Technical data

52 34980A Service Guide
3 Calibration Procedures
Internal DMM
Input Connections
Test connections to the internal DMM are best accomplished using the rear
panel Analog Bus connector (ABus). You may need to remove the cover for
access to this connector. A test fixture can be constructed using a
standard DB9 male connector, some shielded twisted pair PTFE
insulated
cables, and appropriate connectors for the calibrator output 
you are using.
You may also use one of the multiplexer modules to connect the calibrator
output to the DMM. If you use a multiplexer module, you must take into
account any additional relay contacts and resistances in the measurement
path. To do this, use the switch/measure model to set up the DMM and
switches, not the scan model. For example, send:
conf:fres 100;:rout:clos (@1001,1021,1911,1922)
read? (should return something close to zero)
cal:val 0
cal?
In this manual, the direct ABus connection is the one described.
Connections for the ABus connector are shown below.
NOTE
Use shielded twisted pair PTFE insulated cables to reduce settling and
noise errors. Connect the shield to the source LO output.

PTFE is a registered trademark of E.I. du Pont de Nemours and Company.