Model 2790 SourceMeter® Switch System User’s Manual 6-5Offset compensated ohmsThe presence of thermal EMFs (VEMF ) can adversely affect low-resistance measurementaccuracy. To overcome these unwanted offset voltages, you can use offset-compensatedohms (OCOMP). Offset compensated ohms performs two measurements using two differ-ent test currents. The two readings are then averaged to yield a single resistance reading.NOTE Details on offset compensated ohms are provided in Section 3 of the Model 2790Reference Manual.Offset-compensated ohms measurements can be performed on the 100Ω, 1kΩ, and 10kΩranges for the Ω4 function.Front panel operationPerform the following steps to enable offset compensated ohms:1. Press Ω4 to select the 4-wire resistance function (4W annunciator on).2. Use the RANGE up and down keys to select the 100Ω, 1kΩ, or 10kΩ range.3. Press and release SHIFT and then OCOMP to enable offset compensated ohms(OCOMP annunciator on).Remote programmingThe commands to control offset compensated ohms are listed in Table 6-1.Table 6-1Commands to set offset compensated ohmsCommands Description Default[SENSe[1]]:FUNCtion ‘FRESistance’ [, ] Select 4-wire ohms function (Ω4).:FUNCtion? [] Query function.:FRESistance:RANGe [, ] Select range; 0 to 11e3*. 100e6**:FRESistance:RANGe? [] Query Ω4 range.:FRESistance:OCOMpensated [, ] Enable or disable offset compensatedohms; ON or OFF.OFF**:FRESistance:OCOMpensated? [] Query state of OCOMP.* Suggested parameters:To select 100Ω range; let = 100To select 1kΩ range; let = 1e3To select 10kΩ range; let = 10e3** SYSTem:PRESet and *RST disables offset compensatedohms and selects the 100MΩ range for the Ω4 function.
