another good option unless your soldering iron is as crappy as your hot air tool. The original ucurrent has nothing smaller than SOT23 and 805 components. Pretty easy. The new version has some 603 stuff, but still not beyond hand soldering. You may need magnification, depending on your eyesight.

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 21, 2018, 09:33:55 am
content: so, ok, what if I bought this one. It's cheap at 50 bucks.https://www.circuitspecialists.com/csi-hotgun-3.htmlSMD Hot Air Gun with Digital Temperature Controlwill that do the trick?

author: Nusa
author_rank: Super Contributor
timestamp: July 21, 2018, 10:03:29 am
content: That would likely be good enough for what you want to do. Find something to practice on first. Removing parts from junk boards and then putting them back on, for example.

author: janoc
author_rank: Super Contributor
timestamp: July 21, 2018, 10:09:57 am
content: I don't understand why are you messing with hot air and paste on the uCurrent boards. All those components are perfectly solderable by hand and it would likely be also faster and less messy than dealing with paste.Keep the paste for boards with hundreds of parts or stuff that doesn't have accessible pins.Hot air tools are primarily used forrework, not general soldering. They can be used to solder in a pinch but there are better tools/methods for that where you don't risk blowing the components all over the place, melting plastic and delaminating the PCB.Your original Harbor Freight "gun" is literally meant for paint stripping. That should give you a hint that it probablyis notan appropriate tool to use for electronic soldering. That's kinda like trying to solder with a propane torch. Possible but the results will match the tool used ...If you want a hot air tool, you need to have one that has both the temperature and the air flow adjustable. It also needs swappable nozzles so that you don't "cook" half of the board when you are trying to (de)solder one resistor.That Circuit Specialist one is a cheap junk, don't expert any miracles from that especially if you plan to desolder/rework larger components. But you don't need any of this for the uCurrent boards. Just use a normal iron and normal solder, add some flux and you will be fine.

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 21, 2018, 10:56:05 am
content: Quote from: janoc on July 21, 2018, 10:09:57 amMy FG died on me once and I tried to fix it unsuccessfully. It had SMD parts.The biggest problem I had before using a soldering iron was to keep the part aligned to the pads. Is there something I can use that will solve this problem?

author: gnif
author_rank: Unknown
timestamp: July 21, 2018, 11:12:12 am
content: Use a fine tip iron, solder one pad first on the corner of the part, if it's not quite right, re-heat and shift the part until it is correct. Once in place, solder the opposite corner, again double check alignment is all OK, and if so, use the drag solder method. For parts like resistors/caps, etc... get some decent SMD tweezers, they are not expensive, I have a wonderful pair made in Switzerland out of a non ferrous alloy, which make SMD soldering a sinch, simply hold the part in place while you solder it.I normally only use hot air if the part has too many legs to remove it with an iron, or it is soldered down under the IC for thermal transfer. Sometimes I just use hot-air to preheat the PCB if it has a large ground plane, and then use a conventional iron to do the actual rework.In my case, it was like the hammer analogy, everything starts looking like a nail. I was trying to use the hot-air for all SMD work, which I quickly came to realize while it is possible, it is slower and impractical in most cases.

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 21, 2018, 11:20:51 am
content: easier said than done..I once tried to align a small smd to the pad to do just that for 30 mins and I kept moving it off the pad. After carefully taking my time for about an hour, I was able to finally get it soldered correctly.The uCurrent has how many smds?That is why I was interested in the Hot Air Soldering method.I've seen videos where the flux and the solder paste literally realign perfectly to the pads!So I've been thinking that in order to solder 2 uCurrents, it would be more faster, easier, consistant, and professional to use the hot air method.Am I wrong?

author: KL27x
author_rank: Super Contributor
timestamp: July 21, 2018, 12:39:37 pm
content: QuoteIs it possible that you are setting the bar higher than needed? I had this problem in the beginning. It takes awhile to learn how crooked parts can actually be without causing any problem. Before I had a microscope, I used the DMM to figure out what was good or bad. It is slow, but probably a lot faster than 1 part per hour.The other thing is extra flux. Yeah, there's flux in the solder wire, already. It's good to add some flux to the pads, anyway, before you solder.

author: janoc
author_rank: Super Contributor
timestamp: July 21, 2018, 01:13:28 pm
content: Quote from: sourcecharge on July 21, 2018, 11:20:51 amHot air method is certainly not more "professional". Reflow soldering isn't done with hot air but in an oven.Hot air is actually a lot more difficult to use for soldering components that have a lot of pins because unless you have a professional equipment with a nozzle that is exactly the correct size and possibly a board pre-heater, you will have difficulties to heat all the sides simultaneously without resorting to too much heat and scorching the board or destroying the component. And if you are doing it side after side and not at once, then the component can be easily dragged off the pads/misaligned when the solder melts.Re alignment of components - that sounds to me like you are using an incorrect technique. Dave has made several videos on SMD soldering, it shows how it is done, without having to fiddle for 30 minutes with anything.Small parts like passives that have only 2 pins - flux the pads, then hold the component down using tweezers and solder one end. The other end is easy. Don't worry if the part sits crooked - it will still work fine as long as you don't make a short. And you can always add flux and heat it with your hot air to reflow the solder later - the component will straighten itself out due to surface tension of the molten solder.Components that have many pins - SOP, QFP packages and similar - roughly align the component on the pads and tack down one pin to keep it in place. Don't worry about the quality of that joint, you can rework it later. Now align the component and tack down the opposite corner. Once done, drag solder all the pins. Clean up any solder bridges or cold joints. Extra flux is your friend here.Use a magnifier to inspect your work for shorts and bridges. If your eye sight isn't the best, use it even for soldering. A small head-mounted magnifier or (better) a stereo microscope with a 5-7x magnification does wonders for this.If you can't seem to keep a larger component aligned on the pads during the soldering, tape it down using a strip of Kapton tape until you solder a few pins. Another trick is to use a sticky gel flux, that both helps to keep the component in place and also lasts longer on the board so you don't need to constantly re-apply it (the liquid stuff tends to flash into steam the moment the iron touches it).Also make sure you are using a proper iron tip -do notuse a very fine conical tip! Those are pretty useless because it is very hard to get a good thermal contact with the board. Keep that for special situations. Regular 2-3mm wide chisel tip is good enough even for 0.5mm pitch TQFPs.Basically, if it has accessible pins you can solder by hand pretty much anything, even if it has 100+ legs. It only takes a little practice. E.g. I am soldering a TQFP 100 package in about 2 minutes and I am certainly fairly slow at it.

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 30, 2018, 03:38:52 am
content: So after receiving the parts, and looking at the 0603 package, I was like,nope...So I got some solder paste and a cheap hot air solderer unit.I got that one from circuit specialist above, and I got this solder paste:No Clean Solder Pastehttps://www.circuitspecialists.com/smd-291ax.htmlIt doesn't state that it has flux mixed in it, so should I put some flux down on the pads before I put the solder paste on them?I was planning to practice on a old smd pci card that doesn't work anymore, and try different nozzels, temps, and airflow.What I'm not sure of is whether if the flux is required.

author: Bassman59
author_rank: Super Contributor
timestamp: July 30, 2018, 06:03:46 am
content: Quote from: sourcecharge on July 21, 2018, 11:20:51 amDescribe your method and your tools!Soldering 0805 and 0603 passives is simple. You need a pair of tweezers, a magnifying lens/lamp, and a chisel tip the width of the pads for your soldering tool.Put a bit of solder on one of the pads. Place the part with the tweezers onto its place on the board. Hold it with the tweezers while you hit the pad you preloaded with solder. The solder will reflow. Solder the other pad. Done.

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 30, 2018, 06:29:46 am
content: I used a magnifying glass on a stand, it was a 4x.I use a chisel tip with small diameter solder with a flux core.I was under the impression that in order to have good solder joints, you have to heat the part up first, then bring the solder to the heat, not the other way around.I've seen the videos, and heard the comments about putting the solder down on the pads, or on the tip first, but I've been told by an experienced electronics engineer, that this will make bad solder joints.I took my time to align the resistor to the pad, I tried using tape, I tried holding it down with tweezers, but what felt like forever, it kept moving off of the pads.I don't want bad solder joints, and I have way too much small smd parts to place.You might be able to do it, that is a good skill, but I have watched the videos that show what looks like to be a very simple way and professional looking solder joints over many parts.The parts are placed on the pads that have the paste on them which keep the part in place, and they don't have to be even straight as they straighten themselves out.I have already purchased the paste and hot air solderer.I think the paste does not have flux in it, so do I need to put the flux on the pad before I put the paste down.Thank you for your encouragement, but I will pass.If anyone has any experience on hot air soldering, and non flux paste, I would be grateful for your help.

author: sourcecharge
author_rank: Regular Contributor
timestamp: July 30, 2018, 07:42:24 am
content: Never-mind, I noticed the part number and did a quick search and found that it was a chipquick type solder paste which already has the flux in it.Here's the datasheet:

author: janoc
author_rank: Super Contributor
timestamp: July 30, 2018, 03:23:57 pm
content: Quote from: sourcecharge on July 30, 2018, 06:29:46 amYou don't put solder on the tip of the iron (except to initially tin it) but you do need to put solder on the pads! Unless you have 3+ hands you will have hard time to hold the part & and the solder and the iron at the same time if you don't put solder on the pad first.You also need to use flux - the flux in the solder wireis not sufficient! That will flash off the moment the solder melts first time and if you don't add extra flux, next time you melt the solder you have poor joint.Quote from: sourcecharge on July 30, 2018, 06:29:46 amHow can a component move off the pad if you areholding it down with tweezers? Something doesn't compute here.Quote from: sourcecharge on July 30, 2018, 06:29:46 amSorry but the main problem is that you don't know how to solder properly. How are you going to rework the board if something needs getting fixed later?Good luck messing with the paste ... At least use a hot plate and not hot air if you want to use the paste. You will be far less likely to blow you parts all over the place and scorch the board in the process.Quote from: sourcecharge on July 30, 2018, 06:29:46 amThere is no "non-flux" paste. Solder paste is tiny solder balls/particles suspended in flux. Once that flux dries out the paste will become useless - that's why solder paste has limited shelf life and needs to be stored in a refrigerator.I strongly suggest that you actually watch the videos Dave did on soldering (and not random Youtube crap). He shows the basic techniques for through hole parts, SMD, even solder paste and hot air use. Then buy a cheap SMD kit - e.g. one of the Velleman kits, doesn't matter, and practice. Or use a scrap PCB from some device and practice removing and resoldering components.Tools:Through hole soldering:SMD soldering:Drag soldering:

author: mikerj
author_rank: Super Contributor
timestamp: July 30, 2018, 03:25:06 pm
content: Quote from: sourcecharge on July 30, 2018, 06:29:46 amFor items with larger thermal mass (including through hole parts) this is the correct way to solder. For SMD parts that have tiny thermal mass it's easy to make a good joint by reflowing solder with an iron.Quote from: sourcecharge on July 30, 2018, 06:29:46 amThis is simply not true. That said the solder must be able to wet both parts of the joint, and use of a suitable liquid flux in a pen style dispenser will ensure this. With just a little practice soldering SMD parts like this becomes second nature, and far easier and quicker than putting paste down and using hot air. If you have steady hands and a good magnifier (or preferably stereo microscope) then even soldering 0201 parts is not too bad, though I do struggle with 01005.

author: JS
author_rank: Frequent Contributor
timestamp: July 30, 2018, 07:21:14 pm
content: The reason of the bad joints when reflowing the solder on the pad is the lack of flux, if you tin half of your pads for SMD parts (on of each component, don't be stupid and tin both pads of half the components) apply flux in excess to the board and solder all those joints, then solder all the remaining pads your joints will be good. Bad solders are usually due to oxidation and that's because of the lack of flux, working under a tab of flux would be nice... they do it in wave soldering where the atmosphere is oxygen free, usually nitrogen only, that way the solder can't get any oxygen on them.JS

author: rstofer
author_rank: Super Contributor
timestamp: July 31, 2018, 03:03:07 pm
content: Quote from: janoc on July 30, 2018, 03:23:57 pmActually, I do! I put flux on the pads, place the part and then put a dab of solder on the tip and apply it to the component/pad interface. The flux makes sure the solder flows quickly and neatly. Kind of like drag soldering without the drag. I prefer the method to tinning the pad because the component starts out laying flat to the board.If I hold the part down with the tweezers perpendicular to the axis of the part, I can solder both ends without moving the tweezers.I have also done the same kind of thing with solder paste. Put a dab of solder paste on each pad, place the part, hold in place with tweezers and apply the iron tip to the paste. Works well... But not as well as bedding the component in flux. Flux is the key to SMD.For a board with a lot of SMD components, a hot plate works well if the board is small. I haven't tried a frying pan but it may work well if it is flat enough to heat the entire board and I built up a reflow oven from a Black & Decker InfraWave Toaster Oven. It does a fine job.This SMD soldering thing just isn't any big deal. Drag soldering and a little SolderWick to fix the inevitable bridges and it's done.

author: KL27x
author_rank: Super Contributor
timestamp: August 01, 2018, 03:06:01 am
content: ^Yep.There are a lot of NASA and telecom rules which are meant for thru hole parts and for splicing wires, using flux core solderwire, specifically. NASA probably doesn't do a lot of hand-soldering of SMD parts. Their PCB's are mostly going to be oven reflowed, just like every other industry.The thing about loading the tip with solder is you need to consider the type of tip to use for this. Really fine chisels have a section of tinned conical shaft right next to the tip, similar to fine pointed conical tips. Surface tension can suck the bead up the shaft, away from the tip. These fine, conical shaft tips are generally going to be very clumsy and messy if you try to load them with a solder bead.If you want to paint the solder on (to prefluxed pads, of course), you need so choose the right tip for the job.QuoteI have done production SMD soldering for a spell, now. What you're describing will come to pass; that's just you not knowing what you're capable of and what you can get away with. What you are describing, you are totally not taking advantage of several things, not least of which is the soldermask layer and extra flux. When repeatedly doing something that bores you out of your skull, this is where you start learning tricks. If my soldering iron happens to be closer to the part than my tweezers, I will often grab the passives/caps with my solder bead and drag it to the pad. Then by the time my tweezers catch up, they just hold the part while I remove the iron. (I mostly use a huge CF tip for soldering tiny passives. Turned sideways at the right angle, the resistor/cap will align to the tip, pretty straight and flat to the board.)When you know how to do SMD, it is overall much faster and easier than thru hole. The most tedious part is getting the part from the package to the board. This is another reason it helps to flux the pads. When you drop the parts on there, they are glued down; they won't disappear when you nudge the board. If you are placing one part on the board, then soldering it, then going back and getting another part, you will not realize the speed/ease benefit over thru hole.Another thing is learning how trivial it is to fix most mistakes. There are a ton of mistakes I was initially afraid to make. And I end up spending time to avoid making them. When it is faster to occasionally make one and fix it when it happens.

author: Nerull
author_rank: Frequent Contributor
timestamp: August 01, 2018, 05:51:53 am
content: Quote from: sourcecharge on July 21, 2018, 10:56:05 amA pair of tweezers? It's really not hard. Soldering 0603 takes about 5 seconds.Using a hot air gun, especially one not built for soldering, will take far longer and is likely to just scatter your parts across your desk.I've seen people with essentially zero soldering experience learn to hand solder SMDs with just a little bit of practice, and i've seen the same people completely destroy a board the first time they tried a hot air station. It is not the magic solution you think it will be.Get a good pair of tweezers, some paste flux (liquid works, but spreads too far and dries up too quickly for my taste), and a small chisel tip. Tin one of the pads, put the part down, touch the pad you tinned for a second. Part is now attached to the board. Add solder to other pad. If the first pad needs a little more solder, you can add it now. Otherwise, you're done. All of this before your hot air station warms up.

author: KL27x
author_rank: Super Contributor
timestamp: August 01, 2018, 06:26:19 am
content: QuoteThis is a good strategy to teach to a beginner. But it's not very good for doing a large number of components.The reason most people initially prefer a fine pointy tip, like a chisel tip, is because they are afraid of unintentionally touching surrounding board/pads/components. Previous experience with thru hole and solder wire has suggested that this bad, because it leaves bridges and whatnot. Hand in hand with that, they might prefer a gel flux that only goes where they intend the tip to touch. And along with the pointy tip, they find it works a lot better to feed solder wire rather than paint the solder on, because that tip can't hold a solder bead in a usable fashion. The end result is a dance between picking up and putting down iron, tweezers, solder wire, +- pickup tool. In particular, the tweezers and solder wire dilemna is a major problem. If we had 3 arms, this might be the bees knees. But since we don't, the result is highly inefficient. This is all due to the initial starting point, which was chosen due to constraints believed necessary, or at least beneficial, at the time. If you are soldering like this, you are running a self-imposed high precision gauntlet that resembles a game of Operation, when it is not actually necessary. Wave or jet soldering can solder 95% of what you are doing, and the solder touches everywhere.When you lose your (mostly unnecessary) fear of messing up the surrounding board you may find that there are much larger tips that will get the job done faster and easier. Hand in hand with using these larger tips is spreading the flux around a larger area. You are intentionally putting flux where you don't intend to touch the iron (but will, sometimes). Then it makes most of the surrounding area safe for the larger tip to touch without leaving dry solder strands/blobs. You now only have to worry about avoiding contact with unpopulated pads. Even briefly touching and reflowing pre-existing joints mostly won't matter too much. If they are in the path, you might just go right through them, intentionally reflowing them. That said, there is a hierarchy of components which bridge easier, and you have to take that into account.The main problem with fluxing a large area is that the flux will tarnish unpopulated pads. It's not too big a deal for component pads, because when they eventually get populated, the flux will eat right through the tarnish. But you have to avoid fluxing ICSP pads and other contacts/fingers, unless you are going to wash the board, after.With the right techniques, it can be faster and more reliable to hand solder boards than to even use stencil paste and oven (without a PnP machine, anyhow). But a lot of us are spending 90% time and effort designing the circuitry and pcb, and are only soldering a few boards. Or we are purchasing a single board from someone else's design, and there is no room for error. It's hard to lose the fear, when the ratio of time and effort is so skewed. The PCB is the result of a relatively large bucket of sweat and tears plus money and wait time. It's no big deal to spend more time and effort in the final step that brings it all together. And so the baby elephant grows up and never realizes he can break the rope.But the beauty of electronics, in general, and PCB's in particular, is the ease and cheapness of which a complicated thing can be replicated, more or less exactly. The Victorian age produced amazing machines to drive complex mechanical algorithms... but to replicate them required tons of labor and hand-tuning of gears and ports and moving parts. A PCB just needs the connections to be made. Furthermore, the manufacturers of SMD components have put a lot of science and experience into the design and spacing of pins/pads to make this easier, by taking advantage of things which you may not yet be realizing in your soldering technique. "Breaking the rope" opens up an area of small quantity production which would be unreasonably expensive to outsource. And a lot of these tricks will be useful in prototyping and reworking.

author: sourcecharge
author_rank: Regular Contributor
timestamp: August 01, 2018, 06:53:58 am
content: Well, I just got done, soldering the ucurrent boards.I used that cs hot air solderer, and that solder paste.Everything went great, and I found that using the syringe to put the paste on the pads really wasn't controlling the amount of paste on them.So, I laid down a line of paste on the table, and used the exact-o knife to "cut" the right amount of paste for the small teeny tiny itty bitty evil pads which turns out to be about half of what the syringe can blob out. Of course this is just a subjective observation, and I don't know exactly how much that should be use, but it wasn't much.After placing the parts, I used hot air solderer at about 300C with a low air flow.I worked like a charm, except for 1 or 2 small 100k resistors standing up but I was able to get them back in to place while continuing the hot air flow.After the pads had the paste, and the parts were in place, the whole board was soldered in less than about 2 mins give or take a min.I really like that method, it was really easy, just kept moving the nozzle around about 1/2'' away from the board, and it was like magic.Thank you Dave for the great design and easy to make ucurrent.PSAfter I got the boards, I realized that I should have asked for at least the cost of a paste stencil from the pcb manufacturer. When I was first trying the paste on the practice board, I noticed the amount of paste was too much, so I was thinking of making a 3D printed paste stencil. After loading it in cura, I realized that I would have to use the 0.2 mm nozzle which would take 2 hours to install, while 1 hour to print. And that's when I thought, that I could just use the knife, which turned out to be just fine. Anyways, all I did to make the stencil in cura (the slicer program that makes the 3D printer run), was to take a screen shot of the gerber files with the edges and the pads, copied them to a paint file and colored everything black and white. Cura can make 3D images of 2D pictures, and it can size it proportionally to the correct dimensions. I actually don't have any use for it, but if anyone wanted to, they could just use that method.Thanks again.

author: KL27x
author_rank: Super Contributor
timestamp: August 01, 2018, 07:58:06 am
content: A full sized framed stainless steel stencil runs like 150-200.00, IME. I'm sure some manufacturers have cheaper offerings without the frame, or even mylar.I'm surprised no one mentioned it, but there the 858D hot air station has a huge user base because it consistently works as it's supposed to. And it costs less than the thing you linked. If you want to do SMD rework on a budget, I'd highly recommend it. I shelved a $200 hot air station in favor of the 858D. It works good enough and has lasted tons longer than what the more expensive station got before its first heater died. I don't even care about replacement heaters. When the 858D dies, I'll just buy another one.

author: janoc
author_rank: Super Contributor
timestamp: August 01, 2018, 07:31:22 pm
content: I have the Atten 858D but it is not that great station, even if you get the original and not one of the millions of poorly made knockoffs where some even come with live mains on nozzle ...It is OK for small things but if you are getting it hoping to rework larger chips, parts with large thermal pads, BGAs and multilayer boards, you are going to swear a lot. It just doesn't have enough power for that task. The Quick 861DW Dave reviewed recently is much better and while more expensive, it is worth it, IMO.

author: jmelson
author_rank: Super Contributor
timestamp: August 01, 2018, 09:16:32 pm
content: Quote from: janoc on July 21, 2018, 01:13:28 pmYes, I hacked a GE toaster oven to do reflow. It has 4 heating elements, horizontally. 2 above, 2 below the rack.I got a ramp&soak thermocouple controller. I found the best control of temperature was by poking the thermocouple into a plated through hole in the board.I've done several thousand boards with this.Jon

author: sourcecharge
author_rank: Regular Contributor
timestamp: August 04, 2018, 07:42:39 am
content: Well, I tried out the uCurrent, and after figuring out how to connect it correctly to my specific circuit that has more power supplies than I really should have, I measured it against two Mastech bench top meters.I found my ground loop, and I was able to get rid of it too without using isolation, at least for low voltage input.All in all, what I found with the uCurrent, when set at the mA setting, using the 10milliohm shunt, it was about 100uA less than the measurement from the two current meters of about 238mA. These meters are not calibrated, and purchased years ago, but I was reviewing the accuracy of the DC current measurement under the mA setting. The mA setting had a .05% +- 6 digit error, with a 10uA lowest digit.That means the measurement from the Mastech meters were within 0.05% and then you add or subtract 60uA.The uCurrent is well within the 0.05% error as advertised, and now, I have a current meter that can measure mA with only a10 milliohmadded impedance vs about a measured11.88 ohmsfrom those Mastech meters.Thanks Dave Jones!