FOR MEASUREMENT OF THE ENERGY BALANCE

One-component and four-component instruments

Reliable all-weather performance

Light weight and robust

Unique ventilation system

Net Radiometers

CNR 4 is a four-component net radiometer for accurate

and reliable measurements and can be used as the

reference instrument for a network of lower performance

net radiometers. There are four separate signal outputs and

the integrated temperature sensors can be used to calculate

the FIR radiation. The screw-in mounting rod, bubble level,

and cables with waterproof connectors, make installation

easy. The white sun shield reduces solar heating of the

instrument body.

CNR 4 combines two ISO 9060:2018 spectrally flat Class C

pyranometers for solar radiation with two pyrgeometers for

infrared measurements, all integrated into the instrument

body. The upper pyrgeometer has a silicon meniscus dome

so that water rolls off and the ﬁeld of view is 180 °. The

design is very light weight and includes a mounting rod as

standard. An optional heated ventilation unit, the CNF 4, is

available to minimise offsets, maximize stability and remove

precipitation.

Introduction

Net radiation is the balance between incoming radiation

from the sun and sky and outgoing radiation from the

ground. Short-wave radiation of 0.3 to 3 µm wavelength

reaches the Earth’s surface, where some is reﬂected and the

rest of the energy is absorbed by the surface. Incoming

long-wave Far Infrared (FIR) radiation from 4.5 to more than

40 µm is also absorbed by the surface, which heats up and

emits FIR back to the sky.

The four components of net radiation are the incoming and

reﬂected solar radiation, from which the Albedo can be

calculated; and the downward and upward infrared

radiation. These parameters can be measured using a pair of

pyranometers and a pair of pyrgeometers, but more

commonly a net radiometer is used that conveniently

combines four sensors into one compact instrument

The simplest type of net radiometer uses a single sensor to

measure the sum of the four net radiation components. This type

of instrument is sometimes referred to as a net pyrradiometer.

NR Lite2 is a single-component net radiometer widely used

in agriculture and hydrology. The thermopile detector is

ﬁtted with black PTFE coated conical absorbers on both

sides that have a very wide spectral response from the

ultraviolet (UV) to the far infrared (FIR). The signal output is

the difference between the sun and sky radiation and the

ground radiation and can be positive or negative, depending

upon the conditions.

There is an integral mounting rod for ﬁtting to masts and

poles, a bubble level, 15 m long signal cable, and a stick to

prevent birds settling on the instrument. The single output

means that the short-wave and long-wave components and the

upwards and downwards components cannot be separated.

For this, use our four-component CNR 4 net radiometer.

Applications

he main applications for net radiometers are in

agro-meteorology, in particular for the study of evapo-

transpiration and in climatology, meteorology and hydrology

for the measurement of the radiation balance. Monitoring

over glaciers and ice ﬁelds is of particular interest to global

warming studies. Net radiometers are often used in

conjunction with a small automatic weather station and

need to be easily portable

Choice of Net Radiometer

Kipp & Zonen offers a range of robust, lightweight, net

radiometers that do not require power to operate. A

mounting rod, bubble level and calibration certiﬁcate are

always included.

NR Lite2 has a single output for total net radiation. CNR 4

measures all four components separately. Whatever the

application, Kipp & Zonen can supply a suitable net radiometer.

Accessories

CNF 4 Ventilation Unit

The Kipp & Zonen CNR 4 net radiometer is produced as the

standard instrument or with an integrated ventilation unit

and heater. The CNF 4 ventilation unit can also be bought as a

kit for retro-ﬁtting to a CNR 4 that was purchased without it.

CNF 4 provides a clean air ﬂow over all four of the CNR 4

radiometer domes and windows and is designed to operate

under all weather conditions. The only part that needs

maintenance is the air inlet ﬁlter, which should be checked at

regular intervals and cleaned or replaced when necessary.

The integrated 10 W heating can be switched on by the operator

when required. This raises the temperature of the domes and

windows slightly above ambient to prevent the formation of

dew and frost and to disperse precipitation. The ventilation

fan and heater run from 12 VDC and can be operated by the

accessory CVP 2 universal AC-DC power adaptor.

CMB 1 Mounting Bracket

For attaching mounting rods of 12 to 20 mm diameter to

poles, masts or walls. The radiometer can be levelled by

rotating and tilting the rod. The bracket includes u-bolts for

ﬁxing to poles and masts from 22 to 60 mm diameter.

Heater power

Operating temperature

Cable voltage drop

Power required

Ventilator fan power

10 W

-40 °C to +70 °C

0.07 V/m (with heater)

12 Volt DC, 1.3 A (with heater)

Weight 500 g

5 W continuously

Speciﬁcations CNF 4

66 mm

235 mm

47 mm

170 mm

347 mm

111 mm

Ø 16 mm

Response time (95 %)

Temperature dependence of sensitivity

Sensitivity

Operating temperature

Spectral range (50 % points)

Number of signal outputs

Field of view

Mounting rod

< 18 s

Non-linearity (over full range) < 1 %

Pyrgeometer temperature sensors 10 K thermistor and Pt-100

< 5 % from -10 °C to +40 °C

7 to 20 µV/W/m² short-wave

5 to 10 µV/W/m² long-wave

-40 °C to +80 °C

300 to 2800 nm short-wave

4.5 to 42 µm long-wave

4 - incoming and reﬂected short-wave radiation

downward and upward long-wave radiation

180 ° short-wave upper sensor

170 ° short-wave lower sensor

180 ° long-wave upper sensor

150 ° long-wave lower sensor

Screw-in, 350 mm long x 16 mm

Standard cable 10 m with connector

Cable lenght options 25 m, 50 m

Weight with rod (excluding cable(s))

Note: The performance speciﬁcations quoted are worst-case and/or maximum values

850 g

< 60 s

< 1 %

N/A

- 0.1 % / °C (typical)

10 µV/W/m² (nominal)

-40 °C to +80 °C

200 nm to 100 µm

1 - net total radiation

180 ° upper and lower sensor

Fixed, 800 mm long x 20 mm

15 m ﬁxed cable

N/A

490 g

Speciﬁcations NR Lite2 CNR 4

NR Lite2

Ø 80

111

800

235 347

CNR 4

Ø 16

Ø 20

All dimensions in mm