I'm looking to make a latency tester to test keyboard/mouse latency (similar to this) and total system latency (similar to this). I know how to solder, but I don't know the first thing about electronics or what I need to buy to create it. I'll be hiring someone online to program it. I'd prefer to buy off Amazon or some place with quick shipping.
Unless you are an electronics expert, you won't be able to build this. The image you posted radically "glosses over" the details.
Why did you post a project you haven't built, to the "showcase" forum?
I use a digital oscilloscope, it makes the job relative easy. Sorry to say it will cost many times what your link shows. Also schematics of the components will also help so you can determine where to connect.
if you have no clue about electronics and programming and you'll be hiring someone, let them that person recommend / purchase what s/he thinks will be needed for the project rather than impose constraints. that will make your life easier and responsibilities clearer as well if the project does not meet your requirements.
bring it to the Jobs and Paid Consultancy forum and mention your budget
@lovelicot done it for you.
Just spend the $90 and buy it and save yourself the trouble.
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Can we pin down the point at which the measure would be taken? Between a switch activated and data received? Is the data related to the switch?
Are we talking about delay from electric signals going over a wire? That would be tough to measure.
If you want to know about delays in mechanical motion of a mouse or human reaction time, the answer would be very different.
According to the photo, the delay is between activation of either the keyboard or the mouse and when the system responds by changing an element on the monitor.
First question would be how much resolution is needed. i.e., what's the minimum scan rate at the arduino end and the bandwidth of whatever microphone is used to detect the click. Although this might be short enough not to matter. Next, what UI detection component is needed. Photo shows a CdS photocell, but those are notoriously slow, so you'll probably need something like a photodiode that's sensitive in the visible region.
After that I think it's a simple matter of 1) User triggers tester to start 2) Arduino begins scanning microphone and photodiode to establish baseline readings 3) User clicks mouse and arduino detects change in sound (are we doing audio filtering/background elimination here?) and then within a certain timeout, looks for change in the photodiode reading 4) Assuming it got click and UI triggers, records the time interval and sends it to the PC or shows on a display.
Could be a fun project, but doing it for less than the $90 cost of the off the shelf device means placing no value on your time if it's to be done right.
I dont know the answer, but for me a significant issue would be;
If I were to build such a device, how would I check that its accurate ?
That's pretty easy, assuming you have the right test equipment. A loud enough switch for input and an LED for output and an oscilloscope will verify the measurement.
But even before we go there, I'm not sure what the need for the device is. i.e., what use is the data?
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For the peripheral latency portion, all keyboards and mice have different amounts of time and consistencies between physically pressing the button and the signal being sent to the computer. For actual top tier players (the people that can actually make money playing the game) that matters a good bit, but there's no good documentation about almost any products.
For the system latency portion, it would be to test how different settings in different games affect how large the input lag is (its not as simple as more fps = lower lag, surprisingly).
Budget is not a massive issue, I'd like to keep it under $300 though. The LDAT isn't available publicly and the other device I sent doesn't do exactly what I need.
Well, I think I presented a pretty good design document for anyone who wants to implement this 
Yup, you seem to understand what I need. Can you provide a parts list or some guidelines of what I should look for in parts?
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