Home Test Equipment Calibration

Discussion in 'General Electronics Chat' started by toolnuts, Jan 29, 2006.

  1. toolnuts

    Thread Starter New Member

    Jan 29, 2006

    I'm a retired controls engineer wanting to get back into electronics as a hobby. One problem is how can the home hobbiest calibrate his own equipment - without having a huge outlay in a metrolgy lab?

    I thought about getting a good calibrated 6 1/2 digit DMM and making calibration resistors, but then I come back to different AC/DC sources that all need to be calibrated. You have the chicken and egg thing going on here. Are there any sources that never need re-calibrating that a hobbiest can afford or make.

    I generally don't need 6 1/2 digits of accuracy. If the DMM instrument accuracy degraded slowley enough, I might be dead before it became a problem. I could use the DMM to set up the sources.

    Any insights or wisdom would be greatly appreciated.

    Also does anyone have an electrical schematic for a Toshiba SD-M1202 DVD-ROM drive. I am trying to make an autocollimator out of the read head.

    Thank you for your help.

    Best Regards,

    Paul Hoffman
  2. beenthere

    Retired Moderator

    Apr 20, 2004

    What kind of accuracy do you have to have? The really good stuff - traceable to NBS - has to go back every year for recalibration. Any electronic reference standard that is not passive will degrade unpredictably over time. In theory, a really close 1 ohm resistor is all you really need, but something more conveninet might be the thing.

    Some time ago, I worked at an outfit that did industrial contrl computers, built around a 25 bit A to D converter. Hand trimming was an art. The switching diodes were all hand graded, the resistors (.01%) were all taken off the same run of resistance wire. We finally built a fixture to caomapre a new board against one that had been well-calibrated and found that our 22 and 5.6 ohm trim resistors just weren't needed.

    I've also seen equipment that needed daily attention to hold any accuracy. Test equipment generally holds up, though.

    Good luck getting anything like a schematic from Toshiba. Most of the optical functions are under microprocessor control, so the schematic might not help a lot.
  3. toolnuts

    Thread Starter New Member

    Jan 29, 2006