Apogee Instruments S2-432 Manuel utilisateur

APOGEE INSTRUMENTS, INC. | 721 WEST 1800 NORTH, LOGAN, UTAH 84321, USA

TEL: (435) 792-4700 | FAX: (435) 787-8268 | WEB: APOGEEINSTRUMENTS.COM

OWNER’S MANUAL

RED - FAR-RED SENSORS

Models S2-432

Rev: 2-Aug-2021

TABLE OF CONTENTS 
Owner’s Manual ............................................................................................................................................................................... 1 
Certificate of Compliance......................................................................................................................................................... 3 
Introduction ............................................................................................................................................................................. 4 
Sensor Models ......................................................................................................................................................................... 5 
Specifications ........................................................................................................................................................................... 6 
Deployment and Installation.................................................................................................................................................... 8 
Cable Connectors..................................................................................................................................................................... 9 
Operation and Measurement ................................................................................................................................................ 10 
Maintenance and Recalibration............................................................................................................................................. 10 
Troubleshooting and Customer Support................................................................................................................................ 16 
Return and Warranty Policy................................................................................................................................................... 17 
 

CERTIFICATE OF COMPLIANCE

EU Declaration of Conformity

This declaration of conformity is issued under the sole responsibility of the manufacturer:

Apogee Instruments, Inc.

721 W 1800 N

Logan, Utah 84321

USA

for the following product(s):

Models: S2-432

Type: Red - Far-red Sensors

The object of the declaration described above is in conformity with the relevant Union harmonization legislation:

2014/30/EU Electromagnetic Compatibility (EMC) Directive

2011/65/EU Restriction of Hazardous Substances (RoHS 2) Directive

2015/863/EU Amending Annex II to Directive 2011/65/EU (RoHS 3)

Standards referenced during compliance assessment:

EN 61326-1:2013 Electrical equipment for measurement, control and laboratory use –EMC requirements

EN 50581:2012 Technical documentation for the assessment of electrical and electronic products with respect to

the restriction of hazardous substances

Please be advised that based on the information available to us from our raw material suppliers, the products

manufactured by us do not contain, as intentional additives, any of the restricted materials including lead (see

note below), mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), polybrominated

diphenyls (PBDE), bis (2-ethylhexyl) phthalate (DEHP), butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), and

diisobutyl phthalate (DIBP). However, please note that articles containing greater than 0.1% lead concentration are

RoHS 3 compliant using exemption 6c.

Further note that Apogee Instruments does not specifically run any analysis on our raw materials or end products

for the presence of these substances, but we rely on the information provided to us by our material suppliers.

Signed for and on behalf of:

Apogee Instruments, August 2021

Bruce Bugbee

President

Apogee Instruments, Inc.

INTRODUCTION

Specific wavelengths of radiation trigger distinct responses in plants. Red and far-red wavelengths are of particular

interest because they influence photosynthetic and morphogenic activity. Phytochrome pigments in plants are

sensitive to varying ratios of red and far-red radiation, providing information to the plant about the light

environment, and therefore, optimal growth patterns. Increasing the fraction of red radiation indicates less

shading and generally results in more conservative vertical growth patterns, while increasing the far-red radiation

fraction indicates more shading and results in more aggressive vertical growth patterns.

Red - far-red sensors are designed to have spectral sensitivities that approximate the phytochrome absorption

spectrum. Red - far-red sensors quantify properties of radiation sources, not plant responses. However, inferences

of plant responses can be made from measurements of the lighting/shading environment, so it is important that

red - far-red sensors have high sensitivity in the wavelength ranges where plants are most sensitive (i.e., the

wavelength ranges that drive the strongest responses in plants), hence red - far-red sensor spectral responses

should approximate the phytochrome absorption spectrum.

The primary application of red - far-red sensors is monitoring plant light environments, including calculation of the

red to far-red ratio (red photon flux density / far-red photon flux density) and far-red fraction (far-red photon flux

density / sum of red and far-red photon flux densities), in photobiology studies (e.g., researching plant

morphogenic activities).

Apogee Instruments S2 series Red - Far-red sensors consist of a cast acrylic diffuser, pair of photodiodes that

measure specific wavelength ranges, and signal processing circuitry mounted in an anodized aluminum housing,

and a cable to connect the radiometer to a measurement device. Sensors are potted solid with no internal airspace

and are designed for continuous measurement in indoor and outdoor environments. S2-100 series sensors output

two analog voltages, one for each photodetector, that are directly proportional to red and far-red radiation

incident on a planar surface (does not have to be horizontal), where the radiation emanates from all angles of a

hemisphere. The S2-432 model outputs a digital signal using Modbus RTU communication protocol over RS-232 or

RS-485.

SENSOR MODELS

This manual covers the Modbus RTU communication protocol, Red - Far-red model S2-432 (in bold below).

Additional models are covered in their respective manuals.

Model

Signal

S2-131

Self-powered

S2-431

SDI-12

S2-432

Modbus

Sensor model number and serial number are

located on the bottom of the sensor. If you need

the manufacturing date of your sensor, please

contact Apogee Instruments with the serial

number of your sensor.

SPECIFICATIONS

Calibration Traceability

Apogee S2 series Red - Far-red sensors are calibrated through side-by-side comparison to the mean of three

transfer standard sensors under a quartz halogen lamp. The transfer standard sensors are calibrated through side-

by-side comparison to red and far-red photon flux density calculated from solar spectra collected in Logan, Utah,

using an Apogee model PS-300 spectroradiometer. The PS-300 spectroradiometer is calibrated with a quartz

halogen lamp traceable to the National Institute of Standards and Technology (NIST).

S2-432

Power Supply

5.5 to 24 V DC

Average Max Current Draw

RS-232 37 mA;

RS-485 quiescent 37 mA, active 42 mA

Calibration Factor

(reciprocal of sensitivity)

Custom for each sensor and stored in firmware

Calibration Uncertainty

± 5 %

Output Range

Modbus

Measurement Repeatability

Less than 1 %

Long-term Drift

Less than 2 % per year

Non-linearity

Less than 1 % (up to 400 µmol m⁻² s⁻¹)

Field of View

180°

Wavelength Ranges

645 to 665 nm ± 5 nm (Red)

720 to 740 nm ± 5 nm (Far-red)

Directional (Cosine)

Response

± 2 % at 45°; ± 5 % at 75° zenith angle

Temperature Response

Less than 0.1 % per C

Housing

Anodized aluminum body with acrylic diffuser

IP Rating

IP68

Operating Environment

-40 to 70 C; 0 to 100 % relative humidity

Dimensions

30.5 mm diameter, 37 mm height

Mass (with 5 m of cable)

140 g

Cable

5 m of shielded, twisted-pair wire; TPR jacket (high water resistance, high UV stability, flexibility

in cold conditions); pigtail lead wires; stainless steel (316), M8 connector

Cosine Response

Spectral Response

Directional, or cosine, response is defined as

the measurement error at a specific angle of

radiation incidence. Directional error for

Apogee S2 series Red - Far-red sensors is

approximately ± 2 % and ± 5 % at solar zenith

angles of 45° and 75°, respectively.

Mean spectral response

measurements of six replicate red -

far-red sensors (red sensor is

centered near 655 nm, far-red

sensor is centered near 730 nm).

Spectral response measurements

were made at 2 nm increments

across a wavelength range of 600 to

800 nm in a monochromator with an

attached electric light source.

Measured spectral data from each

sensor were normalized by the

measured spectral response of the

monochromator/electric light

combination, which was measured

with a spectroradiometer.

DEPLOYMENT AND INSTALLATION

Mount the sensor to a solid surface with the nylon mounting screw provided to prevent galvanic corrosion. To

accurately measure red and far-red photon flux density incident on a horizontal surface, the sensor must be level.

An Apogee Instruments model AL-100 Leveling Plate is recommended to level the sensor when used on a flat

surface or being mounted to surfaces such as wood. To facilitate mounting on a mast or pipe, the Apogee

Instruments model AL-120 Solar Mounting Bracket with Leveling Plate is recommended.

To minimize azimuth error, the sensor should be mounted with the cable pointing toward true north in the

northern hemisphere or true south in the southern hemisphere. Azimuth error is typically less than 1 %, but it is

easy to minimize by proper cable orientation.

In addition to orienting the cable to point toward the nearest pole, the sensor should also be mounted such that

obstructions (e.g., weather station tripod/tower or other instrumentation) do not shade the sensor. Once

mounted, the black cap should be removed from the sensor. The black cap can be used as a protective covering

for the sensor when it is not in use.

Nylon Screw: 10-32x3/8

Model AL-120

Model AL-100

CABLE CONNECTORS

Apogee sensors offer cable connectors to simplify the

process of removing sensors from weather stations

for calibration (the entire cable does not have to be

removed from the station and shipped with the

sensor).

The ruggedized M8 connectors are rated IP68, made

of corrosion-resistant marine-grade stainless-steel,

and designed for extended use in harsh

environmental conditions.

Cable connectors are attached directly to the head.

Instructions

Pins and Wiring Colors: All Apogee

connectors have six pins, but not all pins are

used for every sensor. There may also be

unused wire colors inside the cable. To

simplify datalogger connection, we remove

the unused pigtail lead colors at the

datalogger end of the cable.

If a replacement cable is required, please

contact Apogee directly to ensure ordering

the proper pigtail configuration.

Alignment: When reconnecting a sensor,

arrows on the connector jacket and an

aligning notch ensure proper orientation.

Disconnection for extended periods: When

disconnecting the sensor for an extended

period of time from a station, protect the

remaining half of the connector still on the

station from water and dirt with electrical

tape or other method.

A reference notch inside the connector ensures

proper alignment before tightening.

When sending sensors in for calibration, only send the sensor head.

Tightening: Connectors are designed to be

firmly finger-tightened only. There is an o-

ring inside the connector that can be overly

compressed if a wrench is used. Pay

attention to thread alignment to avoid

cross-threading. When fully tightened, 1-2

threads may still be visible.

WARNING: Do not tighten the connector by

twisting the black cable or sensor head, only

twist the metal connector (blue arrows).

Finger-tighten firmly

OPERATION AND MEASUREMENT

The S2-432 Red - Far-red sensor has a Modbus output, where red and far-red photon flux density are returned in

digital format. Measurement of S2-432 Red - Far-red sensors requires a measurement device with a Modbus

interface that supports the Read Holding Registers (0x03) function.

Wiring

The Green wire should be connected to Ground to enable RS-485 communication, or it should be connected to 12

V power for RS-232 communication. Text for the White and Blue wires above refers to the port that the wires

should be connected to.

Sensor Calibration

All Apogee Modbus Red - Far-red sensors (model S2-432) have sensor-specific calibration coefficients determined

during the custom calibration process. Coefficients are programmed into the sensors at the factory.

Modbus Interface

The following is a brief explanation of the Modbus protocol instructions used in Apogee S2-432 Red - Far-red

sensors. For questions on the implementation of this protocol, please refer to the official serial line

implementation of the Modbus protocol: http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf

(2006) and the general Modbus protocol specification:

http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf (2012). Further information can be

found at: http://www.modbus.org/specs.php

Overview

The primary idea of the Modbus interface is that each sensor exists at an address and appears as a table of values.

These values are called Registers. Each value in the table has an associated index, and that index is used to identify

which value in the table is being accessed.

Sensor addresses

Each sensor is given an address from 1 to 247. Apogee sensors are shipped with a default address of 1. If using

multiple sensors on the same Modbus line, the sensor’s address will have to be changed by writing the Slave

Address register.

White: RS-232 RX / RS-485 Positive

Blue: RS-232 TX / RS-485 Negative

Green: Select (Switch between RS-232 and RS-485)

Black: Ground

Red: Power +12 V

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