The justification and selection of test equipment for a company lab. - Page 1
Forum section: electronics / testgear

author: CM800
author_rank: Frequent Contributor
timestamp: November 27, 2015, 12:31:03 pm
content: I am going to be working on a new project revolving around the development of a 2 quadrent brushless drive for a customer, (aprox 10,000 per year)We already have a suitable, Lecroy scope (400MHz, 4 channel)however we are rather inequipped with other gear.I have been looking through gear that I think will be needed, I would like a second opinion, as this is a small company I work for we have a limited budget.For a bench power supply, I was thinking of one of these:http://www.rigol-uk.co.uk/Rigol-DP831-DC-Power-Supply-p/dp831.htmAs this drive will be around 12V at higher currents (15-25A) would a high current PSU be required or could I make do with a variac power supply?http://uk.farnell.com/ea-elektro-automatik/ea-ps-5040-40-a/power-supply-1ch-40v-40a-prog/dp/2418749I suspect that it would not do well due to mains noise and regulation however.I am unsure how essential a function generator will be for this job, however I was thinking of this one here possibly:http://www.rigol-uk.co.uk/Rigol-DG1062Z-Waveform-Generator-p/dg1062z.htm#.VlhKbL-vyU0I imagine I will also need some Oscilliscope current probes, any recommendations?I don't think a differential probe will be needed due to the low voltage for now.What other equipment would be recommended?I am also trying to futureproof thing for future projects, I am a HNC electrical engineering student so I am very much still in the process of learning.However I have been told I have a better grip then many of my classmates due to several years of hobbiest experementing and learning / reading.One of my main aim is trying to compile a cost-justified list of test equipment to present to my manager and be able to actually explain why I need each peice and at that specification.Thanks in advance, any advice and tips would be greatly appreciated.

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2015, 12:43:16 pm
content: Quote from: TCWilliamson on November 27, 2015, 12:31:03 pmYes.Quote from: TCWilliamson on November 27, 2015, 12:31:03 pmIf the motor is fixed at 12V then a variac doesn't make any sense.What you need is plenty of amps. Get at least double what your maximum expected load will be, ie. 50A or more.12V @ 50A isn't anything unusual, most PC power supplies can do that and you can get acheap 50A supplyfor about $50.(I'd pay a little bit more than $50 though, just in case).

author: tautech
author_rank: Super Contributor
timestamp: November 27, 2015, 12:48:14 pm
content: These new FG's are worth considering:https://www.eevblog.com/forum/blog/eevblog-806-siglent-sdg2000x-arb-function-generator-first-look/https://www.eevblog.com/forum/blog/eevblog-805-siglent-sdg2122x-arb-generator-teardown/

author: Ian.M
author_rank: Super Contributor
timestamp: November 27, 2015, 12:52:13 pm
content: If "12V" is a euphemism for powered by a 12V lead acid battery, you will need a power supply that's adjustable up to 15V. You will also need an appropriately rated dynamometer for the motor horsepower and speed.

author: Fungus
author_rank: Super Contributor
timestamp: November 27, 2015, 01:00:01 pm
content: Quote from: Ian.M on November 27, 2015, 12:52:13 pmThat's true, I didn't think of that.

author: CM800
author_rank: Frequent Contributor
timestamp: November 27, 2015, 01:11:29 pm
content: Quote from: Ian.M on November 27, 2015, 12:52:13 pmThat is correct, this will be installed on vehicles. A good point I had not concidered.We have can put a rotary encoder to measure the speed during testing and apply torque to it using another motor with a large variable resistor across the terminals. Accuracy is not too important due to the application of the motor.Quote from: tautech on November 27, 2015, 12:48:14 pmThey look nice. I will certainly consider them, could be used for noise testing / filter testing as well.

author: Ian.M
author_rank: Super Contributor
timestamp: November 27, 2015, 01:13:15 pm
content: The first question when someone says "12V" without other context should always be "Is this an automotive application?"You need even more PSU headroom if its for developing an on-vehicle application - under fault conditions you could get a significant over-voltage.The other issue is that USB connected debuggers for most MCU development systems don't do well with the noise a high current drive commonly induces on the system ground, so you may well need a USB isolator compatible with your debugger to break the ground loop back through the host PC to the grounds on your other test equipment.

author: CM800
author_rank: Frequent Contributor
timestamp: November 27, 2015, 01:15:26 pm
content: Quote from: Ian.M on November 27, 2015, 01:13:15 pmA good point there as well, I have noted that down. We were looking at getting one previously but never finalized it due to slow responses from the supplier and lack of immidiate need.EDIT:What kind of multimeter should we get?I already have a Keithly 5 1/2 digit I could bring in if needed.

author: dr.diesel
author_rank: Super Contributor
timestamp: November 27, 2015, 01:20:57 pm
content: I would heavily consult the lead EE in charge of the design/project, he should have a pretty good grasp on what's involved with the design/prototyping/testing and related equipment. We're just kinda guessing based on a 3 word project description.

author: Ian.M
author_rank: Super Contributor
timestamp: November 27, 2015, 01:25:26 pm
content: Multi-channel data-logger, continuously monitoring supply voltage and current, phase voltages and currents to the motor, speed, torque, motor and driver temperatures and any other system parameters you find useful for post-mortem analysis after you convert yet another set of MOSFETs to silicon shrapnel.

author: CM800
author_rank: Frequent Contributor
timestamp: November 27, 2015, 01:31:29 pm
content: Quote from: dr.diesel on November 27, 2015, 01:20:57 pmI am the lead EEI have a good idea of the project management / development stages in developing a product as my father was involved in it heavily in a different but similar industry.The drive is a +/- 10V controlled brushless motor driver, low-cost, medium-quantity, compact / multi-board. 12V automotive supply and around 15-25A current.Quote from: Ian.M on November 27, 2015, 01:25:26 pmThat was actually something I was just discussing with my collegue. I think we will make our own using an Arduino, a quick and dirty C# program and a group of temperature sensors, this will be more cost effective for us, we can also then modify it easily and use it for the testing stages in temperature controlled boxes and so on.

author: Ian.M
author_rank: Super Contributor
timestamp: November 27, 2015, 01:38:24 pm
content: Quote from: TCWilliamson on November 27, 2015, 01:11:29 pmThat dyno solution is likely to have significant torque ripple which will make all measurements much harder to take and may interact undesirably with your control loop.

author: CM800
author_rank: Frequent Contributor
timestamp: November 27, 2015, 01:45:41 pm
content: Quote from: Ian.M on November 27, 2015, 01:38:24 pmwe have some brushed motors here that have a very smooth torque when shorted out, it should do, if not we can use the ol' clamp-it-with-a-wood-block trick. and make use of the motor specs to gauge it.

author: GNU_Ninja
author_rank: Regular Contributor
timestamp: November 27, 2015, 01:46:35 pm
content: Quote from: TCWilliamson on November 27, 2015, 01:15:26 pmThese Tenma ones are OK. Reasonable price and decent spec. Data logging too.http://uk.farnell.com/tenma/72-9380a/multimeter-digital-handheld-trms/dp/2100037http://uk.farnell.com/tenma/72-7730a/multimeter-dig-hand-held-19999/dp/2100035?MER=baynote-2100035-prEDIT: Though in the last 10 minutes, I just ordered myself another Fluke 115. Very basic, very nice

author: dr.diesel
author_rank: Super Contributor
timestamp: November 27, 2015, 01:47:15 pm
content: So you're only responsible for the motor driver? A couple of thoughts:- What provides the demand signal? Can you simulate this?- Duty cycle?- What is it driving? Automotive applications like windshield motors are very abused, do you need to simulate this?- Amb temp considerations.

author: KJDS
author_rank: Super Contributor
timestamp: November 27, 2015, 02:01:51 pm
content: I like these, about the only high current power supply manufacturer that I've had lots of and never seen a failed one. That might have been because the previous user wasn't running them hard, or even much at all, but they did seem well made, though it wasn't this exact model I had a big pile of.http://www.conrad-electronic.co.uk/ce/en/product/512319/VOLTCRAFT-HPS-11530-450W-1-Output-Variable-DC-Power-Supply-Switched-Mode-Remote-Control-Bench?ref=searchDetail

author: CM800
author_rank: Frequent Contributor
timestamp: November 27, 2015, 02:03:26 pm
content: Quote from: dr.diesel on November 27, 2015, 01:47:15 pmThe motor / gearbox is also being handled by our company, however that has been taken care off.Yes I can simulate the demand signals. They are not complex, +/-10V, possibly RS232/485 at worst however we will likely stay with Analogue.- Duty cycle is short, I wouldn't expect this to be used more then 1/2 hour a day max realisticly.- There is the potential for stalls I suppose, I will be discussing further specs with the customer and my manager soon when he is back from the business trip.- Industrial. Running in temperatures between -10 and +40 tops. however I will design it for the full industrial range except lower upper temperature bounds (60*C)

author: dr.diesel
author_rank: Super Contributor
timestamp: November 27, 2015, 02:10:32 pm
content: You're probably well aware of this, but, don't forget that automotive is very noisy. High energy ignition systems and alternators etc, and their noise level will change with vehicle condition, can get very severe. Might be a deciding factor on your demand signal.

author: CM800
author_rank: Frequent Contributor
timestamp: November 27, 2015, 02:20:56 pm
content: Quote from: dr.diesel on November 27, 2015, 02:10:32 pmI am indeed aware, thankfully the engine will not be running in use, however I intend to implement suitable filters and protection regardless.Any thoughts on scope probes for my Lecroy Wavesurfer44MXs-B?

author: Michael Rempel
author_rank: Contributor
timestamp: June 14, 2021, 12:49:46 pm
content: Just a thought on communication, CANbus is already part of most vehicles, and offers noise supression that is hard to beat. You CAN do it pretty cheaply too.

author: Gyro
author_rank: Super Contributor
timestamp: June 14, 2021, 06:55:37 pm
content: Necro-post warning.

author: Ian.M
author_rank: Super Contributor
timestamp: June 14, 2021, 08:34:10 pm
content: Yep its seven years deadand CM800 hasn't even been online here for nearly a year!Hope he's OK, the last year and a half have been difficult and we've lost far too many 'greybeards' . . . .