Fluke 9100 - Page 261

Section 4: Using the Model 9100: RTD Temperature Function 4.15-9
Final Width = 215mm
4.15.4.7 Spans of Source Currents
In the synthesized resistance technology used in the 9100, the constant current sourced from the UUT must fall within one of a
maximum of three spans of values for each resistance value, as a result of setting the RTD 0°C nominal value and dialling each
temperature 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 10.0000 kΩ* 2.5µAto32µA25µA to 350µA 250µA to 3.5mA
* = Resistance span used when the nominal zero of the detector is raised, to give resistance values above
4kΩ for certain temperature readings.
When the RTD function is entered from another function, the default temperature setting is +25°C (resistance a little above 100Ω
as default nominal zero is 100Ω), coupled with the default current span of 'UUTi Low'. As the resistance span is altered within RTD
function, the 9100 will default to the current span nearest to that previously in use. For instance, when decreasing the output setting
from the default 25°C — UUTi high current span (250µA to 3.5mA), to -160°C (approx 35Ω in the 0-40Ω resistance span), the 9100
will automatically select the low 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 4.15-2/3). 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 by the set Output Value of Temperature.
The maximum nominal output voltage is 10V, such
that:
I R x R T = ≤10V.
Any RTD Temperature value within the total span can be selected. However, if the source current exceeds the upper limit, 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 reference point for the 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.