Semilab’s SHR technique is used to make non-contact measurements of emitter sheet resistance.  The output is in ohms/square, similar to a 4-point probe, but it can measure through a layer of glass.  It works by shining a pulse light source at a spot on the cell.  The light creates a voltage by solar cell action.  The voltage spreads through the cell, and capacitive electrodes can determine whether the voltage is decaying quickly (high sheet resistance) or slowly (high conductivity).