Campbell Scientific LI200X-LC User Manual

INSTRUCTION MANUAL

LI200X-LC Pyranometer

for MetData1

4/97

Copyright (c) 1994-1997

Campbell Scientific, Inc.

Warranty and Assistance

The LI200X-LC PYRANOMETER 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, reinstalling, and
shipping defective products to CAMPBELL SCIENTIFIC, INC. CAMPBELL
SCIENTIFIC, INC. will return such products by surface carrier prepaid. This
warranty shall not apply to any CAMPBELL SCIENTIFIC, INC. products
which have been subjected to modification, misuse, neglect, accidents of
nature, or shipping damage. This warranty is in lieu of all other warranties,
expressed or implied, including warranties of merchantability or fitness for a
particular purpose. CAMPBELL SCIENTIFIC, INC. is not liable for special,
indirect, incidental, or consequential damages.

Products may not be returned without prior authorization. The following

act information is for US and International customers residing in countries

cont
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company
serves your country. To obtain a Returned Materials Authorization (RMA),
contact CAMPBELL SCIENTIFIC, INC., phone [phone]. After an
applications engineer determines the nature of the problem, an RMA number
will be issued. Please write this number clearly on the outside of the shipping
container. CAMPBELL SCIENTIFIC's shipping address is:

CAMPBELL SCIENTIFIC, INC.

RMA#_____
815 W
Logan, Ut

CAMPBELL SCIENTIFIC, INC. does not accept collect calls.

est 1800 North

ah 84321-1784

LI200X-LC PYRANOMETER

FOR METDATA1

1. GENERAL

The LI200X measures incoming solar radiation
with a silicon photovoltaic detector mounted in
cosine-corrected head. The detector outputs
current; a shunt resistor in the sensor cable
converts the signal from current to voltage,
allowing the LI200X to be measured directly by
Campbell Scientific dataloggers. The LI200X is
calibrated against an Eppley Precision Spectral
Pyranometer to accurately measure sun plus
sky radiation. Do not use the LI200X under
vegetation or artificial lights, because it is
calibrated for the daylight spectrum (400 to
1100 nm).

During the night the LI200X may read slightly
negative incoming solar radiation. This negative
signal is caused by RF noise. Negative values
may be set to zero in the datalogger program.

For more theoretical information on the silicon
photovoltaic detector see Kerr, J. P., G. W.
Thurtell, and C. B. Tanner: An integrating
pyranometer for climatological observer stations
and mesoscale networks.
688-694.

1.1 SPECIFICATIONS

Stability: < ±2% change over a 1

Response Time: 10 µs
Cosine Correction: Cosine corrected up to 80°
Operating

Temperature: -40 to +65 °C
Temperature

Dependence: 0.15% per °C

J. Appl. Meteor.

year period

, 6,

Weight: 1 oz. (28 g)
Accuracy: Absolute error in natural

daylight is ±5% maximum;
±3% typical

-2

-1

Sensitivity: 0.2 kW m
Linearity: Maximum deviation of 1%

up to 3000 W m

Shunt Resistor: Adjustable, 40.2 to 90.2 Ω,

factory set to give the

above sensitivity
Light Spectrum
Waveband: 400 to 1100 nm

NOTE: The black outer jacket of the cable
is Santoprene® rubber. This 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.

mV

-2

2. INSTALLATION

To ensure accurate measurements, the LI200X
should be mounted using LI2003S base/leveling
fixture. This base incorporates a bubble level
and three adjustment screws. The LI200X and
base/leveling fixture are attached to a tripod or
tower using one of three mounting
configurations (see Figure 2-1 through 2-3).

The LI200X should be mounted such that it is
never shaded by the tripod/tower or other
sensors.

Relative Humidity: 0 to 100%
Detector: High stability silicon

photovoltaic detector (blue
enhanced)

Sensor Housing: Weatherproof anodized

aluminum case with acrylic
diffuser and stainless steel
hardware

Size: 0.94" dia x 1.00" H (2.38 cm

dia x 2.54 cm H)

NOTE:

the sensor. Save this cap for shipping or
storing the sensor.

Remove the red cap after installing

1

LI200X-LC PYRANOMETER FOR METDATA1

FIGURE 2-1. 015 Pyranometer Mounting Arm

3. CONNECTION

The LI200X-LC is attached to the MetData1
connector #3. Open the MetData1 internal
jumpers #2 and #3 as indicated in Figure 3-1.

CS500\HMP45C

Open

Open

HMP35C

LI190SB

LI200S

#1 #2 #3

#4

FIGURE 2-2. 025 Crossarm Stand and

019ALU Crossarm

FIGURE 3-1. MetData1 Jumper

Configuration

4. PROGRAMMING

NOTE: Information in this section is not

necessary when programming the
MetData1 with the Short Cut Program
Builder software.

Solar radiation can be reported as an average
flux density (W m

-2

(MJ m

). The appropriate multipliers are listed
in Table 4-1. Programming examples are given
for both average and daily total solar radiation.

The output from the LI200X is 0.2 kW m

4.1 AVERAGE SOLAR RADIATION

Example 1 shows the program instructions used
to measure the signal from the LI200X. A thirty
minute average is calculated and stored in final
storage.

-2

) or daily total flux density

-2

mV-1.

FIGURE 2-3. UTLI Leveling Fixture and

Crossarm Mount and UT018 Tower

Mounting Bracket and Crossarm

2

TABLE 4-1. Multipliers Required for Average

Flux and Total Flux Density in Sl and

English Units

LI200X-LC PYRANOMETER FOR METDATA1

UNITS MULTIPLIER

-2

W m

MJ m

kJ m

cal cm

cal cm

-2

-2

-2

min

-2

-1

t * 0.2 * (0.02389) Total

200 Average

t * 0.0002 Total

t * 0.2 Total

0.2 * (1.4333) Average

PROCESS

t = datalogger execution interval in seconds

EXAMPLE 1. Sample Instructions used to Measure an Average Flux

;{CR10X}
;

*Table 1 Program

01: 10 Execution Interval (seconds)

01: Volt (Diff) (P2)

1: 1 Reps
2: 22 ± 7.5 mV 60 Hz Rejection Range
3: 3 DIFF Channel
4: 1* Loc [ W_m2 ]
5: 200*** Mult
6: 0 Offset

;Set negative values to zero.
;

02: If (X<=>F) (P89)

1: 1* X Loc [ W_m2 ]
2: 4 <
3: 0 F
4: 30 Then Do

03: Z=F (P30)

1: 0 F
2: 0 Exponent of 10

3: 1* Z Loc [ W_m2 ]
04: End (P95)
05: If time is (P92)

1: 0 Minutes (Seconds --) into a

2: 30 Interval (same units as above)

3: 10 Set Output Flag High (Flag 0)
06: Real Time (P77)

1: 0110 Day,Hour/Minute

3

LI200X-LC PYRANOMETER FOR METDATA1

07: Average (P71)

1: 1 Reps
2: 1* Loc [ W_m2 ]

-Input Locations­1 W_m2

*

Proper entries will vary with program.

***

See Table 4-1 for alternative multipliers.

4.2 TOTAL SOLAR RADIATION

In Example 2 a daily total flux density is found.
This total flux density is in MJ m

-2

day-1.
Negative values are set to zero before they are
added to the running total.

4.2.1 Output Format Considerations

If the solar radiation is totalized in units of kJ

-2

, there is a possibility of overranging the

m
output limits. The largest number that the
datalogger can output to final storage is 6999
in low resolution and 99999 in high resolution
(Instruction 78, Set Resolution).

Assume that the daily total flux density is
desired in kJ m

-2

kW m

, the maximum low resolution output limit

-2

. Assume an irradiance of 0.5

will be exceeded in just under four hours. This
value was found by taking the maximum flux
density the datalogger can record in low
resolution and dividing by the total hourly flux
density.

2

39

..

hr

=

05 3600

()()

6999

21 1

−− −

kJ m s s hr

kJ m

−

(1)

To circumvent this limitation, record an average
flux (see Example 1). Then, during post
processing, multiply the average flux by the
number of seconds in the output interval to
arrive at a output interval flux density. Sum the
output interval totals over a day to find a daily
total flux density.

Another alternative is to record total flux using
the high resolution format (Instruction 78, see
Datalogger manuals for details). The
disadvantage of the high resolution format is
that it requires four bytes of memory per data
point, consuming twice as much memory as low
resolution.

4

LI200X-LC PYRANOMETER FOR METDATA1

EXAMPLE 2. Sample Instructions used to Measure a Daily Total Flux Density with a CR10(X)/21X

;{CR10X}
;

*Table 1 Program

01: 10 Execution Interval (seconds)

01: Volt (Diff) (P2)

1: 1 Reps
2: 22 ± 7.5 mV 60 Hz Rejection Range
3: 3 DIFF Channel
4: 1* Loc [ MJ_m2 ]
5: .002** Mult
6: 0 Offset

;Set negative values to zero.
;

02: If (X<=>F) (P89)

1: 1* X Loc [ MJ_m2 ]
2: 4 <
3: 0 F
4: 30 Then Do

03: Z=F (P30)

1: 0 F
2: 0 Exponent of 10

3: 1* Z Loc [ MJ_m2 ]
04: End (P95)
05: If time is (P92)

1: 0 Minutes (Seconds --) into a

2: 1440 Interval (same units as above)

3: 10 Set Output Flag High (Flag 0)
06: Real Time (P77)

1: 0110 Day,Hour/Minute
07: Totalize (P72)

1: 1 Reps

2: 1* Loc [ MJ_m2 ]

-Input Locations­1 MJ_m2

*

Proper entries will vary with program.

**

See Table 4-1 for alternative multipliers.

5

LI200X-LC PYRANOMETER FOR METDATA1

5. MAINTENANCE

On a monthly basis the level of the pyranometer
should be checked. Any dust or debris on the
sensor head should be removed. The debris
can be removed with a blast of compressed air
or with a soft bristle, camel hair brush. Check
that the drain hole next to the surface of the
sensor is free of debris.

CAUTION: Handle the sensor carefully
when cleaning. Be careful not to scratch
the surface of the sensor.

Recalibrate the LI200X every two years. Obtain
an RMA number before returning the LI200X to
Campbell Scientific, Inc. for recalibration.

6. CALIBRATION

LI200X pyranometers output a current that is
proportional to the incoming solar radiation.
Each LI200X has a unique calibration factor. A
variable shunt resistor in the cable converts the
current to the voltage measured by the
datalogger. Campbell Scientific sets the shunt
resistor so that the pyranometer outputs 5 mV

-1 m2

kW

.

The resistor value is found using Ohms law.
The resistance is found by dividing the desired
output voltage by the calibrated current output.
For example, a pyranometer with a calibration
of 92 µA kW

54.35

-1 m2

, will have the resistor set to:

12 12

Ω=

5 0092

mV kW m mA kW m

−−

..

6

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