take the pulse of
Also, feel the pulse of. Try to determine the intentions or sentiments of a person or group, as in These exit polls allegedly take the pulse of the voters, but I don't believe they're very meaningful. [First half of 1600s] Also see feel out.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.