On Mon, 23 Nov 2009 17:40:36 -0800, "Michael Koblic"
wrote:

I have three sets of cheap digital calipers bought in Canadian Tire. The
have all been working fine and agree with a micrometer to within 0.001". Two
weeks ago I tried to use the one I keep in the workshop to measure something
of the order of 4" when the calipers refused to measure anything past 1.5".
I brought them into the house where they started working fine as soon as
they warmed up.

The second set did exactly the same thing today.

The temperature in the workshop is 9.5 deg C.

Replacing the battery made no difference. What is the likely cause?

It may not be temperature per se, but temp close to where RH
condenses. Those calipers have some very high impedance CMOS
circuitry. I've had Mitutoyo digital calipers do that, never had a
problem with those from HF!