Keithley 77xxCommonMode free download

File name 77xxCommonMode.pdf

How are maximum input voltage and maximum common mode voltage related on the Integra series (e.g.77xx) modules? Each analog channel on a 77xx switch module has a HI and a LO terminal for connection of the signal of interest. This connection has a maximum signal level specification. Additionally, the 77xx module has a Common Mode Voltage specification. Common mode voltage is the potential difference between the 27xx mainframe's chassis ground and the HI or LO terminals. In effect, it is the amount by which the signal can be floated relative to chassis ground. The input voltage and common mode voltage are listed as follows. Switch Maximum Maximum Voltage Maximum Voltage Module Common Mode between module HI between module Voltage(VCM) and LO HI and LO Assume MAXIMUM Assume VCM VCM = 0V 7700 300V 0V 300V 7701 300V 0V 150V 7702 300V 0V 300V 7703 300V 0V 300V 7705 300V 0V 300V 7706 300V 0V 300V 7707 300V 0V 300V 7708 300V 0V 300V 7709 300V 0V 300V 7710 300V 0V 60V 7711 0V 60V 60V 7712 0V 30V 30V The maximum allowed input voltage at the HI and LO terminals is the difference between the maximum allowed common mode voltage (from specification) and the actual common mode voltage present in your system. For example on the 7700 module where the common mode voltage specification is 300V and the maximum input voltage specification is 300V: