How is the Keysight 4142B different from the Keysight 4155C and 4156C?

The key difference between the Keysight 4142B and the Keysight 4155C/4156C is that the Keysight 4142B lacks front panel control. The Keysight 4142B can only be used with an external controller. However, the Keysight 4142B has more module options available than does the Keysight 4155C/4156C, and the Keysight 4142B is faster in making measurements than is the Keysight 4155C/4156C. It should be noted that the addition of Keysight FLEX and program memory to the Keysight 4155C/4156C have made its measurement times much closer to those of the Keysight 4142B (as opposed to the Keysight 4155A/4156A which was significantly slower than the Keysight 4142B). The Keysight 4155C/4156C also has much better low-current resolution capability than does the Keysight 4142B. The following information summarizes the capabilities of each instrument:

Up to 8 MPSMU per mainframe
Wide variety of configurations
HPSMU and MPSMU have 20fA/40uV measurement resolution
HVU capability (Max. 1000V, 10mA force and measure)
HCU capability (Max 10A, 10V force and measure)
Cannot function as system controller (requires external controller)
Sweep and Spot modes available
Program memory and Keysight 4142B user commands

Keysight 4155C/4156C

Easy to use front panel operation
HRSMU (Keysight 4156C) has 1fA/2uV resolution and MPSMU (Keysight 4155C) has 10fA/2uV measurement resolution
Default 4 SMU configuration and can be increased by 1 HPSMU or 2 MPSMU with Keysight 41501B Expander Box
Keysight 41501B Expander Box can contain the following:
#1 HPSMU (200V, 1A)
#2 2 MPSMU (100V, 100mA )
#3 2 PGU
(The following combinations are possible: #1 only, #2 only, #3 only, #1 and #3, or #2 and #3)
Can function as system controller
Sweep (includes Spot), Sampling, and Stress modes available
Program Memory and Keysight FLEX (very similar to Keysight 4142B user commands)
Instrument BASIC (IBASIC) included
Auto Analysis function
VXI plug & play driver
LAN capability