Opinion on headless instruments - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: August 07, 2015, 03:35:47 pm
content: Headless instruments are instruments that does not have a panel to interact with the operator on its own chassis directly. Instead, some means of communication is required to operate such an instrument and/or retrieve readings.Since all my instrument designs (currently M101 multimeter, M102 bench power supply and M108 active load) have USB and I have a few 7-port USB hubs, I am wondering if I can just forgo the human interface on the instrument completely and make the entire stack of instruments USB operated? This is a bit like those GPIB-operated rack-mount instruments, just like assuming the rack is opaque and never will be opened, and the GPIB is replaced with the more consumer-friendly USB bus.How do you think of such instruments?

author: mazurov
author_rank: Frequent Contributor
timestamp: August 07, 2015, 06:53:28 pm
content: If humans never need to operate an instrument directly, i.e., using their limbs, then knobs would be redundant. A display would be nice since humans enjoy staring at glowing things.I do it other way around: take a bench instrument and construct a test jig for it then drive both from a computer. Producing a good multimeter is difficult; if you need the accuracy, the 34401a will always be cheaper to buy rather than make yourself. This multimeter, driven via GPIB, plus power supply, plus a trivial jig (also computer-driven), make a darn good curve tracer for which no ready-made analogs exist - for very little money. The instruments can also be used for something else when you no longer need a curve tracer.

author: eas
author_rank: Frequent Contributor
timestamp: August 08, 2015, 04:28:09 am
content: People rarely regret making things easier to debug. In fact, I'd guess the only time they regret it is when they never end up using the thing in the first place, in which case they may regret making it at all.

author: technix
author_rank: Super Contributor
timestamp: August 08, 2015, 06:34:01 am
content: Quote from: mazurov on August 07, 2015, 06:53:28 pmFor me M101 will not be a 34401a-class instrument. It have a guaranteed accuracy of 16 bits (equivalent to 4.5 digits) and a few more noise-infected bits (that nay or may not be able to be filtered out in software).M103 is an interesting case - since its control circuitry use so little power it is bus powered from the USB port.

author: lapm
author_rank: Frequent Contributor
timestamp: August 08, 2015, 07:09:03 am
content: Personally i think display on device with buttons is good backup. Things brake, even USB brakes sometimes... Having second way to operate device comes handy when one needs to run de-bug on why something is not working, helps narrow it down without need to rip device out of rack right away.

author: Pjotr
author_rank: Frequent Contributor
timestamp: August 08, 2015, 09:31:34 am
content: Controlling instruments remotely is useful for automated test set-ups, like quality control and automated adjustments in production or logging a process. But hooking up my laptop and booting the thing and starting dedicated software, just to measure a voltage somewhere?It all depends on your goals and ease of use.Footnote: I must admit, some feel comfortable only if things are overly complicated

author: German_EE
author_rank: Super Contributor
timestamp: August 08, 2015, 01:55:31 pm
content: As the owner of two 'headless' instruments I'm all in favor. I have a Picoscope 3206 and a USB RF Power Meter that was built from a kit and both operate without problems. If I could build or buy a 10-digit frequency counter I'd add this to the list. I don't see the point in having a shelf of test equipment each with it's own display and controls when I can do it all from the screen of my laptop.

author: HKJ
author_rank: Super Contributor
timestamp: August 08, 2015, 04:40:52 pm
content: I do run a couple of automated test stations, but I like to have display and buttons on most of my equipment. It makes it easier to see actual status and do some quick measurements.My only exception is a Picoscope, I do prefer that for a ordinary scope in most cases. The advantages are less space needed on the workbench and it is much easier to grab screen shoots (I need that fairly often).

author: nctnico
author_rank: Super Contributor
timestamp: August 08, 2015, 04:58:15 pm
content: IMHO it depends on the complexity of an instrument. In case of a logic analyser a PC offers a far superior user interface than you can ever get on a box. A complicated signal generator (AWG) could benefit from a PC interface as well if you need to create complex waveforms.

author: Fsck
author_rank: Super Contributor
timestamp: August 08, 2015, 09:27:06 pm
content: if you take a look at some of the system power supplies/loads from common vendors, you'd note that even though they're meant to be remotely controlled, them have some rudimentary front panel functionality so I'd suggest at the very least having some sort of display (you see this in some mainframes). I can't really think of a multimeter that has zero front panel functionality at all.you should note that by aiming for remote control, you're limiting the scenarios in which it'd be an optimal solution compared to products with decent panel functionality as well as remote capabilities.the only case I can see remote-only being a successful choice is if the cost is significantly reduced compared to having panel functionality.

author: DanielS
author_rank: Frequent Contributor
timestamp: August 08, 2015, 11:57:48 pm
content: Headless instruments intended for automated testing and calibration systems, sure.Headless bench instruments on the other hand, I don't think so: I like being able to move individual instruments from any location to any other location and not having to connect them to anything else to use them or use them in a fire-and-forget sort of way without having to worry about attaching a PC.As Fsck said, tons of system-oriented instruments still provide at least basic controls and status indication directly on the instrument. Having a dial or keypad to enter voltage, current and power limits on a power supply is always nice and having a display for the output voltage is also useful for safety purposes since it tells you whether the outputs are on and how high the voltages and currents on them are. If the unit reminds you that the output is set to 100V 5A without having to run to your PC to check, you or others sharing your work space are less likely to have an accident from forgetting or not knowing what it was set at.

author: technix
author_rank: Super Contributor
timestamp: August 09, 2015, 01:37:04 am
content: Quote from: Pjotr on August 08, 2015, 09:31:34 amMy workbench is a combined CS/EE working area where there are always a few computers around, one of them is a dual Xeon-based computational powerhouse.Also for some headless equipments I can have Bluetooth Low Energy built in and allow iPhones and iPads to control them wirelessly, if I want to.

author: charlespax
author_rank: Regular Contributor
timestamp: August 09, 2015, 10:22:33 am
content: It depends on the application. Multimeters a usually bug chunky bricks that do one thing at a time. But they're reliable, dead simple, and always get the job done. There are other meters like the Voltset, which has yet to ship, that need to be paired with a phone to be used. That's great for remotely measuring something, but a hassle if you just want to measure a battery voltage.I think your designs are in a happy place where they work independently and can be controller over USB.