Campbell Scientific 108-LC User Manual

INSTRUCTION MANUAL

108-LC Temperature Probe

for MetData1

Revision: 4/03

Copyright (c) 1985-2003

Campbell Scientific, Inc.

Warranty and Assistance

The MODEL 108-LC TEMPERATURE PROBE FOR METDATA1 is
warranted by CAMPBELL SCIENTIFIC, INC. to be free from defects in
materials and workmanship under normal use and service for twelve (12)
months from date of shipment unless specified otherwise. Batteries have no
warranty. CAMPBELL SCIENTIFIC, INC.'s obligation under this warranty is
limited to repairing or replacing (at CAMPBELL SCIENTIFIC, INC.'s option)
defective products. The customer shall assume all costs of removing,
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INC. CAMPBELL SCIENTIFIC, INC. will return such products by surface
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SCIENTIFIC, INC. products which have been subjected to modification,
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INC. is not liable for special, indirect, incidental, or consequential damages.

Products may not be returned without prior authorization. The following
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108-LC Table of Contents

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1. General........................................................................1

1.1 Specifications............................................................................................1

2. Accuracy .....................................................................1

3. Installation and Wiri ng ...............................................4

4. Connection..................................................................4

5. Programming ..............................................................5

6. Maintenance and Calibration .....................................5

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Model 108-LC Temperature Probe for MetData1

1. General

The 108 Air/Soil/Water Temperature Probe uses thermistors to measure
temperature. Custom lead lengths are available up to 1000 ft.

For air temperature measurement, a 41303 radiation shield is needed to mount
the 108 Probe and limit solar radiation loading of the 108. The 108 probe is
designed to be buried or submerged in water up to 100 feet.

1.1 Specifications

Temperature Measurement Range: -5° to +95°C

Thermistor Interchangeability Error: Typically <±0.2°C over 0°C to 7 0°C ±0.3
@ 95°C.

Polynomial Linearization Error: <±0.5°C over -7°C to +90°C.

NOTE

2. Accuracy

®

The black outer jacket of the cable is Santoprene
compound was chosen for its resistance to temperature extremes,
moisture, and UV degradation. However, this jacket will support
combustion in air. It is rated as slow burning when tested
according to U.L. 94 H.B. and will pass FMVSS302. Local fire
codes may preclude its use inside buildings.

The overall probe accuracy is a combination of the thermistor's
interchangeability specification, the precision of the bridge resistors, and the
polynomial error. In a "worst case" all errors add to an accuracy of ±0.3°C
over the range of -3° to 90°C and ±0.7°C over the range of -7°C to 95°C. The
major error component is the interchangeability specification of the thermistor,
tabulated in Table 2-1. For the range of 0° to 50°C the interchangeability error
is predominantly offset and can be determined with a single point calibration.
Compensation can then be done with an offset entered in the measurement
instruction. The bridge resistors are 0.1% tolerance with a 10 ppm temperature
coefficient. Polynomial errors are tabulated in Table 2-2 and plotted in Figure
2-1.

rubber. This

1

Model 108-LC Temperature Probe for MetData1

TABLE 2-1. Thermistor Interchangeability Specification

TABLE 2-3. Actual Temperature, Sensor Resistance,

Temperature Resistance Output

-10.00 612366 -9.02

10.00 207807 10.00

12.00 187803 12.04

14.00 169924 14.07

16.00 153923 16.09

18.00 139588 18.10

20.00 126729 20.09

22.00 115179 22.07

24.00 104796 24.05

26.00 95449 26.02

28.00 87026 27.99

30.00 79428 29.97

32.00 72567 31.94

34.00 66365 33.93

36.00 60752 35.93

38.00 55668 37.93

40.00 51058 39.94

42.00 46873 41.96

44.00 43071 43.98

46.00 39613 46.00

48.00 36465 48.02

50.00 33598 50.03

Temperature

Temperature (°C) Tolerance (

−10 0.25

0 to +50 0.20

+70 0.20
+90 0.31

TABLE 2-2. Polynomial Error

-10 to +95 <±1.0°C

-7 to +95 <±0.5°C

-3 to +90 <±0.1°C

and Computed Temperature

°C OHMS °C

-8.00 546376 -7.36

-6.00 488178 -5.63

-4.00 436773 -3.83

-2.00 391294 -1.97

0.00 351017 -0.05

2.00 315288 1.91

4.00 283558 3.91

6.00 255337 5.93

8.00 230210 7.96

±°C)

2

Model 108-LC Temperature Probe for MetData1

52.00 30983 52.03

54.00 28595 54.03

56.00 26413 56.03

58.00 24419 58.02

60.00 22593 60.01

62.00 20921 61.99

64.00 19388 63.98

66.00 17981 65.97

68.00 16689 67.96

70.00 15502 69.96

72.00 14410 71.97

74.00 13405 73.98

76.00 12479 75.99

78.00 11625 78.01

80.00 10837 80.02

82.00 10110 82.03

84.00 9438.1 84.04

86.00 8816.9 86.03

88.00 8241.9 88.00

90.00 7709.7 89.96

92.00 7216.3 91.89

94.00 6758.9 93.80

96.00 6334.5 95.67

98.00 5940.5 97.51

100.00 5574.3 99.31

FIGURE 2-1. 108 Probe Polynomial Error Curve

3

Model 108-LC Temperature Probe for MetData1

3. Installation and Wiring

The 108 must be housed inside a radiation shield when used in the field for air
temperature measurement. The 41303 Radiation Shield (see Figure 3-1)
mounts to a CM6 or CM10 tripod. The UT018 mounting arm and UT6P
Radiation Shield are used to mount the 108 to a UT30 tower.

The standard lead length of 6 feet and 9 feet allow the 108 to be mounted at a 2
meter height on the CM6/CM10 tripod or the UT30 tower respectively.

4. Connection

4

FIGURE 3-1. 108 and 41303 Radiation Shield

on a CM6/CM10 Tripod Mast

The 108 cable is attached to the MetData1 connector #4 or #7. Connector #4
uses single-ended input 4L (channel 8) and connector #7 uses single-ended
input 5H (channel 9). The probe is measured by a single-ended analog input
channel.

5. Programming

Model 108-LC Temperature Probe for MetData1

NOTE

01: AC Half Bridge (P5)

1: 1 Reps
2: 3 ± 25 mV Slow Range
3: 8 or 9** In Chan
4: 3 Ex Chan Option
5: 1000 mV Excitation
6: 11* Loc [ Tmp108C ]
7: 200 Mult
8: 0 Offset

02: Polynomial (P55)

1: 1 Reps
2: 11* X Loc [ Tmp108C ]
3: 11* F(X) Loc [ Tmp108C ]
4: -26.97 C0
5: 69.635 C1
6: -40.66 C2
7: 16.573 C3
8: -3.455 C4
9: .301 C5

Information in this section is not necessary when programming
the MetData1 with the Short Cut Program Builder software.

Instruction 5 (AC Half Bridge) is used to measure the 108 temperature probe.
Instruction 55 (polynomial) is used to find the temperature in degrees Celsius.

MetData1 Datalogger Program Example

* Proper entries will vary with input location assignments.
** Specify input channel #8 for connector #4. Specify input channel #9 for connector #7.

TABLE 5-1. Polynomial Coefficients

Coefficient Value

C0 -26.97
C1 69.635
C2 -40.66
C3 16.573
C4 -3.455
C5 0.301

6. Maintenance and Calibration

The 108 Probe requires minimal maintenance. Check monthly to make sure the
radiation shield is free from debris.

5

Model 108-LC Temperature Probe for MetData1

For most applications it is unnecessary to calibrate the 108 to eliminate the
thermistor offset. However, for those users that are interested, the following
briefly describes calibrating the 108 probes.

A single point calibration can be performed to determine the 108 temperature
offset (thermistor interchangeability). This calibration will not remove the
polynomial error. The value of the offset must be chosen so that the probe
outputs the temperature calculated by the polynomial, not the actual calibration
temperature. For example, a 108 is placed in a calibration chamber that is at
0°C and the probe outputs 0.1°C. The offset is -0.15, because at 0°C the
polynomial calculates a temperature of -0.05°C (Table 5-2).

6

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