Fluke 9100 - Page 175

Section 4: Using the Model 9100: Resistance Function 4.7-11
Final Width = 215mm
4.7.5.7 Spans of Source Currents
In the synthesized resistance technology used in the 9100, the constant current sourced from the UUT must fall within a maximum
of three spans of values for each dialled resistance value. The spans of constant source currents acceptable to the 9100, are shown
against their corresponding spans of output resistance in the following table:
Hardware Configuration Limits Constant Source Current Limits
on Span of Output Resistance UUTi Low UUTi High UUTi Super
00.0000 Ω to 40.0000 Ω 250µA to 3.5mA 2.5mA to 35mA 25mA to 350mA
040.001 Ω to 400.000 Ω 25µA to 320µA 250µA to 3.5mA 2.5mA to 35mA
0.40001 kΩ to 4.00000 kΩ 25µA to 320µA 250µA to 3.5mA 2.5mA to 35mA
04.0001 kΩ to 40.0000 kΩ 2.5µAto32µA25µA to 350µA 250µA to 3.5mA
040.001 kΩ to 400.000 kΩ 250nA to 3.2µA 2.5µAto35µA25µA to 350µA
0.40001 MΩ to 4.00000 MΩ 25nA to 320nA 250nA to 3.5µA 2.5µAto35µA
04.0001 MΩ to 40.0000 MΩ 8nA to 32nA 25nA to 350nA 250nA to 3.5µA
040.001 MΩ to 400.000 MΩ 4nA to 32nA 25nA to 200nA N/A
When the Ohms function is entered from another function, the default resistance setting is 1kΩ, coupled with the default current
span of 'UUTi Low'. As the resistance span is altered within Ohms function, the 9100 will default to the current span nearest to
that previously in use. For instance, when using the X10 screen key to increase the output setting from 2kΩ — UUTi high current
span (250µA to 3.5mA), the 9100 will automatically select 20kΩ — super current span (250µA to 3.5mA). If a different Current
span is required, it will be necessary to select it manually by pressing the CHANGE CURRENT screen key until the chosen span
is selected (refer to pages 4.7-2/3). The indications given on the screen for the three different spans are as follows:
UUTi Low UUTi High UUTi Super
U
U
T
i
U
U
T
i
U
U
T
i
Output Voltage Limitation
At any UUTi span, the 9100 will seek a suitable configuration of hardware to accommodate both the value of source current within
the limits, and the value of resistance set as Output Value.
The maximum nominal output voltage is 10V, such that: IR x RT = ≤10V.
Any Resistance value within the total span can be selected. However, if the source current exceeds the upper limit of the selected
span, the circuit will be saturated, and a warning will be given. Also, a warning will be given if the source current is less than the
lower limit. When a warning appears, the instrument will still function, but the specification will be compromised. In the 0Ω to
40Ω configuration, low current warnings will not be given as this configuration may be used as a zero point for all Resistance
configurations.
Always choose the lowest possible UUTi setting at which no 'Sense current high' warning appears; i.e. if a warning is given on a
particular UUTi span, work up to use the first span at which the warning disappears. Normally the 9100 toggles between just two
of the three possible settings. To force the third setting: turn the output off, make your selection, then turn the output back on.