Section 4: Source-measure considerations Model 2461 Interactive SourceMeter® Instrument Reference Manual4-8 2461-901-01 A/November 2015In the following graph, the resistive load is decreased to 800 Ω. The DUT load for 800 Ω intersectsthe current limit, which causes the instrument to limit the voltage that it is sourcing. For the 800 ΩDUT, the instrument will only output 40 V at the 50 mA limit.Figure 150: Model 2461 current limit boundary example limitedVoltage source = Current * DUT resistance= (50 mA)(800 Ω)= 40 VNotice that as resistance decreases, the slope of the DUT load increases. Conversely, as resistanceincreases, the slope of the DUT load decreases. At zero resistance (shorted output), the instrumentwill source virtually 0 V at 50 mA. Regardless of the load, current will never exceed the limit of 50 mA.Output transient recoveryThe time required for the voltage source to recover to its original value (within 0.1 % plus loadregulation errors) after a step change in load current is < 250 μs. This does not include the responsetime of autoranging or the second order effects on loads that are not purely resistive.Load regulationThe voltage specification for voltage source mode load changes is 0.01 % +1 mV. This means that onthe 200 mV range, the load current can be changed from zero to full scale with less than 1.02 mV oferror. Calculation:Error = (0.01% x 0.2 V) + 1 mV = 1.02 mVAssuming a 0 to 1 A change in current, the output impedance equates to 1.02mΩ (1.02 mV/1 A = 1.02 mΩ). This level can only be achieved using 4-wire remote sensing.
