Time Electronics 9814 IEEE-488 Interface testing

I mentioned in an earlier post about this instrument that I might try to get IEEE-488 working with it. I'd naively assumed that one could simply search on eBay for "USB to IEEE-488 interface" and pick something up that would have an open source Linux driver for about £10.  I was slightly surprised to find that the new price for such an item was actually over £1000, which I suppose just demonstrates that IEEE-488 was never used outside of labs, and as such, why leave money on the table by making it cheap ?

Anyway, it turned out that there's a very nice Arduino project that just needs a cable to be wired up, so I thought I'd have a go at that since I had a Mega in the cupboard.

AliExpress obliged with a cheap cable that I could butcher, and I set to work with a set of pins and some crimping pliers

After a bit of crimping, sorting out the wiring diagram from the AR488 manual, and full checking for connectivity, I had this mess

The AR488 software needs some minor configuration to tell it what board you're using and to set up a few options, but once that was done, it loaded cleanly into the board. 


I plugged the IEEE-488 connector into the 9814, switched it to Remote mode, and tried typing a decimal number into the AR488 console. I was quite surprised to find that it worked first time, the 9814 accepted the input and displayed it !

As mentioned in the earlier post, this unit has a very basic version of the instrument software, so the remote interface is minimal.  You send it a voltage string in ASCII, in the form "13.10715" terminated by a carriage return.  "R1" to "R4" select 10mv to 10V ranges, and "RA" (default) sets auto-ranging, where it'll select the most appropriate range for the input voltage (expressed in volts). If you explicitly select a millivolt range, it expects the voltage to be specified in millivolts.  The only other choices are "G1" and "G2" which select and de-select Group Execute Trigger mode, and "P" which selects Percentage mode.  

In GET mode, the instrument will only execute the input it's received on receipt of an IEEE-488 GET command.  The idea being that on a shared bus you can pre-program multiple instruments, and then start them all off simultaneously via a broadast GET command.

Percentage mode allows the output to be modified by from 0.001 to 9.999 percent. This is for use in  calibration, where you would set a known output (say 1.00000V), and then use Percentage mode to adjust it until you see the expected result on some other measuring device. That then directly gives you the percentage error in the device being measured.

Hooking it up to a simple Python script to ramp the voltage up and down:

It'd be nice to try to get it recalibrated, just to see whether it's still capable of the original specs, but I don't happen to know anyone with an appropriate and calibrated high spec DVM.




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