Compression column load cell
Simple and inexpensive electrical compensation for off-axis and off-center loading sensitivity is possible in compression column load cells comprising a pair of compensation strain gages in series with each of the main strain gages in the load cell. The compensation gages are arranged crosswise to each associated main strain gage, and connected in series with their associated main strain gage. Each set of one main strain gage and two series connected compensation gages form one bridge arm in a strain gage bridge. Two compensation gages meet at each bridge corner, and are shunted by a common trimming resistor. The loading sensitivity compensation works for both conventional fixed axis load cells and Rocker Pin load cells.
1. A compression column strain gage load cell, comprising:
a first strain gage arranged to measure a principal strain in the compression column; and
a pair of second strain gages in orthogonal alignment with and arranged symmetrically to said first strain gage, said second strain gages having substantially lower resistance than said first strain gage.
2. A compression column load cell according to claim 1 , wherein said first strain gage is electrically connected between said pair of second strain gages.
3. A compression column load cell according to claim 1 , wherein four first strain gages are distributed around the periphery of the compression column and arranged alternately to measure longitudinal and transverse strain.
4. A compression column load cell according to claim 2 , wherein four sets of first and second strain gages are distributed around the periphery of the compression column, with the first strain gages oriented to measure alternately longitudinal and transverse strain.
5. A compression column load cell according to claim 4 , wherein said four sets of strain gages are connected to form a bridge circuit with two second strain gages at each bridge corner, and further comprising trimming resistors shunting each pair of two second strain gages at each bridge corner.
6. A compression column load cell according to claim 2 , wherein said first strain gage comprises two parallel strain gages arranged symmetrically with respect to said pair of second strain gages, and wherein all of said strain gages are formed as one composite strain gage.