Python programming

Larry Hudson orgnut at
Fri Mar 7 08:56:00 CET 2014


>>> 	I spotted a device on the table of the company calibration office...
>>> 	As I recall, it was a 100A capable resistor... 0.10 OHM.
>>> 	No idea what it was meant for; big binding posts at one end, and a slab
>>> of sheet steel in a "W" shape (smooth curves, not sharp bends).
>> External shunt for an ammeter?
> More likely a dummy load for power supply testing.  (Normally, ammeter shunts are sized to dissipate as little power as possible.)
> -Bill

Another (OT) story...

I used to work in an electronic calibration lab, but I don't recall having a resistor of that 
description -- however, it reminds me of another story...

While our job was calibrating and maintaining our company's electronics, we occasionally had to 
do some incoming inspection work -- checking incoming components for accuracy.  This particular 
time I had a batch of 0.1 ohm 1% resistors (I think those were the numbers, at least something 
on that order).  I found by checking them right at the body of the resistors they were 
out-of-spec low, and checking at the end of the leads they were out-of-spec high.  Fun!   :-)

To measure them, I used the lab's Current Calibrator -- a special power supply whose voltage was 
controlled to give a constant (dialed-in) current.  Then with a DVM and mini-hooks I could 
attach these DVM leads anyplace along the resistor's leads.  At 1 amp, the voltage (read on the 
DVM) was equal to the resistance.  Ohm's law, of course:  R = E/I, where I is a constant 1.  And 
1 amp was well within the power specs of these resistors.

I ended up checking them at a distance of about a quarter inch from the body, because I expected 
that would be about the way they would be eventually mounted.  They all passed that way.  And 
fortunately I never had another batch of these resistors!   :-)

      -=- Larry -=-

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