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Category — My Toolbox

My Toolbox — Oscilloscope

Fluke 196 with Pelican Case

Fluke 196 with Pelican Case

Why do I have an oscilloscope?  The real answer is that scopes are cool, and many years ago, I couldn’t resist when Fry’s had Fluke Scopemeters on sale — at 50% off!  So I own a 100MHz dual trace Fluke 196 Scopemeter.  Later I bought the yellow the Pelican case for it; the two are a great combination.

Since software ties everything together, I’m also the “systems” guy, and thus I should be able to troubleshoot the entire machine.  I do use my multi-meter much more than my scope, but the oscilloscope is essential when troubleshooting encoders, hall sensors, and the occasional electrical glitch which won’t show up on a DMM.

I’ve used other scopes, such as the Tek THS720 handheld, the Tek TDS 210 desktop, Tek analog scopes, and a Heathkit analog scope.  Recently, I participated in a hands-on demo of the new Rhode and Schwartz RTO1014 1GHZ oscilloscope.  It’s quite impressive, even intimidating at first, with all the buttons and things it can do.  Fortunately, such high powered scopes aren’t needed for typical factory troubleshooting; a dual channel, 20-100MHz real time digital does fine most of the time.

There is uncommon feature that’s really handy: isolated channels (each channel’s ground is isolated from the others).  With a typical dual channel scope such as the TDS 210, I can only view one differential encoder signal (channel 1 probe on A+ signal, channel 2 on A- signal, display mode set to combine channels).  But with a dual isolated channels, I can view two differential signals (channel 1 probe on A+, channel 1 ground on A-, channel 2 probe on B+, channel 2 ground on B-).

Hand-held scopes, such as the Fluke 196 and Tek THS 720, typically have isolated channels, along with ruggedness, battery power, small size, and a hefty price tag.  However, a 4 channel desktop scope is often cheaper than a 2 channel isolated channel scope.

I once spent a lot of extra time because I was too enamored with isolated channels.  The system had a servo motor with the differential encoder output split, with one set of signals going to a motion controller and the other set going to a custom board.  The motion controller was counting correctly, but the custom board wasn’t.

I set up my Fluke 196 to look at the differential signals.  The B+/B- signal did look smaller (less voltage swing) than the A+/A- signal, but it had to be OK because the motion controller was picking it up.  So I started swapping out components — and kept getting the same problem.

I figured it out when I looked at each signal (A+, A-, B+, B-) individually; the B- signal was dead (because of a broken wire in the cable from the motor).  The motion controller worked because it was less sensitive, managing to count the smaller transitions.  My lesson learned: check everything, and don’t make unsupported assumptions.

May 10, 2011   3 Comments

My Toolbox — Software

What software do I like on my service laptop?

  • All my development software.  I never know when I might need a particular software package.
    • However, licensing can be an issue; nobody wants to pay extra money for a license that sits mostly unused on a laptop.  Some software allows for multiple installations.
    • If the software only allows for one installation, I prefer using a dongle to a software key, because it’s easy to move the dongle around — and way too easy to “lose” the software key (I’ve seen it happen every time with software keys, which why I hate software keys).
    • Software licensing based on the MAC address or such, that can be moved around easily (e.g. return key via internet, then check it out on another computer) is better, but is still a hassle.
    • Of course, the best vendors say: “You can copy the software; just don’t tell us” (said to me by a saleswomen for a large German automation vendor).
  • Electrical Schematic viewer
    • I don’t always have a paper schematics with me, so it’s important to be able to view schematics on my laptop.
    • Since our schematics are in DWG files, I use eDrawings as a convenient DWG file viewer.  You can also use a full AutoCAD clone; DoubleCAD XT (Windows only) and DraftSight (Windows, Mac, Linux) are both high quality, free AutoCAD clones.
  • Merge software with directory comparisons
    • I’ve found file comparison software to be a life-saver.  Version control is great, but a machine in the field might be in a different state.  I can use the directory comparison to quickly see what files have changed, and then zero in on the changes using file comparison, and then merge between the two versions if needed.  Some software handles three-way merges.
      • I just did this kind of directory comparison recently when upgrading two almost-but-not-quite-identical machines.
    • I’ve been using Araxis Merge for a long time, and have no regrets about spending my money on it.  I’ve used some free options (such as TortoiseMerge with TortoiseSvn), but I feel Araxis works better for some file comparisons.   TortoiseMerge doesn’t do directory comparisons.
  • If you use a personal laptop for work, consider using a Virtual Machine (VM) to keep your private and professional lives separate.  With USB pass through features, you should be able to access USB, serial (via USB to serial converters), and networked equipment from within the VM.
  • In the future, I might look at taking my version control system with me; since I’m currently running Subversion and Trac in a Virtual Machine, I could do it easily by copying the VM to my laptop.

April 18, 2011   2 Comments

My Toolbox: Laptop

My Toolbox series is about my tools for working on machines, including some stories.  I’m going to talk about my tools; your toolbox will be different, but hopefully I’ll give some useful ideas.

Yeah, I’m a software guy, but as the automation software guy, I have the privilege of understanding the whole machine and making sure it is all working right.  That’s why I have a toolbox filled with mechanical tools and electrical test equipment, but I’ll start with service laptops.

Service Laptop

  • I’m using Win7 64-bit on my own laptop, but Win7 32-bit is probably the best choice for a field service laptop,  since you should not need >3G RAM, and many device drivers are still not available for 64-bit Windows.
  • Since almost all automation software is Windows only, you really have to use Windows.
    • Siemen’s SoftComfort Logo! development environment is a notable exception (it’s written in Java).
    • However, if you can talk to all your equipment via USB (including USB to serial converters) and Ethernet, you could use Linux or Mac OS X as your host OS and run the Windows software in a VM (Virtual Machine) with networking and USB pass through for outside access.  Or you can dual boot.
  • I’m partial to Lenovo Thinkpads because of their excellent keyboards and overall quality.  Besides, most Thinkpads support using a FDE (full disk encryption) hard drive, which is a good idea when venturing out with gigabytes of proprietary information.
    • Not all Thinkpads come with with FDE drives, but it’s an affordable do-it-yourself upgrade.
    • Thinkpads are more affordable at the Lenovo Outlet, and you still get a 1 year warranty.  If an older Thinkpad is good enough, and a shorter warranty is OK, then TigerDirect often has great deals (<$400) on off-lease Thinkpads.
  • Of course there are plenty of other good possibilities.  My advice is always get a business class laptop; I’ve seen way too many problems with consumer laptops.

Don’t forget the cables

  • I typically bring along an extra RJ-45 cable, a standard DB9M/F serial cable, USB extension cable, USB A to micro-B cable, Panasonic FP0 serial cable, and USB to serial port converter (since my laptop doesn’t have a serial port).
  • I normally don’t bring along all the special serial stuff, like null modem (laplink) cables, DB9/DB25 cables, and assorted gender changes.  I’ve only needed something weird once in the past 5 years.

Other Computer Hardware

  • A 4G or larger USB memory stick.
    • I frequently have to transfer files without using a network.
    • If you work with really old computer systems, a USB floppy drive would be useful.
    • Don’t forget the memory stick!  Always remember to put it back in your bag or pocket.
  • 3G/4G wireless is a nice option, so you can access the internet to research problems, download files you forget to do earlier, and such without needing access to the customer’s network.
    • On the other hand, 3G is another monthly fee (typically $40-$80/month in the US) for a service that’s typically not often needed.  If AT&T does complete its acquisition of T-Mobile, expect prices to go up.
    • Pre-paid (from Virgin Mobile and others) gives the option of paying only when needed, but pre-paid is more expensive for heavy data use. Walmart probably has the best pre-paid deal: $20 for 1G for 1 month.
    • Another option is tethering (via USB cable, Bluetooth, or WiFi) to a cell phone with 3G/4G.  However, tethering usually adds another monthly charge (often about $15) on top of the data fee.

March 31, 2011   No Comments