Measurement Computing WEB-TEMP - Manual (Page 33)

WEB-TEMP User's Guide Specifications
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Note 11: Error shown does not include errors of the sensor itself. The sensor linearization is performed
using a Steinhart-Hart linearization algorithm. The accuracy and tempco specifications include the
accuracy of the Callendar-Van Dusen linearization algorithm. These specifications are for one year
while operation of the device is between 15 °C and 35 °C. The specification does not include lead
resistance errors for 2-wire thermistor connections. Contact your sensor supplier for details on the
actual sensor error limitations. Total thermistor resistance on any given channel pair must not exceed
180 kΩ. Typical resistance values at various temperatures for supported thermistors are shown in Table
8.
Table 8. Typical thermistor resistance specifications
Temp (°C) 2252 Ω
thermistor 3000 Ω
thermistor 5 kΩ
thermistor 10 kΩ
thermistor 30 kΩ
thermistor
–40 76 kΩ 101 kΩ 168 kΩ 240 kΩ (Note 12) 885 kΩ (Note 12)
–35 55 kΩ 73 kΩ 121 kΩ 179 kΩ 649 kΩ (Note 12)
–30 40 kΩ 53 kΩ 88 kΩ 135 kΩ 481 kΩ (Note 12)
–25 29 kΩ 39 kΩ 65 kΩ 103 kΩ 360 kΩ (Note 12)
–20 22 kΩ 29 kΩ 49 kΩ 79 kΩ 271 kΩ (Note 12)
–15 16 kΩ 22 kΩ 36 kΩ 61 kΩ 206 kΩ (Note 12)
–10 12 kΩ 17 kΩ 28 kΩ 48 kΩ 158 kΩ
–5 9.5 kΩ 13 kΩ 21 kΩ 37 kΩ 122 kΩ
0 7.4 kΩ 9.8 kΩ 16 kΩ 29 kΩ 95 kΩ
Note 12:
Resistance values greater than 180 kΩ cannot be measured by the WEB-TEMP in the thermistor
mode. The 180 kΩ resistance limit includes the total resistance across the current excitation (±Ix) pins,
which is the sum of the thermistor resistance and the lead resistances.
Note 13: For accurate three wire compensation, the individual lead resistances connected to the ±Ix pins
must be of equal ohmic value. To ensure this, use connection leads of equal lengths.
Throughput rate
Table 9. Throughput rate specifications
Number of input channels Maximum throughput
1 2 S/s
2 2 S/s on each channel, 4 S/s total
3 2 S/s on each channel, 6 S/s total
4 2 S/s on each channel, 8 S/s total
5 2 S/s on each channel, 10 S/s total
6 2 S/s on each channel, 12 S/s total
7 2 S/s on each channel, 14 S/s total
8 2 S/s on each channel, 16 S/s total
Note 14: The analog inputs are configured to run continuously. Each channel is sampled twice per second.
The maximum latency between when a sample is acquired and the temperature data is provided by the
Ethernet unit is approximately 0.5 seconds.