Friday, July 13, 2007

USB instruments - new Keithley DMM

So I just found out today that Keithley has a new digital multimeter (DMM) out that a) is connectible via USB and b) is less than $1000. The 2100/120 appears to have most of the standard functionality you'd expect for a good DMM. I've used plenty of Keithley's equipment in the past and I've had very few complaints. One of these days I'll post something comparing different test mfg companies, but not today.

What interests me the most is that it's USB compliant. In my experience, test engineers are pretty conservative about switching to new technologies. It makes no sense to switch to something until you're sure it won't screw up your measurements. When I worked at HP I was part of a team introducing a new spectrometer that had an Ethernet port. That port was used for internal access to the embedded code, among other things, and I thought it would be great for customers to have TCP/IP access to the instrument instead of just HP-IB. The idea was shot down by marketing because it was considered "too new".

The GPIB interface has been around for a LONG time, and even longer as HP-IB (I think it's in the HP/Agilent handbook that you have to call it HP-IB). Is it time to get rid of it? The downsides include
  • Those cables can be very expensive
  • You have to buy and configure a separate interface card
  • The cables and connectors are bulky
  • Interface speed can be a limiting factor
Of course there are a couple of upsides as well: the cables can be well-shielded, and connectors can be daisy-chained.

But personally, I've already used two instruments with USB interfaces, and I really like the idea. Now that other companies appear to be offering USB, I'm read to kick the GPIB habit. Is there a 12-step program for that?