I have recently acquired Seaward PrimeTest 250 and PrimeTest 350 PAT testers. Ever since my manager sent me to a PAT seminar by Seaward I have longed for the PrimeTest 350, it has Bluetooth data transfer (drool), backlit screen (drool), rechargeable batteries and in-situ charger (drool)… in a moment of madness I purchased one on eBay 2nd-hand, but later realised I could have had a better one with calibration certificate and more extras for less money, oh well! Such is life.
My PT350 is in good working order though, I sent it away for calibration and it passed so that proves that it works correctly.
I was very pleased with my purchase, and tried it out on a few items, but found that I wasn’t able to download via Bluetooth to my Mac, which I had running Windows in VMWare Fusions; the Mac would see the PAT tester as a Bluetooth device, but seemingly would not recognise the Bluetooth data download request, and because Bluetooth is shared between VMs and the host OS, I had the same problem from within Windows – the data transfer just wasn’t recognised. I learned through this experience that, although the Mac does support the COM emulation part of Bluetooth (which is used to emulate a serial RS232 port), there was no Mac OS X facility to do anything with it, seemingly it was the same case in Windows (even Seaward’s own PatGuard Elite software could not see the COM emulation). I had one final stab it this, and eventually stumbled upon someone’s own home-brew Bluetooth COM sniffer / download program, exactly what I had been asking for in the Apple forums!
This is called Serial Tools, and was written by a chap called Kok Chen, I thank that man. Anyway, here it is in case you are looking for it – http://www.w7ay.net/site/Applications/Serial%20Tools/index.html (opens in new window).
This at least allowed me to download the PAT results data directly to the Mac, but then what to do with it? I also managed to get Bluetooth downloads working fine on my works PC laptop, so I knew the Bluetooth in the PAT tester was OK. I used a Belkin Bluetooth adaptor, model F8T017; I could not use this with the Mac as OS X spits its dummy out if it sees two Bluetooth hosts, and as keyboard and mouse are both Bluetooth this is not a good thing. Anyway, back to the plot.. what there was of it.
The major part that was missing from the PT350 bundle that I bought was the RS232 serial download cable. Not a problem, you might say, they are ten a penny. Not so! This is a DB9 to 3.5mm stereo jack plug serial cable, so pretty rare to find these days. One thing was certain, I was not about to pay Seaward a ridiculous amount of money for one, nor was I going to pay a similarly silly amount of money for the one officially supported RS232 to USB adaptor they recommended (and said was the only one officially supported and tested by them).
I set about making my own serial cable – I purchased parts for the DB9 plug and a smart looking metal 3.5mm stereo jack plug, used a length of Cat5 network cable which was a perfect size for the plugs and feels nice and solid; I only needed three of the wires, so basically chose three colours that I liked and cut the rest short so that they couldn’t touch anything.
The basic wiring was simple – just Signal GND, Rx, and Tx was used, I found a serial wiring diagram online for an old digital camera download cable which used RS232, I opened up my PT350 and had a look at how they had wired the pins for the stereo jack in case they were doing anything clever, it was just three wires. The wiring of the DB9 uses the standard RS232 pin assignments for Signal GND, Rx, and Tx; no other connections are used.
DB9 pin 2 to tip
DB9 pin 3 to base
DB9 pin 5 to middle
Base is nearest the plug body, tip is at the end of the plug, middle is, well, in the middle. I used a multimeter to make sure I was connecting to the correct solder bucket, wired it up, and hey presto it worked first time!
I should backtrack a little here as I did download drivers for the RS232 to USB adaptor that I picked up for 50 pence from a car boot sale, which works with PC and Mac. It uses a controller chip which the computer recognises as FT232R UART, drivers for just about every operating system are available from the official website for this product here – http://www.ftdichip.com/FTDrivers.htm (opens in new window).
I used the VCP (Virtual COM Port) driver as I assumed that is what my PAT tester and the OS would recognise. Sure enough, it works a treat on the Mac and on PC (Windows XP, Windows 7), it even works in VMWare Fusions on the Mac running Windows.
So now I can download via Bluetooth or via RS232 serial cable, on Mac or PC. Here’s my cable wiring diagram:
The PrimeTest 250 is nowhere near as fancy, it uses simple pre-set sequences which are selected using buttons on the front of the unit, it is not particularly clever and doesn’t hold any test results, so these need to be recorded manually in a book. It is good for what it does, but the PT350 is in a different class. For the kind of tests I am most likely going to be performing, IT equipment, the PT350 should be all that I ever need. The much larger mains-only Europa Plus PAT tester that work own is capable of more powerful stress or load tests, but that is probably only really useful where mains leads receive heavy use or abuse, such as for power tools; IT mains leads sit under a desk most of their life and never move.