Measurement-computing USB-TEMP-AI Manual do Utilizador descarregar pdf (Página 23)

USB-TEMP-AI User's Guide Specifications

Note 11: 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.

Thermistor measurement accuracy: T0x-T3x

Table 7. Thermistor measurement accuracy specifications, I

= 10 µA. All specifications are (±)

Thermistor

Sensor

temperature range

Accuracy error

maximum

(°C)

Accuracy error

typical

(°C)

Tempco

(°C/°C)

2252 Ω

-40 °C

0.001

0.0007

0.001

0 °C

0.021

0.008

0.001

50 °C

0.263

0.130

0.001

120 °C

3.473

1.750

0.001

5000 Ω

-35 °C

0.001

0.0006

0.001

0 °C

0.009

0.004

0.001

50 °C

0.115

0.049

0.001

120 °C

1.535

0.658

0.001

10000 Ω

-25 °C

0.001

0.0005

0.001

0 °C

0.005

0.002

0.001

50 °C

0.060

0.028

0.001

120 °C

0.771

0.328

0.001

30000 Ω

-10 °C

0.001

0.0005

0.001

0 °C

0.002

0.001

50 °C

0.019

0.009

0.001

120 °C

0.267

0.128

0.001

Note 12: 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 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 measurement range

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 13)

885 kΩ (Note 13)

–35

55 kΩ

73 kΩ

121 kΩ

179 kΩ

649 kΩ (Note 13)

–30

40 kΩ

53 kΩ

88 kΩ

135 kΩ

481 kΩ (Note 13)

–25

29 kΩ

39 kΩ

65 kΩ

103 kΩ

360 kΩ (Note 13)

–20

22 kΩ

29 kΩ

49 kΩ

79 kΩ

271 kΩ (Note 13)

–15

16 kΩ

22 kΩ

36 kΩ

61 kΩ

206 kΩ (Note 13)

–10

12 kΩ

17 kΩ

28 kΩ

48 kΩ

158 kΩ

–5

9.5 kΩ

13 kΩ

21 kΩ

37 kΩ

122 kΩ

7.4 kΩ

9.8 kΩ

16 kΩ

29 kΩ

95 kΩ

Note 13: Resistance values greater than 180 kΩ cannot be measured by the device in the thermistor mode.

The 180 k Ω 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 14: 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.

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