@vindoline suggested this belonged in the USA Cal Club: Round 2 thread. However, in writing this I realized it really is a thread of its own.
for prior context start here:
https://www.eevblog.com/forum/projects/ar488-arduino-based-gpib-adapter/msg2565660/#msg2565660As a use case consider checking my RF gear. I need to step through a series of frequencies and power levels and feed the output of my 8648C to the spectrum analyzers, frequency counter and power meter. I could use a splitter to feed the SAs and counter, but I need to use an SMA relay to feed the power meter. My 8560A can't check 8648C harmonics of 3 GHz, but the 8566B can. By switching the 8548C to the 8560A, 8566B, 5386A and 438A in sequence using SMA relays I can check them all against each other. At each step of the 8648C I'll want to step the attenuators and ranges on the 8560A and 8566B. That's a *huge* amount of work to do manually. What it needs is a host PC program that reads tables in CSV format which describe each step in the test sequence.
With a GPSDO feeding the counter all I need is a good cal on the 438A and one the power sensors. Ideally that could come from a fast rise time square wave tied to the primary voltage reference and a limited range Kelvin-Varley divider. So all that would need a regular cal is the voltage reference and the divider. Everything else would be derived from those by first principles. The GPSDO either works or it doesn't.
TiN is critical of using relays, which is quite legitimate at the level of accuracy he's pursuing. But he doesn't do RF and I don't need basic voltage and resistance accuracies below 10 ppm. In fact, I'd be hard pressed to come up with a use case that required 100 ppm. My goal is to be able to do an annual cal of my own bench without it requiring so much effort I don't do it.
If the relay selection is not built into AR488, then I either need a GPIB relay controller or I need to control two USB devices. AR488 can be a controller or a device. So a GPIB controlled switching unit needs all the functionality of AR488. I have three 44421A boards with terminal blocks, but nothing to drive them yet. So a Mega controlling those would give me 60 channels. That's overkill for the lab cal application. But being able to use the same FW base for a bare bones GPIB-USB interface, an enhanced version able to control a small number of relays for the cal application or a GPIB port scanner device by simply changing compile time flags seems to me a very sensible thing to project. It scratches the itch.
I bought a $40 GPIB-USB device on Amazon, but it was Windows only and would not work on Win 7 Pro 64. I've been rather less than enthused about buying one of the flood of counterfeit HPAK and NI devices. Via the Cal Club I discovered a good solution, the AR488 FW.
my primary concern at present is simple. Is there other functionality which would be desirable? I do things in small steps and test at each little step. But knowing where I am going is important. It's painful to realize you have to discard a bunch of work because you didn't recognize a fundamental limitation in the initial design.
Have Fun!
Reg