USB-TEMP User's Guide
Specifications
5-4
RTD measurement accuracy
Table 5-6. RTD measurement accuracy specifications
RTD Sensor
Temperature
Maximum Accuracy Error (°C)
I
x+
= 210 µA
Typical Accuracy Error (°C)
I
x+
= 210 µA
-200 °C
±0.15
±0.08
-0 °C
±0.18
±0.11
100 °C
±0.26
±0.15
300 °C
±0.37
±0.23
PT100, DIN, US or
ITS-90
600 °C
±0.43
±0.27
Note 8:
Error shown does not include errors of the sensor itself. The sensor linearization is
performed using a Callendar-Van Dusen linearization algorithm. These specs are for one
year while operation of the USB-TEMP unit is between 15 °C and 35 °C. The
specification does not include lead resistance errors for 2-wire RTD connections. Please
contact your sensor supplier for details on the actual sensor error limitations.
Note 9:
Resistance values greater than 660 ohms cannot be measured by the USB-TEMP in the
RTD mode. The 660 ohm resistance limit includes the total resistance across the current
excitation (±Ix) pins, which is the sum of the RTD resistance and the lead resistances.
Note 10:
For accurate three wire compensation, the individual lead resistances connected to the ±Ix
pins must be of equal value.
Thermistor measurement accuracy
Table 5-7. Thermistor measurement accuracy specifications
Thermistor Temperature
Range
Maximum Accuracy Error (°C)
I
x+
= 10 µA
2252
Ω
-40 to120 °C
±0.05
3000
Ω
-40 to120 °C
±0.05
5000
Ω
-35 to120 °C
±0.05
10000
Ω
-25 to120 °C
±0.05
30000
Ω
-10 to120 °C
±0.05
Note 11:
Error shown does not include errors of the sensor itself. The sensor linearization is
performed using a Steinhart-Hart linearization algorithm. These specs are for one year
while operation of the USB-TEMP unit is between 15°C and 35°C. The specification does
not include lead resistance errors for 2-wire thermistor connections. Please contact your
sensor supplier for details on the actual sensor error limitations. Total thermistor
resistance on any given channel pair must not exceed 180k ohms. Typical resistance
values at various temperatures for supported thermistors are shown in Table 5-8.
