sr555Model SR555 Stand-On Scale Operating and Service Manual - SN 1800+ Part No. MAN555_060829 Page 13 of 18 CALIBRATION IMPORTANT CALIBRATION CHECKPreamplifier SR555 — Current preamplifier The SR555 is a low-noise, hh-bandwidth, fixed-gain current (trans-impedance) amplifier desned to work with SRS lockin amplifiers. Current