Are the 8402B and 8477A compatible? More specifically, if I need to calibrate HP 431C (which GIDEP procedure calls for HP 8402B as the range calibrator), is the 8477A compatible for use on the 431C. We own the 8477A for our 432A's, but someone is sending in a 431C for cal. Just want to know if the 8402B will for for the 431C...