George, I too have an old Simpson 260. The last time I tried to use it, it wouldn't work. I suppose the switch contacts are corroded from lack of use.
The reason the old analog units had a zero adjustment wasn't so much to allow for the lead resistance as it was to compensate for the battery condition. They don't have a real stable current source (I think it's just a resistor), so the zero would be all over the map.
Something to be aware of with digital units is that the "continuity" or "diode check" scale is NOT a resistance measurement! It actually displays VOLTS, not OHMS. The reason for this is that a good diode has a forward bias voltage of around 0.7 volts. A lot of folks use the diode check range, see a reading of less than 1.0 and assume the resistance is zero. NOT SO! When in doubt, double-check the actual resistance.
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Today's Featured Article - An Old-Time Tractor Demonstration - by Kim Pratt. Sam was born in rural Kansas in 1926. His dad was a hard-working farmer and the children worked hard everyday to help ends meet. In the rural area he grew up in, the highlight of the week was Saturday when many people took a break from their work to go to town. It was on one such Saturday in the early 1940's when Sam was 16 years old that he ended up in Dennison, Kansas to watch a demonstration of a new tractor being put on by a local dealer. It was an Allis-Chalmers tractor dealership,
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