Building my First Bench, Please Critique? - Page 1
Forum section: electronics / testgear

author: mpfishe2
author_rank: Newbie
timestamp: March 28, 2018, 01:02:10 am
content: If these kinds of posts aren't allowed please feel free to delete.I'm fresh out of college and wanting to piece together a nice workbench for embedded work and vacuum tube amplifier design/repair.I've currently got a Tektronix 2465A that is in need of calibration.Here's a list of what else I'm thinking?- Sencore PR570 Variable Isolation Transformer- HP 33125A DDS 20MHz Function Generator for signal injection/burn in use- B&K Precision 891 Impedance Analyzer to be used for checking LCR components- Keithley 2000 Bench 6.5 Digit Multimeter for precision measurements- Fluke 8808A Bench 5.5 Digit Multimeter for circuit design- Keysight MSOX2024A 200MHz Mixed Signal Oscilloscope for embedded work- Fluke 179 handheld Meter for troubleshooting/mobile use- Fluke TIS75 Infrared Camera for all purpose useI'm not sure whether I could get by with the DSO model instead of the MSO for embedded work. Having the decoding capability would be extremely helpful in troubleshooting embedded designs in circuit.I also don't have a bench supply chosen? I'm not even sure where to start for those to be honest for what I would like to work on. I've looked at old Kepko, Lambda, and Surplus HP rack-mountable supplies. What is the general consensus for these?Is the BK Precision a decent choice for an LCR meter?I'd like to have some professional opinions and guidance pleaseThanks and take care,-Matt

author: TK
author_rank: Super Contributor
timestamp: March 28, 2018, 01:23:07 am
content: MSOX2000 scopes cannot decode serial protocol on digital inputs, only on the 4 analog channels. Also it only has 8 digital channels. An MSO is good for a quick serial procotol check, but I prefer to use a logic analyzer for a more serious serial decode (I use the Zeroplus LAP-C 16128) as I can analyze over 100 protocols that are included for free in the software. Most digital analysis on embedded systems today is serial protocols (i2c, SPI, I2S, etc), so an MSO is not as useful as in the past.

author: DaJMasta
author_rank: Super Contributor
timestamp: March 28, 2018, 01:55:12 am
content: That's quite a heap of a purchase, it may be good as a general strategy to start with the parts you know you will use for your first project or two and then scan around for deals or different models or whatnot and build up the collection of equipment that way. A bit less of an initial hit on the pocket book, but also perhaps you'll find that you want some specific feature or don't need such high precision in something and you can swap in a more appropriate instrument to suit your needs/habits.Looking at the general list, you've got a pretty thorough set of things. I would consider something like a Siglent SDG2042X or comparable... I can't actually find the part you're talking about directly, but the Siglent 2000X AWGs have been great in the performance and value segment for a while now, and would more than surpass the capabilities of a 20MHz DDS.The B&K LCR meter seems..... really beefy. How accurate do you need? If you want to be finely characterizing parts, maybe something like a bench LCR meter like that is a good choice, but if you're doing coarser binnings or just parts verification, then a handheld meter can do plenty. I'm pretty happy with my DE-5000 and it's like an eighth of the price... and the base accuracy is still pretty good! If you want extreme accuracy, maybe consider something like a low frequency network analyzer.Personally, I don't know if a 6.5 and a 5.5 digit meter are worth it. Having a couple of meters (or a few if you don't have an SMU or a dedicate power meter or whatever) is fine and good, but there's really nothing keeping the Keithley 2000 from doing anything that 5.5 digit meter can do just as fast and easily. Having a bench meter and a handheld meter can be really useful, as they're suited for different things, but I don't know if it's worth bothering getting a high precision bench meter and a higher precision bench meter unless you know you want two and definitely can't afford a matched pair. Having only one kind of interface and setup/characteristics would be a benefit to me if I wanted to measure things with two or more bench meters, and if I'm going to use the bench meter instead of the handheld, I'm not going to bother with a 5.5 digit if there's a 6.5 digit sitting next to it unless the 6.5 has some annoying quirk in its usage. All that said, I also really like modern meters with trend charts, it's just a nice thing to have when you're paying attention to several things at once or want to see very small changes over time (monitoring drift and stuff), and something like a 34461A do a good job with that (maybe for the price of that 6.5 and 5.5, though).I've definitely liked having my thermal camera around and think it's a great inclusion, but unless you have a great deal on a Fluke TIS75 or already have one... consider other options. The faster update rate is great, but it doesn't matter much for most inspection work, so you can save a bit and go with one of those federally-restricted 9Hz models, even in that nice high resolution. You pay a premium for the export restricted fast updating cameras, and while they are nice, I haven't run into many situations in electronics work where it would have been a big improvement over a run of the mill 9Hz camera.A bench power supply (or two) is definitely one to add. If it's for embedded work you probably don't need much current, but maybe a triple output linear supply with a few amps to play with and then something with a high voltage output for your tube stuff? Also could be worth considering getting a high voltage probe for your scope for the tube work as well, the meters won't complain at a couple hundred volts, but nothing else will be usable there, really.Anyways, it sounds like quite a bench. If you have the opportunity to space out the purchases over a couple of months you'll better be able to determine what you want, what you need, and what you are missing, and I think you'll end up with a more complete setup as a result.

author: tkamiya
author_rank: Super Contributor
timestamp: March 28, 2018, 02:39:55 am
content: I'm going to suggest starting a project or two with nothing more than a handheld VOM and a scope, and see what you feel is needed.Everyone has a "style". That dictates what instruments you'll want. I tend to stare at diagram for long time and think. So my bench time is really not spent at my bench. I prefer analog VOM rather than digital for repair work. You can do a lot of "tube stuff" with minimal instrumentations.I don't know what kind of embedded work you have in mind.

author: mpfishe2
author_rank: Newbie
timestamp: March 28, 2018, 03:05:31 am
content: Thanks for the very detailed replies and critiquesI just finished an MS in graduate school and was a technician in the field for a while, so that somewhat explains the equipment choices.I'm currently an RF Engineer by trade so the monetary investment aspect isn't really of concern; all except for the Keysight of course which is a heavy hit to the wallet. I reviewed the datasheet for the MSO serial decode protocol list and I do see I2C and SPI supported, but was surprised RS232 required a $500 hardware upgrade. I'd love to have a digital scope for the math features, digital image capturing (I have horror memories of having to take camera pictures of o-scopes in the past), and generally more user-friendly touch screen. I guess I could do without the MSO model, grab the DSO 4 channel model, and look into investing in a less expensive logic analyzer? I'm primarily an analog guy, so the digital debugging is more of a nicety, not so much a necessity. I don't plan on real-time OS embedded applications, less common digital communications protocols, or need to debug overtly complex interrupt routines.Good call on the HV probes. Didn't cross my mind!The accurate impedance analyzer is for measuring transformers and possibly future RF work for old tube radio repair utilizing superhets. I just feel more comfortable knowing it's on my bench if that makes sense? Knowing this, if you still feel it's not the best choice I'd love to hear what you'd recommend?I'll look into getting the fidelity limited 9Hz update rate for sure. I don't believe I'll need fast ramp thermal gradient analysis capabilities, as my intent as a bench investment was more at-op temperature gradient analysis.I was thinking of getting a kepko 2kV unit for the high tension supply, but I'm not an expert for HV supplies and the possibility of needing to repair an older one somewhat frightens me.I'll look into getting a linear supply for the embedded projects. I know for embedded work CC and CV would be nice to protect the chips from overvoltage.I'll also look into the Siglent AWGThank you again for your replies. This is very very helpful. I appreciate all of the feedback!

author: rx8pilot
author_rank: Super Contributor
timestamp: March 28, 2018, 03:59:30 am
content: My humble opinion....What you think you need now is probably going to be different than what you actually need down the road. My approach would be to buy what you need as you need things for specific projects.Start with a modest scope that will eventually become your backup scope. A modest DMM that will become your backup. A modest solder station that will eventually become your backup. Even if money is not an immediate concern - it may be as you hone in on the more capable gear. As you get settled in, your projects will likely start to define what you need.

author: mpfishe2
author_rank: Newbie
timestamp: March 28, 2018, 05:18:27 am
content: Thanks for your replyAlthough this post comes across as holistic, what I have now is exactly as you mentioned. A $20 Craftsman Multimeter, an 8 year old weller adjustable soldering station, and the o-scope mentioned above. I currently have a project I'd like to start building which would benefit greatly from many of the components listed above and going forward. Little details like quality sharp probes, accurate measurement capabilities, waveform injection, continuity checking, a microscope for re-work, etc. really make all the difference in design time and troubleshooting capabilities. I have little to no capabilities as is with my current bench setup.Take care,-Matt

author: SWR
author_rank: Regular Contributor
timestamp: March 29, 2018, 01:59:11 pm
content: Quote from: rx8pilot on March 28, 2018, 03:59:30 amThat's a pretty good aproach to get started.You can get a pretty decent collection of instruments in one integrated package with the GW Instek MDO-2204EX for €1411.- 4ch 200MHz scope with 40M sample memory, 29K segments with search and downloadable apps (Go-Nogo, DVM, Data logger, Filters, Mask, Bode plot)- Spectrum analyzer from DC to 500MHz with >80dB dynamic range- Serial protocol decoder with memory decode and multi byte trigger/search with wildcards- 2ch 14bit 200Ms arbitrary waveform generator with tracking, modulation and sweep- Digital multimeter with Vdc,Vac,Idc,Iac,Ohm,Beep,Diode and Thermister with °C/F and 8 thermister curve types- Dual 1A adjustable power supply with overload protectionThat's 6 instruments in one compackt package but the PSU is only for powering logic boards, so you will propably need a beefier one.Here's a cheap 32V 5A PSU for $39:https://www.aliexpress.com/item/Digital-Adjustable-DC-Power-Supply-OVP-OCP-OTP-low-power-32V-5A-30V-110V-230V-0/32830418011.html?spm=a2g0s.9042311.0.0.Ilb1eaThere are many others if your needs are different.It would also be nice with a progrmmable load. I use this 4,5A $15 model for light loads:https://www.aliexpress.com/item/35w-usb-tester-electronic-load-adjustable-constant-current-aging-resistor-voltage-capacity-qualcomm-qc2-0-3/32677950277.html?spm=a2g0s.9042311.0.0.w73Bu1For higher loads up to 20A I use this $28 model:https://www.aliexpress.com/item/150W-DC-Digital-voltmeter-Constant-Current-Electronic-Load-200V-20A-Tester-Discharge-meter-car-battery-Capacity/32822372034.html?spm=a2g0s.9042311.0.0.w73Bu1Good luck with your bench.

author: rx8pilot
author_rank: Super Contributor
timestamp: March 29, 2018, 11:03:49 pm
content: Not sure how much space you have, but I saved a pile of money getting old HP power supplies. They can be very cheap, but big and heavy. Great bullet proof performance. I needed 6 channels and two of them fairly high power (500 watts) - so getting cheap was a good thing.I am now setting up a Labview Home program to control them, the user interface is rather sad but they have GPIB.

author: coromonadalix
author_rank: Super Contributor
timestamp: March 30, 2018, 03:53:04 am
content: hum the BK precision lcr maybe overkill for you, an deer de5000 or an usb pc lcr meter like the Accuhard A101 could do a very good job, the software is well made, and the conceptor can be reached if help needed, i'm waiting for restocking to buy one, at 119$ usd its very good, you will save some place6.5 and 5.5 digits meter, do you really need that kind of precisiondid you take to account the calibration price, a 50,000 or 60,000 count dmm wil provide you excellent results EX: Brymen 8xx series, fluke 87iv, 187 or 189 ... i've paid a fortune (over 1k $ in 2 month) to get Gossen Metrawatt meters like 28s and 29s, recently added Fluke 189 meters and his rare bp189 extended battery pack to my collection, i wanted easy acces to fuses and the possibility to expand working hours with external psu added to them and data logging features ... and don't cost to much to calibrate (75$ for fluke, 120$ for the gossen) near my town.has others said, invest in good psu's with constant voltage and current, an isolation transformer variac, an good scope, an good signal gen, an good solder station like hakko, and hot air station is a good start.In time you will adjust your needs, but dont pay too much at start, check feedbacks here and there ...I would not suggest any smps based psus, from 30 years experience, linear based ones will be more efficient with inductives or capacitives loads ... burned a few good branded ones ... with thoses kind of loads. The only ones i know who can survive anything where the Xantrex rackmount psu's, boy i've thrown everything at them, they never failed, i was given a chance to evaluate them.has a last comment, if you can buy some equipment with services manual already available, it would be very helpful in time. Take time to evaluate carefully your needs.