What is the market size (in dollars) for electronic signal
conditioners in the United States?  The signal conditioners are the
type used with sensors to control industrial machinery.

I can't even guess the dollars, but perhaps I can help you rephrase
your question. My experience is with sensors developed several decades
ago. The signal conditioners generally were part of the circuitry of
the display (typically a meter or chart recorder, or a mechanical
computer which automatically adjusted the machinery to keep the
product in spec. I don't think this has changed except large scale
integration solid state chips now do what a few cams and gears did
then. Mostly it is not an improvement, but I will concede an
occasional amazing improvement.  I should think the signal
conditioners are typically built into the sensor or contained in a
computer interface that does several other things. If the signal
conditoners are part of a multipurpose chip, a meaningful dollar
amount will be difficult unless ie $4 dollar chip, 4 funtions, $1 each
add 50% as one of the funtions isn't useful in typical applications =
1.50 for the signal conditioning funtion.   Neil